Sperm quality in fish: Determinants and affecting factors

Crude Oil-Induced Reproductive Disorders in Male Goldfish: Testicular Histopathology, Sex Steroid Hormones, and Sperm Swimming Kinematics

Crude oil contamination has been shown to impair reproduction in aquatic animals through carcinogenic and genotoxic properties. Here, we assessed the endocrine-disrupting function of crude oil on male reproductive system based on testicular histology, sex steroid hormones, and fertility endpoints in adult male goldfish (Carassius auratus), which were exposed to 0.02- to 2-mg/L crude oil for 21 days (Experiment #1) or to 5- to 250-mg/L crude oil for 9 days (Experiment #2). The crude oil contained 0.22-mg/L nickel (Ni), 1.10-mg/L vanadium (V), and 12.87-mg/L polycyclic aromatic hydrocarbons (PAHs). Twenty-four hours after adding crude oil, the sum of PAHs ranged from 0.30 to 2.28 μg/L in the aquaria containing 0.02- and 250-mg/L crude oil, respectively. Water analyses for heavy metals in Experiment #2 showed high concentrations (mg/L) of Ni (0.07-0-09) and V (0.10-0.21). For both experiments, exposure to crude oil did not impact gonadosomatic index; however, testes showed histopathological defects including hyperplasia or hypertrophy of Sertoli cells, depletion of the Leydig cells, necrosis of germ cells, and fibrosis of lobular wall. In Experiment #1, sperm production and motility, testosterone (T), and 17β-estradiol (E2) were not significantly different among treatments. In Experiment #2, the number of spermiating males decreased by ~50% following exposure to 250-mg/L crude oil. Sperm production, motility kinematics, T, and the T/E2 ratio significantly decreased in males exposed to ≥ 50-mg/L crude oil; however, E2 remained unchanged. Results show crude oil-induced imbalance of sex steroid hormones disrupts spermatogenesis resulting in diminished sperm production and motility.

Dietary Melatonin Boosts Reproduction and Growth Performance of Ornamental Fish Giant Danio (Devario aequipinnatus): A Transformative Approach for Scrapping Wild-Caught Fish Business

The present global trade of endemic ornamental fishes is heavily relied wild-caught species that concerns long-term sustainability. This study examined the effects of dietary melatonin on the reproductive performance and health of Devario aequipinnatus (giant danio). A basal diet of 35% protein (basal diet as control) was supplemented with four different doses of melatonin (2 mg [M1], 10 mg [M2], 50 mg [M3] and 100 mg [M4] per 100 g of feed) given to experimental groups in triplicate. Fish (average weight: 1.13 ± 0.15 g) was stocked in tanks (n = 10) and fed 5% of body weight twice daily. After 60-day feeding, key reproductive metrics such as the gonadosomatic index (GSI), fecundity, egg diameter and histological changes were analysed along with growth and physiological status. The GSI was observed to be better with the increase in dosage and was higher in M3 (3.05 ± 0.03%) (p  < 0.05). Histological examination revealed the presence of advanced oocyte stages IV and V in M3, while higher (>50 mg) melatonin levels suppressed the GSI. Egg diameter increased with the dosage of melatonin up to 50 mg/100 g (1.18 ± 0.6 mm). Testicular development was most advanced in 50 mg (M3) dose of melatonin with significant higher appearance of stage II spermatids or spermatozoa. In addition, M3 exhibited markedly elevated levels of vitellogenin (VG) (3.38 ± 0.22 nmol/L) in female fish and testosterone (16.4 ± 1.11 nmol/L) in male fish compared to the control. Broken-line regression analysis indicates that the optimal dose for improved growth performance was identified at 63 mg/100 g of diet. Melatonin supplementation significantly increased (p  < 0.05) haematological indices such as haematocrit value, leucocyte count, haemoglobin (Hb) and packed cell volume (PCV) compared to the control, except for the 100 mg group (M4). Although stress markers such as glucose and cortisol were similar to the control, there was a plausible rise in the amount of antioxidant enzyme (p  < 0.05) in the melatonin groups. Overall findings of the study demonstrate the potential of melatonin improving the reproductive and physiological status of endemic ornamental fish for accelerating the captive breeding programme for sustainable trade.

Simulated climate change and atrazine contamination can synergistically impair zebrafish testicular function

Elements that interfere with reproductive processes can have profound impacts on population and the equilibrium of ecosystems. Global warming represents the major environmental challenge of the 21st century, as it will affect all forms of life in the coming decades. Another coexisting concern is the persistent pollution by pesticides, particularly the herbicide Atrazine (ATZ), which is responsible for a significant number of contamination incidents in surface waters worldwide. While it is hypothesized that climate changes will significantly enhance the toxic effects of pesticides, the actual impact of these phenomena remain largely unexplored. Here, we conducted a climate-controlled room experiment to assess the interactive effects of the projected 2100 climate scenario and environmentally realistic ATZ exposures on the reproductive function of male zebrafish. The gonadosomatic index significantly decreased in fish kept in the extreme scenario. Cellular alterations across spermatogenesis phases led to synergic decreased sperm production and increased germ cell sloughing and death. ATZ exposure alone or combined with climate change effects, disrupted the transcription levels of key genes involved in steroidogenesis, hormone signaling and spermatogenesis regulation. An additive modulation with decreased 11-KT production and increased E2 levels was also evidenced, intensifying the effects of androgen/estrogen imbalance. Moreover, climate change and ATZ independently induced oxidative stress, upregulation of proapoptotic gene and DNA damage in post-meiotic germ cell, but the negative effects of ATZ were greater at extreme scenario. Ultimately, exposure to simulated climate changes severely impaired fertilization capacity, due to a drastic reduction in sperm motility and/or viability. These findings indicate that the future climate conditions have the potential to considerably enhance the toxicity of ATZ at low concentrations, leading to significant deleterious consequences for fish reproductive function and fertility. These may provide relevant information to supporting healthcare and environmental managers in decision-making related to climate changes and herbicide regulation.

Coupling artificial neural network and sperm swarm optimization for soil temperature prediction at multiple depths

Soil temperature (ST) stands as a pivotal parameter in the realm of water resources and irrigation. It serves as a guide for farmers, enabling them to determine optimal planting and fertilization timings. In the backdrop of regions like Iran, where water resources are scarce, a proficient and economical prediction model for ST, particularly at lower depths, becomes imperative. While recent models have demonstrated adeptness in predicting ST, in general, their error decreases with increasing depth, so that they had the lowest error at a depth of 100 cm. Addressing this gap, our study pioneers a novel hybrid model that excels in accurate daily ST prediction as it delves deeper. The models deployed encompass the multilayer perceptron (MLP) and an enhanced version, MLP coupled with the Sperm Swarm Optimization Algorithm (MLP-SSO). These models prognosticate daily ST across varying depths (5-100 cm), leveraging meteorological parameters such as air temperature, relative humidity, wind speed, sunshine hours, and precipitation. These parameters are anchored to the Ahvaz and Sabzevar synoptic stations in Iran, spanned over the period from 1997 to 2022. Evaluation of our research outcomes unveils that the root mean square error (RMSE) witnesses its most substantial reduction at a depth of 100 cm. For instance, at the Ahvaz station, the MLP-SSO model diminishes the RMSE value from 1.25 to 1.12 °C, in contrast to the MLP model. Similarly, at the Sabzevar station, the RMSE value drops from 1.78 to 1.49 °C using the coupled MLP-SSO model. These results robustly highlight the considerable enhancement brought about by the utilization of the MLP-SSO model, clearly surpassing the performance of the standalone MLP model. This emphasizes the potential and promise of the MLP-SSO model for future investigations, offering insights that can significantly advance the domain of soil temperature prediction and its implications for agricultural decision-making.

Enhancing Cryopreserved Sperm Quality in Chinese Rare Minnow Gobiocypris rarus: The Impact of Antifreeze Proteins

The Chinese rare minnow (Gobiocypris rarus), an important model fish in China, faces endangerment in the wild. Sperm cryopreservation facilitates the development of new strains and germplasm conservation, but the quality of its cryopreserved sperm remains low. This study evaluates the protective effects of different concentrations of antifreeze proteins (AFP I and AFP III) on the cryopreservation of Chinese rare minnow sperm. Cryopreserved sperm showed significant declines in progressive motility, curvilinear velocity (VCL), average path velocity (VAP), and lifespan compared to fresh sperm, except for straight-line velocity (VSL). The cryomedium containing 10 μg/mL AFP I improved these parameters to their highest levels. However, no significant difference was found in progressive motility and kinetic parameters between cryopreserved sperm with and without AFPs. Cryopreserved sperm with 10 μg/mL AFP I showed the highest plasma membrane integrity, mitochondrial activity, and DNA integrity, significantly better than without AFPs; importantly, the fertilization rate of cryopreserved sperm with 10 μg/mL AFP I was not significantly different from that of fresh sperm. These results indicate that the addition of 10 μg/mL AFP I to the cryomedium for Chinese rare minnow sperm does not improve kinetic parameters but significantly enhances sperm quality, aiding in its new strain development and germplasm conservation.

Change in the swimming pattern of Salmo salar spermatozoa caused by the high temperature of the sperm motility activation medium

Fish are ectotherms and many have an external reproductive mode. An environmental factor which triggers fish reproductive activity in fish is water temperature. However, climate change is causing increasingly frequent events in which the water temperature varies rapidly; as a result, both in hatchery and in natural conditions, fish sperm are exposed to varying environmental temperatures during their journey toward the egg. This study was based on two experiments: The first experiment was designed to determine how storage at 4 °C for four days affected the sperm functions of Atlantic salmon (Salmo salar) sperm collected by either abdominal massage (stripping/Pure) or testicular dissection (testicular macerate/Macerated). Further, computer-assisted semen analysis (CASA) was used to compare sperm velocity parameters (VCL, VSL, and VAP) and progressivity (STR, LIN, and WOB) after motility activation at different temperatures (8 and 16 °C) of sperm collected by both methods (Pure vs Macerated). The results show that spermatozoa from Macerated samples maintained a higher sperm function when stored at 4 °C for 4 days compared to Pure sperm samples. In the second experiment, CASA determined that all parameters for sperm velocity (VCL, VSL, and VAP) and progressivity (STR (50%/55%), LIN (25%-32%), and WOB (51%-57%) were affected by activation temperature (P < 0.05) and that the motility patterns after activation at 16 °C (P < 0.05), specifically the LIN or STR swimming trajectories of the sperm differed between the two groups. In conclusion, the sperm quality of testicular Macerate was superior to that of Pure sperm abdominal mass, based on the higher quality of various sperm functions during short-term storage. Moreover, there was a significant effect of the temperature of the activation medium on sperm speed and progressivity (motility pattern) in the collected samples of testicular macerate. The sensitivity of Salmo salar spermatozoa to elevated temperature varies markedly between collection methods (Pure and Macerated).

Transferrin maintains the motility rate, ATP content, and DNA integrity of common carp spermatozoa during short-term storage

Short-term sperm storage is a straightforward and cost-effective method of managing logistics in large scale fish hatchery operations but may result in decline in sperm quality. For effective artificial reproduction of fish, use of an appropriate additive to optimize sperm storage conditions is essential. In this study, it was investigated the effect of purified seminal plasma transferrin (Tf) at 10 μg/ml on relevant parameters in common carp Cyprinus carpio sperm during short-term storage. We compared sperm motility and curvilinear velocity, adenosine triphosphate (ATP) content and DNA fragmentation of fresh spermatozoa to that stored for 24, 48, 72, and 144 h with or without Tf. The percentage of motile cells and the curvilinear velocity of spermatozoa in stored samples for 72 h with transferrin supplementation were greater compared to samples with no added protein. The ATP content in samples without added transferrin was reduced (P < 0.05) after 72 h of storage, in contrast to the levels observed in transferrin-supplemented sperm. A time-dependent increase in DNA fragmentation was observed. Significantly lower DNA damage, expressed as percent tail DNA (10.99 ± 1.28) and olive tail moment (0.54 ± 0.12), was recorded in Tf-supplemented samples stored for 48 h compared to that with no Tf. Hence, it is concluded that the beneficial effects of transferrin on common carp sperm could serve as an additional tool for developing and enhancing short-term sperm preservation procedures commonly used in aquaculture.

Artificial reproduction of wild and pond-cultured common tench (Tinca tinca) under controlled conditions

The common tench is an important thermophilic freshwater fish used for aquaculture diversification. This species is farmed in ponds as well as caught in the wild in many European and China. Artificial reproduction under controlled conditions is one of the most important part of modern aquaculture. In this study, two experiments were conducted in which the influence of hormonal agents (Ovopel and Ovaprim - experiment I) and the origin of the spawning stock (wild and pond-cultured - experiment II) on the success of reproduction in terms of ovulation rate (%), latency time (h), pseudo-gonadosomatic index (PGSI, %), hatching rate (%), abnormal larvae rate (%), and spawning efficiency coefficient (Se) were examined. While the wild fish could not reproduce in the absence of hormonal treatment with 0 % ovulation rate. In all tested hormonal treatment allowed to obtain high-quality eggs with hatching rates of over 83 %. Significant differences in latency time were observed among groups from different origins, such as differences in ovulation rate (79 % vs. 90 %, for pond-cultured and wild fish, respectively), PGSI (8.2 vs. 8.9), and hatching rate (63.8 % vs. 84.3 %), which showed significantly better quality in fish from the wild than those from pond culture. This means that when spawners of common tench of various origins are available, it is better to choose spawners from natural waters for artificial reproduction.

Physiological evaluation of seasonal sperm quality in a biannual spawner, Pacific abalone: Effects on in-vitro fertilization and cryotolerance

Pacific abalone, Haliotis discus hannai, is a highly valuable gastropod mollusk commonly found in Southeast Asia. The present study aims to analyze the seminal plasma quality, sperm quality, and cryotolerance of the Pacific abalone sperm during its reproductive season. The seminal plasma quality was evaluated by analyzing biochemical and metabolite composition, enzymatic activity (superoxide dismutase, catalase, and glutathione), and lipid peroxidation (LPO) activity. The sperm quality was evaluated by analyzing motility, concentration, volume, ATP content, acrosome integrity (AI), plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), DNA integrity, and fertilization potential. The cryotolerance capacity was evaluated by analyzing post-thaw motility, AI, PMI, MMP, and DNA integrity. Seminal plasma osmolarity was significantly higher (1123.3 ± 1.5 mOsmL-1) in May compared to other reproductive periods, with Cl- (516.8 ± 0.5 mM) and Na+ (460.2 ± 0.4 mM) as the dominant ions. The seminal plasma pH remained constant at 6.8 throughout the reproductive season. Improved enzymatic activity and lower LPO were detected in May or June. Sperm quality indicators were similar in May and June, except for sperm production. The fertilization potential (May: 93.0 ± 4.4%, June: 86.0 ± 7.2%) and hatching rate (May: 86.6 ± 5.78%, June: 82.3 ± 3.2%) of Pacific abalone were significantly higher in May or June than they were in other reproductive seasons. The motility (May: 50.19 ± 2.35%, June: 49.96 ± 1.60%), AI (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%), PMI (May: 54.12 ± 3.29%, June: 52.82 ± 2.58%), and MMP (May: 44.02 ± 3.46%, June: 42.16 ± 3.61%) of the cryopreserved sperm were similar in May and June compared with those preserved in other reproductive seasons. The DNA integrity of the cryopreserved sperm was similar in May (80.3 ± 6.7%) or June (78.9 ± 7.4%) and had a higher cryotolerance than in other reproductive seasons. Hence, it can be suggested that May and/or June are suitable periods for sperm physiology experiments, artificial reproduction, and sperm cryopreservation of Pacific abalone.

Oxidative stress and cryoresistance of sturgeon sperm: A review

Currently, the majority of sturgeons are relict fishes of high economic value yet endangered with extinction. Cryopreservation of sperm has great potential in fish farming and conservation, but the problem of low cryoresistance of sturgeon sperm has not yet been solved. The goal of this work was to review current literature data on the causes of low tolerance of sturgeon sperm to cryodamage. The influence of cryopreservation on the parameters of physiology and metabolism of sturgeon sperm (morphology and fine ultrastructure, mobility and fertilization ability, integrity of the plasma membrane, protein, lipid and metabolite profiles, antioxidant status, DNA damage), as well as on biomarkers of oxidative stress (lipids peroxidation levels and carbonyl derivatives of proteins) is discussed. Since the development of oxidative stress is an important mechanism of sperm cryodamage induction, the review presents the literature on the role of oxygen-derived species in damage of sturgeon reproductive cells caused by cryopreservation. Particular attention is paid to the system of antioxidant protection of sturgeon seminal plasma and spermatozoa, represented by antioxidant enzymes and low molecular weight antioxidants capable of utilizing various reactive forms of oxygen and nitrogen. The review discusses the results of lipidomic and proteomic studies of sturgeon sperm, which made it possible to obtain new data on the lipid composition of cell membranes, to detect proteins involved in the protection of sturgeon spermatozoa from oxidative damage during cryopreservation. This review presents the use of «omics» technology to elucidate the mechanism of cryodamage in sturgeon sperm. Additionally, the review summarizes information on the unique anatomical, morphological, biochemical, and physiological features of sturgeon sperm, which may be associated with low cryoresistance of sturgeon, in order to establish prospects for further research on improving the methods of the conservation of sperm of these threatened species.

The investigation of post-thaw chilled storage and the applicability of large-scale cryopreservation in chub (Squalius cephalus) sperm

Chub (reophillic cyprinids) is one of the most sensitive bioindicator fish of environmental changes following anthropogenic activities. The improvement of different biotechnological procedures could help support its conservation and strengthen the natural populations. The aim of this study was to compare the effects of two different hormonal agents (carp pituitary extract and Ovopel™) on various motility parameters (pMOT-%, DAP-μm, VCL μm s-1, VSL-μm s-1, LIN-%, ALH-μm, BCF-Hz) of fresh and cryopreserved/thawed sperm (stored at 4 °C for 6 h). Additionally, we sought to develop a novel, large-scale cryopreservation method for chub sperm, assessing freezing methods (Styrofoam box and a controlled-rate freezer) and different containers (0.5, 5 mL straw and 4 mL cryotube) for sperm cryopreservation. The results of this study indicated no difference between the carp pituitary extract and Ovopel treated groups in either the fresh or frozen/thawed sperm (at 0, 3, 6, hour post thawing, P = 0.4351). In contrast, the quality of the thawed chub sperm was negatively affected after 3 h chilled storage in both hormonal treatments (P = 0.0036, P < 0.0001). When assessing the motility parameters of the sperm between the 5 mL straw and 4 mL cryotube groups cryopreserved in a Styrofoam Box, no difference was observed (P = 0.103). Additionally, sperm loaded in 4 mL cryotubes showed no difference in motility when cryopreserved with either the Styrofoam box or controlled-rate freezer methods (P = 0.109). A similar hatching rate was observed in sperm preserved using the Styrofoam box (35 ± 7 %) and controlled rate freezer (25 ± 9 %) methods (P = 0.300). In a second fertilization trial, hatching rate was similar between control (72 ± 19 %) and cryopreserved (4 mL cryotube and Styrofoam box, 61 ± 5 %) groups. (P = 0.257). Based on our findings and its standard features (less species specific, precise dose calculation), Ovopel can be a good candidate for the stimulation of spermiation in chub sperm prior to cryopreservation. Furthermore, our study presents a novel and applicable method for the large-scale cryopreservation of chub sperm.

Comparative evaluation of the effects of different activating media and temperatures on European eel (Anguilla anguilla) sperm motility assessed by computer assisted sperm analysis

The European eel is a critically endangered teleost fish with very poor success rate for captive breeding and artificial reproduction. Therefore, to support its conservation, new strategies are needed to ensure fertilization. Objective analysis of sperm motility may be critical as it potentially represents one of the most important reproductive quality parameters. Spermatozoa acquire motility once in contact with hyperosmotic solutions as saltwater, yet the exact mechanisms and the role of temperature are still to be clarified. The main aim of the study was to assess the effects of 3 activating media (artificial sea water, tank water and commercial Actifish®) at 4 and 20 °C on sperm motility, by means of computer assisted sperm analysis. Secondary aim was to test 2 different concentrations of Actifish® mimicking sea water pH/osmolality, at 4 °C. The results suggested how both temperature and activating media have effects on spermatozoa motility and kinematics, with temperature mainly acting upon interaction with the media type. The samples activated with tank water at 20 °C showed the poorest motility outcomes (mean 38.1%), while the ones activated with Actifish® diluted 1:4 and artificial sea water, at 4 °C, the highest (means 51.8 and 51.5% respectively). Additionally, diluting Actifish® to reach same pH and osmolality of seawater led to worse motility outcomes, suggesting that composition may be the critical factor for activation rather than osmolality itself.

Sperm of more colourful males are better adapted to ovarian fluids in lake char (Salmonidae)

Fish often spawn eggs with ovarian fluids that have been hypothesized to support the sperm of some males over others (cryptic female choice). Alternatively, sperm reactions to ovarian fluids could reveal male strategies. We used wild-caught lake char (Salvelinus umbla) to experimentally test whether sperm react differently to the presence of ovarian fluid, and whether any differential sperm reaction could be predicted by male breeding coloration, male inbreeding coefficients (based of 4150 SNPs) or the kinship coefficients between males and females. Male coloration was positively linked to body size and current health (based on lymphocytosis and thrombocytosis) but was a poor predictor of inbreeding or kinship coefficients. We found that sperm of more colourful males were faster in diluted ovarian fluids than in water only, while sperm of paler males were faster in water than in ovarian fluids. We then let equal numbers of sperm compete for fertilizations in the presence or absence of ovarian fluids and genetically assigned 1464 embryos (from 70 experimental trials) to their fathers. The presence of ovarian fluids significantly increased the success of the more colourful competitors. Sperm of less inbred competitors were more successful when tested in water only than in diluted ovarian fluids. The kinship coefficients had no significant effects on sperm traits or fertilization success in the presence of ovarian fluids, although parallel stress tests on embryos had revealed that females would profit more from mating with least related males rather than most coloured ones. We conclude that sperm of more colourful males are best adapted to ovarian fluids, and that the observed reaction norms suggest male strategies rather than cryptic female choice.

Seasonal and age-related changes in sperm quality of farmed arctic charr (Salvelinus alpinus)

BACKGROUND

Substantial variation in male fertility is regularly observed in farmed Arctic charr. However, detailed investigations of its fluctuation during a reproductive season and across years are lacking. Furthermore, information about the effect of underlying genetic factors influencing sperm quality is scarce. The current study focused on seasonal and age-related factors that may affect sperm quality characteristics in males reared in natural and delayed photoperiods. Animals were sampled three times for two consecutive years, and sperm quality parameters were recorded using a computer-assisted sperm analysis (CASA) system. Thereafter, high-throughput sequencing technologies were applied, aiming to identify genomic regions related to the variation of sperm quality throughout the reproductive season.

RESULTS

An across-season variation in the recorded sperm quality parameters was evident. Overall, 29% and 42% of males from the natural and delayed spawning groups had a highly variable total progressive motility. Males at four years of age showed significantly higher sperm motility and velocities during the early October and November recordings compared to the following year when the same animals were five years of age. On the other hand, the opposite was observed regarding sperm concentration during the last sampling. A genome-wide FST scan detected SNP differentiation among males with high and low variability in total progressive motility (PM) on eight chromosomes (FST > 0.17), Genome wide windows with the highest FST contained SNPs in proximity (within 250 kb up- and downstream distance) to 16 genes with sperm quality biological functions in mammalian species.

CONCLUSION

Our findings provide a detailed view of seasonal, age-related, and genetic effects on sperm quality and can be used to guide decisions on broodstock selection and hatchery management.

Silver nanoparticles and silver ions indistinguishably decrease sperm motility in Pacific oysters (Magallana gigas) after short-term direct exposure

The present study aimed to evaluate the reprotoxicity of environmental (0.25μg.L^-1) and supra-environmental (25μg.L^-1 and 250μg.L^-1) levels of silver nanoparticles (Ag NP) on the Pacific oyster (Magallana gigas), by determining sperm quality. For that, we evaluated sperm motility, mitochondrial function and oxidative stress. To determine whether the Ag toxicity was related to the NP or its dissociation into Ag ions (Ag⁺), we tested the same concentrations of Ag⁺. We observed no dose-dependent responses for Ag NP and Ag⁺, and both impaired sperm motility indistinctly without affecting mitochondrial function or inducing membrane damage. We hypothesize that the toxicity of Ag NP is mainly due to adhesion to the sperm membrane. Blockade of membrane ion channels may also be a mechanism by which Ag NP and Ag⁺ induce toxicity. The presence of Ag in the marine ecosystem is of environmental concern as it may affect reproduction in oysters.

Reproductive toxicity in marine medaka (Oryzias melastigma) due to embryonic exposure to PCB 28 or 4'-OH-PCB 65

Previous studies have shown that juvenile or adult exposure to polychlorinated biphenyls (PCBs) induces alterations in reproductive functions (e.g., reduced fertilization rate) and behavior (e.g., reduced nest maintenance) in fish. Embryonic exposures to other endocrine disrupting chemicals have been reported to induce long-term reproductive toxicity in fish. However, the effects of embryonic exposure to PCBs or their metabolites, OH-PCBs, on long-term reproductive function in fish are unknown. In the present study, we used the marine medaka fish (Oryzias melastigma) as a model to assess the reproductive endpoints in response to embryonic exposure to either PCB 28 or 4'-OH-PCB 65. Our results showed that the sex ratio of marine medaka was feminized by exposure to 4'-OH-PCB 65. Fecundity was decreased in the medaka treated with either PCB 28 or 4'-OH-PCB 65, whereas the medaka from embryonic exposure to 4'-OH-PCB 65 additionally exhibited reduced fertilization and a reduction in the hatching success rate of offspring, as well as decreased sperm motility. Serum 11-KT concentrations were reduced in the PCB 28-treated medaka, and serum estradiol (E2)/testosterone (T) and E2/11-ketotestosterone (11-KT) ratios were decreased in the 4'-OH-PCB 65-treated medaka. To explain these observations at the molecular level, transcriptomic analysis of the gonads was performed. Bioinformatic analysis using Gene Ontology and Ingenuity Pathway Analysis revealed that genes involved in various pathways potentially involved in reproductive functions (e.g., steroid metabolism and cholesterol homeostasis) were differentially expressed in the testes and ovaries of either PCB- or OH-PCB-treated medaka. Thus, the long-term reproductive toxicity in fish due to embryonic exposure to PCB or OH-PCB should be considered for environmental risk assessment.

Dietary supplementation of multi-strain probiotic in male rainbow trout (Oncorhynchus mykiss) broodstock: Effects on feed efficiency, hemato-biochemical parameters, immune response, and semen quality

The present study aimed to determine the effects of dietary probiotic supplementation on feed efficiency, physiological parameters, and semen quality of male rainbow trout (Oncorhynchus mykiss) broodstock. For this purpose, a total of 48 breeders with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 10⁹ (P1), 2 × 10⁹ (P2), and 4 × 10⁹ (P3) CFU multi-strain probiotic kg^-1 diet for 8 weeks. According to the results, P2 treatment significantly enhanced body weight increase, specific growth rate, and protein efficiency ratio and decreased feed conversion ratio. Moreover, the highest values of red blood cells count, hemoglobin, and hematocrit values were observed in P2 treatment (P < 0.05). The lowest levels of glucose, cholesterol, and triglyceride were found in P1, P2, and P3 treatments, respectively. Also, the highest levels of total protein and albumin were obtained in P2 and P1 treatments (P < 0.05). Based on the results, plasma enzymes contents were significantly decreased in P2 and P3 treatments. In terms of immune parameters, the complement component 3, complement component 4, and immunoglobulin M levels were increased in all probiotic-fed treatments (P < 0.05). For spermatological features, the highest spermatocrit value, sperm concentration, and motility time were observed in the P2 treatment (P < 0.05). Consequently, we conclude that multi-strain probiotics can be used as functional feed additives in male rainbow trout broodstock to enhance semen quality, improve physiological responses, and better feed efficiency.

Effects of dietary supplementation of multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of rainbow trout (Oncorhynchus mykiss) broodstock spermatozoa

The present experiment aims to study the effects of dietary multi-strain probiotics on semen quality, seminal plasma compositions, and fertilization ability of male rainbow trout. For this purpose, a total of 48 broodstocks with an average initial weight of 1366.1 ± 33.8 g were divided into 4 groups and 3 replicates. Fish were fed with diets containing 0 (control), 1 × 10⁹ (P1), 2 × 10⁹ (P2), and 4 × 10⁹ (P3) CFU probiotic kg^-1 diet for 12 weeks. Results showed that dietary supplementation of probiotics significantly increased plasma testosterone level, motility time of spermatozoa, sperm density, and spermatocrit value in P2 and P3 treatments and Na⁺ level in P2 treatment compared to the control group (P < 0.05). The activities of aspartate aminotransferase and lactate dehydrogenase had significantly decreased in the P2 treatment compared to the control group (P < 0.05). No considerable variations were observed between control fish and treatment groups (P > 0.05) in semen biochemical parameters, percentage of motile spermatozoa, osmolality, and pH of seminal plasma. Based on the results, the highest fertilization rate (97.2 ± 0.9%) and eyed egg survival (95.7 ± 1.6%) were observed in the P2 treatment, and those values showed remarkable differences with the control group (P < 0.05). The results indicated that multi-strain probiotics have potential efficacy on semen quality and fertilization ability of rainbow trout broodstock spermatozoa.

Use of cryoprotectors and antioxidants in sturgeon semen cryopreservation

In recent years, the possibility of increasing the low cryoresistance of sturgeon sperm by using antioxidants in basic cryoprotective media has been studied. The goal of this work was to review the current literature on impact of the cryoprotectors, well-known antioxidants and new multifunctional compounds on the activity indicators and fertilizing capability of sperm, as well as on biomarkers of cryostress. A special attention is given to the radical scavenging activity of studied compounds in relation to the highly reactive oxygen species, to prevent and negate oxidative stress damage of sturgeon sperm. Also, new trends for future research through the application of novel polyfunctional antioxidants to sturgeon sperm cryopreservation were indicated.

Effect of Different Activation Solutions and Protein Concentrations on Ide (Leuciscus idus) Sperm Motility Analysis with a CASA System

The purpose of this study was to compare four activation solutions (AS)-Woynarovich, Lahnsteiner, Kucharczyk, and Perchec-with the addition of 0.5% bovine serum albumin (BSA) for ide (Leuciscus idus) sperm activation and analysis with a CASA system. It was found that ide sperm can be activated using each AS within a pH range of 7.4-9.0 and an osmolality range of 160-200 mOsm kg^-1. The effect of Woynarovich and Perchec solutions supplemented with BSA and casein at concentrations of 0.25, 0.5, 1.0, and 2.0% were also analyzed during the experiment. These two AS without protein supplementation (pure solutions) were the controls. Woynarovich and Perchec solutions supplemented with the minimum BSA concentration (i.e., 0.25%) significantly improved sperm motility (89.05% and 86.63%, respectively) compared to the controls (20.39 and 28.48%, respectively). Similar increases were also noted in progressively motile sperm (PRG, %), the curvilinear velocity of sperm (VCL, µm s^-1), and the amplitude of lateral head displacement (ALH, µm). A similar trend in CASA parameters was also noted when casein was added to Woynarovich and Perchec solutions at a concentration of 0.25%. We concluded that 0.25% doses of each of the proteins were sufficient to prevent sperm adhesion to glass slides, and they can be used in research on ide sperm motility measurements.

Dimethyl acetamide and dimethyl sulfoxide associated at glucose and egg yolk for cryopreservation of Pseudoplatystoma corruscans semen

Abstract This study aimed to develop a protocol for the cryopreservation of Pseudoplatystoma corruscans semen. For this, mature males were hormonally induced with a single dose of carp pituitary extract (5 mg/kg body weight). Semen was collected and evaluated. Two cryoprotectants were tested to compose the diluents: dimethyl acetamide (DMA) and dimethyl sulfoxide (Me2SO), in two concentrations (8% and 10%), + 5.0% glucose + 10% egg yolk. The semen was diluted in a 1: 4 ratio (semen: extender), packed in 0.5 mL straws and frozen in a dry shipper container in liquid nitrogen vapors. After thawing, sperm kinetics, sperm morphology and DNA integrity of cryopreserved sperm were evaluated. Pseudoplatystoma corruscans males produced semen with sperm motility > 80%. After thawing, all treatments provided semen with total sperm motility > 40%, with no significant difference (P < 0.05) between them, as well as between the other sperm kinetic parameters evaluated. The treatments with DMA provided a smaller fragmentation of the DNA of the gametes. Sperm malformations were identified in both fresh and cryopreserved semen, with a slight increase in these malformations being identified in sperm from thawed P. corruscans semen samples.

In vivo and in vitro aging of common carp Cyprinus carpio sperm after multiple hormonal application and stripping of males

The present study was designed to evaluate sperm phenotypic variables during in vivo and in vitro storage following multiple sperm stripping in common carp (Cyprinus carpio L.). Each male was injected 3 times with carp pituitary 3 days apart. Sperm was stored in vivo in the body cavity for 0.5 days (Fresh sperm) and 3 days (Old sperm) after hormonal stimulation. Then sperm was collected and diluted with a carp extender at a ratio of 1:1, and stored in vitro on ice for 0, 3, and 6 days. The phenotypic parameters, including the number of total motile spermatozoa, number of fast motile spermatozoa, number of motile spermatozoa, percentage of fast motile spermatozoa, and percentage of spermatozoa motility were the major components of principal component analysis (PCA). In general, Fresh sperm from the first stripping showed slightly better quality than Old sperm from the second and third stripping, especially in the phenotypic parameters of a number of total spermatozoa and a number of total motile spermatozoa (P < 0.05). The highest kinetic and quantitative spermatozoa variables were obtained in Fresh and Old sperm just after sperm collection (0-day storage in vitro), and then they were decreased during the period of in vitro storage up to 6 days (P < 0.05). However, the fertilization, hatching, and malformation rates from Fresh sperm were similar compared with the Old sperm. Sperm could be stripped 0.5 days post hormonal treatment and stored in vitro up to 6 days with good fertilization performance (fertility, hatching, and malformation rates were 92.5%, 91.5%, and 1.3%, respectively). Therefore, our results suggested that multiple hormonal treatments with multiple stripping could be used in artificial reproduction in common carp.

Sperm quality of artificially matured shortfinned eel is not affected by human chorionic gonadotropin dose and route of administration

Background

Acquisition of high quality sperm is key to the artificial propagation of eels in captivity, but fertility drugs are expensive and repeated handling is stressful to the fish. An interrupted treatment regime (an initial hormone injection to stimulate spermatogenesis, followed several weeks later by weekly booster injections to induce sperm maturation) for acquisition of sperm in captive male eels has promise for high sperm quality on the one hand, and animal welfare benefits on the other. To further develop this approach for shortfinned eel, Anguilla australis, we evaluated the efficacy of (i) different initial doses of human chorionic gonadotropin (hCG) and (ii) route of administration.

Methods

Male eels were artificially induced to mature with a single injection of 0, 250, 500 or 1,000 IU/fish of hCG, administered either intramuscularly (IM) or intraperitoneally (IP). Sperm maturation was induced with 150 IU hCG/fish from week 5 onwards and sperm collected for evaluation of quality by computer-assisted sperm analysis.

Results

Control males did not mature and hence, sperm could not be retrieved and analysed, but all other treatments were effective in inducing testicular maturation. Milt volume tended to be higher for fish injected IM compared to those injected IP, whereas hCG dose had no effect. Conversely, the concentration of spermatozoa tended to be higher for several sperm collection time points in IP-injected than in IM-injected fish. Sperm quality, represented by percent motility, percent progressive motility and curvilinear velocity, was equal in fish given an initial dose of 250 IU hCG to those given higher initial doses of hCG.

Conclusions

We recommend that an initial dose of 250 IU hCG/fish be administered to induce spermatogenesis in male A. australis, and, after a period of 4-5 weeks, weekly booster injections of ∼150 IU hCG/fish be administered in the day prior to sperm collection; both routes of administration (IM or IP) are equally effective. We contend that an interrupted treatment regime has notable benefits for induced maturation in male anguillids, as it reduces fish handling and manipulation and reduces the resources required to produce high quality sperm.

Evaluation of Russian sturgeon (Acipenser gueldenstaedtii) Semen Quality and Semen Cryopreservation

The alarming decline in sturgeon populations doubled by growing demands for sturgeon products, urge us to prevent the loss of these species. Fish stocking in natural habitats and developing fish farms are viable solutions, which can be successfully implemented with the help of reproductive biotechnologies. Despite the fact that semen cryopreservation is admittedly an important step for saving the Russian sturgeon, a reproducible standard method with good results has yet to be identified. Sperm quality assessment is essential for quantifying the impact of cryopreservation on spermatozoa. The purpose of our study was to provide additional information regarding semen cryopreservation and semen quality evaluation for the Russian sturgeon. Our study method is based on the use of two yolk-free extenders (with different cryoprotectants: DMSO and methanol) for freezing semen, using a simple freezing protocol. Parameters such as volume, concentration, motility, morphology and membrane integrity were evaluated. In conclusion, cryopreservation of Russian sturgeon spermatozoa using an extender containing methanol as cryoprotectant led to high egg fertilization percentages (72.67 ± 5.4%) even if the total motility values recorded for thawed semen were quite low (18–25%). Additionally, we identified two optimal stains for morphological studies and morphometry (Spermac stain kit and Trypan Blue Solution).

Boat noise impacts Lusitanian toadfish breeding males and reproductive outcome

Anthropogenic noise is a growing threat to marine organisms, including fish. Yet very few studies have addressed the impact of anthropogenic noise on fish reproduction, especially in situ. In this study, we investigated the impacts of boat noise exposure in the reproductive success of wild Lusitanian toadfish (Halobatrachus didactylus), a species that relies on advertisement calls for mate attraction, using behavioural, physiological and reproductive endpoints. Two sets of artificial nests were deployed in the Tagus estuary and exposed to either ambient sound or boat noise during their breeding season. Toadfish males spontaneously used these nests to breed. We inspected nests for occupation and the presence of eggs in six spring low tides (in two years) and assessed male vocal activity and stress responses. Boat noise did not affect nest occupation by males but impacted reproductive success by decreasing the likelihood of receiving eggs, decreasing the number of live eggs and increasing the number of dead eggs, compared to control males. Treatment males also showed depressed vocal activity and slightly higher cortisol levels. The assessment of oxidative stress and energy metabolism-related biomarkers revealed no oxidative damage in noise exposed males despite having lower antioxidant responses and pointed towards a decrease in the activity levels of energy metabolism-related biomarkers. These results suggest that males exposed to boat noise depressed their metabolism and their activity (such as parental care and mate attraction) to cope with an acoustic stressor, consistent with a freezing defensive response/behaviour. Together, our study demonstrates that boat noise has severe impacts on reproductive fitness in Lusitanian toadfish. We argue that, at least fishes that cannot easily avoid noise sources due to their dependence on specific spawning sites, may incur in significant direct fitness costs due to chronic noise exposure.

A chronic exposure to bisphenol A reduces sperm quality in goldfish associated with increases in kiss2, gpr54, and gnrh3 mRNA and circulatory LH levels at environmentally relevant concentrations

The bisphenol A (BPA)-disrupted reproductive functions have been demonstrated in male animals. In fish, it has been shown that environmentally relevant concentrations of BPA decrease sperm quality associated with inhibition of androgen biosynthesis. However, BPA effects on neuroendocrine regulation of reproduction to affect testicular functions are largely unknown. In the present study, reproductive functions of hypothalamus and pituitary were studied in mature male goldfish exposed to nominal 0.2, 2.0 and 20.0 μg/L BPA. At 90 d of exposure, sperm volume, velocity, and density and motility were decreased in goldfish exposed to 0.2, 2.0, and 20.0 μg/L BPA, respectively (p < 0.05). At 30 d of exposure, there were no significant changes in circulatory LH levels and mRNA transcripts of kiss1, Kiss2, gpr54, and gnrh3. At 90 d of exposure, circulatory LH levels showed trends toward increases in BPA exposed goldfish, which was significant in those exposed to 2.0 μg/L (P < 0.05). At this time, Kiss2, gpr54, and gnrh3 mRNA levels were increased in goldfish exposed to any concentrations of BPA (p < 0.05). This study shows that BPA-diminished sperm quality was accompanied by an increase in circulatory LH levels associated with increases in mRNA transcripts of upstream neuroendocrine regulators of reproduction in goldfish. Further, this is the first study to report circulatory levels of LH in fish exposed to BPA.

Transgenerational effects and phenotypic plasticity in sperm and larvae of the sea urchin Paracentrotus lividus under ocean acidification

In marine organisms, differing degree of sensitivity to ocean acidification (OA) is expected for each life stage, and disturbance at one stage can carry over into the following stage or following generation. In this study we investigated phenotypic changes of sperm and larvae of the sea urchin Paracentrotus lividus in response to different pH conditions (8.0, 7.7, 7.4) experienced by the parents during gametogenesis. In sperm from two-months exposed males, sperm motility, velocity, ATP content, ATP consumption and respiration rate were evaluated at three pH values of the activating medium (8.0, 7.7 and 7.4). Moreover, larvae from each parental group were reared at pH 8.0 and 7.7 for 20 days and larval mortality and growth were then assessed. Sperm motility and respiration rate were not affected either by exposure of males to low pH or by the post-activation pH. Sperm velocity did not differ among post-activation pH values in all sperm groups, but it decreased slower in sperm developed under acidified conditions, suggesting the presence of positive carryover effect on sperm longevity. This positive carryover effect of exposure of males to low pH values was highlighted also for the sperm ATP content, which was higher in these groups of sperm. ATP consumption rate was affected by post-activation pH with higher values at pH 8.0 in sperm from males maintained at control condition and pH 7.7 while the energy consumption appeared to be differently modulated at different experimental conditions. A negative carry over effect of OA was observed on survival of larvae from parents acclimated at pH 7.4 and additive negative effects of both parental and larval exposure to low pH can be suggested. In all groups of larvae, decreased somatic growth was observed at low rearing pH, thus larvae from parents maintained at low pH did not show an increased capability to cope with OA.

Effect of Application of Different Activation Media on Fertilization and Embryo Survival of Northern Pike, (Esox lucius) under Hatchery Conditions

One of the finfish species that European and North American breeders are most interested in is the northern pike, Esox lucius. Artificial reproduction and the production of viable larvae has a huge impact on further culture. The quality of stripped gametes is highly variable. Therefore, it is important to use gametes with maximum efficiency, which has a direct impact on the amount of stocking material produced and therefore on the economics of production. The aim of this study was to compare northern pike fertilization efficiency, expressed as the survival rate of embryos until hatching. In the first experiment, the highest percentage of hatched embryos was observed in groups of eggs fertilized in a saline diluent prepared with deionized water (after reverse osmosis: group D), at 61.2% and 56.5% in the NaCl5-D and NaCl6-D groups, respectively. The highest percentage of hatched embryos in the second experiment was observed in the egg groups activated with Woynarovich solution (V) at 75.5% and 74.7% for V-D (D—deionized water) and V-T (T—tap water), respectively. In all cases, preparing the activation medium using T versus D water resulted in lower fertilization percentages and lower percentages of hatched larvae. At the same time, two variants (V and B1—Billard solution) were tested during mass spawning in three hatcheries using hatchery water (tap water). The results showed that repeatability was the highest when using activation medium B1.

Ex vivo exposure to titanium dioxide and silver nanoparticles mildly affect sperm of gilthead seabream (Sparus aurata) - A multiparameter spermiotoxicity approach

Nanoparticles (NP) are potentially reprotoxic, which may compromise the success of populations. However, the reprotoxicity of NP is still scarcely addressed in marine fish. Therefore, we evaluated the impacts of environmentally relevant and supra environmental concentrations of titanium dioxide (TiO₂: 10 to 10,000 μg·L^-1) and silver NP (Ag: 0.25 to 250 μg·L^-1) on the sperm of gilthead seabream (Sparus aurata). We performed short-term direct exposures (ex vivo) and evaluated sperm motility, head morphometry, mitochondrial function, antioxidant responses and DNA integrity. No alteration in sperm motility (except for supra environmental Ag NP concentration), head morphometry, mitochondrial function, and DNA integrity occurred. However, depletion of all antioxidants occurred after exposure to TiO₂ NP, whereas SOD decreased after exposure to Ag NP (lowest and intermediate concentration). Considering our results, the decrease in antioxidants did not indicate vulnerability towards oxidative stress. TiO₂ NP and Ag NP induced low spermiotoxicity, without proven relevant ecological impacts.

Ginseng® as a reproductive enhancer agent for African catfish, Clarias gariepinus (Burchell, 1822)

Ginseng (Ge) is one of the most famous and precious consumed herbal medicines around the world. Ge plant roots have many advantages regarded as important in increasing fish production. Thus, the present study was conducted to investigate the possibility of using different levels (0.0, 100, and 200 mg/kg diet) of Ge as a reproductive enhancer agent for African catfish, Clarias gariepinus males. Results revealed that fish fed 200 mg Ge/kg diet significantly (P ˂ 0.05) increased growth performance, feed efficiency, gonado-somatic index, hematological parameters, serum follicle-stimulating hormone, total antioxidant capacity, sperm quality parameters, and ultrastructure of spermatozoa, as well as led to positively improved of the histological structure of the testes tissue compared to other treatments. Based on the obtained findings, it could be concluded that the effective use of dietary Ge at a level of 200 mg/kg as a promising reproductive agent for adult African catfish males consequently led to the sustainability of aquaculture for African catfish.

Reproductive toxicity due to herbicide exposure in freshwater organisms

Excessively used pesticides in agricultural areas are spilled into aquatic environments, wherein they are suspended or sedimented. Owing to climate change, herbicides are the fastest growing sector of the pesticide industry and are detected in surface water, groundwater, and sediments near agricultural areas. In freshwater, organisms, including mussels, snails, frogs, and fish, are exposed to various types and concentrations of herbicides. Invertebrates are sensitive to herbicide exposure because their defense systems are incomplete. At the top of the food chain in freshwater ecosystems, fish show high bioaccumulation of herbicides. Herbicide exposure causes reproductive toxicity and population declines in freshwater organisms and further contamination of fish used for consumption poses a risk to human health. In addition, it is important to understand how environmental factors are physiologically processed and assess their impacts on reproductive parameters, such as gonadosomatic index and steroid hormone levels. Zebrafish is a good model for examining the effects of herbicides such as atrazine and glyphosate on embryonic development in freshwater fish. This review describes the occurrence and role of herbicides in freshwater environments and their potential implications for the reproduction and embryonic development of freshwater organisms.

Successive seminal collections from Leiarius marmoratus during the reproductive period

This study aim was to verify whether milt quality of male Leiarius marmoratus is maintained among successive samples collected during the same reproductive period. Ten reproductively mature males were used to evaluate four successive sperm samples collected at 10-day intervals. For these collections, seven males were injected with carp pituitary homogenate (CPH) at a dosage of 3.0 mg/kg body weight, in two applications (30% and 70%), at an interval of 10 h. The other three males were administered only saline (control). Injection with CPH or saline occurred prior to each of the four collections. Only one male from the control group released a small volume of milt (0.33 mL), and only during the first collection period. Of the seven males treated with CPH, five released milt during all four collections. Milt volume of the first sample collected (0.63 mL) did not differ from that of other samples (0.59-1.38 mL; P > 0.05). Sperm concentration was greater in the first samples collected (1.98 × 10⁹ spermatozoa/mL) compared to the other samples (0.35 × 10⁹ at 0.92 × 10⁹ spermatozoa/mL; P < 0.05). Sperm motility, curvilinear velocity, straightness, and morphological normality did not differ among the consecutive samples (P > 0.05). Average path velocity, straight-line velocity, oscillation, linearity, progression, and membrane integrity decreased slightly in the samples collected subsequent to the first sample (P > 0.05). In conclusion, milt quality decreased among successive collections; however, quality of all samples from all collections was sufficient for use for fertilization of oocytes.

A Review on Environmental Contaminants-Related Fertility Threat in Male Fishes: Effects and Possible Mechanisms of Action Learned from Wildlife and Laboratory Studies

Increasing global rates of diminished fertility in males has been suggested to be associated with exposure to environmental contaminants (ECs). The aquatic environments are the final repository of ECs. As the reproductive system is conserved in vertebrates, studies on the effects of ECs on fertility endpoints in fishes provide us with valuable information to establish biomarkers in risk assessment of ECs, and to understand the ECs-related fertility threat. The aim of the present review was to evaluate associations between ECs and fertility determinants to better understand ECs-related male fertility threat in male fishes. Wildlife studies show that the reproductive system has been affected in fishes sampled from the polluted aquatic environment. The laboratory studies show the potency of ECs including natural and synthetic hormones, alkylphenols, bisphenols, plasticizers, pesticides, pharmaceutical, alkylating, and organotin agents to affect fertility determinants, resulting in diminished fertility at environmentally relevant concentrations. Both wildlife and laboratory studies reveal that ECs adverse effects on male fertility are associated with a decrease in sperm production, damage to sperm morphology, alternations in sperm genome, and decrease in sperm motility kinetics. The efficiency of ECs to affect sperm quality and male fertility highly depends on the concentration of the contaminants and the duration of exposure. Our review highlights that the number of contaminants examined over fertility tests are much lower than the number of contaminants detected in our environment. The ECs effects on fertility are largely unknown when fishes are exposed to the contaminants at early developmental stages. The review suggests the urgent need to examine ECs effects on male fertility when a fish is exposed at different developmental stages in a single or combination protocol. The ECs effects on the sperm genome are largely unknown to understand ECs-related inheritance of reproductive disorders transmitted to the progeny. To elucidate modes of action of ECs on sperm motility, it is needed to study functional morphology of the motility apparatus and to investigate ECs-disrupted motility signaling.

Sperm characterization and cryopreservation of the endangered freshwater fish Chirostoma estor (Atheriniformes)

The knowledge of the physiology of sperm of an endangered species allows the implantation of reproductive biotechnologies that aim at conservation. The aim of this study was to characterize fresh sperm and evaluate different cryopreservation solutions for sperm in Chirostoma estor. The characterization of Chirostoma estor fresh sperm (n = 22 males) was performed through analyzes of sperm concentration, membrane integrity, sperm morphology, motility rate, motility quality score, and motility duration. For cryopreservation (n = 42 males), 3 extenders (BTS™, MIII™, or Androstar Plus™) in combination with 2 permeable cryoprotectants (dimethyl sulfoxide (DMSO) or methyl glycol (Methyl)) were used. Analyzes of post-thaw sperm were performed as described for fresh sperm and additionally the fertilization rate analysis was performed. Fresh sperm presented a sperm concentration of 29.2 × 10⁹ spermatozoa/mL, membrane integrity of 82.4%, and morphologically normal cells of 53%. After glucose activation (150 mM) a motility rate of 87.5%, sperm quality score of 5.0, and a duration of motility of 285 s were observed. For post-thaw sperm, MIII + Methyl and Androstar + Methyl solutions resulted in the highest motility rates of 40-48%. No differences were observed for motility duration, membrane integrity, and sperm morphology. Samples cryopreserved in Methyl (12-20%) showed a higher fertilization rate than DMSO, independently of the extender. In conclusion, the fresh sperm collected artificially from Chirostoma estor presents a compatible quality to carry out fertilization and can be cryopreserved in the commercial extenders MIII™ and Androstar Plus™ together with the cryoprotectant Methyl glycol.

Sperm motility analysis of Cobitis hankugensis, Iksookimia longicorpa (Teleostei, Cypriniformes, Cobitidae) and their unisexual natural hybrids

Hybrid sterility is an inevitable phenomenon in the speciation process to avoid indiscriminate increases in species, but it is not always unconditional. We used computer assisted sperm analysis (CASA) to analyze sperm motility of Cobitis hankugensis, Iksookimia longicorpa, and their unisexual natural hybrids. In parental species, the sperm concentrations of C. hankugensis and I. longicorpa were 11.6 ± 4.8 × 10⁹ and 16.5 ± 6.8 × 10⁹ , respectively. For sperm motility, the total motility was higher in the parental species (C. hankugensis, 91.3%; I. longicorpa, 87.5%) than other hybrids. After 1 min, the motility duration was reduced to 14% in C. hankugensis and 3.3% in I. longicorpa. This result could indicate that the duration of sperm motility of C. hankugensis is longer than that of I. longicorpa up to 1 min after spermatozoa activation. All of the hybrids had a low concentration and it was distinct from their parent species. Total motility and other velocity parameters also showed significantly lower values except for the HHL (one from the C. hankugensis genome with two from the I. longicorpa genome) type motility measurement (13.6%). These results suggest that the hybrids derived from C. hankugensis and I. longicorpa, are not completely infertile, contrary to histological observations.

Is it possible to store spotted wolffish (Anarhichas minor) sperm by refrigeration?

Spotted wolffish Anarhichas minor reproduction in captivity is dependent on in vitro fertilization. However, it is often challenging to acquire sufficient fresh sperm to fertilize the eggs that are obtained. In this study, we evaluate the possibility to store spotted wolffish sperm by refrigeration. Spotted wolffish sperm has the particularity that is already motile on stripping, and currently it is not possible to immobilize and reactivate. Thus, sperm refrigeration protocols should focus in extending this motility period that usually lasts up to 2 days. In a first experiment, we evaluated the possibility that the motility period of the sperm was limited by contamination with urine. The urea concentration in the sperm obtained both by stripping (17.10 ± 1.98 mg/dL) and directly from the testis (12.59 ± 2.37 mg/dL) was similar (p > 0.05), which indicate that the sperm collection method used avoid contamination with urine. Afterwards, we tested the possibility that the sperm motility period was limited by energy stores. The ATP concentration (initial value 5.65 ± 0.86 nmol/109 cells) remained stable (p = 0.099) during 30 h after sperm collection, and similar values (p = 0.329) were recorded at end of sperm storage in both diluted (3.88 ± 1.35 nmol/109 cells) and undiluted samples (4.76 ± 1.08 nmol/109). This indicates that the low intracellular ATP consumption, derived from the slow sperm motility, can probably be compensated rapidly enough by mitochondrial synthesis of ATP in the spotted wolffish sperm. In both experiments, diluted sperm kept higher percentage of motile cells during the storage time.

Aluminum at environmental concentrations affects the sperm quality of the freshwater teleost Astyanax altiparanae: An in vitro study

Aluminum (Al) is present in rivers and reservoirs in concentrations above that is allowed by regulatory agencies (e.g. 0.5 mg L^-1 Al), which can impair fish reproduction. The present study evaluated the in vitro effects on the sperm of Astyanax altiparanae upon Al exposure at different concentrations (0, 0.05, 0.1, 0.3, and 0.5 mg L^-1) with various exposure periods (50 s, 10 min, and 30 min). The following biomarkers were evaluated: membrane vitality, DNA fragmentation, morphology, kinetics (10 s and 30 s after sperm activation), and sperm mitochondrial activity. Al damages the membrane vitality of gametes at 0.3 and 0.5 mg L^-1 after 50 s of exposure. After 30 min of exposure, there was a decrease in membrane vitality at 0.1 and 0.5 mg L^-1, and the membrane vitality decreased with increased exposure time. Within 30 s after sperm activation, Al (0.3 and 0.5 mg L^-1) reduced sperm motility by more than 50% at the longest exposure time, while at 0.1 and 0.5 mg L^-1, Al exposure reduced motility over time. The average path speed (VAP; 10 s post-sperm activation) was reduced at longer exposure times at 0.05 and 0.5 mg L^-1 of Al. Increased exposure time had deleterious effects on mitochondrial activity at the highest concentrations tested. Al did not damage DNA and sperm morphology. In conclusion, Al negatively influences the sperm quality of A. altiparanae with a potential effect of exposure time and increasing concentrations.

Sperm quality of greater amberjack Seriola dumerili throughout the reproductive season and in response to GnRHa treatment with controlled release implants

A wild-caught stock of greater amberjack Seriola dumerili reared in sea cages in two commercial aquaculture facilities in Greece was administered gonadotropin-releasing hormone agonist (GnRHa), loaded in controlled release implants, and was used in spawning induction experiments throughout the reproductive season. Sperm quality was evaluated using computer-assisted sperm analysis (CASA) before and after GnRHa administration and the extent of the spermiation period was determined. Males were in spermiation throughout the monitoring period from May 30 until July 18, at temperatures between 19 and 24 °C. However, lower sperm motility duration, density, and survival under cold storage were observed from early July onwards. Sperm quality did not recover after the end of spawning induction experiments in tanks and the return of the fish for 14-28 days to the sea cage in mid-July, which could be related to the high temperatures of this period. An improvement trend was observed in the quality of the milt collected on day 7 after a single GnRHa administration, but a significant decrease was observed on day 21 in sperm density, survival under cold storage, and straight line velocity (VSL). On the contrary, a double GnRHa administration spaced 14 days apart maintained the same sperm quality for a longer period of 29 days. Further spermiation enhancement experiments should be conducted in the future to describe in more detail the kinetics of sperm production after GnRHa therapy and its effects on sperm quality.

Paternal exposure to aluminum, acidity, and temperature affect fatty acid seminal profile, embryonic and larval development of Astyanax altiparanae

We investigated the effects of water acidity, temperature, and aluminum (Al) on the fatty acid (FA) seminal profile, reproductive parameters (fertilization and hatching) and embryonic development of Astyanax altiparanae. We treated males with different experimental treatments, corresponding to the combination of water temperature (20 °C; 25 °C), pH (neutral - 7.0; acidic - 5.5), and the absence or presence of Al (0.5 mg L^-1). After 96 h, we analyzed the FA profile of semen and performed artificial fertilization in activating medium with neutral pH or activating medium in the same experimental conditions of the males (neutral pH, acidic pH, and Al) to evaluate fertilization and hatching rates and to monitor embryonic development. Polyunsaturated FA percentage decreased in semen of fish from the neutral group, while monounsaturated FA increased in all groups maintained at 20 °C compared to 25 °C. Aluminum exposure decreased the percentage of C20:4n6 and increased the percentage of C22:5n3 at 20 °C. Males exposed to acidic pH and Al showed lower fertilization and hatching rates, as well as increased mortality of embryos and larvae. Moreover, Al favoured a higher percentage of abnormal larvae. Fertilization in Al activating medium harmed the embryos and larvae since fertilization and hatching rates decreased. Finally, temperature influenced fertilization time, hatching rate, and the morphology of embryos and larvae. Males exposed to Al had lower fertilizing capacity, which negatively affected the embryonic development of the species. Furthermore, Al activating medium reduced the number of fertilized oocytes, hatched embryos, and normal larvae. All events were temperature dependent.

Comparison of responses to artificial spawning of ruffe (Gymnocephalus cernua) specimens captured from their natural habitat to those produced in cultured conditions

Although ruffe (Gymnocephalus cernua) are widely distributed in Eurasia, in some regions (i.e., North America) ruffe are considered an invasive species. There have been no reports on artificial reproduction of this species. A study, therefore, was conducted to evaluate reproduction of ruffe with results of specimens captured from their natural habitat and cultured (F₁ generation) specimens being compared. Spawning specimens from both stocks were treated with hormonal preparations: carp pituitary homogenate (CPH), Ovopel, Ovaprim and human chorionic gonadotropin (hCG) and results were analyzed by comparing response to the specimens of control groups. Spermiation outcomes and sperm motility of the captured and cultured ruffe were similar and with all hormonal treatments, there was a slightly greater sperm motility (55.6 %-57.1 %) in comparison to specimens of control groups (46.7 %-47.1 %). For captured specimens, there was no asynchronous development of oocytes, whereas in cultured specimens 32 % of females had asynchronous development of oocytes. The ovulation rate in specimens of all treated groups was 100 %, whereas specimens in the control groups did not reproductively mature and have ovulations. The latency time from time of hormonal treatments to initiation of reproductive functions depended on the spawning agent used and oocyte maturation stage and there was the shortest latency after using CPH and the longest with hCG treatment. The embryo survival and hatching rates varied with use of different hormonal preparations to induce reproduction: greatest hatching rates with hCG treatment (86.4 %-88.9 %), followed by Ovaprim (78.2 %-80.2 %) and least hatching rate with Ovopel and CPH treatments (66.0 %-67.1 % and 64.0 %-66.0 %, respectively).

Endocrine regulation of long-term enhancement of spermiation in meagre (Argyrosomus regius) with GnRHa controlled-delivery systems

Meagre (Argyrosomus regius) undergo spermatogenesis and spermiation when reared in captivity, but often produce low milt volumes, sometimes with reduced quality and for a limited time period. In the present study we a) compared the efficiency of gonadotropin releasing hormone agonist (GnRHa) implants versus injections on testicular stimulation and spermiation enhancement, b) investigated the effect of GnRHa on the endocrine spermiation regulation (sex steroid hormones), and c) evaluated a commercial induced spawning simulation scenario. Firstly, males (n = 5) were injected with 15.0 ± 0.2 μg GnRHa kg^-1 (Injections) or implanted with 51.0 ± 5.1 μg GnRHa kg^-1 (Implant) and compared their sperm production response. Secondly, the best hormonal treatment (Implant) was tested treating males (n = 8) with 57.5 ± 7.5 μg GnRHa kg^-1 every 3 weeks for a period of 70 days. Milt production was improved by the GnRHa implants with only minor sperm quality alterations (improved sperm motility percentage). Elevated plasma testosterone (T) and 11-ketotestosterone (11-KT) levels were recorded in response to GnRHa implants, while no significant difference for 17,20β-dihydroxy-4-pregnen-3-one (17,20β-P) was observed. In the commercial induced spawning simulation, it was shown that meagre females are capable of on-demand induction of spawning at random intervals (5-21 days) using GnRHa injections, over a period of at least 2.5 months. During this period, spermiation enhancement was achieved with GnRHa implants every 3 weeks, producing sperm with stable, in general, quality and motility parameters. Percentage of motile cells, motility duration and density fluctuated significantly, but remained within levels that are considered appropriate for high fertilization success in this species.

Inhibiting the influence of ovarian fluid on spermatozoa activation and spermatozoa kinetic characteristics in the common barbel Barbus barbus

As a result of evolution, various finfish species have developed different breeding strategies. However, there are some similarities, and one of them is the positive effect of ovarian fluid on spermatozoa. The opposite of this phenomenon was found in the common barbel (Barbus barbus). The present study analyzed the effect of ovarian fluid (OF), distilled water (DW) and Woynarovich solution (WS) on the motility, longevity and kinetics of barbel spermatozoa. These spermatozoa parameters were also evaluated with various dilutions of ovarian fluid (OF) in relation to distilled water [0:4 (Group OF 0%), 1:3 (Group OF 25%), 1:1 (Group OF 50%), 3:1 (Group OF 75%), 4:0 (Group OF 100%)] and spermatozoa reactivation after a 30 s (Group OFR_30s 100%) treatment in ovarian fluid. The motility analysis was carried out using computer-assisted semen analysis (CASA). The negative interaction of ovarian fluid with spermatozoa motility in the same fish species was recorded for the first time. In pure ovarian fluid, the average spermatozoa motility (MOT) decreased significantly (1.40 ± 0.94%). The negative effect of ovarian fluid-to-spermatozoa motility was reversible, and after a 30 s treatment in ovarian fluid and later dilution with water, spermatozoa motility was reactivated (from 2.25 ± 0.53% vs 69.78 ± 6.02%). The use of Woynarovich solution as an activator of spermatozoa movement had a positive effect (P < 0.05) on spermatozoa movement longevity (motility up to 90 s) and the percentage of motile spermatozoa compared to distilled water (up to 45 s) and ovarian fluid (P < 0.05).

Seminal characterization of the Amazonian fire-eye tetra Moenkhausia oligolepis (Günther, 1864)

The seminal characteristics of Moenkhausia oligolepis are described. Three males were induced with a single dose of carp pituitary. Semen was collected 6 h after induction, and diluted in dibasic sodium phosphate extender solution. For motility analysis, 1 µl of diluted semen was added to 10 µl of distilled water to achieve gamete activation. The average duration of total motility was 76.67 s; while the average sperm motility rate at intervals of 15 s was 95.3, 85.3, 59.6, 31.7, 13.0, 4.6 and 1.2%. To determine sperm concentration in samples, 0.5 μl of semen was diluted with 500 μl of glutaraldehyde. An aliquot of 10 μl of this dilution was utilized for cell counting. An average count of 4.97 × 109 ± 3.46 sperm/ml was obtained. Morphological analyses were performed using eosin-nigrosine dye; 20.33% of the sperm were observed to be dead. Live sperm, comprising the other 79.67%, had an average length of approximately 30 µm, with a head diameter of 4.488 ± 0.7 µm; and a flagella plus mid-piece length of 26.071 ± 12.4 µm. Of those sperm, 69% had a normal morphology, while 31% had primary and secondary abnormalities. The observed abnormality rate did not have a detrimental effect on artificial fertilization potential for the species. The description of the seminal characteristics of a species is one of the most important sets of information required for artificial reproduction of fish in captivity. It also contributes significantly to the total biological knowledge of the studied species.

Cryoprotective activity of phosphorus-containing phenol

The antioxidant and cryoprotective efficiencies of a 3,5-di-tert-butyl-4-hydroxyphenyl)methylenediphosphonic acid (MDPA) differ significantly for sperm cells of various species of sturgeon fish (Russian sturgeon, beluga and Stellate sturgeon). The ability of phosphorus-containing phenol MDPA to decrease the level of lipid peroxidation of sperm, beneficial effect on the activity indicators of the sperm of native sturgeon and of the defrosted one after deep freezing as well as on the fertility of sperm cells was shown.

Going beyond conventional parameters to unveil sperm quality in fish: the use of fibre optic technology to assess mitochondrial respiratory performance

Sperm fertilisation success depends on both intrinsic quality and the interactions with the surrounding reproductive fluids. In several fish species, these interactions have a variable effect on sperm performance. Although specific responses to reproductive fluids may depend on intrinsic differences in sperm quality, variations in the traditionally recorded sperm functional traits do not fully account for the observed patterns. New methods to enhance the evaluation of sperm quality may prove to be valuable at both applied and theoretical levels, by improving the breeding protocol of reared species and the understanding of mating success in sperm competition contexts. Here we develop a fibre optic-based technique, also adequate for small ejaculate samples, to test the role of mitochondrial respiratory efficiency in deciphering sperm performance variability. We purposely used as model the grass goby, Zosterisessor ophiocephalus, a fish with guard-sneaker mating tactics where the sperm in each male tactic have similar intrinsic qualities (velocity, viability, ATP content), but sneakers' sperm exploit territorial males' seminal fuid, overall displaying better fertilization ability. We found that sperm differed in their mitochondrial respiratory efficiency, which was higher in sneakers' sperm compared to territorial ones. This result draws the attention to an indicator of sperm quality that might be helpful in disentangling the mechanisms driving sperm-reproductive fluid interactions.