Reproductive impairment of sea urchin upon chronic exposure to cadmium. Part II: Effects on sperm development

Ovaries and testes of Lithobius forficatus (Myriapoda, Chilopoda) react differently to the presence of cadmium in the environment

Proper reproduction depends on properly functioning gonads (ovaries and testes). Many xenobiotics, including heavy metals, can cause changes in somatic and germ line cells, thus damaging the reproductive capacity. The aim of this study was to investigate the effect of the heavy metal cadmium on the gonads, including germ line and somatic cells. It is important to determine whether cell death processes are triggered in both types of cells in the gonads, and which gonads are more sensitive to the presence of cadmium in the environment. The research was conducted on the soil-dwelling arthropod Lithobius forficatus (Myriapoda, Chilopoda), which is common for European fauna. Animals were cultured in soil supplemented with Cd for different periods (short- and long-term treatment). Gonads were isolated and prepared for qualitative and quantitative analysis, which enabled us to describe all changes which appeared after both the short- and long-term cadmium treatment. The results of our study showed that cadmium affects the structure and ultrastructure of both gonads in soil-dwelling organisms including the activation of cell death processes. However, the male germ line cells are more sensitive to cadmium than female germ line cells. We also observed that germ line cells are protected by the somatic cells of both gonads.

Ocean Acidification, but Not Environmental Contaminants, Affects Fertilization Success and Sperm Motility in the Sea Urchin Paracentrotus lividus

Ocean acidification poses an increasing concern for broadcast spawning species that release gametes in the water column where fertilization occurs. Indeed, the functionality of gametes and their interactions may be negatively affected by reduced pH. Susceptibility to other environmental stressors, such as pollutants, may be also altered under acidified conditions, resulting in more detrimental effects. To verify this hypothesis, combined exposures to CO2-driven acidification and environmentally relevant concentrations (0.5 µg/L) of three contaminants (caffeine, diclofenac, and PFOS, all singularly or in mixture) were carried out to highlight potential negative effects on fertilization success and motility of sperm in the sea urchin Paracentrotus lividus. Our results showed a significant reduction in the percentage of fertilized eggs when sperm were pre-exposed to reduced pH (ambient pH minus 0.4 units) compared to that of controls (ambient, pH = 8.1). Sperm speed and motility also decreased when sperm were activated and then exposed at reduced pH. Conversely, at both pH values tested, no significant effect due to the contaminants, nor of their interaction with pH, was found on any of the biological endpoints considered.

PAHs and PCBs Affect Functionally Intercorrelated Genes in the Sea Urchin Paracentrotus lividus Embryos

Polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) represent the most common pollutants in the marine sediments. Previous investigations demonstrated short-term sublethal effects of sediments polluted with both contaminants on the sea urchin Paracentrotus lividus after 2 months of exposure in mesocosms. In particular, morphological malformations observed in P. lividus embryos deriving from adults exposed to PAHs and PCBs were explained at molecular levels by de novo transcriptome assembly and real-time qPCR, leading to the identification of several differentially expressed genes involved in key physiological processes. Here, we extensively explored the genes involved in the response of the sea urchin P. lividus to PAHs and PCBs. Firstly, 25 new genes were identified and interactomic analysis revealed that they were functionally connected among them and to several genes previously defined as molecular targets of response to the two pollutants under analysis. The expression levels of these 25 genes were followed by Real Time qPCR, showing that almost all genes analyzed were affected by PAHs and PCBs. These findings represent an important further step in defining the impacts of slight concentrations of such contaminants on sea urchins and, more in general, on marine biota, increasing our knowledge of molecular targets involved in responses to environmental stressors.

Relative gene expression, micronuclei formation, and ultrastructure alterations induced by heavy metal contamination in Pimelia latreillei (Coleoptera: Tenebrionidae) in an urban-industrial area of Alexandria, Egypt

The present research aims to evaluate the impact of industrial processes and anthropogenic activities on the beetle Pimelia latreillei inhabiting the polluted site at Zawya Abd El- Qader, Alexandria, Egypt. Beetles were collected from the vicinity of five factories. The genotoxic effects of environmental exposures to industrial heavy metals were monitored using a broad range of assays, including energy-dispersive X ray microanalysis and X-ray diffraction (SEM and EDX)), qRT-PCR gene expression assay, micronuclei formation, and transmission electron microscope (TEM). Energy dispersive X-ray microanalysis for the soil and testicular tissues of beetles collected from the polluted site revealed a higher percentage of heavy metals than the beetles collected from the reference site (Sidi Kirier, Alexandria, Egypt). To analyze/monitor genotoxicity in P. latreillei sampled from the polluted site, the transcription levels of levels of heat shock proteins (Hsps) and accessory gland seminal fluid protein (AcPC01) in testicular tissues were recorded. The incidence of micronuclei (MN) formation in the testicular cells was also observed. Quantitative RT-PCR (RT-qPCR) analysis was carried out to detect the changes in the gene expression of the aforementioned proteins. Genes encoding heat shock proteins (Hsp60, Hsp70, and Hsp90) were significantly overexpressed (> 2-fold) in specimens sampled from the polluted site; however, AcPC01 gene expression was under-expressed (<1.5-folds). The incidence of MN was significantly increased in specimens sampled from the polluted site. Ultrastructure anomalies (nuclear and cytoplasmic disruption) were also observed in the testicular cells of the beetles sampled from the polluted site compared to those sampled from the unpolluted site. Our results, therefore, advocate a need for adequate measures to reduce increasing environmental pollution in the urban-industrial areas.

Nickel oxide nanoparticles induce genotoxicity and cellular alterations in the ground beetle Blaps polycresta (Coleoptera: Tenebrionidae)

Nickel nanoparticles (Ni-NPs) have advantageous applications in the industry; however, little is known of their adverse effects on biological tissues. In the present study, the ground beetle Blaps polycresta was employed as a sensitive indicator for nickel oxide nanoparticles (NiO-NPs) toxicity. Adult male beetles were injected with six dose levels of NiO-NPs (0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mg/g body weight). Mortality was reported daily over 30 days under laboratory conditions to establish an LD₅₀. Nickel was detected in the testicular tissues of the beetles using X-ray analysis and transmission electronic microscopy. Beetles treated with the sublethal dose of 0.02 mg/g were selected to observe molecular, cellular, and subcellular changes. Gene transcripts of HSP70, HSP90, and MT1 were found to be increased >2.5-, 1.5-, and 2-fold, respectively, in the treated group compared with the controls. Decreased gene expression of AcPC01, AcPC02, and AcPC04 (≤1.5-, ≤2-, and < 2.5-fold, respectively, vs. controls) also were reported in the treated group. Under light microscopy, various structural changes were observed in the testicular tissues of the treated beetles. Ultrastructure observations using scanning and transmission electron microscopy showed severe damage to the subcellular organelles as well as deformities of the heads and flagella of the spermatozoa. Therefore, the present study postulated the impact of NiO-NPs in an ecological model.

Bioaccumulation of Metals/Metalloids and Histological and Immunohistochemical Changes in the Tissue of the European Hake, Merluccius merluccius (Linnaeus, 1758) (Pisces: Gadiformes: Merlucciidae), for Environmental Pollution Assessment

Pollution and other types of environmental stress do not spare marine environments, especially those affected by high industrial pressure. Fish, especially coastal species, are used for monitoring the marine environment because they are particularly efficient as bioindicators thanks to their ability to bioaccumulate and biomagnify along the trophic chain. The aim of this research is to evaluate the bioaccumulation and the indirect bioindication ability of the European Hake, Merluccius merluccius (Linnaeus, 1758), one of the most important commercial fish species of the Mediterranean Sea. Morphological and histological alterations of the main target organs, such as liver and gills, have been investigated and the results showed a steatosis in the hepatic tissue. The accumulation of heavy metals has been analyzed by inductively coupled plasma mass spectrometry and for several metals it was showed a different concentration in the two sexes. Moreover, the expression of metallothioneins 1 and Heat Shock Protein 70 has been assessed by immunohistochemistry and did not show high level of expression. We underline the importance of contamination evaluation in commercial fish species and the utilization of the ichthyofauna as bioindicator of environmental quality.

Efficiency and cell viability implications using tip type electroporation in zebrafish sperm cells

Sperm-mediated gene transfer (SMGT) has a potential use for zebrafish transgenesis. However, transfection into fish sperm cells still needs to be improved. The objective was to demonstrate the feasibility of tip type electroporation in zebrafish sperm, showing a protocol that provide high transfection efficiency, with minimal side-effects. Sperm was transfected with a Cy3-labelled DNA using tip type electroporation with voltages ranging from 500 to 1500 V. Sperm kinetics parameters were assessed using Computer Assisted Semen Analysis (CASA) and cell integrity, reactive oxygen species (ROS), mitochondrial functionality and transfection rate were evaluated by flow cytometry. The transfection rates were positively affected by tip type electroporation, reaching 64.9% ± 3.6 in the lowest voltage used (500 V) and 86.6% ± 1.9 in the highest (1500 V). The percentage of overall motile sperm in the electrotransfected samples was found to decrease with increasing field strength (P < 0.05). Increase in the sperm damaged plasma membrane was observed with increasing field strength (P < 0.05). ROS and sperm mitochondrial functionality did not present a negative response after the electroporation (P > 0.05). Overall results indicate that tip type electroporation enhances the internalization of exogenous DNA into zebrafish sperm cells with minimal harmful effects to sperm cells.

Effects of cadmium exposure on sperm and larvae of the neotropical fish Prochilodus magdalenae

Cadmium (Cd) is a heavy metal with known deleterious effects on animal reproduction, decreasing the rate of fertilization of organisms such as fish. Prochilodus magdalenae is a very important fish species in Colombia, widely used by riparian communities from many rivers. Unfortunately, its population has been declining, whereas Cd seems to be more frequently detected in environmental matrices at Colombian ecosystems. The aim of this work was to determine the toxic effects of cadmium chloride on fertilization, sperm quality and mortality at 0, 1, 6 and 7 days post-hatching (dph) in this vulnerable species. The results indicated that Cd altered the fertilization and sperm quality by decreasing total motility and rapid and medium motilities of swimming spermatozoa. Results showed Cd produced 16.4 and 46.5% sperm motility inhibition, at 2.5 and 25 ppm, respectively. The heavy metal also impaired sperm curvilinear and straight-line velocities in a concentration-response dose. Cadmium-induced a dose-dependent effect on the mortality of the exposed larvae that depends on its development stage, with greater effects after 6 and 7 dph, observed at concentrations as low as 0.025 ppm. The results showed that the exposure to environmentally relevant Cd concentrations causes physiological changes in the initial stages of development of P. magdalenae, likely increasing the risk of reducing the fertility rate of this valuable fish species.

Cadmium stress effects indicating marine pollution in different species of sea urchin employed as environmental bioindicators

In recent years, researches about the defense strategies induced by cadmium stress have greatly increased, invading several fields of scientific research. Mechanisms of cadmium-induced toxicity continue to be of interest for researchers given its ubiquitous nature and environmental distribution, where it often plays the role of pollutant for numerous organisms. The presence in the environment of this heavy metal has been constantly increasing because of its large employment in several industrial and agricultural activities. Cadmium does not have any biological role and, since it cannot be degraded by living organisms, it is irreversibly accumulated into cells, interacting with cellular components and molecular targets. Cadmium is one of the most studied heavy metal inductors of stress and a potent modulator of several processes such as apoptosis, autophagy, reactive oxygen species, protein kinase and phosphatase, mitochondrial function, metallothioneins, and heat-shock proteins. Sea urchins (adults, gametes, embryos, and larvae) offer an optimal opportunity to investigate the possible adaptive response of cells exposed to cadmium, since these cells are known to accumulate contaminants. In this review, we will examine several responses to stress induced by cadmium in different sea urchin species, with a focus on Paracentrotus lividus embryos. The sea urchin embryo represents a suitable system, as it is not subjected to legislation on animal welfare and can be easily used for toxicological studies and as a bioindicator of environmental pollution. Recently, it has been included into the guidelines for the use and interpretation of assays to monitor autophagy.

Aberrant gene expression profiles in Mediterranean sea urchin reproductive tissues after metal exposures

Marine organisms are simultaneously exposed to numerous pollutants, among which metals probably represent the most abundant in marine environments. In order to evaluate the effects of metal exposure at molecular level in reproductive tissues, we profiled the sea urchin transcriptional response after non-lethal exposures using pathway-focused mRNA expression analyses. Herein, we show that exposures to relatively high concentrations of both essential and toxic metals hugely affected the gonadic expression of several genes involved in stress-response, detoxification, transcriptional and post-transcriptional regulation, without significant changes in gonadosomatic indices. Even though treatments did not result in reproductive tissues visible alterations, metal exposures negatively affected the main mechanisms of stress-response, detoxification and survival of adult P. lividus. Additionally, transcriptional changes observed in P. lividus gonads may cause altered gametogenesis and maintenance of heritable aberrant epigenetic effects. This study leads to the conclusion that exposures to metals, as usually occurs in polluted coastal areas, may affect sea urchin gametogenesis, thus supporting the hypothesis that parental exposure to environmental stressors affects the phenotype of the offspring.

Maternal antioxidant provisioning mitigates pollutant-induced oxidative damage in embryos of the temperate sea urchin Evechinus chloroticus

One mechanism of pollution resistance in marine populations is through transgenerational plasticity, whereby offspring capacity to resist pollution reflects parental exposure history. Our study aimed to establish correlations between oxidative stress biomarkers and key reproductive fitness parameters in the temperate sea urchin Evechinus chloroticus following exposure to dietary polycyclic aromatic hydrocarbons (PAHs). PAH-exposed adults exhibited total gonad tissue concentrations of PAHs in excess of 4 and 5 times baseline levels, for females and males respectively. Antioxidant enzymes were upregulated and oxidative lipid and protein damage to gonad tissues occurred. In addition, early stage offspring reflected maternal antioxidant status, with progeny derived from exposed females demonstrating significantly higher baselines than those derived from control females. Maternal exposure history enhanced the capacity of embryos to minimise oxidative damage to lipids and proteins following exposure to additional PAHs, but provided less of an advantage in protection against oxidative DNA damage. Abnormal embryonic development was largely independent of oxidative damage, remaining high in all embryo populations regardless of parental PAH-history. Overall, results document evidence for maternal transfer of antioxidant potential in E. chloroticus, but imply that a short-term inherited resilience against oxidative stress may not necessarily translate to a fitness or survival gain.

Effects of exposure to cadmium in sperm cells of zebrafish, Danio rerio

Cadmium is a natural element found in the earth’s crust; it is usually associated with other metals, but due to the impacts caused by human activity, its concentration has increased in the aquatic environment. This metal may damage aquatic animal reproduction, decreasing the rate of fertilization of organisms such as fish. Thus, this study aimed to evaluate the in vitro toxicity of different concentrations of cadmium (0 (control), 0.5, 5, and 10 μg/L) using sperm cells of model organism zebrafish, Danio rerio. Structural parameters, including integrity and fluidity of the plasma membrane, concentration of oxygen species, mitochondrial function and DNA fragmentation were measured by flow cytometry. The following sperm movement parameters were also measured using the computer assisted sperm analysis (CASA) system: motility, time of motility, curvilinear velocity, average path velocity and straight line velocity in μm/s. Significant effects were observed on path speed, straight speed, curvilinear velocity, motility time, progressive and total motility, and plasma and DNA integrity. The results showed that cadmium can negatively affect some reproductive parameters in D. rerio, which may reduce the fertility rate of these animals.

Dietary pollutants induce oxidative stress, altering maternal antioxidant provisioning and reproductive output in the temperate sea urchin Evechinus chloroticus

Evidence is growing to suggest that the capacity to withstand oxidative stress may play an important role in shaping life-history trade-offs, although little is known on the relationship in broadcast spawning marine invertebrates. In this group, variation in gamete quantity and quality are important drivers of offspring survival and successful recruitment. Therefore the provisioning of eggs with antioxidants may be an important driver of life history strategies because they play a critical role in preventing damage from reactive oxygen species to macromolecules. In this study, a suite of oxidative stress biomarkers was measured in the gonads and eggs of the sea urchin Evechinus chloroticus exposed to polycyclic aromatic hydrocarbons (PAHs). Links between oxidative stress markers and core components of fitness including fecundity, gamete quality and maternal transfer of antioxidants were assessed. Experimental induction of oxidative stress was achieved via exposure to a mix of four PAHs over a 21-day period. In PAH exposed individuals, we observed a significant upregulation of the antioxidant defence and detoxification enzymes SOD, CAT, GR, GPx and GST, as well as a greater pool of the non-enzymatic antioxidant glutathione in gonad tissue and eggs. In contrast, glutathione redox status was not affected by PAH exposure, with the percentage of reduced glutathione remaining at approximately 80% in both gonad tissue and released eggs. PAH-exposed adults experienced greater than three- and five-fold increases in oxidative protein and lipid damage, respectively, in gonad tissue. In contrast, eggs maintained low levels of damage, not differing from baseline levels found in eggs released from PAH-naïve mothers. PAH exposure also resulted in a 2-fold reduction in fecundity of reproductively mature females but no significant alteration to egg diameter. Although PAH-exposed females released fewer eggs, successful fertilisation of those eggs was slightly enhanced with average rates ranging from 90-99% in comparison to 76-90% in control eggs. Early-stage offspring reflected maternal antioxidant status with populations derived from PAH-exposed mothers demonstrating significantly higher antioxidant levels than those derived from PAH-naïve mothers. This maternally inherited protection enhanced the capacity of embryos to minimise oxidative damage to lipids and proteins during early development but, despite this, did not reduce the proportion of morphological abnormalities in the population. Overall, these findings indicate that when faced with short-term contaminant stress E. chloroticus has the capacity to trade high reproductive output during a spawning event for a greater antioxidant investment in eggs. However, this production of potentially more resilient offspring did not translate to a fitness gain, at least for the early larval stages in the present experimental conditions.

The effects of metals of emerging concern on the fertilization success of gametes of the tropical scleractinian coral Platygyra daedalea

The demand for nickel and cobalt as important commodities has increased significantly over the past decade and a decline in the global nickel sulphide reserves has resulted in a shift toward the exploitation of the less favourable nickel laterite ores. These deposits, which are found associated with cobalt, are located predominantly in the tropical regions of the world where there is limited understanding of the toxicities of their extracted products and wastes. This study investigated the effects of nickel, cobalt and combinations of nickel and cobalt on the fertilization success of the common and widespread scleractinian coral Platygyra daedalea. We also present the first assessment of the effect of copper on fertilization success of this species. The EC50 value for copper was 33 μg L(-1) (95% confidence limits: 30-37 μg L(-1)) and is consistent with published values for other coral species. Our results provide the first EC50 value for the effect of nickel on fertilization success in a scleractinian coral, with an estimated value of 1420 μg L(-1) (95% confidence limits: 1160-1780 μg L(-1)). Concentrations of cobalt as high as 2500 μg L(-1) did not significantly reduce fertilization success nor did combinations of nickel (500 μg L(-1)) and cobalt (up to 1000 μg L(-1)). These are important findings given the emerging nickel-cobalt mining industry in the tropics and provide much needed toxicity data regarding the early-life histories of ecologically relevant tropical marine species.

Maternal Exposure to Cadmium and Manganese Impairs Reproduction and Progeny Fitness in the Sea Urchin Paracentrotus lividus

Metal contamination represents one of the major sources of pollution in marine environments. In this study we investigated the short-term effects of ecologically relevant cadmium and manganese concentrations (10^-6 and 3.6 x 10^-5 M, respectively) on females of the sea urchin Paracentrotus lividus and their progeny, reared in the absence or presence of the metal. Cadmium is a well-known heavy metal, whereas manganese represents a potential emerging contaminant, resulting from an increased production of manganese-containing compounds. The effects of these agents were examined on both P. lividus adults and their offspring following reproductive state, morphology of embryos, nitric oxide (NO) production and differential gene expression. Here, we demonstrated that both metals differentially impaired the fertilization processes of the treated female sea urchins, causing modifications in the reproductive state and also affecting NO production in the ovaries. A detailed analysis of the progeny showed a high percentage of abnormal embryos, associated to an increase in the endogenous NO levels and variations in the transcriptional expression of several genes involved in stress response, skeletogenesis, detoxification, multi drug efflux processes and NO production. Moreover, we found significant differences in the progeny from females exposed to metals and reared in metal-containing sea water compared to embryos reared in non-contaminated sea water. Overall, these results greatly expanded previous studies on the toxic effects of metals on P. lividus and provided new insights into the molecular events induced in the progeny of sea urchins exposed to metals.

Pollutant resilience in embryos of the Antarctic sea urchin Sterechinus neumayeri reflects maternal antioxidant status

Legacy pollutants, including polycyclic aromatic hydrocarbons (PAHs) and metals, can occur in high concentrations in some Antarctic marine environments, particularly near scientific research stations. Oxidative stress is an important unifying feature underlying the toxicity of many chemical contaminants to aquatic organisms. However, the potential impacts of pollutants on the oxidative physiology of Antarctic marine invertebrates are not well documented. Sterechinus neumayeri is a common animal in the shallow subtidal benthos surrounding Antarctica, and is considered an important keystone species. The aim of the present study was to collect baseline oxidative biomarker data for S. neumayeri and to investigate the impacts of field exposure to chemical contaminants on gamete health and parent-to-offspring transfer of oxidative stress resilience. We analysed antioxidant enzyme activities, levels of the molecular antioxidant glutathione, protein carbonylation, lipid peroxidation and levels of 8-OHdG as oxidative stress biomarkers in S. neumayeri from a contaminant-impacted site near McMurdo Station and a relatively pristine site at Cape Evans. Biomarkers were analysed in adult gamete tissue and in early stage embryos exposed to AN8 fuel oil. PAHs were quantified as a proxy for contamination and were found to be elevated in urchins from the contaminated site (up to 231.67ng/g DW). These contaminant-experienced adult urchins produced eggs with greater levels of a broad suite of antioxidants, particularly superoxide dismutase, catalase and glyoxalase-I, than those from Cape Evans. In addition, embryos that were derived from contaminant-experienced mothers were endowed with higher baseline levels of antioxidants, which conferred an enhanced capacity to minimize oxidative damage to lipids, proteins and DNA when exposed to AN8 fuel. This pattern was strongest following exposure to 900ppm AN8, where lipid and protein damage was 5-7 times greater than baseline levels in contaminant-naïve female embryos in comparison to 3-4 times greater in contaminant-experienced female embryos. Despite this inherited resilience against oxidative stress, abnormal development was as high in these embryos when exposed to AN8 as in those derived from contaminant-naïve mothers (up to 80% abnormality), implying the conferred advantage may not translate to a fitness or survival gain, at least up to the blastulae stage. Our findings document the first evidence for parent-to-offspring transfer of oxidative stress resilience in an Antarctic marine invertebrate.

An ultrastructural study of testes permeability in sea urchins, Strongylocentrotus intermedius

Permeability of testes in sea urchins, Strongylocentrotus intermedius, was investigated by using an electron-opaque tracer, lanthanum nitrate. This tracer is able to enter the basal compartment of germinative epithelium, where developing germ cells are located. However, its ability to penetrate the gonadal lumen was reduced. An incomplete permeability barrier between the basal compartment and the gonadal lumen is supposed to exist in testes of S. intermedius.

Endocrine disruption and reproduction impairment in zebrafish after long-term exposure to DE-71

The objective of the present study was to investigate the impact of polybrominated diphenyl ethers (PBDEs) on fish reproduction over 2 generations. Zebrafish (Danio rerio) embryos (F0) were exposed to low concentrations (3 µg/L, 10 µg/L, and 30 µg/L) of the PBDE mixture DE-71 until they were sexually mature, and steroid hormone production, expression of genes involved in steroidogenesis, gonadal development, and gamete characteristics were examined. Exposure of female zebrafish to DE-71 resulted in lower estradiol production and downregulation of cytochrome P450 aromatase mRNA. In males, exposure to DE-71 resulted in greater testosterone production and greater cytochrome P450 c17 α-hydroxylase,17,20-lase mRNA expression. Moreover, hepatic vitellogenin mRNA and estrogenic receptor β gene transcription were downregulated in females and males. Expression of the follicle-stimulating hormone β gene in the pituitary was upregulated, and the expression of luteinizing hormone β was downregulated in both sexes. Histological examination showed inhibition of oocyte maturation in females and retarded spermiation in males. The average number of eggs (F1) produced was also reduced. Additionally, exposure of F0 embryos to DE-71 did not result in developmental toxicity, whereas delayed hatching, reduced survival, and decreased growth were observed in the F1 embryos derived from parent fish exposed to DE-71. Therefore, long-term exposure to low concentrations of PBDEs in zebrafish could cause reproductive impairment, suggesting that PBDEs might have significant adverse effects on fish population in the highly PBDEs-contaminated aquatic environment.

Long-term incubation of adult Nereis virens (Annelida: Polychaeta) in copper-spiked sediment: the effects on adult mortality, gametogenesis, spawning and embryo development

Late gametogenic Nereis virens were incubated for up to 2.5 months in environmentally relevant concentrations of copper-spiked sediment. Sequential extraction confirmed that much more labile copper (in actual and percentage terms) was present as spiked concentrations increased, although the residual fractions contained similar amounts across concentrations. This is also reflected in the tissue concentration of the worms which increased in line with the sediment concentrations. Adult mortality was not dependent on the exposure time, but higher concentrations usually induced greater mortality for both sexes. Oocytes were significantly smaller at higher concentrations although pairwise comparisons did not show specific differences. Spawning of males occurred a number of days earlier in the higher concentrations. Differences in the number of embryos developing normally after in vitro fertilizations of oocytes fertilized with sperm from exposed males and non-exposed males showed that sperm were more susceptible to toxicity, but oocytes were also affected at the highest concentration. These results show that there are direct and indirect reproductive consequences of parental exposure to copper with implications for recruitment and subsequent colonization of polluted sediments for this ecologically and commercially important species.

Infertility in male aquatic invertebrates: a review

As a result of endocrine disruptor studies, there are numerous examples of male related reproductive abnormalities observed in vertebrates. Contrastingly, within the invertebrates there have been considerably less examples both from laboratory and field investigations. This has in part been due to a focus of female related endpoints, inadequate biomarkers and the low number of studies. Whether contaminant induced male infertility is an issue within aquatic invertebrates and their wider communities therefore remains largely unknown and represents a key knowledge gap in our understanding of pollutant impacts in aquatic wildlife. This paper reviews the current knowledge regarding pollutants impacting male infertility across several aquatic invertebrate phyla; which biomarkers are currently being used and where the science needs to be expanded. The limited studies conducted so far have revealed reductions in sperm numbers, examples of poor fertilisation success, DNA damage to spermatozoa and inhibition of sperm motility that can be induced by a range of environmental contaminants. This limited data is mainly comprised from laboratory studies with only a few studies of sperm toxicity in natural populations. Clearly, there is a need for further studies in this area, to include both laboratory and field studies from clean and reference sites, with a focus on broadcast spawners and those with direct fertilisation. Biomarkers developed for measuring sperm quantity and quality in vertebrates are easily transferable to invertebrates but require optimisation for particular species. We discuss how sperm tracking and techniques for measuring DNA strand breaks and sperm viability have been successfully transferred from human infertility clinics to aquatic invertebrate ecotoxicology. Linking sperm toxicity and male infertility effects to higher level impacts on the reproductive biology and dynamics of populations requires a much greater understanding of fertilisation dynamics and sperm competition/limitation for invertebrate species and represents the next challenge in our understanding of male toxicity effects in natural populations.

The involvement of metallothionein in the development of aquatic invertebrate

The many documents on metallothioneins (MTs) in aquatic organisms focus especially on their use as biomarkers in environmental monitoring programs, but there are a few papers that summarize the physiological role of MTs in aquatic organisms especially in their development. The multifaceted role of MTs include involvement in homeostasis, protection against heavy metals and oxidant damage, metabolic regulation, sequestration and/or redox control. MTs could be induced by heavy metals which are able to hinder gametogenesis, suppress embryogenesis, and hamper development. Here we pay more attention on the non-essential metal cadmium, which is the most studied heavy metal regarding MTs, and its effects on the development of aquatic invertebrates. In this paper, we have collected published information on MTs in aquatic organisms - mollusks, crustaceans, etc., and summarize its functions in aquatic invertebrates, especially those related to their development.

Broodstock diet effect on sea urchin Paracentrotus lividus (Lamarck, 1816) endotrophic larvae development: potential for their year-round use in environmental toxicology assessment

The effect of captive broodstock diet on fertilization and endotrophic larvae development of the sea urchin Paracentrotus lividus was assessed. Maize grain and five inert pelleted diets were tested, during a three-month experimental period. Maize flour, wheat flour, soybean flour, maize/wheat flour (MWF) and maize/soybean flour mixes were used as vegetal sources for inert feed. Gonad index, percent egg fertilization and larvae malformation occurrence were compared with the results obtained from wild sea urchins (W). Whole egg total amino acid composition was concomitantly analyzed as a tool to explain eventual endotrophic larvae malformations caused by lack of specific nutrients. For all treatment groups (wild and captive), percent egg fertilization values above 96% were always observed, fulfilling the requisites (70-90%) necessary to conduct environmental monitoring bioassays, according to USEPA (2002). Similar values for normal percent larval development were only obtained from P. lividus broodstock subjected to an inert feeding diet based on a maize/wheat flour mix (85.0±1.45%), in comparison to wild P. lividus (82.5±1.75%). Likewise, no statistical differences on resultant whole egg total amino acid composition were observed between P. lividus fed MWF and wild treatments. Moreover, statistical differences between MWF and all the other captive feeding treatments were found for six out of the seventeen amino acids analyzed. This study demonstrates the possibility to obtain high values for P. lividus endotrophic larvae percent normal development based on broodstock held in captivity as long as an appropriate inert diet is provided.

Cadmium toxicity at low concentration on rabbit spermatozoa motility, morphology and membrane integrity in vitro

In this study the effect of cadmium on various parameters of spermatozoa motility, morphology as well as on the spermatozoa membrane integrity in rabbits was analyzed in vitro, experimental concentrations ranging from 0.62 to 0.98 micro g CdCl(2)/mL. Pooled rabbit (n = 5) semen was cultured in vitro with cadmium and subsequently diluted to various experimental concentrations apart from control which received no cadmium exposure. Using computer assisted semen analysis method (CASA) we detected decrease of total motility with in the higher concentration range at Time 0. However, with increasing time (after 1 and 2 h of culture), cadmium exerted deleterious effect leading to significant motility reduction in comparison to control. A similar trend was exhibited in case of progressive motility, too. Most of the spermatozoa distance and velocity parameters detected no significant change in comparison to control at the beginning of culture (Time 0), although the toxic effect became significant (P < 0.05) with the passage of culture time (Times 1 and 2 h) in all concentrations. Analysis of spermatozoa morphology detected significant (P < 0.05) alterations at higher concentrations. At higher concentrations acrosomal changes, head without flagellum/separated flagellum, broken flagellum and other abnormalities were significantly higher (P < 0.05), while knob-twisted flagellum and small heads differed significantly (P < 0.05) in comparison to control at all concentrations. In regards to flagellum torso, flagellum ball and retention of cytoplasmic drop statistically higher values (P < 0.05) were noted at the maxium experimental concentration only. Annexin analysis for detection of spermatozoa with disordered membranes revealed higher occurrence of positive spermatozoa in cadmium exposed groups. Annexin-positive reactions suggested alterations in anterior part of head (acrosome) and in flagellum (mitochondrial segment) of spermatozoa. This paper underlines that cadmium is highly toxic for rabbit spermatozoa, as visualized by the toxic effects on parameters of spermatozoa motility, morphology and membrane integrity. The toxic effect is more drastic at higher concentrations. This study also indicates that cadmium requires a minimum one hour incubation time to exert its deletorious effects on various parameters of spermatozoa, particularly at low concentrations.

Morphology of spermatogenic and accessory cells in the mussel Modiolus kurilensis under environmental pollution

A comparative light- and electron microscopic study of the male gonads of the bivalve mollusk Modiolus kurilensis from the reference and polluted sites in Amursky Bay (Sea of Japan) was conducted. Testicular acini in the mussels from the reference site had well-ordered structure (vertical spermatogenic columns located among the accessory cells bodies) whereas in the testes of the mollusks from the polluted site, the accessory and spermatogenic cell populations were disarranged. Mussels from the polluted station had about 26% of spermatogenic cells with marginal localization of nuclear chromatin, swollen outer nuclear membrane and heavily vacuolated cytoplasm and about 8% of spermatozoa with transformed or destructed acrosome; in mussels from the reference station, these values were close to zero. The accessory cells in the mussels from the polluted site were underdeveloped, and their phagocytic activity was inhibited. Our ultrastructural observations provide evidence that both spermatogenic and accessory cells are targets of environmental pollution in marine mussels.

Gonadal lesions of female sea urchin (Psammechinus miliaris) after exposure to the polycyclic aromatic hydrocarbon phenanthrene

Histopathological alterations in the reproductive tissue of the female sea urchin Psammechinus miliaris after exposure to the polycyclic aromatic hydrocarbon (PAH) phenanthrene were investigated using light microscopy. Sexually mature sea urchins were exposed to 500 microg L(-1) phenanthrene for 20 days. A severe disorganisation of the acinal structure of the gonads was observed in phenanthrene-treated animals, mainly as a result of aggregates of degenerating previtellogenic oocytes. Growth and maturation of previtellogenic oocytes were inhibited, whereas there were no obvious effects on vitellogenic oocytes and mature ova. The acinal wall showed signs of fibrosis as well as dilation of the two epithelial layers. Phenanthrene severely affected the reproductive function of the sea urchins since a proper oogenesis of the ovarian tissue is very unlikely. Generally, the observed alterations are similar to histopathological changes in reproductive tissue in other invertebrates after exposure to PAHs and oil.

Adverse effects of cadmium exposure on mouse sperm

The effects of cadmium chloride exposure on sperm functional parameters were evaluated on eight-week-old ICR-CD1 male mice administered with a single s.c. injection of 1, 2 and 3 mg CdCl(2)/kg bw. Groups of animals treated with each dose, as well as their respective controls, were sacrificed after 24h to detect short-term (acute) effects and after 35 days. Sperm cells were collected from the epididymis and several parameters of sperm quality and function were evaluated, namely density, morphology, motility, viability, mitochondrial function, acrosome integrity, together with DNA fragmentation assessed by the TUNEL assay. The short-term effects of cadmium chloride resulted in an increased fraction of sperm with abnormal morphology, premature acrosome reaction and reduced motility. Late term effects (after 35 days) included a drastic reduction of sperm cell numbers and sperm motility. An increase in DNA fragmentation was also detected.

Measuring Ca2+-signalling at fertilization in the sea urchin Psammechinus miliaris: alterations of this Ca2+-signal by copper and 2,4,6-tribromophenol

During fertilization, eggs undergo a temporary rise in the intracellular concentration of free Ca(2+) ions. Using the membrane permeable acetoxymethylester of the fluorescent calcium indicator dye Fura-2, Fura-2 AM, the Ca(2+)-signal at fertilization was not detectable in eggs of the sea urchin Psammechinus miliaris. However, after treatment of the eggs with Fura-2 AM in combination with MK571, an inhibitor for multidrug resistance associated proteins, clear Ca(2+)-signals at fertilization could be measured without microinjection of the dye. We used this methodology to detect possible alterations of Ca(2+)-signalling at fertilization by exposure of eggs to environmental pollutants. For this purpose, the heavy metal copper, the bromophenol 2,4,6-tribromophenol, the organic compound bisphenol A and the polycyclic aromatic hydrocarbon phenanthrene were tested for their potential to inhibit fertilization success of P. miliaris. Copper and 2,4,6-tribromophenol showed a dose-dependent effect on fertilization rates of P. miliaris and significantly inhibited fertilization at 6.3 microM Cu(2+) and 1 microM 2,4,6-tribromphenol. Bisphenol A significantly inhibited fertilization success at 438 microM while phenanthrene had no effect up to 56 microM. 6.3 microM copper and 100 microM 2,4,6-tribromophenol significantly increased the Ca(2+)-signal at fertilization. This alteration may contribute to the reduced fertilization rates of P. miliaris after exposure to copper and 2,4,6-tribromophenol.

The relative sensitivity of sperm, eggs and embryos to copper in the blue mussel (Mytilus trossulus)

Copper, an essential element, is toxic at elevated concentrations, and as a result of anthropogenic activities is becoming increasingly prevalent in marine environments. In this study, we examined the effects of copper on early life stages of the blue mussel, Mytilus trossulus. We assessed the impacts of increasing copper concentrations on embryo development, egg viability, sperm fertilization capacity and, in particular, on sperm swimming speed using computer-assisted sperm analysis. Sensitivity to copper followed the pattern: embryos > sperm > eggs. A dramatic increase in abnormal embryo development was observed following exposure to copper concentrations exceeding 10 microg/L. Sperm swimming speeds decreased significantly when exposed to 100 microg/L of copper, but lower doses did not influence sperm swimming speed. Copper exposure (at any tested concentration) did not affect sperm flagellum length, or alter egg viability. Based on our results, we suggest that exposure of sperm to copper may interfere with mitochondrial activity, which reduces sperm swimming speed during the extended duration of sperm motility in blue mussel.

Contrasting effects of heavy metals on sponge cell behavior

Mediterranean coastal areas are highly contaminated by heavy metals, which have been reported to produce harmful effects in marine organisms. Sponges are particularly vulnerable to waterborne metals because they are able to process large amounts of water. Dissociated sponge cells can move in response to external stimuli, and the cell body changes shape through production of pseudopodia and phylopodia. We studied for first time the effects of heavy metals (cadmium copper and mercury) on motility and aggregation of isolated sponge cells. Cell shape was assessed by using several shape indices. The three metals studied induced changes of different sign on cell shape. Mercury arrested movement of sponge cells, which tended to be rounded, without pseudopodia. In contrast, moderate concentrations of copper and cadmium enhanced pseudopodia formation and cell motility. On the other hand, the three metals enhanced cell aggregation at the concentrations assayed. Our results show that sponge cells respond to metal pollution in different ways and that these responses can be assessed by calculating several shape indices.

Cadmium induces an apoptotic response in sea urchin embryos

Cadmium is a heavy metal toxic for living organisms even at low concentrations. It does not have any biological role, and since it is a permanent metal ion, it is accumulated by many organisms. In the present paper we have studied the apoptotic effects of continuous exposure to subacute/sublethal cadmium concentrations on a model system: Paracentrotus lividus embryos. We demonstrated, by atomic absorption spectrometry, that the intracellular amount of metal increased during exposure time. We found, using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, that long treatments with cadmium triggered a severe DNA fragmentation. We demonstrated, by immunocytochemistry on whole-mount embryos, that treatment with cadmium causes activation of caspase-3 and cleavage of death substrates alpha-fodrin and lamin A. Incubating the embryos since fertilization with Z-DEVD FMK, a caspase-3 inhibitor, we found, by immunocytochemistry, that cleavage by caspase-3 and cleavage of death substrates were inactivated.

Sublethal effects of phenol on spermatogenesis in sea urchins (Anthocidaris crassispina)

Adult sea urchins, Anthocidaris crassispina, were exposed to 0.1 and 10 mgL(-1) phenol for 4 weeks. Abnormal sperm development was clearly evident in phenol-treated sea urchins, although no mortality was found throughout the exposure period. Occurrences of multinucleate sperm cells (including spermatocytes to spermatozoa) showed a significant increase from 0.07% in the control to 10.7% and 43.3% in the 0.1- and 10-mgL(-1) treatments, respectively (P<0.01). Likewise, sperm with electron dense, dark tails increased significantly from 8% in the control to 36.6% and 43.4% in the 0.1- and 10-mgL(-1) phenol-treated sea urchins, respectively (P<0.01). In addition, disruption of cytoplasmic membranous structures such as loss of mitochondrial cristae and distortion of mitochondrial membranes and nucleus envelope were commonly found in phenol-treated spermatogonia and spermatocytes. Previous studies have clearly demonstrated motility impairment and a concomitant reduction of fertilization capability in sea urchin sperm with dark tails and/or distorted mitochondria. Our current findings therefore suggest that chronic exposure to phenol at 0.1 mgL(-1) could lower the quality of sperm and reproductive success in sea urchins, which may threaten the survival of these ecologically important species. The observed impairment of spermatogenesis by phenol might also occur in other invertebrate species.

Impairment of sea urchin sperm quality by UV-B radiation: predicting fertilization success from sperm motility

Sperm quality of the sea urchin, Anthocidaris crassispina, after exposure to environmentally realistic UV-B irradiances, was assessed by changes in sperm motility (measured by the computer-assisted sperm analysis (CASA) system), and related to subsequent fertilization success. Percentage motile sperm of A. crassispina declined significantly after exposure to a UV-B dose of 16.2 kJ m(-2), while sperm motion velocity as measured by curvilinear velocity (VCL), straight line velocity (VSL), and average path velocity (VAP) showed significant reduction after exposure to a UV-B dose of 5.4 kJ m(-2). A parallel study showed that fertilization success was significantly reduced after sperm were exposed to UV-B doses > or = 5.4 kJ m(-2). Notably, the four sperm motility parameters were strongly correlated with fertilization success (P < 0.001), followed the increasing order: VSL (r = 0.8) < % motile sperm (r = 0.804) < VCL (r = 0.912) < VAP (r = 0.928). Fertilization success is best predicted by VAP using the exponential model: y = 8.678 + 90.202/[1 + exp(82.83 - x)/10.27)] (r(2) = 0.95). Thus, impairment of sperm motility of sea urchin, as measured by the CASA method, can be used to predict reproductive success and ecological effects.

Effects of inorganic and organic phosphate exposure on aspects of reproduction in the common sea urchin Lytechinus variegatus (Echinodermata: Echinoidea)

The common nearshore sea urchin Lytechinus variegatus is capable of surviving exposure to inorganic phosphate concentrations as high as 3.2 mg/l(-1) and organic phosphate concentrations of 1,000 mg/l(-1). However, chronic exposure to low, medium, or high sublethal concentrations of these phosphates inhibits gonadal tissue indices and spawning activity while altering biochemical composition of gonads, reducing size frequencies of oocyte diameters, and changing gonadal volume fractions. Gonad indices declined significantly in individuals maintained in all phosphate concentrations after both one- and two-month exposures, while percentages of ripe individuals (oozing gametes upon dissection) were reduced after a two-month exposure in individuals maintained in medium and high organic phosphate concentrations. Levels of carbohydrates and lipids were lower in gonads of individuals maintained in all concentrations of both phosphates. Size frequency distributions of oocyte diameters revealed a dramatic decrease in oocyte size with increasing concentrations of both phosphates. Gonadal volume fractions of developing male and female gametes decreased with exposure to increasing phosphate levels. Volume fractions of nutritive phagocytes declined in testes of individuals held in the highest concentration of organic phosphate but displayed no significant change in ovaries. Volume fractions of mature gametes also decreased in gonads of individuals exposed to increasing concentrations of inorganic phosphate, but they remained constant in individuals exposed to all concentrations of organic phosphate. These findings indicate that shallow-water populations of L. variegatus subjected to inorganic and organic phosphate pollutants will exhibit stress that may impair reproductive output, gametogenesis, and spawning in the natural environment.

Reproductive impairment of sea urchins upon chronic exposure to cadmium. Part I: Effects on gamete quality

Successful reproduction is a determining factor for species survival. Pollution may impair reproductive success of adults through effects on gamete quality. Reproductive impairment of the sea urchin Anthocidaris crassispina upon chronic (4 weeks) exposure to 0.01 and 0.1 mg l-1 Cd2+ was investigated. Criteria used for assessing gamete quality included sperm motility, egg morphology, fertilization rate and dynamics of first cleavage. A dose-response relationship was found between Cd2+ levels and changes in sperm motility, and percentage fertilization. Sperm motility, measured by computer-assisted sperm analysis, indicated that percent motile sperm, velocities, and percent sperm with normal trajectory were significantly affected by chronic exposure to > or = 0.1 mg l-1 Cd2+. A decline in sperm motility was also accompanied by a decrease in fertilization success of sea urchin sperm. Width/height ratio of sea urchin eggs was not affected by cadmium, but larger egg sizes were found when sea urchins were exposed to 0.1 mg l-1 Cd2+. Male sea urchins exposed to Cd2+ produced poorer quality sperm, as indicated by a lower percent fertilization and lower cleavage rate, implying that male sea urchins were more sensitive than females to chronic Cd2+ exposure. Results of the present study provide an explanation of reproductive impairment in marine invertebrates upon chronic exposure to Cd2+.