Sperm quality as reflected through morphology in salmon alternative life histories

Reproductive-tactic-specific variation in sperm swimming speeds in a shell-brooding cichlid

Theory predicts that males experiencing elevated levels of sperm competition will invest more in gonads and produce faster-swimming sperm. Although there is ample evidence in support of the first prediction, few studies have examined sperm swimming speed in relation to sperm competition. In this study, we tested these predictions from sperm competition theory by examining sperm characteristics in Telmatochromis vittatus, a small shell-brooding cichlid fish endemic to Lake Tanganyika. Males exhibit four different reproductive tactics: pirate, territorial, satellite, and sneaker. Pirate males temporarily displace all other competing males from a shell nest, whereas sneaker males always release sperm in the presence of territorial and satellite males. Due to the fact that sneakers spawn in the presence of another male, sneakers face the highest levels of sperm competition and pirates the lowest, whereas satellites and territorials experience intermediate levels. In accordance with predictions, sperm from sneakers swam faster than sperm from males adopting the other reproductive tactics, whereas sperm from pirates was slowest. Interestingly, we were unable to detect any variation in sperm tail length among these reproductive tactics. Thus, sperm competition appears to have influenced sperm energetics in this species without having any influence on sperm size.

Effects of a pyrethroid pesticide on endocrine responses to female odours and reproductive behaviour in male parr of brown trout (Salmo trutta L.)

Reproductive behaviour of brown trout (Salmo trutta L.) from an anadromous stock was studied in a large stream water aquarium. Four adult males and two ovulated females were placed in the aquarium together with eight mature male parr. Four of the parr were exposed during the previous 4 days to two concentrations (0.1 or 1.0 microgl(-1)) of the pyrethroid pesticide cypermethrin (a disrupter of olfactory receptor function) and four of the parr to the solvent ethanol. The behaviour of all fish was followed for 24h and then blood and milt was collected. Exposure to the higher concentration of cypermethrin disturbed the reproductive behaviour of the parr. They displayed fewer courting events, spent less time near the nesting females and had lower volumes of strippable milt. They also had significantly lower amounts of 11-ketotestosterone (11-KT) in the blood plasma than the control group. The higher cypermethrin group also had significantly lower levels of all these variables than the lower cypermethrin group, apart from strippable milt that showed no significant differences between two groups. No significant differences in non-reproductive behaviours were observed between any of the groups. In the control fish, there were significant positive correlations between (a) the number of courting events and the amount of time spent near the female, (b) blood plasma levels of 17alpha,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) and time spent near the female and (c) plasma levels of 17,20beta-P and the number of courting events. Further, in control fish, higher plasma levels of 17,20beta-P were observed in parr interacting with a female compared to those with no female contacts. A priming experiment confirmed a previous study that cypermethrin damages olfactory reception. Parr exposed to cypermethrin had significantly lower blood plasma levels of 17,20beta-P and 11-KT than control males after exposure to ovarian fluid and urine (known to contain reproductive priming pheromones). When ethanol-exposed males were exposed to ovarian fluid and urine they had significantly higher plasma levels of 17,20beta-P compared to those exposed to water only.

Development of a novel CASA system based on open source software for characterization of zebrafish sperm motility parameters

Although computer-assisted sperm analysis (CASA) outperforms manual techniques, many investigators rely on non-automated analysis due to the high cost of commercial options. In this study, we have written and validated a free CASA software primarily for analysis of fish sperm. This software is a plugin for the free National Institutes of Health software ImageJ and is available with documentation at . That it is open source makes possible external validation, should improve quality control and enhance the comparative value of data obtained among laboratories. In addition, we have improved upon the traditional velocity straight line (VSL) algorithm, eliminating inaccurate characterization of highly curved fish sperm paths. Using this system, the motion of zebrafish (Danio rerio) sperm was characterized relative to time post-activation and the impact of acquisition conditions upon data analysis determined. There were decreases in velocity and path straightness (STR), but not linearity (LIN), relative to time. From 30 to 300 frames/s, frame rate significantly affected curvilinear velocity (VCL) and STR measurements. Sperm density in the field of view did not affect any measured parameter. There was significant inter-male variation for VCL, VSL, velocity average path (VAP), percent motility, path character (STR, LIN), and duration of motility. Furthermore, relative sperm output (a measure reflecting both semen volume and concentration) was positively correlated to percent motility. For all motion parameters measured (except duration), the average CV was < or =10%, comparable to values obtained using commercial systems.

Influence of developmental environment on male- and female-mediated sperm precedence in Drosophila melanogaster

Length of the sperm flagellum and of the female's primary sperm-storage organ, the seminal receptacle (SR), exhibit a pattern of rapid correlated evolution in Drosophila and other lineages. Experimental evolution studies with Drosophila melanogaster indicate that these traits have coevolved through sexual selection, with length of the SR representing the proximal basis of female sire discrimination, biasing paternity according to sperm length. Here, we examine the impact of experimentally varying the developmental environment, including larval density and larval and adult nutrition, on sperm length, SR length and on the pattern of sperm precedence. Expression of SR length was far more sensitive to variation among developmental environments than was sperm length. Nevertheless, there was striking co-variation in sperm and SR length. The developmental environment of both females and second males, but not first males, significantly contributed to variation in male competitive fertilization success.

Effects of the antidepressant mianserin in zebrafish: molecular markers of endocrine disruption

Due to their environmental occurrence and intrinsic biological activity, human pharmaceuticals have received increasing attention from environmental and health agencies. Of particular, ecotoxicological concern are drugs that affect nervous- and endocrine-systems. Zebrafish genome-wide oligo arrays are used to collect mechanistic information on mianserin-induced changes in gene expression in zebrafish. Gene expression analysis in brain and gonad tissue clearly demonstrated the estrogenic activity of mianserin and its potency to disrupt normal endocrine (estrogenic) signaling, based on induction of molecular biomarkers of estrogenicity (e.g., vitellogenin1 and zona pellucida proteins). The possible mechanism underlying this estrogenic activity of mianserin is disturbance of the Hypothalamo-Pituitary-Gonadal (HPG) axis by direct interference of mianserin with the serotonergic and adrenergic systems in the brain of zebrafish. Taking into account the importance of the HPG-axis, and considering the concept of 'critical window of exposure', our results reveal the importance for more elaborate testing of endocrine disruptive effects of aquatic antidepressants at different lifestages and during longer exposure periods (e.g., life cycle studies). Although there is a low concordance between the gene expression results in this study and previous cDNA microarray hybridizations, the global mechanistic expression patterns are similar in both platforms. This argues in favor of pathway-driven analysis of gene expression results compared to gene-per-gene analysis.

Spermatozoal competition in common carp (Cyprinus carpio): what is the primary determinant of competition success?

The percentage of sperm motility (92–100%), spermatozoan velocity (112–163 μm·s−1) and control hatching rates (83–96%) were evaluated for each of six gold and five green male common carp (Cyprinus carpio). In all 30 possible paired combinations of sperm-competition tests, hatching rates of 90–97% were achieved. The mean percentage of offspring sired was strongly influenced by the male used (P < 0.001, R 2 = 0.91). The best male sired an average of 88% of the offspring in its competition tests, and the worst male sired only 5%. Spermatozoan-quality parameters could explain only part of the variation in male competitive ability. The male effects alone explained 91.4% of the observed variance, consisting of 17.1% explained by spermatozoan motility and 32.5% by control hatching rates in single fertilizations. Undetermined male effects explained 41.8%. The velocity of spermatozoa had no effect on the outcome of sperm competition. Neither was there any link between spermatozoan velocity and hatching rate in a control hatching test, whereas there was an effect of motility on hatching rate in this same test.

Sperm and spermatozeugma ultrastructure in the inseminating speciesTyttocharax cochui,T. tambopatensis, andScopaeocharax rhinodus (Pisces: Teleostei: Characidae: Glandulocaudinae: Xenurobryconini)

This article presents the scanning and transmission electron microscopy of the spermatozoa and sperm packets of three inseminating species of the glandulocaudine tribe Xenurobryconini. All three species, Scopaeocharax rhinodus, Tyttocharax cochui, and T. tambopatensis produce unencapsulated sperm packets (= spermatozeugmata) of similar morphology. The external anterior surface of each spermatozeugma is comprised of elongate sperm heads arranged in parallel, and the posterior part is made up of tightly packed flagella. The interior of the anterior portion consists of alternating layers of sperm heads and flagella. The remarkable integrity of each packet appears to be maintained through an electron-dense secretion seen among all parts of the cells. Spermatozeugma formation takes place within the spermatocysts at the end of spermiogenesis and at spermiation fully formed packets are released. Morphology of the mature spermatozoa was similar in all three species. Each nucleus is elongate, flattened along most of its length, and tapers at either end. The two centrioles are nearly parallel to one another and are located just anterior to the nucleus. Elongate mitochondria are located along the nucleus. The single flagellum, which lacks axonemal fins, is initially contained within a short cytoplasmic collar. Accessory microtubules run parallel to the long axis of the nucleus just beneath the plasma membrane. During spermiogenesis, no nuclear rotation occurs and the cytoplasmic canal containing the flagellum elongates along with the nucleus. However, prior to spermiation all but the anterior portion of the collar degenerates. The sperm modifications observed in these species are discussed as adaptations to the unique reproductive habit of insemination.