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The production of growth hormone (GH) transgenic animals has raised a host of social and scientific concerns regarding their potential impacts on ecosystems should they escape into nature. Indeed, theoretical models suggest that GH transgenic animals could, under specific conditions, decimate local populations. However, while there are numerous laboratory examinations of factors affecting survival of transgenic and wild animals, we know little about the competitive reproductive capacity of transgenic animals. Here, we examined the reproductive capabilities of cultured GH transgenic coho salmon (Oncorhynchus kisutch) when in competition with wild coho derived from nature using semi-natural mating arenas (within a contained facility). To account for the well-known reproductive impairments associated with culturing salmon in laboratory facilities we contrasted the competitive reproductive success of GH transgenic coho against that of cultured non-transgenic coho. We also performed in vitro sperm analyses to assess the postcopulatory competitive ability of GH transgenic coho. In competitive mating arenas, transgenic coho performed fewer courtship and aggressive behaviours than coho from nature and sired less than 6% of offspring. Non-transgenic cultured coho, despite their smaller body size, sired more than twice as many offspring than transgenic coho when competing against wild coho in mating arenas. Transgenic males also face a postcopulatory reproductive disadvantage as their ejaculates contained fewer sperm that swam slower and for shorter durations than sperm from wild males. Together, these findings suggest limited potential for the transmission of transgenes from cultured GH transgenic coho salmon through natural matings should they escape from a contained culture facility into nature and reproductively interact with a local wild coho salmon strain. However, as responses of wild-reared fish can differ greatly from those of cultured fish, we stress the importance of understanding genotype-by-environment interactions for reproductive phenotypes when developing risk assessment information. (C) 2011 Elsevier B.V. All rights reserved.

Alternative male reproductive tactics are taxonomically widespread. In such species, parental, or conventional, males express secondary sexual characteristics, court females and guard offspring, while smaller parasitic or sneaker males avoid the costs of courtship and parental care by performing sneak fertilizations. Theory predicts that sneakers will invest more in testes mass and produce more competitive ejaculates than parentals because sneakers always experience sperm competition while parental males experience sperm competition only when a sneaker is present. Here we present convergent lines of evidence supporting the existence of alternative male reproductive tactics in round gobies (Apollonia melanostoma, formerly Neogobius melanostomus), a recent invader in the Great Lakes. Dark morph males exhibited secondary sexual characteristics, were larger and had higher plasma 11-ketotestosterone concentrations than light morphs, while light morph males invested more in ejaculates (both testes mass and sperm density). Both male morphs had enlarged urogenital papillae, but papillae were relatively longer in light morph males. Sperm tail length did not differ between morphs, and sperm from dark morphs swam faster than sperm from light morphs. Our data strongly argue for the presence of alternative tactics in round gobies, support some predictions from sperm competition theory and align with empirical observations in other taxa. For species of concern like the invasive round goby, it is critical to consider such evidence of alternative male mating tactics when constructing population growth models and assessment of invasion success and impacts. © 2009 Elsevier Inc. All rights reserved.

Polygyny is regarded as a beneficial strategy for males, whereas females mated with polygynous males (males simultaneously paired to more than one female) often suffer a reduction in pair male contributions. This study examined the costs and benefits associated with polygyny in the cooperatively breeding cichlid Neolamprologus pulcher. In this species, males are facultatively polygynous; some males hold only one territory with one breeding female whereas other males hold multiple territories, each with its own breeding female. Polygynous males were larger than monogamous males and body-scraped less, a behaviour often associated with ectoparasite loads. Polygynous males also had larger testes (controlling for body mass) and higher circulating 11-ketotestosterone levels than monogamous males. Paradoxically, monogamous males occupied higher-quality territories with more shelter and fewer predators. Monogamous males also provided more parental care than polygynous males but the number and survival of young did not vary according to male mating behaviour. The results of our study suggest that females trade-off between male genetic quality and resources in N. pulcher. Our results imply that males holding only one territory may provide their mates with significant assets but may not be able to outcompete neighbours for additional breeding positions because of their small body size and possible higher parasite load. The lack of differences between monogamous and polygynous groups in terms of offspring survival (a measure of reproductive success) suggests that there may be few if any fitness consequences of polygynous pairing for females. © 2008 The Association for the Study of Animal Behaviour.

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 μg/L. Sperm swimming speeds decreased significantly when exposed to 100 μg/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. © 2008 Elsevier Inc. All rights reserved.

In social groups, subordinates may gain dominant breeding status either by inheriting the top position in their current group or by dispersing to join a new group. The pathway to breeder status is likely to vary between males and females as a result of sex differences in the costs of dispersal and inbreeding. We report results from a field study conducted to explore sex differences in the rates of territory joining and inheritance in a cooperatively breeding cichlid, Neolamprologus pulcher. We experimentally created 34 breeding vacancies and investigated the effects of breeder removal on the degree of cooperative behaviour and how changes in status influenced reproductive physiology. We found that 71% of male vacancies were filled by joiners (incoming fish, not previously members of the group) entering the territory. In contrast, only 15% of female vacancies were filled by joiners entering the group from elsewhere. Helpers increased their frequency of cooperative behaviour following the removal of a female breeder, but not following removal of a male breeder. Our results suggest that female breeder vacancies are typically filled by subordinate helpers who inherit from within the group and that male breeder vacancies are commonly filled by joining individuals (existing breeders or former helpers from other groups). Male social status and gonadal investment were positively correlated. This study represents one of the first experimental attempts to examine sexual differences in the pathway to breeding status in a cooperatively breeding species.

Endocrine technologies and sex modification of fish stocks are playing an increasingly important role in commercial aquaculture production. The characteristics and fertilization success of sperm from masculinized coho salmon (Oncorhynchus kisutch) were examined and compared to that of regular coho salmon sperm. Sperm from masculinized XX males was stripped, or when the efferent ducts were not developed the semen was collected from the testis, and compared with semen from normal XY males. Stripped masculinized genetic females exhibited similar measures of sperm velocity and sperm density as normal male coho salmon, with both of these groups differing significantly from testicular sperm from masculinized females. In commercial fertilization trials, fertilization success was not altered by the dichotomy observed between testicular and stripped milt from masculinized females. Treatment with leutenizing hormone releasing analogues had no effect on sperm motility, density, or fertility. Much of the difference in sperm characteristics can be attributed to the difference between stripped sperm and testicular sperm.