Impact of Environmental Contaminants on Sperm

Abstract

<p>Aquatic contaminants are known to negatively impact reproductive behaviour and physiology. However, the influence of chronic exposure to aquatic contaminants on gamete traits has largely been explored using species with simple mating systems. In this thesis I explored how sperm is impacted using wild caught round gobies (Neogobius melanostomus) and plainfin midshipman (Porichthys notatus), two species that inhabit bodies of water polluted with industrial and urban contaminants, and also exhibit complex mating systems with male alternative reproductive tactics (MARTs). Species with MARTs generally have two male morphs: a guarding male morph that courts females and aggressively defends a territory, females and/or young, and a sneaking male morph that does not court females or defend a territory but instead parasitizes territories held by guarding males and simply sheds sperm within the nests. Guarding males are larger, older and remain fairly stationary in/near their nests for long periods of time are likely to have had greater exposure to contaminants compared with non-sedentary younger, smaller sneaker males that roam from nest to nest. These behavioural and physiological differences may result in differential impacts or exposure to contaminants between male mating tactics. Thus, species with MARTs living in polluted environments make excellent models to investigate interactive effects of contaminant exposure and mating strategy on gametes. Using round gobies from clean and contaminated areas of Hamilton Harbour, Lake Ontario I show that interactions between sites (clean versus contaminated) and male morphs (guarding versus sneaker) on testicular investment, relative sperm tail length and sperm velocity are limited. Few interactions between site and tactic suggest that guarding and sneaker male round goby sperm are equally affected by environmental factors or that both tactics are not influenced by contaminants. Both guarding and sneaker round gobies appear resilient to complex combinations of anthropogenic based pollutants. Using plainfin midshipman populations that inhabit areas close versus distant to sources of industrial and urban effluents, I show that living in contaminated areas influences gametic quality of guarding males. Guarding males from contaminated areas occupied nests with greater proportions of dead eggs, had greater testicular asymmetry and shorter sperm heads. Exploration of how these findings correlate with sperm velocity is forthcoming. Collectively my results show that extended exposure to aquatic contaminants can alter gametic characteristics but that these alterations appear to have similar effects across male mating tactics.</p>