Data supporting: Molecular, behavioural and morphological comparisons of sperm adaptations in a fish with alternative mating tactics

In species with alternative reproductive tactics, there is much empirical support that sneaker males have larger testes size and greater sperm numbers. However, support for higher sperm performance by sneakers is inconsistent. We used the sand goby (Pomatoschistus minutus) to test whether sperm performance differed between breeding-coloured males (small testes, but large mucus-filled sperm-duct glands; builds a nest lined with a sperm-containing mucus, provides care) and sneaker-morph males (no breeding colouration, large testes, rudimentary sperm-duct glands; no nest, no care). We compared motility (proportion motile sperm), velocity and longevity of sperm, between the two morphs. Furthermore, we compared gene expression of testes, and tested if the sperm-duct gland contents affected sperm performance, and if sperm morphometrics differed between male morphs. We found a clear difference in gene expression of testes between the male morphs with 109 transcripts differentially expressed be...