Multiple paternity but no evidence of biased sperm use in female dumpling squid Euprymna tasmanica

摘要

Assessing the natural level of multiple paternity and sperm-use patterns provides important information regarding sperm competition and the potential for cryptic female mate choice. We developed 5 novel polymorphic microsatellites for the dumpling squid Euprymna tasmanica and used them to measure multiple paternity from both field- and laboratory-laid clutches. All clutches had multiple paternity, with a minimum of 2 to 4 sires per clutch, consistent with benefits to females of polyandry in this species, and indicating strong potential for sperm competition. We found a higher level of multiple paternity within field-laid eggs than in the first and second clutches from females that laid in the laboratory. The level of multiple paternity did not change over successive clutches from individual laboratory females and sperm from different males did not consistently dominate separate clutches, although individual females differed in patterns of sperm use. This suggests that spermatangia may be somewhat mixed within the female spermatheca at the time of fertilisation. Sperm competition is enhanced by high sperm longevity, and we found that viable sperm could be stored for up to 145 d in the laboratory. Overall, our results suggest strong potential for post-copulatory sexual selection in this species, due to the presence of sperm from multiple males in the female sperm storage organ competing for fertilisation of the female's eggs.