Temporal dynamics of mating and paternity in the squid Loligo pealeii

We investigated short-term changes in relative paternity among a female's offspring in the long-finned squid Loligo pealeii. We conducted mating trials in the laboratory in which a single female mated with 2 males over the course of a few hours while laying successive egg capsules. Through microsatellite typing, we determined the males' relative paternities for the first and second egg capsules laid during each of 10 mating trials. Relative paternity of the first egg capsule was typically in favor of the first male to mate in the trial, although this was the only male to mate before the the first egg capsule was laid. When the female mated with an additional male before the second egg capsule was laid (all 10 trials), the first male to mate typically continued to achieve high relative paternity in the second capsule when the interval between first mating and second egg laying was relatively brief (i.e. 40 min or less). Dramatic differences in relative paternity were observed in the second capsule when the interval between the first mating and the laying of the second egg capsule was longer than 140 min. The present study argues against routine second and later-male sperm precedence in loliginid squids, pointing to other influences on paternity, such as the interval between insemination and egg laying.