Data set for sperm storage in female squid, Todarodes pacificus

Female eumetazoans often develop sperm storage organs (SSOs). Although the
processes of sperm storage may influence post-copulatory sexual selection
in polyandrous species, the significance of multiple SSOs is not
understood. In contrast to coastal squids (which develop no more than two
SSOs), the female Todarodes pacificus, a more oceanic species, develops
more than 20 SSOs, which take the form of specialized pockets, called
seminal receptacles (SRs), near the mouth. We investigated the sperm
storage pattern of SRs by paternity analysis of hatchlings obtained after
artificial insemination using sperm retrieved from 6 arbitrarily selected
SRs. The results showed that females were capable of storing sperm
contributed by 9 to 23 males, indicating that females are broadly
promiscuous. In the pattern of sperm storage, the number of males and
proportion of their sperm present in the SRs varied among SRs, and sperm
storage was biased towards particular males at the individual SR level.
However, when calculated as a proportion of all the SRs within a female,
the number of sires increased and the paternity bias towards any
particular male weakened. These results suggest that one function of
having multiple SRs in T. pacificus may be to ensure genetic diversity of
the offspring.