Within-female sperm allocation—Males inseminate at three different female body sites according to female mating history in a squid

Theory predicts that males should allocate their costly sperm according to future mate availability and focal female conditions, e.g. promiscuity and fecundity, to maximise lifetime reproductive success. Some squids show insemination site polymorphism within a female—males deposit sperm capsules at different female body locations. Whether the choice of insemination site is influenced by the sperm-storing status of the female remains untested. We studied the squid Loliolus sumatrensis – the females possess three insemination sites: the buccal membrane (BM), basal left IV arm (ARM) and lateral head behind the left eye (EYE). Analysis of seasonal dynamics identified a set priority for the initial use of insemination sites as BM then ARM then EYE, whereas the maximum number of stored spermatangia was greater as EYE>ARM>BM. The maturity status of females was correlated with the pattern, but not number, of inseminations. We found multiple paternity at all sites and the same genotypes in spermatangia collected from all three sites, suggesting male squids allocate their sperm to multiple insemination sites during a single mating episode according to the status of female sperm-storage. This study uncovered unusual within-female sperm allocation – male mating behaviours were influenced by female mating history.