Within-female sperm allocation in Enoploteuthis chunii is associated with polyandry and male-biased sex ratio.

One of the unusual reproductive features in cephalopods is the flexibility of sperm deposition sites in females. Recently we reported that female Enoploteuthis chunii possess not only a major sperm receptacle (MSR) but also a cryptic sperm pocket (CSP) and CSP utilization increases towards the end of the reproductive season. This may occur due to male-male competition over insemination sites, as a male-biased sex ratio and CSP utilization are tightly correlated. The microsatellite-based genotyping revealed that both MSR and CSP are used by the same males, a similar phenomenon previously found in Loliolus sumatrensis , which is herein hypothesized to be a strategy associated with sperm allocation.