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

## TL;DR

Female squid store sperm in two places, and this behavior is linked to male competition and a higher number of males in the population.

## Contribution

The study shows that the same males use both sperm storage sites in Enoploteuthis chunii, suggesting a new strategy for sperm allocation.

## Key findings

- Females of Enoploteuthis chunii use both a major sperm receptacle and a cryptic sperm pocket.
- CSP utilization increases as the reproductive season progresses.
- Male-biased sex ratios correlate with CSP use, indicating male competition.

## Abstract

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.