Linking male and female morphology to reproductive success in captive southern calamary (Sepioteuthis australis)

Abstract

Sexual selection theory predicts that mating success influences the evolution of traits. Previous behavioural observations of male Sepioteuthis australis have revealed two main mating strategies in the field: (1) large dominant males pair and mate with females, which they defend from (2) smaller males attempting to mate using ‘sneaker’ tactics. The current study examined whether fertilisation of squid eggs laid by polyandrous females within a mesocosm reflected this field-observed size-based mating system. Polymorphic microsatellite loci were used to identify mothers and fathers of embryos, which in turn allowed us to determine the effect of body size, age, and nine other morphological traits on reproductive success. Parentage of 112 embryos was assigned among 14 possible females and 20 candidate males of varying sizes. The mating behaviour observed in captivity was consistent with the size-based strategies seen in the field yet large males did not sire proportionally more offspring; instead nearly all males, regardless of size, sired some offspring. Regression analyses indicated that females did not select sperm based on male size, shape or age. Surprisingly, female contributions were skewed, with younger females contributing more eggs than older females. The possibility of male mate-choice was explored. - See more at: http://www.publish.csiro.au/paper/MF04287