Promiscuous squid fatigued after mating

Our research into the energetic costs of mating in dumpling squid (Euprymna tasmanica) revealed that copulation significantly reduces the endurance of both sexes, and they can take up to 30 minutes to recover.

The costs of mating, particularly the energetic costs, are poorly studied in most taxa despite the contribution this research can make to our understanding of the evolution of life histories, particularly in promiscuous species. Cephalopods provide an ideal model system to investigate costs of copulation because they are promiscuous (which compounds the costs of mating) and live for less than a year (which concentrates the costs within a short period). Research into copulatory costs in cephalopods can provide an insight into the evolution of reproductive strategies and behaviours in this group.

We used wild-caught dumpling squid to investigate the energetic cost of copulation and subsequent recovery time. Copulation in dumpling squid can last up to three hours and the male must physically restrain the female. We found that the swimming ability of males and females was reduced by mating, and squid took approximately 30 minutes post-copulation to recover their endurance capacity. We suspect the reduced endurance of males arises because they must physically restrain the female, while the reduction in female endurance is likely to be due to a reduced intake of oxygen while being gripped by the male.

This reduction in endurance can have important ecological implications for squid. Reduced swimming may mean that squid are more vulnerable to predation, have temporarily reduced foraging ability, or be less competitive in seeking further mating opportunities. We believe that the results of this study highlight the need to account for energetic costs when assessing the costs of mating.

To learn more, read the full paper here:

Franklin, A.M., Squires, Z.E. and Stuart-Fox, D. 2012. The energetic cost of mating in a promiscuous cephalopod.
Biology Letters, 8: 754-756. PDF

Or view the media coverage of the study:

Sex makes squid exhausted, says scientists – Australian Geographic (19 July 2012)
Ink or swim: exhausted lover’s squid pro quo – The Age (19 July 2012)
The price of heavy mating – Science Alert (19 July 2012)
Dumpling squid slowed down by sex – BBC News (18 July 2012)
Sex under the sea – Cosmos Magazine (9 July 2012)

Photo credit: Mark Norman