A study published Dec. 31 in PLOS ONE demonstrates how fear of danger does not deter the dumpling squid from mating, illustrating the trade-off between survival and reproduction.
In order to reproduce, the male uses his arms to hold the female in place and inserts the hectocotylus, the sperm-insertion organ, into the female's spermatheca, the sperm-storage organ. The sperm transfer occurs at the start of copulation, but the act lasts up to three hours to ensure the sperm has reached its destination. The encounter ends when the male jerks his hectocotylus out of the female.
The male must survive long enough to complete this act, but the female must live long enough to lay eggs and raise the resulting offspring, so use of survival methods, such as inking or jetting, differ among the male dumpling squid and the female.
For the experiment, the researchers used a sand flathead (Platycephalus bassensis) as the predator. They are "medium-sized, ambush predators" found in the same areas as dumpling squid. The flatheads will eat crabs, shrimp, small fish and squid.
The researchers observed the mating ritual of the dumpling squid when there was no predator involved, when the predator was present before copulation and when the predator was introduced during the act.
Females inked (ejected ink as a distraction or smokescreen) more often than males before mating began when there was a sand flathead present. The inclusion of a predator did not hinder copulation, change duration or likelihood, researchers found. Males were generally undeterred by the threat of a predator.
When the sand flathead was introduced during copulation, the instance of inking or jetting was lower. Researchers believe there could be a few reasons, such as the energy required for inking or jetting would not be available during the energy-zapping copulation or possibly that the male's grip on the female is too hard for her exhibit a physical reaction to predators.
"Overall, dumpling squid may show little change in mating behavior in response to the presence of sand flathead because the benefits of mating outweigh the perceived risk of predation," researchers wrote.
