Life history, mating behavior, and multiple paternity in Octopus oliveri (Berry, 1914) (Cephalopoda : Octopodidae)

Abstract

Extremely little is known about Octopus oliveri, its life history, distribution, or behavior. It was originally found in the Kermadec Islands, and since then has been described in Japan and Hawai´i. This study establishes the identity of Octopus oliveri through the use of genetic testing (COI marker) and morphological characteristics. In addition, mating behavior, brooding time, egg development, and paralarvae of Octopus oliveri, are described for the first time. Females lay approximately 5000 eggs and brood them for 33 to 47 days. Females and males mate with multiple partners when housed communally in tanks. As is true with most octopuses, female O. oliveri have two oviducts for sperm storage and may be able to store viable sperm for at least 100 days and up to 10 months. This suggests that sperm selection or competition may be occurring, however it has rarely been studied in octopods and never in O. oliveri. Through a combination of behavioral and genetic studies, this research found multiple paternity to be the rule in Octopus oliveri, both in the field and in captivity. Four sets of behavioral experiments were recorded wherein six females were mated with three males in varying order, for a total of 24 females and 12 males. Mating pairs mated in the reach, mount and beak-to-beak positions. In the behavioral trials, the largest females mated for the longest amount of time. Five microsatellite markers were developed and used to test paternity in eleven egg broods resulting from the behavioral trials. The results showed skewed paternity in most broods, suggesting that sperm competition is present in this species. The two predictive variables in determining male mating success were mate order and male size. The first male to mate with a female in behavioral experiments was more likely to sire more offspring, as were the largest males. This is the first study in an octopus that combines both behavioral and genetic information to determine fertilization success. This study contributes to the growing research on cephalopod mating systems and in particular shows that octopus mating dynamics may be more complex than previously thought.