Reproductive status of Opisthoteuthis sp. over an annual cycle

Abstract

The reproductive biology of deepwater cephalopods has received relatively little attention. The cirrate octopus Opisthoteuthis sp. is a regular bycatch in deep benthic trawls from 800 to 1 200 m deep west of Scotland. Specimens were sampled throughout the seasonal cycle. Mature females occurred over a broad size range (600 - <3 000 g wet mass), suggesting considerable growth after maturity, with eggs released singly over a long period of time. Them was no significant difference in the gonadosomatic index between spring, autumn and winter samples (p > 0.05), suggesting that there is no seasonal influence on the reproductive status of the population. The ovary of mature females contains eggs ranging in size from <1 mm to a maximum of 12 mm, and each egg is attached in the ovary by a short stalk. Mature females with mature eggs in the distal oviduct, after encapsulation by the single oviducal gland and ready for release, were recorded throughout the annual cycle, further suggesting that timing of spawning is not related to season.