Nothing vulgar about Octopus vulgaris!
The common octopus (Octopus vulgaris) received its unprepossessing name because it is supposedly common everywhere. It occurs in every ocean where the water is warm enough for exploration by wetsuited divers. The vulgar octopus hates cold waters and established itself worldwide between latitudes 50 of both North and South. However, the well established point of view that this species is a cosmopolitan citizen began to be shaken because, one by one, different populations were found to be different species.
The common octopus from Ascension Island was already supposed to be a distinct creature, and was once upon a time described as Octopus occidentalis. However, later on this name was considered to be a junior synonym of Octopus vulgaris though it is still likely to be a new species. The Ascension octopus could be thought of as underscribed … or more precisely, under-described.
[caption id="attachment_337" align="aligncenter" width="584"] The octopus resident in his den during the day. Nicknamed "Roger" by the team, we'll be visiting regularly to see what scraps he leaves outside.
Virtually nothing is known about the biology of this octopus, and because of this when Dr Jude Brown discovered a den during one of her dives surveys, we decided to have a closer look at the behaviour of this animal, and to include repeated return visits to the den when possible. Whenever we arrived at its shelter at each day we would find the creature sitting inside and watching us with its wise and wrinkled eyes of an elderly gentleman.
The den itself consisted of a few random volcanic pebbles scattered around and was a perfect disguise for a predatory ambusher. Leftovers of the day’s food betrayed the fact that this soft bodied animal used to leave its den at night, invisible to predators. With many hungry fish lurking around any camouflage would be useful.
During the first week of observation its daily prey consisted of one to three bivalve molluscs Americardia media, sometimes spiced by some meaty cowrie Luria lurida. No fish, no crustaceans. Our octopus appears to have a very particular diet but we shall see whether it will change its food preferences during the forthcoming two weeks.
- Post supplied by Dr Vladimir Laptikhovsky.