Akera bullata from Dorset, UK

Dear Helen,
Thanks for these very welcome photos. Apart from D.P.Wilson's photos in Thompson (1976) of swimming animals I don't think I have seen photos of them crawling like this. Although externally they look nothing like a sea hare, their anatomy [see Fact Sheet] shows their close relationship. Their large external, thinly calcified shell, like those in many cephalasideans and sacoglossans, suggests that all these opisthobranch groups arose from ancestors in which the calcified external shell of a snail was gradually lost as they evolved into 'slugs'.

 I am very interested to hear that it will eat the red alga Chondrus as I can find no information on its diet. Thompson & Seaward (1989) observed that in summer Akera fed on rafts of the green alga Enteromorpha and during the remainder of the year the brown gritty faeces suggested they fed directly on the sediment.  Certainly aplysiids tend to prefer red algae and are facultatively 'de-inked' if they have no red algae in their diet. I would be interested to hear of any other information you have on its diet, because we have no information on the Indo-West Pacific species A. soluta.

• Thompson, T. E. (1976) Biology of opisthobranch molluscs. London, Ray Society no. 151.  1-207.

Best wishes,
Bill Rudman