Volvulella acuminata
Bruguiere, 1792

Order: CEPHALASPIDEA
Family: Retusidae

DISTRIBUTION

North west Europe from Norway to the Mediterranean

PHOTO

Locality: Off Gnejna Bay, 20 metres, Malta, Mediterranean, August 2007, in fine sand near Posidonia seaweeds. Length: 3 mm. Photographer: C. Mifsud.

Species of Volvulella are distinguished externally from other small, shelled cephalaspideans by the pointed extension at the posterior end of the shell. They are usually considered to be related to the Retusidae but lack both radula and gizzard plates. Little is known of their biology and natural history other than they live in sand and sandy mud.

Volvulella and Rhizorus. Unfortunately many shelled opisthobranchs have been named on the basis of their shells alone, and this is a case in point. For the last 100 years there has been an on-going debate, unhappily still unresolved, over the names Volvulella Newton, 1891 [for Bulla acuminata Bruguiere, 1792] and Rhizorus Montfort, 1810 [for R. adelaidis Montfort, 1810] and whether they are synonyms. The shells certainly look the same but as they were described only on the shell it is very difficult. On top of that, Mediterranean and Nth American workers seem to prefer Volvulella while workers on the Nth Atlantic and Australian - New Zealand regions have opted for Rhizorus.

Authorship details
Rudman, W.B., 2008 (June 30) Volvulella acuminata Bruguiere, 1792. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/volvacum

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