Umbraculum umbraculum ([Lightfoot], 1786)

Location: Akinohama, Izu Oshima, Tokyo, Japan
Date: 2015/02/12
Length: 150mm
Depth: 6.0m
Water temperature: 16.0℃

Description

A large pleurobranchomorph reaching about 280 mm in length, with a flat parasol-like external shell sitting on top of the dorsum. Body colour highly variable through reddish brown, brown and orange, sometimes green. The fleshy mantle is decorated with low pale yellow to greyish-white wart-like tubercles. The pair of short rhinophores sits between the soft body and the shell. Lives on rocky substrates and feeds on sponges; produces a yellow to red defensive secretion when disturbed.

Distribution

Circumtropical and warm-temperate, occurring across the Indian Ocean, the entire Pacific (including Hawaii) and the Mediterranean. Records include South Africa, Tanzania, Madagascar, Aldabra, Japan, Hawaii, Central America and the Mediterranean. The Portland Catalogue 1786 listed the type material as "from China", citing Humphrey's Conchology pl. 5 fig. 5.

Etymology

The specific epithet umbraculum is the Latin for "small parasol" or "sunshade", in reference to the conspicuous external shell that resembles a flat parasol — the basis of the English vernacular "umbrella slug".

Remarks

Originally described as Patella umbraculum in lot 3830 of the [Lightfoot] (1786) Catalogue of the Portland Museum. The species is the type of the genus Umbraculum Schumacher, 1817, leading to the curious tautonym now in use. The 1786 Portland Catalogue is anonymous; ICZN attributes authorship to the Rev. John Lightfoot with the year in brackets to indicate inferred authorship.