Previously known only from Hawaii, but see records on Forum [#13665] from Solomon Ids and Marshall Ids.
Kwajalein Atoll, Marshall Islands; Depth 10m; Length 32mm; Date 4 September 1989, daytime; under rock; Photographer: Scott Johnson.
Pease (1860) placed this species in a new genus Histiophorus but although his description was not illustrated, his mention of a 'vertically compressed tail' and dorso-ventral tufts with a 'oval glandular body' at the tip clearly suggest he was describing a species of Plocamopherus. I have summarised and amalgamated his descriptions of the genus and species below:
‘Animal oblong, no distinct mantle. Body rounded; posterior portion prolonged into a vertically compressed tail, furnished above with a membranaceous crest. Branchiae three, inserted at the middle portion of the dorsal region. Dorsal tentacles, no labial appendages. Head furnished with a veil. Foot linear. …. Three tufts of filaments on each side, disposed longitudinally, and also two on dorsal region: to each of the hinder tufts is attached an oval glandular body … Colour pale whitish-ash, irregularly dotted with orange above, and four small crimson dots near base of branchial plumes. Branchiae pale and freckled with brown. Dorsal tentacles green-olive, tips pale. Veil yellow. Length 1.25 inches. … An active animal, using its compressed tail for swimming ' (Pease, 1860).
To my knowledge it has not been recognised again until Kay & Young's (1969) report on 3 further specimens from Hawaii, 7 - 21 mm long. They describe the colour as 'almost transparent white and spotted with orange and yellow'. Unlike the 3 pairs of dorso-lateral processes described by Pease, their animals have 2 processes on either side of the body, the anterior pair filamentous, the posterior pair just behind the branchiae with spherical termini.
Bertsch, H. & Johnson, S., 1981. Hawaiian Nudibranchs. Honolulu: Oriental Publishing Co. [as P. tilesii ]
Pease, W.H. (1860) Descriptions of a new species of mollusca from the Sandwich Islands. Part 1. Proceedings of the Zoological Society of London, 28: 18-36
Kay, E.A. & Young, D.K. (1969) The Doridacea (Opisthobranchia; Mollusca) of the Hawaiian Islands. Pacific Science, 23(2): 172-231
Rudman, W.B., 2003 (November 12) Plocamopherus maculatus (Pease, 1860). [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/plocmacu
New distribution records for Plocamopherus maculatus
From: Scott Johnson, April 29, 2005
Plocamopherus maculatus from Hawaii
From: Keoki Stender, November 14, 2003