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/find/plocmacu
April 29, 2005
From: Scott Johnson
I noticed that Plocamopherus maculatus is thought to be restricted to Hawaii. Actually, I have also found the species here in the Marshall Islands and in the Solomon Islands as well. H107 shows a Hawaiian specimen, while E206 was photographed at Kwajalein, Marshall Islands, and S049 off Guadalcanal in the Solomons. It is primarily found at night, usually wandering around in ledges and small caves at depths of about 5 to 20 meters. This is one of those species that "lights up" when disturbed, with spots of glowing light that last a few seconds after the animal is touched. I seem to remember this was the feature that encouraged me to misidentify it as P. tilesii in Hans Bertsch's and my Hawaiian Nudibranchs (page 81); I had read of similar phosphorescence in P. tilesii and figured ours was a variation - now an obvious error. It is a fascinating species and does indeed use that flattened tail to swim upside down if it falls off the cave walls.
Since the three specimens pictured are from different areas, I'm including three sets of data:
H107 Pupukea, Oahu, Hawaii; Depth 14m; Length 30mm; Date 21 April 1985, night dive; crawling in ledge; Photographer: Scott Johnson.
E206 Kwajalein Atoll, Marshall Islands; Depth 10m; Length 32mm; Date 4 September 1989, daytime; under rock; Photographer: Scott Johnson.
S049 Boneghi, Guadalcanal, Solomon Islands; Depth 15m; Length 26mm; Date 26 August 1987, night dive; in small ledge; Photographer: Scott Johnson
Bertsch, H. & Johnson, S., 1981. Hawaiian Nudibranchs. Honolulu: Oriental Publishing Co.
email@example.comJohnson, S., 2005 (Apr 29) New distribution records for Plocamopherus maculatus. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/13665
It's good to get a better idea of this species, and you records, especially from the Solomons certainly suggest we should look through our unidentified species from the Indo-West Pacific.
November 14, 2003
From: Keoki Stender
You can add Plocamopherus maculatus to the species list with this photo if you'd like. This is a rare species here.
Date: Aug. 2003
Location: Pupukea Beach Park, North Shore, Oahu, Hawaii
Habitat: On cave ceiling, 7 meters
firstname.lastname@example.orgStender, K., 2003 (Nov 14) Plocamopherus maculatus from Hawaii. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11344
As far as I know, there have only been two previously published reports of this species, and they have both been from Hawaii. So your message is a valuable addition to our knowledge and the first opportunity most of us have had to see a photo of the living animal.