Plocamopherus cf ceylonicus (Kelaart, 1858)

Plocamopherus cf ceylonicus is known in the Marshalls from many specimens found at Enewetak and Kwajalein Atolls. The 16 Enewetak specimens were found under dead coral or aluminum siding storm debris on lagoon reefs and pinnacles at depths of 3 to 11 meters. The rest are from Kwajalein, where they can be fairly commonly found feeding on bryozoans growing on clumps of Halimeda algae on a particular shallow lagoon sand spit in 6 to 8 meters. Specimens ranged from 6 to 27mm in length. Like some other members of the genus Plocamopherus, this species has several patches on the body that phosphoresce when the animal is disturbed. Also, the tail is flattened into a kind of keel, which the animal can use for swimming. It swims by laterally bending the body back and forth, lifting the animal up in the water in an upside down position. One specimen deposited an orange yellow egg mass in captivity. Ova measured 90 to 100 µm in ovoid capsules measuring 173 to 205µm.

Although I reported this as Plocamopherus ceylonicus in an earlier publication on Marshall Islands nudibranchs (Johnson & Boucher, 1984), looking at photographs attributed to this species on the Sea Slug Forum have given me second thoughts. I now believe this is a different, possibly undescribed, species.

The first two photos below are of Enewetak specimens.

The remaining photos were taken at Kwajalein. The one just below shows an animal in the clump of Halimeda cylindracea where it was living.

Created 3 January 2007
Updated 24 October 2008

Reference:

Johnson, S. & L.M. Boucher. 1984. Notes on some Opisthobranchia (Mollusca: Gastropoda) from the Marshall Islands, including 57 new records. Pacific Science 37(3)251-291.