Platydoris cinereobranchiata is not particularly common in the Marshalls, known from maybe 30 specimens from Kwajalein and Enewetak Atolls. The species seem to be most common in shallow water, with several of the recorded specimens coming from the intertidal to a depth of 2.5 meters. One was found at a depth of 16 meters. Several have been found in lagoon patches of Halimeda algae. Sizes of four measured specimens ranged from 45 to 95mm. This species is a bit of a puzzle. Dorsally, with its brown rhinophores with white tips, grayish gills, and lack of dark spots on the rhinophore and gill sheaths, it is close to the description of Platydoris cinereobranchiata. However, Dorgan et al (2002) describe the underside as "scattered with very small dark spots" while our specimens are scattered with variably sized red blotches. One specimen (not figured) found by Lori Bell on the Kwajalein interisland intertidal reef appeared to have the brown sieve-like network of P. cinereobranchiata overlaying a fainter pattern of brown lines like those in P. cruenta. We formerly had this as the very similar Platydoris formosa, which differs in having red rhinophore clubs and distinct black spotting on white around the rhinophore and branchial sheaths.
The specimen below was small for the species.
This one was under a dead table Acropora coral that had brown gorgonian growing around its edges.
The white-tipped brown rhinophores of Platydoris cinereobranchiata.
The red-spotted underside was not reported in the original description of the species.
The two shots below are of a 70mm specimen from Enewetak that had autotomized the front portion of its mantle.
These have also been seen at Rongelap Atoll by John and Lynette Flynn (as P. formosa) and by Ken Cone and Beth Van Zummeren.
Created 15 December 2006
Updated 3 May 2021