Phyllodesmium karenae Moore & Gosliner, 2009

Location: Gorilla Chop, Okinawa Island (Motobu and Northern area), Okinawa, Japan
Date: 2023/09/05
Length: 10mm
Depth: 10.0m
Water temperature: 27.0℃

Description

Phyllodesmium karenae is a small, delicate aeolid nudibranch. The living animal is elongate, with the edges of the foot extending just beyond the mantle. The body is predominantly transparent with a bluish hue, so that the viscera and gonad show through the mantle, and there are no opaque markings on the dorsum. The cerata are elongate, smooth and cylindrical, largest toward the middle of the back, with curled, prehensile-looking tips. Inside each ceras the digestive gland is straight and unbranched, a uniform brownish-purple, while the extreme tip is capped by yellow-cream epithelium. The cerata contain no zooxanthellae and lack a cnidosac and nematocysts. The rhinophores are smooth and about two-thirds the length of the oral tentacles, shading from brownish-purple to a yellow-cream tip; the oral tentacles are transparent to faintly bluish at the base with yellow-cream tips. The single preserved type specimen measured about 8 mm.

Distribution

The type locality is Matotonggil Rock, Mabini, Batangas Province, southern Luzon Island, Philippines, at 0–17 m. At the time of its description the species was known from southern Luzon and from Indonesia, where it had been figured as Phyllodesmium sp. 7 by Gosliner, Behrens & Valdés (2008).

Etymology

The specific epithet karenae honours the senior author Elizabeth Moore's mother, Karen, for her years of support and enthusiasm for the study of marine life.

Remarks

Most members of the genus Phyllodesmium feed on octocorals (soft corals) and store symbiotic zooxanthellae in their cerata, functioning as “solar-powered” sea slugs that use the products of photosynthesis. P. karenae is unusual in lacking zooxanthellae, and its prey has not yet been observed; in phylogenetic analysis it falls near the base of the genus. It most closely resembles the transparent Phyllodesmium opalescens but differs in lacking opaque white markings on the dorsum. It has been found among sand and rocks.