Euselenops luniceps (Cuvier, 1816)

Description

A medium-sized side-gilled sea slug reaching 50–110 mm in length. The body is dorsoventrally flattened, broad and rounded, with a large crescent-shaped oral veil extending in front of the head. The veil bears dense sensory papillae along its front edge, used to detect prey. Ground colour is brown to greyish brown, scattered with irregular black blotches over the entire body. The rhinophores have a translucent white base, a black band in the middle, and a white tip. The foot is larger than the mantle, and the mantle extends posteriorly into a slender siphon. A small reduced internal shell lies under the right side of the mantle.

Distribution

Widespread across the tropical and warm-temperate Indo-West Pacific, recorded from eastern Africa (Tanzania, Mozambique, South Africa) eastward through Indonesia, the Philippines, Australia, Papua New Guinea, Japan, and as far as the Hawaiian Islands.

Etymology

From Latin luna (moon) and -ceps (head), referring to the crescent or half-moon shape of the broad oral veil.

Remarks

A nocturnal sand-dweller. During the day the animal buries itself in sand; at night it crawls across the sand surface, and when disturbed it can swim briefly with undulating movements of the body. The fringe of sensory papillae along the oral veil is held against the substrate and used to detect prey buried in the sand, thought to include small crustaceans and other animal matter. Like other heterobranchs the species is a simultaneous hermaphrodite and reciprocal mating between partners has been observed. The animal also shows a notable capacity to regenerate lost tissue within days. Originally described as Pleurobranchus luniceps and later transferred to Euselenops.

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References

• Pleurobranchus luniceps, Cuvier G. (1816). Le règne animal distribué d'après son organisation, pour servir de base à l'histoire naturelle des animaux et d'introduction à l'anatomie comparée. Tome 4. Deterville, Paris. 255 pp.
• マダラウミフクロウ, 生物學御研究所編. (1955). 相模湾産後鰓類図譜〈補遺〉. 岩波書店.
• マダラウミフクロウ, 鈴木敬宇. (2000). ウミウシガイドブック〈2〉. TBSブリタニカ.
• マダラウミフクロウ, 殿塚孝昌. (2003). ウミウシガイドブック〈3〉. TBSブリタニカ.
• マダラウミフクロウ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• Euselenops luniceps, Terrence Gosliner, Ángel Valdés and David Behrens. (2015). Nudibranch and Sea Slug Identification Indo-Pacific. New World Pubns Inc.