Desmopterus papilio Chun, 1889

Description

A thecosomatous pteropod that completely lacks a shell in the adult stage. The body is rounded-cylindrical, 0.5–2 mm in length. The parapodia are fused into a disc-shaped swimming plate 2–4 mm in diameter, composed of five lobes. The swimming plate is transparent with only a few visible muscle fibers. A pair of reddish, flattened, elongate wing tentacles arise between the lateral lobes of the swimming plate. The posterior end of the body is slightly coiled. Small reddish gland cells are scattered in the integument.

Distribution

Widely distributed in warm waters of the Indian Ocean, Red Sea, Pacific Ocean, and Atlantic Ocean, tending to avoid upwelling zones. Common in the Kuroshio-influenced warm waters around Japan. Type locality: eastern Atlantic Ocean off the Canary Islands.

Etymology

The genus name Desmopterus derives from Greek desmos (band) and pteron (wing), referring to the band-like parapodia. The specific epithet papilio is Latin for "butterfly", alluding to the butterfly-like shape of the swimming plate. The Japanese common name kochō-kamegai (胡蝶亀貝, "butterfly shell") likewise refers to this resemblance.

Remarks

A member of the family Desmopteridae. Protandric hermaphrodite. Phytophagous, feeding on microplankton captured with mucus. Epipelagic. Belongs to the suborder Pseudothecosomata and completely lacks a shell in the adult stage. Cymbulia cirroptera Gegenbaur, 1855 may be a larval stage of this species; if confirmed, that name would take priority. The congeneric D. pacificus Essenberg, 1919 from the Pacific differs in having shorter wing tentacles.

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References

• コチョウカメガイ Desmopterus papilio Chun, 1889, 奥谷喬司. (2016). わが国近海に見られる浮遊性巻貝類―VI. 有殻翼足類・ミジンウキマイマイ科及び擬有殻翼足類. うみうし通信, 93, 4–5.