Elysia mercieri (Pruvot-Fol, 1930)

Description

A small sacoglossan reaching about 7 mm in body length. According to the original description, the body shape resembles Elysia. The parapodia are erect, and their margins bear erect, branched processes arranged in four pairs on each side (the anterior-most pair being very small). In life the ground colour is green, mottled with darker green; the appendages are colourless. The back is also dotted with fine green lines and small opaque white spots. Each parapodium bears two knob-like swellings whose apices give rise to branched processes. A pale red band runs behind each eye and along the parapodial margin.

Distribution

Type locality: Kuto Bay, Île des Pins, New Caledonia, based on specimens collected by Mme A. Pruvot-Fol in 1929. The species has subsequently been recorded across the tropical Indo-West Pacific, with reports from the Red Sea, Malaysia, Australia, New Caledonia, Papua New Guinea, Japan, Guam, and the Line Islands.

Etymology

The original Etymology section (Pruvot-Fol, 1930, p.230) reads: "Dédiée à M. Mercier, négociant à Nouméa" (dedicated to Mr. Mercier, merchant of Nouméa). The specific epithet mercieri honours Mr. Mercier, a merchant in Nouméa, New Caledonia, presumably someone who assisted Mme Pruvot-Fol during her stay in the territory.

Remarks

In the original description Pruvot-Fol erected the new genus Elysiobranchus in the family Elysiidae and placed this species as its type. Elysiobranchus was characterised as having an Elysia-like body shape with erect parapodia bearing four pairs of erect branched processes along the margin. The genus was subsequently synonymised with Elysia, and the species was transferred accordingly (the parentheses in the author citation reflect this generic transfer).

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References

• Elysiobranchus Mercieri n. sp. (genus Elysiobranchus n. g.), Pruvot-Fol A. (1930). Diagnoses provisoires (incomplètes) des espèces nouvelles et liste provisoire des Mollusques nudibranches recueillis par Mme A. Pruvot-Fol en Nouvelle-Calédonie (Île des Pins). Bulletin du Muséum National d'Histoire Naturelle, Paris. (2)2(2): 229-233.
• キスマークミドリガイ (新称: kissmark緑貝), Fukuda H., 1994. Marine Gastropoda (Mollusca) of the Ogasawara Islands (Bonin) Islands. Part 2 : Neogastropoda, Heterobranchia and fossil species, with faunal accounts. Ogasawara Research 20, 1-126
• メルキエリ, 小野篤司. (1999). ウミウシガイドブック. TBSブリタニカ.
• ラクダミドリガイ（新称）, 小野篤司. (2000). ウミウシガイドブック. 第2版. TBSブリタニカ.
• キスマークミドリガイ, 中野理枝. (2004). 本州のウミウシ. ラトルズ.
• キスマークミドリガイ, 小野篤司. (2004). 沖縄のウミウシ. ラトルズ.
• ラクダミドリガイ（改称）, 中野理枝. (2018). 日本のウミウシ. 文一総合出版.
• Elysia mercieri, Terrence Gosliner, Ángel Valdés and David Behrens. (2018). Nudibranch and Sea Slug Identification Indo-Pacific 2nd Edition. New World Pubns Inc.
• キスマークミドリガイ, 小野篤司 & 加藤昌一. (2020). 新版 ウミウシ. 誠文堂新光社.