幻のエビ、ムラサキエビモドキを45年ぶりに発見―共生するユムシ類の種も明らかに―

2026-09-07 京都大学

京都大学などの研究グループは、和歌山県南部の潮間帯で、約45年間確認されていなかったテッポウエビ類「ムラサキエビモドキ」を再発見しました。本種はユムシ類が掘った巣穴や体表を住みかとして利用し、ユムシの粘液を餌としていると考えられています。さらに遺伝子解析から、ムラサキエビモドキは特定の1種だけでなく、サビネミドリユムシ属とタテジマユムシ属に属する少なくとも2属4種を宿主として利用することが判明しました。潮間帯は比較的調査が進んだ環境であるにもかかわらず、長期間見つからなかった生物とその共生関係を明らかにした点で重要です。ユムシ類を中心とする共生系の理解を深め、潮間帯の生物多様性や保全生態学に貢献する成果です。

幻のエビ、ムラサキエビモドキを45年ぶりに発見―共生するユムシ類の種も明らかに―

再発見されたムラサキエビモドキAthanopsis dentipes(撮影者:花岡朋哉)

<関連情報>

紅白色の体色を持つ、ユムシ共生性テッポウエビ類エビムラサキエビモドキの再発見と宿主範囲の拡張 Rediscovery of the Red-And-White Commensal Shrimp Athanopsis dentipes (Alpheidae), Revealing an Expanded Host Range Among Spoon Worms (Annelida: Thalassematidae)

Tomoya Hanaoka, Isao Hirabayashi, Takahiro Sugiyama, Keiichi Nomura, Gyo Itani, Michitaka Shimomura, Ryutaro Goto

Zoological Science  Published:5 August 2026

DOI:https://doi.org/10.2108/zs250106

Abstract

The commensal shrimp genus Athanopsis Coutière, 1897 (Alpheidae) includes nine species worldwide. Almost all congeners have been confirmed to be associated with spoon worms (Annelida: Thalassematidae). Athanopsis dentipes Miya, 1980 was originally described about 45 years ago based only on the male specimens collected along with the thalassematid spoon worm Anelassorhynchus cf. mucosus (Ikeda, 1904) in Kyushu Island, western Japan. However, it has never been collected since its original description. In this study, we rediscovered this species in the intertidal zone of the southern Kii Peninsula, Wakayama Prefecture, central Japan, and redescribed it based on both male and female specimens. Morphologically, this species is distinguished from its closest relative, Athanopsis australis Banner and Banner, 1982, by its ventrally straight rostrum, a large tooth at the cutting edge on the dactylus of major chela, and a small subacute tooth at the ventrolateral distal angle on the merus of third pereopod. All of the specimens were associated with thalassematid hosts, including two genera and four species of Thalassematini—i.e., Listriolobus cf. sorbillans (Lampert, 1883) and three species of Anelassorhynchus Annandale, 1922—substantially expanding the known host range of this shrimp species. The shrimps were observed to scuttle over the body surface of the host in the aquaria. One male–female pair was collected from the same host in February, and two ovigerous females were collected in February and April.

1903自然環境保全
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