100年ぶりにボラに寄生が確認されたヒダビル

2007年7月に三重県の鍋田川河口部に近い汽水域で採集したボラMugil cephalus幼魚の鰓腔壁，2013年3月に岡山県沿岸の瀬戸内海に続く汽水路で採集したボラ未成魚の体表にヒダビルLimnotrachelobdella okae（Moore, 1924）の寄生を認めた。ヒダビルのボラへの寄生は1914年に記録されていたが，それはこれまで見落とされてきた。本報告は，ボラからのヒダビルの100年ぶりの記録である。

One and seven specimens of the fish leech Limnotrachelobdella okae (Moore, 1924) were collected, respectively, from the branchial cavity of a young flathead grey mullet (Mugil cephalus) (Mugiliformes: Mugilidae) in the brackish-water estuary near the mouth of the Nabeta River, Mie Prefecture, central Japan, in June 2007, and from the body surface of five immature flathead grey mullet in a brackish waterway connected to the Seto Inland Sea on the coast of Okayama Prefecture, western Japan, in March 2013. Although the leech was reported from M. cephalus as early as in 1914 in Japan, its record has been overlooked for 100 years. The present collections represent a rediscovery of L. okae from M. cephalus.