日本近海で採集されたマンボウ属（Mola spp. A and B）の形態異常個体

2007年6月から2008年12月までの日本近海におけるマンボウ属2種（ Mola spp. A and B）の調査の中で（全145個体），胸鰭変形7個体，背鰭短縮2個体，背鰭軟条配置異常1個体，舵鰭臀部側欠損1個体，舵鰭欠損1個体，人為的な損傷3個体，精巣肥大2個体，幼形形態1個体を得た。これら異常がみられた18個体の内訳には先天的な奇形，捕食生物による損傷，人為的な損傷，寄生虫による変形などがあり，また長期間飼育された個体（1個体）は天然水域の個体と体形が異なる可能性が示唆された。人為的な損傷がみられた3個体と長期飼育された1個体を除く，天然水域で採集された異常個体（14個体）は採集された全体の約1割（14/145）で，ある程度は天然水域にも存在するものと推測された。

Of 145 ocean sunfish specimens obtained from Japanese coastal waters between June 2007 and December 2008, morphologically abnormal forms were confirmed in a total of 18 specimens. Seven had transformed pectoral fins; two had shortened dorsal fins; one had abnormally arranged dorsal soft rays; one was missing the lower part of the clavus; one was missing the whole clavus; three had partially damaged bodies or fins, probably because of artificial cutting; two had hypertrophied testes; and one was a young fish in the juvenile-specific morphological form. These abnormal forms were thought to have occurred as a consequence of congenital malformation or damage by predation, parasites, humans, or other factors. One suffered a transformation in body shape from a natural form, probably because it was reared for a long period of time in an aquarium. According to the frequency of non-artifically abnormal individuals (ca. 10%, 14/145), the occurrence of abnormalities is not rare in natural populations.