ヘミウリ科（Digenea）の精子の特徴：Aphanurus stossichii (Aphanurinae)とEctenurus lepidus (Dinurinae)の最初のデータ

Sperm characters in the Hemiuridae (Digenea): first data on Aphanurus stossichii (Aphanurinae) and Ectenurus lepidus (Dinurinae).

• Hichem Kacem
• Elane G Giese
• Jordi Miquel

抄録

本研究では、ヘミウリ科の未踏亜科であるAphanurinaeとDinurinaeに属する2つのジギネス（Aphanurus stossichii (Monticelli, 1891)とEctenurus lepidus Looss, 1907）の精子の超微細構造解析を初めて行った。2019年3月に、これらのヘミウリ科は、地中海沿岸部のラ・チェバ（チュニジア）沖で捕獲されたボーグ・ブープス（Teleostei, Sparidae）と大西洋アジのトラクルス・トラクルス（Teleostei, Carangidae）の消化管からそれぞれ採集されました。その結果、両精子は、9+'1'軸索が2本、皮質微小管とは無関係な形質膜の外側装飾が精子の前部にあり、皮質微小管の束が1本、皮質微小管の最大数が精子の中央部にあり、ミトコンドリアが1個あることを特徴とする、Bakhoumらのジゲニアン精子細胞のII型を示すことが明らかになった。また、9+'1'トレパクソネマタンパターンを持つ軸索が2本存在すること、平行に並んだ皮質微小管の数が少なく、その数の最大値は中央部（A.stossichii）または後方（E. lepidus）の精子、精子の前部の形質膜の外部装飾、ミトコンドリア1個、核、少量のグリコーゲン顆粒。しかし，研究した2種のヘミウロス類は，精子月前端部と後端部の形態と，A. stossichiiのミトコンドリア基質顆粒の存在によって区別された。

The present work provides the first ultrastructural analysis of spermatozoa of two digeneans (Aphanurus stossichii (Monticelli, 1891) and Ectenurus lepidus Looss, 1907) belonging to the unexplored subfamilies of the Hemiuridae, namely, the Aphanurinae and the Dinurinae. In March 2019, these hemiurids were collected respectively from the digestive tract of the bogue Boops boops (Teleostei, Sparidae) and the Atlantic horse mackerel Trachurus trachurus (Teleostei, Carangidae) captured in the coastal zone of the Mediterranean Sea, off La Chebba (Tunisia). The ultrastructural study reveals that both spermatozoa exhibit the Bakhoum et al.'s type II of the digenean sperm cells characterized by the presence of two 9+'1' axonemes, an external ornamentation of the plasma membrane not associated with cortical microtubules and located in the anterior part of the spermatozoon, a single bundle of cortical microtubules, the maximum number of cortical microtubules located in a middle part of the sperm cell, and one mitochondrion. Moreover, they share several ultrastructural features with the studied spermatozoa of Hemiuridae such as the presence of two axonemes with the 9+'1' trepaxonematan pattern, a reduced number of parallel cortical microtubules organized into one field with their maximum number located in the median (A. stossichii) or posterior (E. lepidus) part of the spermatozoon, an external ornamentation of the plasma membrane in the anterior part of the spermatozoon, one mitochondrion, a nucleus, and a small amount of glycogen granules. However, the two studied hemiurids could be distinguished by the morphology of the anterior and posterior spermatozoon extremities and the presence of mitochondrial matrix granules in A. stossichii.