The present study describes the ultrastructural organization of the mature spermatozoon of the lepocreadioid digenean Prodistomum polonii (Lepocreadiidae) by means of transmission electron microscopy (TEM). Live digeneans were collected from the digestive tract of the Atlantic horse mackerel Trachurus trachurus (Teleostei, Carangidae) captured in the coastal zone of the Mediterranean Sea, off La Chebba (Tunisia). The study reveals that the mature sperm cell of P. polonii is a filiform cell, which is tapered at both extremities. It exhibits the Bakhoum et al.’s type III of the digeneans spermatozoon characterized by the presence of: two 9+‘1’ axonemes, external ornamentation of the plasma membrane associated with cortical microtubules and located in the posterior part of the anterior region, two bundles of parallel cortical microtubules with their maximum number (15 microtubules) located in the middle part, and the presence of two mitochondria (one of them of moniliform type). According to the location of the external ornamentation, the male gamete of P. polonii presents a Quilichini et al.’s type 2 spermatozoon. Moreover, in the anterior spermatozoon extremity, there is a discontinuous and submembranous layer of electron-dense material. Whereas, the posterior spermatozoon extremity belongs to the Quilichini et al.’s cryptogonimid type. Our results are compared with the available data on digenean spermatology, in particular with species belonging to the superfamily Lepocreadioidea to highlight the potential criteria useful for phylogeny.

本研究通过透射电子显微镜（TEM）描述了类脂双歧双子球菌Prodistomum polonii（Lepocreadiidae）的成熟精子的超微结构。从大西洋鲭鱼Trachurus trachurus（Teleostei，Carangidae）的消化道中收集了活的双基因属动物，该消化道捕获于地中海沿岸的拉切布（La Chebba）（突尼斯）沿海地区。研究发现，P。polonii的成熟精子细胞丝状细胞，在两个末端逐渐变细。它显示出Bakhoum等人的III型双基因精子，其特征是存在：两个9 +'1'轴突，与皮质微管相关的质膜的外部装饰，位于前部区域的后部，两束平行的皮质微管，最大数量（15个微管）位于中间，并存在两个线粒体（其中一个呈线虫型）。根据外部装饰的位置，P。polonii的雄配子提出了Quilichini等人的2型精子。此外，在精子前肢的末端，有一个不连续且膜下的电子致密材料层。而精子后肢属于Quilichini等人的隐腺酰亚胺类型。我们的结果与双基因精子学的可用数据进行了比较，特别是与属于Lepocreadioidea超科的物种进行了比较，以突出显示对系统发育有用的潜在标准。