Sperm characters of the bucephalid digenean Prosorhynchoides arcuatus and their phylogenetic significance

The present study describes the ultrastructural organisation of the mature spermatozoon of the bucephalid digenean Prosorhynchoides arcuatus (Bucephalinae) collected from the Bluefish Pomatomus saltatrix (Teleostei: Pomatomidae) caught from the Gulf of Gabès in the Chebba (Tunisia) by means of transmission electron microscopy. The ultrastructural study reveals that the mature spermatozoon of P. arcuatus is a filiform cell which is tapered at both extremities. It exhibits the Bakhoum et al.'s type V of spermatozoon of digeneans characterised by the presence of two axonemes with the 9 + '1' pattern of the Trepaxonemata, lateral expansion, external ornamentation of the plasma membrane located in the anterior part of the proximal region of the spermatozoon and associated with cortical microtubules, two bundles of parallel cortical microtubules with maximum number located in the anterior part of the spermatozoon, and one mitochondrion. Other characteristics are the presence of spine-like bodies, a posterior extremity containing only the nucleus, and the presence of a large amount of glycogen granules. Results of the present study are compared with the existing data in other digeneans, particularly bucephalids.