| Popis: |
This study provides the first description of the ultrastructure of the spermatozoon of a lecanicephalidean cestode. Based on our observations on Adelobothrium sp. (Cestoda: Lecanicephalidea), we confirm the placement of the spermatozoa of lecanicephalideans in the Type IV spermatozoan category. A new feature, the anterior spiral structure, is described at the anterior extremity of the mature spermatozoon. The crested body is present in the anterior half of the spermatozoon and is identified by its ovoid to lunar shape, becoming circular and decreasing in size near its posterior limit. A row of ten parallel cortical microtubules persists in the anterior region of the mature spermatozoon, terminating at the level of the nucleus. The nucleus continues after the disassociation of the axoneme in the posterior region. A review of other cestodes with Type IV spermatozoa is presented, including confirmation that members of the Rhinebothriidea have spermatozoa of this type. That phyllobothriid tetraphyllideans have Type IV spermatozoa is called into question. Spermatozoa of a mere 2.6% of all cestode species have been studied. Further studies are needed to better understand spermatozoan character variation, especially if it is to be useful in elucidating evolutionary patterns among cestodes. |
