Spermatozoon ultrastructure in two monorchiid digeneans.

Area of Science:

• * Helminthology and Ultrastructural Biology
• * Comparative Spermatology

Background:

• * The Monorchiidae family of trematodes is diverse, but detailed ultrastructural studies of their spermatozoa are limited.
• * Previous research has not utilized transmission electron microscopy to investigate spermatological characteristics within this family.

Purpose of the Study:

• * To conduct the first ultrastructural investigation of mature spermatozoa from Opisthomonorchis dinema and Paramonorcheides selaris.
• * To compare spermatological features within the Monorchiidae family and with other related families.
• * To establish the general spermatozoon morphology for all described monorchiid species.

Main Methods:

• * Transmission electron microscopy (TEM) was employed to analyze the ultrastructure of mature spermatozoa.
• * Detailed morphological examination of sperm components including axonemes, nucleus, mitochondria, microtubules, and external structures.

Main Results:

• * Mature spermatozoa of O. dinema and P. selaris share key ultrastructural features: two axonemes (9+1 pattern), nucleus, two mitochondria, cortical microtubules, external ornamentation, spine-like bodies, and glycogen granules.
• * Minor differences were observed in axoneme length and mitochondrion position between the two species.
• * A unique monorchiid spermatozoon type was identified, consistent across described species.
• * Similarities were noted between monorchiid and apocreadiid (Neoapocreadium chabaudi) spermatozoa.

Conclusions:

• * The study defines a unique spermatozoon type for the Monorchiidae family.
• * Observed spermatological similarities suggest a close phylogenetic relationship between Monorchiidae and Apocreadiidae.
• * Further research on unexplored taxa is recommended to confirm these phylogenetic inferences.