Spermatozoon and its relationship with the ovarian lamellae in the internally inseminating catfish Trachelyopterus galeatus.

We examined the spermatozoa and their relationship with the ovarian lamellae in the catfish Trachelyopterus galeatus by classical light microscopy, high-resolution light microscopy, and transmission electron microscopy. Trachelyopterus galeatus is an internally inseminating species the spermatozoon of which presented an elongated cylindrical head (12.3 +/- 1.5 microm), elongated midpiece (5.0 +/- 0.7 microm), and flagellum (23.9 +/- 2.8 microm). Fertilized eggs or embryos were not found in its ovaries. Spermatozeugmata were demonstrated for the first time in this species. At the ultrastructural level, the anterior region of the head was devoid of chromatin with its shape being rounded with a hyaline tip in frontal sections and flattened in sagittal sections. The proximal centriole and most of the distal centriole were contained within a nuclear fossa. Mitochondria with lamellar cristae, as well as glycogen granules, were located just caudal to the nuclear fossa and distally in the midpiece. A single row of accessory microtubules ran peripherally in the midpiece. The flagellar axoneme had the typical 9 + 2 arrangement, having electron-dense and electron-lucent A-tubules at different points along the flagellum; flagellar fins were lacking. The ovarian lamellae were covered by a simple cuboidal epithelium. In maturing/mature females, spermatozoa were free in the ovarian lumen or inserted in pits of the lamellar epithelial cells. Tight junctions and desmosomes were seen between the epithelial cells. In addition to nourishment of the spermatozoon, the lamellar epithelial cells may play a role in protecting the spermatozoa against the female immune system.