Spermatophore Transfer and Subsequent Sperm Development in a Homalorhagid Kinorhynch

Abstract

The cuticular morphology and precise location of male and female gonopores and penile spines of the homalorhagid kinorhynch Kinorhynchus phyllotropis Brown & Higgins, 1983 are described and illustrated. In this species spermatozoa are transferred from male to female by a spermatophore. This is the first record of the mechanism of sperm transfer in a kinorhynch. The spermatophore is presumably extruded through the male gonopore and directed towards the female by the ductless penile spines. Spermatozoa in the spermatophore are rod‐shaped and catenulate. The spermatophore is pressed directly against the cuticular plates of the female, and usually covers the female gonopores. The spermatophore contains a mass of intertwined spermatids and spermatozoa surrounded by clear material covered with a layer of debris. Spermatozoa are found in the female lodged in the seminal receptacle tissue applied to the dorsal aspect of posterior oocytes. There the spermatozoa complete their development. Nuclei change from filiform to geniculate, and oval corpuscles surrounding the nuclei disappear, so that the spermatozoa are seen as densely‐packed, polyhedral cells. These observations conform with literature reports of aberrant spermatozoa of unknown origin seen in female Pycnophyes. The fertilization process remains unknown.