Sperm morphology and ultrastructure of Patagonian blenny (Eleginops maclovinus)

In this study, the morphology and ultrastructure of Eleginops maclovinus spermatozoa were characterized through scanning and electron microscopy. Findings revealed that E. maclovinus spermatozoa can be differentiated into three major parts: a spherical head without acrosome (typical for externally fertilizing teleost), a midpiece containing 2-5 spherical mitochondria, and a long flagellum. The mean length of the spermatozoa was 40.08 ± 2.30 μm, with flagella accounting for 38.38 ± 2.08 μm. The head was 1.31 ± 0.17 μm long, and 1.63 ± 0.01 μm wide. The midpiece was 0.39 ± 0.05 μm in length and 0.95 ± 0.12 μm in width. It was located below the nucleus and contained 2 to 5 spherical mitochondria. The mitochondria were separated from the axoneme by a cytoplasmic canal. There was no evidence of the flagellum membrane forming sidefins, and the axoneme was composed of the typical 9 + 2 microtubular doublet structure enclosed by cell membrane. The present study reveals that E. maclovinus sperm can be categorized as a primitive type. This study is the first to provide comprehensive details on the ultrastructure of spermatozoa in E. maclovinus.