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.
Keywords: Fish spermatozoa; Scanning electron microscopy; Teleost; Transmission electron microscopy.
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