The spermatozoa and eggs of the cardinal fish

The gametes of the cardinal fish Apogon imberbis had the following characteristic: the semen contained both biflagellate (  c . 20% in the investigated samples) and monoflagellate (  c . 80%) spermatozoa. The spermatozoa were acrosomless, had an ovoid head, and a cylindrical midpiece. The midpiece contained a high number of mitochondria (seven–10). The distal centriole was fastened to the nucleus via electron-dense material. The proximal centriole was completely reduced. The eggs were spherical, had a smooth surface and one micropyle consisting of the micropylar channel, the vestibulum and a ring-like convulsion bordering the vestibulum. The zona radiata was formed out of four layers which could be distinguished by their fine structural and histochemical features. It was only c . 1·5 µm thick and therefore much thinner than in other marine teleosts. The internal organization of the eggs (homogenous protein yolk containing cortical granules and lipid droplets) as well as the qualitative and quantitative biochemical composition of proteins, lipids and carbohydrates was similar to that of the pelagic eggs of other marine species.