101. Jamieson, B.G.M. 1989g. Complex spermatozoon of the live-bearing half-beak, Hemirhamphodon pogonognathus (Bleeker): ultrastructural description (Euteleostei, Atherinomorpha, Beloniformes). Gamete Research 24, 247-259.

The spermatozoon of H. pogonognathus shows modifications that are frequent though not obligate in internally fertilizing sperm, notably elongation of the nucelus and extension of the mitochondria of the midpiece as an elongate sheath around the proximal region of the axoneme. These  similarities to poecilid and jenynsid sperm are considered homoplasic. As  in the mature sperm of all but one investigated teleost, an acrosome is  absent. The elongate, blade-shaped, electron-dense nucleus has a mean  length of 3.2 um; its basal implantation fossa, less than one-tenth of the length of the nucleus, houses the anterior half of the distal and only centriole (of triplet construction with satellite rays), a centriolar plug, and a mass connecting the centriole of the wall of the fossa. A  unilateral putative centriole adjunct is present. The anterior region of the axoneme is surrounded by a mitochondrial sleeve, and internal to this, separated by a cisterna, by a submitochondrial sleeve. The mitochondrial sleeve units posteriorly with the submitochondrial sleeve. Between the submitochondrial sleeve and the axoneme is a space, the cytoplasmic canal,  that is open to the exterior posteriorly. The discrete, cristate mitochondria, in their sleeve, are unique in investigated atherinomorph sperm in being bilateral, grouped on only two opposing sides of the axoneme, with an arc-shaped "intermitochondrial link" between. The 9 + 2 flagellum is unique for the Animalia in having 23 radial subplasmalemmal rods, repeated longitudinally (periodicity 0.025 um) in a quasicrystalline array. Internal fertilization is deduced to have arisen  in the Exocoetoidei independently of that in the Cyprinidontiformes.