Testis structure, spermatogenesis, spermatocytogenesis, and sperm structure in cardinal fish (Apogonidae, Perciformes)

Abstract

The testes in all 16 of the studied cardinal fish species are shown to be bilobed, with spermatogonia dispersed throughout the gametogenic epithelium of the seminiferous tubules. Each testicular lobe is covered luminally by an epithelium consisting of primary germ cells and Sertoli cells. At maturation the seminiferous tubules reach around 0.6-2.3 mm in length. They number from 60 in the smallest species to over 300 in the largest one, increasing both in dimension and number with increase in length of the male, and are species-specific. The highest number of spermatogonia is found at the apical ends of the tubules. During maturation extensions of Sertoli cells surround single or small groups of B-spermatogonia, forming the spermatocysts, the final dimensions of which reflect the final number of contained spermatozoids. Back-calculations of serial sections reveal that within the spermatocysts the spermatogonia undergo eight generations of mitotic divisions before the first and second meiotic divisions and formation of spermatids. The largest mature spermatocysts in large species attain around 180 microm in diameter, a volume of 25 mm(3), and contain around 8,200 spermatids. The total volume of sperm in the mature spermatocysts leaves enough space for the discarded cytoplasm and developing flagella. The bursting cysts liberate the ripe sperm and maturing spermatids, into the tubule lumen and spermduct, with the spermatids often still connected by cytoplasm bridges. The sperm, with one or two flagella, features round or oval heads and a cytoplasmic collar bearing a few mitochondria. The percentage of biflagellate or monoflagellate sperm differs in proportion in males of different lengths and in different species. Differences in spermatogenesis of small and larger species of cardinal fish are discussed.

Reproductive biology of the endangered percid <i>Zingel asper</i> in captivity: a histological description of the male reproductive cycle

“…Generally, as the result of successive divisions, cells have reduced in size [9], as observed in the Rhône streber. The diameters of the type A spermatogonia of Z. asper are among the highest reported for perciform fish, while SPGB, SPC I, SPC II and SPD diameters correspond to those generally reported for perciform fish [7,70].…”

“…Unlike other studies using light microscopy [7,79], no evolution of these cells during Z. asper sexual cycle has been pointed out. Other cells, very elongated, along the basement membrane, are certainly identifiable as myoid cells [21,80].…”

“…Many authors [7,69] have characterized SPC I using the presence of an irregular condensed chromatin. The nucleoli have not always been distinguished [12,65,70].…”

“…Testis structure and spermatogenesis in teleost species have been extensively studied in adult fish, generally from natural populations [1,2], and most especially in perciform species [3][4][5][6][7]. During spermatogenesis, when germ cells differentiate from spermatogonia to spermatozoa [8,9], the germ cells go through three major phases: mitotic proliferation (spermatogonial stem cells to differentiated spermatogonia [SPG]), meiosis (spermatocytes [SPC] to spermatids [SPD]), and spermiogenesis (SPD to spermatozoa [SPZ]) [10,11].…”

Intra‐ and intermale variability of mature sperm traits analysed in two brackish water populations of the pipefish Syngnathus abaster (Syngnathidae)

“…Teleost parasperm varies in morphology among species. In cardinal fish (Apogonidae) and in a marine cottoid, (Blepsias cirrhosis), parasperm possessed two flagella, (Mattei and Mattei 1984;Lahnsteiner 2003 andFishelson et al 2006;Hayakawa 2007), whereas in another non-copulatory marine cottoid (Hemilepidotus gilbert) and in a marine sculpin (Cottus kazika), parasperm are unflagellate cells (Hayakawa 2007;Daisuke et al 2010).…”