Uribe Mari Carmen, Grier Harry J, Mejía-Roa Víctor
Laboratorio de Biología de la Reproducción; Departamento de Biología Comparada; Facultad de Ciencias; Universidad Nacional Autónoma de México; Ciudad Universitaria ; México, México.
Division of Fishes; National Museum of Natural History; Smithsonian Institution ; Washington, DC USA ; Florida Fish and Wildlife Conservation Commission; Fish and Wildlife Research Institute ; Saint Petersburg, FL USA.
Spermatogenesis. 2015 Feb 23;4(3):e983400. doi: 10.4161/21565562.2014.983400. eCollection 2014 Sep-Dec.
In most bony fishes, testes are paired elongated organs that are attached to the dorsal wall of the body by a mesorchium. Histological examination of teleost testes, and also in all vertebrates, shows that the testes are formed of germ cells and somatic cells, comprising the germinal and interstitial compartments. Both compartments are separated by a basement membrane. The germ cells may be spermatogonia, meiotic spermatocytes and haploid spermatids that differentiate into spermatozoa. The process of spermatogenesis includes a sequence of morphological and physiological changes of germ cells that begin with the differentiation of spermatogonia that become meiotic spermatocytes. After the second meiotic division, through a process of spermiogenesis, these differentiate into spermatozoa. Spermatogonia associate with Sertoli cells to form spermatocysts or cysts. The cyst is the unit of spermatogenic function, composed of a cohort of isogenic germ cells surrounded by encompassing Sertoli cells. The teleost testis is organized morphologically into 3 types of testis: 1) tubular testis type, present in lower bony fishes as salmonids, cyprinids and lepisosteids; 2) unrestricted spermatogonial testis type, found in neoteleosts except Atherinomorpha; and 3) restricted spermatogonial testis type, characteristic of all Atherinomorpha. The morphology of the testicular germinal epithelium changes during the annual reproductive cycle, reflecting reproductive seasonality.
在大多数硬骨鱼类中，睾丸是成对的细长器官，通过睾丸系膜附着于身体的背壁。硬骨鱼以及所有脊椎动物的睾丸组织学检查表明，睾丸由生殖细胞和体细胞组成，包括生精区和间质区。这两个区域由基膜分隔。生殖细胞可以是精原细胞、减数分裂的精母细胞和分化为精子的单倍体精子细胞。精子发生过程包括生殖细胞一系列形态和生理变化，始于精原细胞分化为减数分裂的精母细胞。第二次减数分裂后，通过精子形成过程，这些细胞分化为精子。精原细胞与支持细胞结合形成精小囊或小囊。小囊是生精功能的单位，由一群同基因生殖细胞组成，周围环绕着支持细胞。硬骨鱼的睾丸在形态上分为3种类型：1）管状睾丸型，存在于低等硬骨鱼类如鲑科、鲤科和雀鳝科鱼类中；2）不受限制的精原细胞睾丸型，见于除银汉鱼目以外的新硬骨鱼；3）受限制的精原细胞睾丸型，是所有银汉鱼目的特征。睾丸生精上皮的形态在年度繁殖周期中会发生变化，反映出繁殖的季节性。
