RESUMO

In viviparous teleosts, intraovarian gestation occurs intrafollicularly, as in poeciliids, or intraluminally, as in goodeids and anablepids. Furthermore, there are two different forms of embryonic nutrition: lecithotrophy and matrotrophy; depending on the species, these can be exclusive or coexist during gestation. In matrotrophic species, nutrients are transmitted from the mother to the embryo and are especially important in species with intraluminal gestation. Jenynsia lineata is a South American viviparous teleost with intraluminal gestation, characterized by eggs with scarce yolk, which is resorbed when embryos are 6 mm long, thus developing a branchial placenta. Using histological, histochemical, and immunohistochemical techniques, the present study describes the characteristics and changes of the ovarian mucosa in J. lineata during gestational and nongestational phases, and analyzes the embryonic pharyngeal epithelium in the branchial placenta. The ovaries of 30 adult female specimens were processed using histological techniques and stained with hematoxylin-eosin, Masson's trichrome, and Alcian Blue pH 2.5/periodic acid Schiff reagent. To detect cell proliferation, we used antiproliferating cell nuclear antigen antibody. In nonpregnant females, eosinophilic granular cells (EGCs) and lymphocytes were identified in the lamina propria of the tunica mucosa, and melanomacrophage centers (MMCs) and fibroblasts were identified adjacent to tissue debris in the ovarian folds'. In the cellular debris, an embryo in resorption was observed. In pregnant females, the ovarian mucosa has thin vascularization branches entering the opercular chamber of the embryos, in close contact with the forming gill processes, thereby establishing a branchial placenta. Active cell replacement was observed in these ovarian branches. The identification of fibroblasts, lymphocytes, EGCs, and MMCs adjacent to tissue debris could indicate that these cell types are involved in the embryonic resorption process. Considering the new data obtained in this study on the branchial placenta of J. lineata, we conclude that cell proliferation could be involved in the development of maternal-embryonic interaction.

Assuntos

Ciprinodontiformes , Ovário , Feminino , Animais , Gravidez , Placenta , Núcleo Celular , Proliferação de Células

RESUMO

The structure of the ovary and oogenesis of Poecilia mexicana from an active sulfur spring cave is documented. Poecilia mexicana is the only poeciliid adapted to a subterranean environment with high hydrogen sulfide levels and extreme hypoxic conditions. Twenty females were captured throughout one year at Cueva del Azufre, located in the State of Tabasco in Southern Mexico. Ovaries were processed with histological techniques. P. mexicana has a single, ovoid ovary with ovigerous lamella that project to the ovarian lumen. The ovarian wall presents abundant loose connective tissue, numerous melanomacrophage centers and large blood vessels, possibly associated with hypoxic conditions. The germinal epithelium bordering the ovarian lumen contains somatic and germ cells forming cell nests projecting into the stroma. P. mexicana stores sperm in ovarian folds associated with follicles at different developmental phases. Oogenesis in P. mexicana consisted of the following stages: (i) oogonial proliferation, (ii) chromatin nucleolus, (iii) primary growth, subdivided into: (a) one nucleolus, (b) multiple nucleoli, (c) droplet oils-cortical alveoli steps; (iv) secondary growth, subdivided in: (a) early secondary growth, (b) late secondary growth, and (c) full grown. Follicular atresia was present in all stages of follicular development; it was characterized by oocyte degeneration, where follicle cells hypertrophy and differentiate in phagocytes. The ovary and oogenesis are similar to these seen in other poeciliids, but we found frequent atretic follicles, melanomacrophage centers, reduced fecundity and increased of offspring size.

Assuntos

Cavernas , Extremófilos/fisiologia , Oogênese , Ovário/anatomia & histologia , Poecilia/anatomia & histologia , Poecilia/fisiologia , Enxofre/química , Viviparidade não Mamífera , Animais , Nucléolo Celular/metabolismo , Proliferação de Células , Cromatina/metabolismo , Feminino , Masculino , México , Oócitos/citologia , Oogônios/citologia , Ovário/crescimento & desenvolvimento , Espermatozoides/citologia

RESUMO

Histological structure of the testes and development of spermatozoa in Jenynsia species is described using light, scanning and transmission electron microscopy. The testis type is restricted spermatogonial, wherein spermatogonia are restricted to the distal ends of lobules, typical of the Atherinomorpha, and spermatogenesis is continuous throughout the year in wild-caught fish. Within the testicular lobes there are lobular germinal compartments wherein the functional units are spermatocysts, whose borders are formed by Sertoli cells. Spermatocysts may contain meiotic primary spermatocytes, secondary spermatocytes, spermatids, undergoing spermiogenesis, or spermatozoa. Spermatocysts with later stages of developing sperm are located proximal to the testicular ducts. During spermiogenesis, spermatid nuclei become elongated. As this occurs, the nucleus develops a deep, central fossa that contains the centriolar complex. As the flagellum grows, enlarging spermatid mitochondria migrate posteriorly alongside the flagellum but remain separated from it by the cytoplasmatic canal, an indentation of the plasma membrane. Between the enlarged mitochondria and plasma membrane, a sub-mitochondrial net develops. In longitudinal sections, the enlarged mitochondria are stacked in a zig-zag fashion, and in transverse sections they appear as a ring surrounding the flagellum, but separated from it by the cytoplasmic canal. Spermatozoa of the 3 jenynsiid species have an introsperm complex composed of a long mid-piece whose flagellum has a single "wing." Within the efferent ducts and the tubular gonopodium, sperm are lightly packed in a side by side fashion which facilitates their transfer into the female reproductive tract. This study presents detailed descriptions of testicular organization and cytological characterization of the stages of spermatozoa differentiation in 3 species of Jenynsia from northwestern Argentina (J. alternimaculata, J. multidentata and J. maculata), in order to contribute to the understanding of testicular structure and development of spermatozoa in the context of evolution of viviparity in this fish lineage.