Gonadal characterization of the Amazonian fish Serrapinnus kriegi (Characidae: Cheirodontinae)

The knowledge of the testicular and ovarian morphology of a particular fish species is of paramount importance. Such analyze enables the development of studies and techniques aiming the improvement of their reproduction, management, commercialization and even their conservation. This study performed the ovarian and testicular characterization of the ornamental Amazon fish Serrapinnus kriegi. A total of three males and three females had their gonads analyzed by optical microscopy. Females present ovaries filled with oocytes in asynchronous development, indicating partial spawning in the species. Moreover, the micropyle and micropilar cell formation was observed in primary growing oocytes, representing a precocious oocyte development; and the zona radiata in the final vitellogenic oocytes is thicker than other related species, evidencing the development of a better protection to the embryos in function of the waters’ turbulence that characterize it spawning sites in the Amazonian streams. The male specimens’ present anastomosed tubular testes with unrestricted spermatogonia spread along the entire seminiferous tubules. The present data elucidate the dynamic of spermatogenesis and oogenesis of an ornamental Amazonian species, through the description of the male and female germ cells development.

Subfamily hypostominae: similarities and differences in testicular structure of amazonian fish

Background Hypostominae is a subfamily of the family Loricariidae that has a great diversity of species. Accordingly, testicular studies in fish can contribute to the phylogeny and taxonomy of species and to the comparison of reproductive aspects between species. Thus, this work aimed to characterize the testicular morphology and spermatogenesis of the Hypostominae species Baryancistrus xanthellus, Peckoltia oligospila and Hypancistrus zebra. Results B. xanthellus, P. oligospila and H. zebra had an anastomosed tubular type of testis. The germinal epithelium was continuous with unrestricted spermatogonia, and the proliferative, meiotic and spermiogenic phases were defined in all species. In the spermiogenic phase, spermatids were classified as initial, intermediate and final. Only in B. xanthellus in the final phase was there nuclear rotation. The sperm for the three species had a head with an oval shape and a single flagellum composed of the short midpiece, principal piece and end piece. B. xanthellus and P. oligospila showed a cylindrical flagellum and H. zebra showed projections that produced a flattened appearance. Conclusions On the basis testicular structure and ultrastructural characteristics of the germ cells, there was a greater relationship between B. xanthelus and P. oligospila, while H. zebra had particular characteristics. These aspects show that despite belonging to the same subfamily, the species have distinct biological characteristics.

Heterochromatin Dynamics in Response to Environmental Stress in Amazonian Fish

Transcriptionally inactive portions of genomic DNA, condensed with histones and architectural proteins, are known as heterochromatic regions, often positive C band. The advent of epigenetics and new methodological approaches, showed that these regions are extremely dynamic and responsive to different types of environmental stress. The relationship of the constitutive heterochromatin with the transposable elements inactivation, especially from the Rex family, seems to be a frequent condition in fish. In this manuscript we review the existing knowledge of the nature and function of these genomic regions, based on species-based studies, with a focus on species of fish from the Amazon region.