Early gonadogenesis in Columba livia (birds: Columbiformes): Migration, colonization, and differentiation of germ cells.

In birds, primordial germ cells (PGCs) use the bloodstream to travel to a specific region, where the cells undergo extravasation followed by intrastromal migration to the gonadal crest for further colonization. Currently, DDX4, SSEA1, and Oct4 are used to identify germ cells. Other germline cell-associated molecules are N-cadherin, GnRHR, and 3ß hydroxysteroid dehydrogenase (3ßHSD), which have been used in mice and birds during gonadal development; however, its role in early gonadogenesis in birds is poorly described. This study aimed to evaluate the differential immunodetection of N-cadherin binding molecule, Oct4 pluripotency protein, GnRHR receptor, and 3ßHSD enzyme in Columba livia embryos during migration colonization of PGCs in the gonadal crest and early gonadogenesis. These markers were revealed by immunohistochemistry in histological preparations of C. livia corresponding to stages (S)15 to S40. Immunodetection of N-cadherin, Oct4, GnRHR, and 3ßHSD in the germ line of C. livia allowed the identification of PGCs in the yolk sac membrane at the level of the splanchnic mesoderm during migration to the genital crest and its colonization. In the same way, it was possible to characterize and localize PGCs during early gonadogenesis. This study in C. livia demonstrates that Oct4, N-cadherin, GNRHR, and 3ßHSD are immunodetected in PGCs and could be used as potential germline cell markers during cell migration out of blood vessels, colonization in the genital crest, and early gonadogenesis. Furthermore, this study could be used as a novel general model to understand the early gonadogenesis in altricial species.

Comparative study of the gular gland of three species of Molossidae bats (Mammalia: Chiroptera) from South America.

The gular gland is a skin gland located in the suprasternal region of adult males of some bat families. Knowledge of the morphology and functional aspects of these gland types is often limited. This study aimed to describe the structure and composition of the gular glands of three molossid species (Eumops patagonicus, Molossus fluminensis and Molossus molossus) with respect to their reproductive activity and to define the mechanism involved in secretion release. Different histological, histochemical and immunohistochemical techniques were used to achieve these goals. The results revealed that the size and composition of this gland are variable and are mostly related to the lipid content during the reproductive season. The results also documented, for the first time, the occurrence of mechanoreceptors associated with the surface of the glandular duct by detecting an S100 protein, indicating that an external stimulus activates secretion. Previous studies on other species have classified the gland using obsolete criteria; hence, we adopted a new classification of adenomeres in this study. Moreover, we investigated the gland secretion mechanism previously proposed. This study defines the implications of this gland in the reproduction of this species. Our preliminary interpretation of the function of the gular gland is that it is a cutaneous exocrine gland activated by mechanoreceptors involved in the reproductive behaviour of the Molossidae family.

Ultrastructure of eggshell and embryological development of Salvator merianae (Squamata: Teiidae).

The objective of this study was to characterize the external morphology of Salvator meriane embryos in different stages of embryonic development and establish a relationship with the ultrastructure of the shell from oviductal transit to hatching. A total of 120 embryos were analyzed to describe their external morphology, and 78 eggs were used for the analysis of the shell. For embryonic development, the series was established according to the total length of the body. We established 40 embryonic stages from the primitive streak. In the early stages, the external morphological features are the C-shaped body, the maxillary, and mandibular fusion processes with the frontal process and the fusion of the forelimb with the digital plate. In the middle stages, the eyelid appears, and there are claws on the toes, cornification of fingers, and the onset of pigmentation. The last stage of embryonic development is characterized by the beginning of the formation of the scales, appear the toenails, and finalize the entire pigmentation. Regarding the relationship that exists with the ultrastructure of the egg during development, it was possible to observe a marked change in the composition of the shell and well-marked compaction during embryonic development, which may be related to the transport of calcium during embryonic ossification. Our results allowed us to show the complete sequence of embryonic development, determining the laying stage for this species. It was possible to establish a relationship with the ultrastructure of the eggshell from the oviductal transit to the moment of hatching.

Histological and immunohistochemical characterization of the integument and parotoids glands Rhinella bergi (Anura: Bufsonidae): Development and differentiation.

A detailed description of the tegument and parotoid glands of pre-metamorphic, post-metamorphic, juvenile and adult individuals of Rhinella bergi is presented to provide an exhaustive analysis of the integumentary characteristics of this species. Fragments of the tegument were fixed in Bouin solution and preserved in buffered Formol 10%. Subsequently, scanning electron microscopy (SEM) was performed to characterize the macroscopic structure of these regions. Microscopic observations were made from histological sections stained with Hematoxylin and Eosin, Alcian Blue (pH 2,5), PAS-H, Coomassie Blue, Oil Red, and Bielschowsky Impregnation.. There were three types of protuberance: warts, tubers, and thorns. These structures became evident from post-metamorphic stages. The ventral surface shows elevations similar to flat warts; however, tubers and spines are absent. Histologically, each structure consists of a spongy dermis of lax connective tissue and dense and compact dermis, associated with granular glands and a keratinized epidermis. The latter, in the dorsal region, forms projections called thorns. The granular glands accumulate, and their alveoli increase in size progressively. This work provides a morphological and histological description of the integument and the parotoid glands during the larval and post-metamorphic stage of the genus Rhinella, with aspects described for the first time in the genus.