Gametogenesis and seminatural reproduction of the Amazon twospot astyanax Astyanax bimaculatus (Linnaeus, 1758) cultivated in an enriched environment.

Environmental enrichment is used to provide well-being to the animals, such as fish, in captive conditions, mimicking their natural habitat. It may influence fish behavior, physiology, and survival. In terms of reproduction, however, the relationship between environment enrichment and successful reproduction in captivity is still poorly explored in fish species. Aiming to understand any possible benefits of structural enrichment on fish reproduction, 10-days-hatched larvae of the twospot astyanax Astyanax bimaculatus were raised for 18 weeks in tanks with different elements of structural environmental enrichment (PVC pipes, stones, and artificial plants). In the 5th month of life, those animals were hormonally induced to reproduce to assess gamete formation and offspring quality. Animals raised in a sterile-reared environment (non-enriched) showed earlier spawning than the enriched one, presenting significant quantities of Postovulatory follicle complexes (POCs) and cells in atresia in female ovaries, indicating possible reproductive dysfunction or stress, as well as a greater quantity of empty testicular lumen in males, indicating great release of sperm. On the contrary, animals cultivated in enriched environments showed gonads filled with semen in males and vitellogenic oocytes in females. Furthermore, offspring from the sterile-reared group presented significant rates of larval abnormality compared to the enriched group. In conclusion, the results of this study show that environmental enrichment can interfere with the reproduction of fish in captivity, mainly by preventing early maturation of gametes, which can result in low-quality offspring and, consequently, low production of fish species.

A multi-evidence approach in an Amazonian river based on land use, water quality, histopathological effects and habitat selection behavior in fish.

The Amazon rivers constitute the largest river basin in the world, with a high level of biodiversity. The Tocantins River is one of the most important rivers in this region, which has been impacted by different land uses. The objective of this study was to carry out a multi-evidence analysis focusing on the water quality of the Tocantins River, close to the municipality of Marabá-PA. We analyzed forest cover and water quality and, using the model organism Danio rerio, performed toxicity tests for histopathological effects, as well as the habitat selection approach by exposing fish to different river water samples in a multi-compartment device. The results showed that the studied area has already lost almost 30% of its forests in recent decades. Regarding water quality, the upstream (C1) and downstream (C5) points are the least impacted. On the other hand, the other points (C2-C4), closer to the city, greater input of pollutants was detected. Fish exposed to water samples from the most impacted sites showed several oedemas and hyperplastic cells in the gills. Regarding habitat selection behavior, there was a marked avoidance by samples with the highest contamination load. The results of this study lead to the understanding of the potential negative effects of human activities on local Amazonian biodiversity, since the potential toxicity of the environment, in conjunction with changes in the habitat selection process, could lead to a decline in populations of aquatic organisms, altering the environmental balance.

First report of complete albinism in Mazama americana (Erxleben, 1777) in the Biological Reserve of Tapirapé, Oriental Amazon, Brazil

Albinism is a genetic condition that results in total hypopigmentation of the eyes, fur, skin, hair, scales, and feathers of an organism. Albinism might result in a selective disadvantage for affected animals. Cases of albinism have been previously recorded in Neotropical vertebrates, such as reptiles, mammals, birds, and fish. However, observing albinism in a wild population is still considered to be a rare event. This paper reports a unique case of complete albinism in a red-brocket deer (Mazama americana) living in the Brazilian Amazon rainforest. The individual was observed within the Biological Reserve of Pará State, one of the most deforested regions of the Brazilian Amazon. The survival of the albino red-brocket deer in the wild can be related to mechanisms of apostatic selection, which theorize the survival of individual prey animals whose mutations make them less likely to be attacked by predators. In other words, the more different a prey animal is from others, the less likely it will be targeted by predators. The high abundance prey animals within the Biological Reserve of Tapirapé seems to support this prediction. This report exemplifies the importance of monitoring the biodiversity and promoting the conservation of favorable habitats to support species multiplicity in highly fragmented regions, as in the Brazilian Amazon.

Morphology of the urogenital papilla and its component ducts in Astyanax altiparanae Garutti & Britski, 2000 (Characiformes: Characidae)

The histological description of the urogenital papilla is an important tool to comprehension of the reproductive mechanisms in fish, as well as a pre-requisite to germ cell transplantation in adult fish, besides to be a good biological indicator to environmental changes. Was performed the histological description of the urogenital papilla and its component ducts in the tetra Astyanax altiparanae. The genital and urinay ducts pass separately throughout most part of its extension, joining in a single duct before opening. In males this opening is asymmetric and seems to have double origin, being completely surrounded by striated muscle fibers, while in females it is symmetric and the muscle fibers does not surround it totally. Spermatic duct and oviduct undergo changes throughout their extension, mainly in the morphology of the surrounding epithelium. In the spermatic duct, squamous epithelial cells change to columnar and cuboid with possible secretory activity, close to testes. In the oviduct, anteriorly epithelial cells are also squamous, however, close to ovary there are lamellae composed by a pseudostratified epithelium with columnar and cuboid cells. The urinary duct is highly similar for both sexes presenting globoid cells, which description is known in mammals, however, rare in fish.

A descrição histológica da papila urogenital é uma importante ferramenta para a compreensão dos mecanismos reprodutivos em peixes, assim como um pré-requisito para a realização do transplante de células germinativas em peixes adultos, além de um bom indicador biológico de possíveis alterações ambientais. Foi realizada a investigação histológica da papila urogenital e seus ductos constituintes no lambari Astyanax altiparanae. Os ductos genital e urinário ocorrem separadamente ao longo de maior parte de sua extensão, entretanto, unem-se em um ducto simples antes de abrir para o meio externo. Nos machos esta abertura é assimétrica e parece ter dupla origem, sendo completamente envolvida por fibras musculares estriadas, enquanto nas fêmeas ela é simétrica e as fibras musculares não a envolve totalmente. O ducto espermático e oviducto sofrem alterações ao longo de sua extensão, principalmente na morfologia do epitélio que os envolve. No ducto espermático as células epiteliais passam de pavimentosas a colunares e cuboides, com possível atividade secretora, à medida que se aproxima dos testículos. No oviducto, anteriormente as células também são epiteliais pavimentosas, entretanto, próximo aos ovários, formam-se lamelas compostas por um epitélio pseudoestratificado composto por células cuboides e colunares. O ducto urinário é bastante similar em ambos os sexos apresentando células globosas, cuja descrição é conhecida em mamíferos, porém rara em peixes.

Reproductive cycle of the neotropical cichlid yellow peacock bass cichla kelberi: a novel pattern of testicular development

The present study describes the testicular maturation phases (associating the germ cells development and the morphological changes suffered by the germinal epithelium along the whole year), and the testicular morphology in the yellow peacock bass Cichla kelberi, relating it to other species. For this purpose, 78 specimens were studied according conventional techniques of light microscope. The testes in C. kelberi were classified as unrestricted spermatogonial lobular, an apomorphic characteristic in the recent groups of Teleost. Furthermore, were defined five testicular maturation phases: Preparatory phase; Early Germinal Epithelium Development; Mid Germinal Epithelium Development; Late Germinal Epithelium Development and; Regression. Similar classifications were described to other species indicating that the testicular classifications based on this propose, can be applied to lots of fishes. However, besides it similarity, the testicular reproductive cycle of C. kelberi follows a different pattern in the Regression phase, on which the gonadal restructuration and the spermatogonial proliferation gathers at the same time. So, the testes in C. kelberi never return to the Preparatory phase to start a new reproductive cycle, being this one present only at the first reproductive cycle in this species. This fact also explains the absence of individuals totally spent after their first reproductive cycle.

O presente estudo descreve as fases de maturação testicular (associando o desenvolvimento das células germinativas e as alterações morfológicas sofridas pelo epitélio germinativo ao longo do ano), e a morfologia testicular do tucunaré amarelo Cichla kelberi, relacionando a outras espécies. Com este propósito, 78 indivíduos foram estudados de acordo com técnicas convencionais para microscopia de luz. Os testículos em C. kelberi foram classificados como lobular espermatogonial irrestrito, uma característica apomórfica encontrada nos grupos recentes dos teleósteos. Além disso, cinco fases de maturação testicular foram definidas para C. kelberi: Fase Preparatória; Desenvolvimento Inicial do epitélio germinativo; Desenvolvimento Intermediário do epitélio; Desenvolvimento Final do epitélio germinativo e Regressão. Classificações similares foram descritas para outras espécies, indicando que a classificação gonadal baseada nesta proposta, pode ser aplicada a muitas espécies de peixes. Entretanto, apesar desta similaridade, o ciclo reprodutivo testicular de C. kelberi segue um padrão diferente na fase de Regressão, na qual a reestruturação gonadal e a proliferação espermatogonial ocorrem ao mesmo tempo. Deste modo, os testículos em C. kelberi nunca retornam à fase Preparatória para começar um novo ciclo reprodutivo nesta espécie. Este fato também explica a ausência de indivíduos totalmente esgotados após seu primeiro ciclo reprodutivo.