Reproduction and fecundity of invader of internal insemination Trachelyopterus galeatus in a Neotropical floodplain

After the formation of Itaipu Reservoir, the invader Trachelyopterus galeatus colonized the upper Paraná River. Light microscopy was used to describe gametogenesis and the reproductive phases of females and males. The following data were verified: diameter of the oocytes, spawning type, batch fecundity by ovary weight, standard length, and total weight of the fish, along with the regions where this species reproduced in the upper Paraná River floodplain. A total of 470 specimens were collected quarterly in 2016, 2018 and 2019, and bimonthly in 2017. The gonads were fixed in a Karnovsky solution, dehydrated, infiltrated, and embedded in historesin. The histological slides were stained using PAS + iron hematoxylin + metanil yellow, analyzed and photographed under an image-capturing microscope. As regards diameter of the oocytes and fecundity estimates, ovaries whose oocytes were measured under a stereomicroscope were sampled. In the oogenesis, undifferentiated and differentiated oogonia, early primary growth oocytes, secondary growth oocytes, full-grown oocytes and maturing oocytes were recorded. In the spermatogenesis, primary and secondary spermatogonia, primary and secondary spermatocytes, spermatids and spermatozoa were recorded. The reproductive phases found for females and males were: immature, early development, late development, spawning/sperm-releasing capable, regression, and regeneration. Trachelyopterus galeatus prefers to occupy and reproduce in the Ventura, Patos, Guaraná, Fechada, Garças, and Pau Véio lagoons. The diameter of the oocytes varied from 0.4 to 2.9 mm. Females spawn, on average, 113 oocytes per batch. Batch fecundity variation shows that the larger the ovary, standard length, and total weight, the larger the number of oocytes to be spawned. This invader possesses reproductive success in the upper Paraná River floodplain, especially in lagoons.

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.