Abstract Macrobrachium acanthurus is a caridean prawn native to Brazil, and studying techniques to assist in its cultivation is important due to economic interest in it. Eyestalk ablation is commonly used to promote ovarian development and maturation of captive crustaceans, but it can have possible consequences on fertility and brood quality. Histological and histochemical dynamism of oogenesis was analyzed under control (non-ablated females) and unilateral eyestalk ablated females. Females with ovaries in the spent stage of gonadal development were divided into two treatments: unilaterally ablated and non-ablated. A second experiment with the same treatments was conducted using females with mature gonads. Histological and histochemical analyses of the ovaries indicated that the ablation did not affect oogenesis based on ovarian structure, oocyte size, histochemical properties, and atretic oocytes. Ovarian maturation was not accelerated by ablation, either. Survival, nuptial molting, and spawning were also unaffected. From an applied point of view, unilateral eyestalk ablation is not needed in M. acanthurus farming because it does not improve reproductive performance.

A morfologia dos ovários de Uca rapax foi descrita baseada nas análises macroscópica e microscópica. As fêmeas foram coletadas no manguezal de Itamambuca, Ubatuba, Estado de São Paulo, Brasil. No laboratório, os ovários de 18 fêmeas foram retirados e preparados para histologia. Os estágios gonadais foram caracterizados previamente por meio de análises da morfologia externa e macroscopia e posteriormente cada estágio foi descrito microscopicamente. Os ovários das fêmeas de U. rapax apresentaram uma diferenciação macroscópica pronunciada no tamanho e coloração durante o processo de maturação, sendo caracterizados seis estágios de desenvolvimento ovariano: imaturo, rudimentar, em desenvolvimento, desenvolvido, avançado e esgotado. Microscopicamente, estes estágios diferiram quanto ao tamanho, cor e proporção de oogônias e oócitos presentes. Na análise histológica, oogônias, oócitos primários e secundários e células foliculares foram descritos e mensurados. As modificações observadas nos oócitos durante o processo de maturação dos ovários das fêmeas de U. rapax são similares às descrições de gônadas de outras fêmeas de braquiúros. As semelhanças foram especialmente observadas nas mudanças morfológicas das células reprodutivas e, também no arranjo das células foliculares durante o processo de maturação ovariana. Quando as características morfológicas externas das gônadas foram comparadas com as descrições histológicas, foi possível observar modificações que caracterizam o processo em diferentes estágios de desenvolvimento do ciclo ovariano e conseqüentemente, a classificação macroscópica das gônadas coincide com as modificações nas células reprodutivas.

The morphology of the ovaries in Uca rapax (Smith, 1870) was described based on macroscopic and microscopic analysis. Females were collected in Itamambuca mangrove, Ubatuba, state of São Paulo, Brazil. In the laboratory, 18 females had their ovaries removed and prepared for histology. Each gonad developmental stage was previously determined based on external and macroscopic morphology and afterwards each stage was microscopically described. The ovaries of U. rapax showed a pronounced macroscopic differentiation in size and coloration with the maturation of the gonad, with six ovarian developmental stages: immature, rudimentary, developing, developed, advanced and spent. During the vitellogenesis, the amount of oocytes in secondary stage increases in the ovary, resulting in a change in coloration of the gonad. Oogonias, primary oocytes, secondary oocytes and follicular cells were histologically described and measured. In female’s ovaries of U. rapax the modifications observed in the oocytes during the process of gonad maturation are similar to descriptions of gonads of other females of brachyuran crustaceans. The similarities are specially found in the morphological changes in the reproductive cells, and also in the presence and arrange of follicle cells during the process of ovary maturation. When external morphological characteristics of the gonads were compared to histological descriptions, it was possible to observe modifications that characterize the process in different developmental stages throughout the ovarian cycle and, consequently, the macroscopic classification of gonad stages agree with the modifications of the reproductive cells.