Dynamics of ovarian maturation during the reproductive cycle of Metynnis maculatus, a reservoir invasive fish species (Teleostei: Characiformes)

In this study, we evaluated the dynamics of ovarian maturation and the spawning processes during the reproductive cycle of Metynnis maculatus. Adult females (n = 36) were collected bimonthly between April 2010 and March 2011. The mean gonadosomatic index (GSI) was determined, ovarian and blood samples were submitted for morphometric evaluation and the steroid plasma concentration was determined by ELISA. This species demonstrated asynchronous ovarian development with multiple spawns. This study revealed that, although defined as a multiple spawning species, the ovaries of M. maculatus have a pattern of development with a predominance of vitellogenesis between April and August and have an intensification in spawning in September; in October, a drop in the mean GSI values occurred, and the highest frequencies of post-ovulatory follicles (POFs) were observed. We observed a positive correlation between the POF and the levels of 17α-hydroxyprogesterone. Metynnis maculatus has the potential to be used as a source of pituitary tissue for the preparation of crude extracts for hormonal induction; the theoretical period for use is from September to December, but specific studies to determine the feasibility of this approach must be conductedNeste estudo, avaliamos a dinâmica da maturação ovariana a desova durante o ciclo reprodutivo de Metynnis maculatus. Fêmeas adultas (n = 36) foram coletadas bimestralmente entre abril de 2010 e março de 2011. O índice gonadossomático (IGS) foi calculado e amostras de ovário e de sangue foram submetidas à avaliação morfométrica e das concentrações plasmáticas dos esteroides por ELISA, respectivamente. A espécie apresenta desenvolvimento ovariano assincrônico, com múltiplas desovas. Neste estudo revelamos que mesmo sendo de desova parcelada, os ovários do M. maculatus mostraram um padrão de desenvolvimento com predomínio de atividade vitelogênica entre abril a agosto e intensificação da desova em setembro. Em outubro houve uma diminuição nos valores médios de IGS, bem como registramos as maiores frequências de folículos pós-ovulatórios (FPOs). Observamos uma correlação positiva entre a frequência de FPOs e a concentração plasmática de 17 α-OHP. O M. maculatus tem potencial para ser usado como fonte para uso de hipófise para preparo de extrato bruto para indução hormonal, sendo o período teórico para coleta de hipófises de setembro a outubro, mas estudos específicos para esta finalidade ainda precisam ser desenvolvidosThe authors thank Msc. Camila N. P. Boscolo (CAUNESP, Jaboticabal, Brazil) for technical support and for critical suggestions for this manuscript and Dr. Francisco Langeani for the identification of species. We also thank the Nomura-Boscolo family for their support during data collection

Dynamics of ovarian maturation during the reproductive cycle of Metynnis maculatus, a reservoir invasive fish species (Teleostei: Characiformes)

In this study, we evaluated the dynamics of ovarian maturation and the spawning processes during the reproductive cycle of Metynnis maculatus. Adult females (n = 36) were collected bimonthly between April 2010 and March 2011. The mean gonadosomatic index (GSI) was determined, ovarian and blood samples were submitted for morphometric evaluation and the steroid plasma concentration was determined by ELISA. This species demonstrated asynchronous ovarian development with multiple spawns. This study revealed that, although defined as a multiple spawning species, the ovaries of M. maculatus have a pattern of development with a predominance of vitellogenesis between April and August and have an intensification in spawning in September; in October, a drop in the mean GSI values occurred, and the highest frequencies of post-ovulatory follicles (POFs) were observed. We observed a positive correlation between the POF and the levels of 17α-hydroxyprogesterone. Metynnis maculatus has the potential to be used as a source of pituitary tissue for the preparation of crude extracts for hormonal induction; the theoretical period for use is from September to December, but specific studies to determine the feasibility of this approach must be conducted

Testicular structure and description of the seminal pathway in Leporinus macrocephalus (Anostomidae, Teleostei)

The present study examined the testicular structure and the seminal pathway in freshwater fish Leporinus macrocephalus (Garavello and Britski, 1988). Twenty-five specimens of this species were studied. Testicular structure was analyzed using light and transmission electron microscopy. The testicular main ducts were examined by means of conventional histology, corrosion-cast technique and scanning electron microscopy. Additional techniques were applied for polysaccharides histochemistry and immunohistochemistry for androgen receptor. The testicular parenchyma was classified as the anastomosing tubular testis type with spermatogonia occurring along the lengths of the seminiferous tubules. The seminiferous tubules emptied directly into the testicular main ducts. The wall of the testicular main ducts in L macrocephalus consisted of three layers: epithelium, connective tissue and peritoneum. The epithelium changed from simple cuboidal to pseudostratified. The histochemical analysis revealed the presence of granules PAS positive in the epithelial cells. The immunoreactivity to androgen receptor was noted in the testicular main ducts through all cytoplasmic areas of epithelial cells. (C) 2011 Elsevier Ltd. All rights reserved.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Gonadal steroids levels and vitellogenesis in the formation of oocytes in Prochilodus lineatus (Valenciennes) (Teleostei: Characiformes)

The objective of this study was to obtain information about the possible mechanisms related to poor reproductive performance in tropical rheophilic fish. To that effect, cages (Cs) and earthen ponds (EPs) were used as experimental systems to provide unsuitable and suitable conditions, respectively, for curimbatá (Prochilodus lineatus) breeders. Fish were maintained under experimental conditions for 18 months, and during this period females were randomly sampled every two months for biometric analysis (n=30), blood (n=5/sampling) and ovary (n=5/sampling). After this period EPs females (EPFs) and Cs females (CFs) were submitted to the induced breeding experiments. The results showed that rearing curimbatá for such long time in a cage at this stocking density, reduces its growth, plasma E2 levels and vitellogenesis. During vitellogenesis, the mean plasma estradiollevels of CFs were three times lower than those of EPFs (PEste estudo teve como objetivo gerar informações básicas sobre os possíveis mecanismos relacionados com os resultados desfavoráveis obtidos com o desempenho reprodutivo em peixes reofílicos tropicais. Para isso tanques-rede (Cs) e viveiros escavados (EPs) foram utilizados como sistemas experimentais para propociar respectivamente condições inadequadas e adequadas para reprodutores de Prochilodus lineatus. Os peixes foram mantidos por 18 meses em viveiros escavados (EPs) e tanques-rede (Cs), e durante este período, foram aleatoriamente coletados a cada dois meses para análise biométrica (n=30), coleta de sangue (n=5/tratamento) e amostragem do ovário (n=5/tratamento). Após este período as fêmeas mantidas em EPs (EPFs) e as fêmeas mantidas em Cs (CFs) foram submetidas aos experimentos de reprodução induzida. Os resultados mostraram que manter curimbatás por este período em Cs, na densidade de estocagem utilizada, reduz seu crescimento, níveis plasmáticos de E2 e vitelogênese. Durante a vitelogênese, os níveis plasmáticos de estradiol das CFs foram três vezes menores do que os das EPFs (P <0,01). As CFs apresentaram resultados inferiores aos das EPFs para todos os parâmetros analisados de desempenho reprodutivo. Em conjunto, estes dados mostram que os níveis reduzidos de estradiol durante a vitelogênese (bem como o consequente atraso na transição da fase previtelogênica para a vitelogênica) e as quantidades reduzidas de vitelo são mecanismos associados com a formação de ovócitos de baixa qualidade; redução e atraso na época de desova nesta espécie. Além disso, nossos dados mostraram que o início da vitelogênese (seis meses antes da época de desova) é um período-chave para formação de ovócitos de boa qualidade, e o manejo adequado deve ser aplicado durante todo o ano

Gonadal steroids levels and vitellogenesis in the formation of oocytes in Prochilodus lineatus (Valenciennes) (Teleostei: Characiformes)

The objective of this study was to obtain information about the possible mechanisms related to poor reproductive performance in tropical rheophilic fish. To that effect, cages (Cs) and earthen ponds (EPs) were used as experimental systems to provide unsuitable and suitable conditions, respectively, for curimbatá (Prochilodus lineatus) breeders. Fish were maintained under experimental conditions for 18 months, and during this period females were randomly sampled every two months for biometric analysis (n=30), blood (n=5/sampling) and ovary (n=5/sampling). After this period EPs females (EPFs) and Cs females (CFs) were submitted to the induced breeding experiments. The results showed that rearing curimbatá for such long time in a cage at this stocking density, reduces its growth, plasma E2 levels and vitellogenesis. During vitellogenesis, the mean plasma estradiollevels of CFs were three times lower than those of EPFs (P<0.01). CFs presented poorer results than EPFs for all the examined parameters of reproductive performance. Taken together these data showed that the reduced estradiol levels during vitellogenesis (and the consequently less intense transition from the previtellogenic to vitellogenic phase) and reduced amounts of yolk are mechanisms associated with the formation of low quality oocytes and shortened and delayed breeding season in this species. Moreover, our data showed that the onset of vitellogenesis (six months before the spawning season) must be considered as a key period related to the formation of oocytes of good quality, and adequate management should be provided throughout the year

Gonadal steroids levels and vitellogenesis in the formation of oocytes in Prochilodus lineatus (Valenciennes) (Teleostei: Characiformes)

The objective of this study was to obtain information about the possible mechanisms related to poor reproductive performance in tropical rheophilic fish. To that effect, cages (Cs) and earthen ponds (EPs) were used as experimental systems to provide unsuitable and suitable conditions, respectively, for curimbata (Prochilodus lineatus) breeders. Fish were maintained under experimental conditions for 18 months, and during this period females were randomly sampled every two months for biometric analysis (n=30), blood (n=5/sampling) and ovary (n=5/sampling). After this period EPs females (EPFs) and Cs females (CFs) were submitted to the induced breeding experiments. The results showed that rearing curimbata for such long time in a cage at this stocking density, reduces its growth, plasma E2 levels and vitellogenesis. During vitellogenesis, the mean plasma estradiol levels of CFs were three times lower than those of EPFs (P&lt;0.01). CFs presented poorer results than EPFs for all the examined parameters of reproductive performance. Taken together these data showed that the reduced estradiol levels during vitellogenesis (and the consequently less intense transition from the previtellogenic to vitellogenic phase) and reduced amounts of yolk are mechanisms associated with the formation of low quality oocytes and shortened and delayed breeding season in this species. Moreover, our data showed that the onset of vitellogenesis (six months before the spawning season) must be considered as a key period related to the formation of oocytes of good quality, and adequate management should be provided throughout the year.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo [FAPESP-2009/00541-6]Fundacao de Amparo a Pesquisa do Estado de Sao PauloPROPe UNESP Programa Primeiros Projetos"Programa Primeiros Projetos"- PROPe- UNESPCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES

Anti-androgenic activities of diuron and its metabolites in male Nile tilapia (Oreochromis niloticus)

Diuron (3-(3,4-dichlorophenyl)-1,1-dimethylurea) is a widely used herbicide which has been frequently detected in surface waters throughout the world. In vivo bioassay guided fractionation studies indicated that diuron may have estrogenic activity augmented by biotransformation. This study evaluated the effects of diuron and three of its metabolites on plasma hormone concentrations and spermatogenesis of the freshwater fish Nile tilapia (Oreochromis niloticus). Sexually mature male fish were exposed for 25 days to diuron, as well to its metabolites 3,4-dichloroaniline (DCA), 3,4-dichlorophenylurea (DCPU) and 3,4-dichlorophenyl-N-methylurea (DCPMU), at concentrations of 200 ng/L. Testosterone levels were decreased by diuron, but had limited effects on gonadal histology. Diuron metabolites, however, caused significant decreases in testosterone and in 11-ketotestosterone, gonadosomatic index, diameter of seminiferous tubules and in the mean percentages of germ cells (spermatids and spermatozoa). We conclude that these metabolites have antiandrogenic activity to male Nile tilapia, potentially causing reproductive impairment in male fish.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq