In rheophilic tropical fish, the use of carp pituitary extract (CPE) is still the main protocol since the use of gonadotropin-releasing hormone (GnRH) induces ovulation, but usually does not provide viable embryos. Thus, in order to generate knowledge to support the establishment of a successful protocol using GnRH, we compared the ovulatory process and reproductive performance of Leporinus macrocephalus using CPE (0.5 and 5.0 mg kg-1) and mGnRHa (7 lg kg-1) associated with metoclopramide. Females of both treatments ovulated, but the mGnRHa treatment did not provide viable embryos, which was associated with a more potent ovulation, lower latency period and less intense hydration of eggs, suggesting a possible treatment overstimulation. This is the first report associating a less intense egg hydration process to a failure in obtaining viable eggs in induced fish spawning. Considering that the mGnRHa doses applied here were quite low, it is possible that L. macrocephalus as well as other rheophilic tropical species present a higher sensibility to mGnRHa and/or metoclopramide (or derived substances) and future approaches must consider using even lower doses of these substances as well as testing different types of GnRH and dopamine inhibitors.

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Diuron and its biodegradation metabolites were recently reported to cause alterations in plasma steroid hormone concentrations with subsequent impacts on reproductive development in fish. Since steroid hormone biosynthesis is regulated through neurotransmission of the central nervous system (CNS), studies were conducted to determine whether neurotransmitters that control hormone biosynthesis could be affected after diuron and diuron metabolites treatment. As the same neurotransmitters and steroid hormones regulate behavioral outcomes, aggression was also evaluated in male Nile tilapia (Oreochromis niloticus). Male tilapias were exposed for 10 days to waterborne diuron and the metabolites 3,4-dichloroaniline (DCA), 3,4-dichlorophenyl-N-methylurea (DCPMU), at nominal concentrations of 100 ng L. In contrast to Diuron, DCA and DCPMU significantly diminished plasma testosterone concentrations (39.4% and 36.8%, respectively) and reduced dopamine levels in the brain (47.1% and 44.2%, respectively). In addition, concentrations of the stress steroid, cortisol were increased after DCA (71.0%) and DCPMU (57.8-%) exposure. A significant decrease in aggressive behavior was also observed in animals treated with the metabolites DCA (50.9%) and DCPMU (68.8%). These results indicate that biotransformation of diuron to active metabolites alter signaling pathways of the CNS which may impact androgen and the stress response as well as behavior necessary for social dominance, growth, and reproduction.

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.Neste 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 desenvolvidos.

Descriptive anatomical studies of wild animals are fundamental, since they provide subsidies for the elaboration of more adequate techniques of sustained management, contributing to the preservation of species threatened with extinction. Thus, the aim of the study is to anatomically describe the salivary glands: parotid, mandibular and sublingual of the crab-eating-fox (Cerdocyon thous). For this purpose, three carcasses of crab-eating-fox donated by Ibama were used. The animals were fixed with 10% aqueous formaldehyde solution, dissected, analyzed descriptively and photographed. It was found that the parotid gland of the crab-eating-fox is located caudally to the branch of the mandible, in the rostroventral margin of the auricular cartilage. The mandibular gland is located in the atlantal fossa and extends to the basi-hyoid bone. The sublingual gland of the crab-eating-fox shows two parts: monostomatic and polystomatic. The monostomatics are located in the occipitomandibular region of the digastric muscle and the portion polysomatic is situated between the tunica mucosa of the oral cavity and the buccinator muscle. Based on the results, we conclude that the salivary glands of the crab-eating-fox are found distributed in the facial region and present anatomical characteristics that follow the same structural pattern described for other species of carnivorous mammals.