Characterization of Gnrh/Gnih elements in the olfacto-retinal system and ovary during zebrafish ovarian maturation.

Gonadotropin releasing hormone (GnRH) is one of the key players of brain-pituitary-gonad axis, exerting overall control over vertebrate reproduction. In zebrafish, two variants were characterized and named as Gnrh2 and Gnrh3. In this species, Gnrh3, the hypohysiotropic form, is expressed by neurons of the olfactory-retinal system, where it is related with food detection, intra/interspecific recognition, visual acuity and retinal processing modulation. Previous studies have reported the presence of Gnrh receptors in the zebrafish retina, but not yet in the zebrafish olfactory epithelium. The current study analyzed the presence of gnrh2 and gnrh3, their receptors (gnrhr 1,2,3 and 4) and gnih (gonadotropin inhibitory hormone) transcripts, as well as the Gnrh3 protein in the olfactory epithelium (OE), olfactory bulb (OB), retina and ovary during zebrafish ovarian maturation. We found an increase of gnrh receptors transcripts in the OE at the final stages of ovarian maturation. In the OE, Gnrh3 protein was detected in the olfactory receptor neurons cilia and in the olfactory nerve fibers. Interestingly, in the OB, we found an inverse expression pattern between gnih and gnrh3. In the retina, gnrhr4 mRNA was found in the nuclei of amacrine, bipolar, and ganglion cells next to Gnrh3 positive fibers. In the ovary, gnrh3, gnrhr2 and gnrhr4 transcripts were found in perinucleolar oocytes, while gnih in oocytes at the cortical alveolus stage. Our results suggested that Gnrh/Gnih elements are involved in the neuromodulation of the sensorial system particularly at the final stages of maturation, playing also a paracrine role in the ovary.

Diferentes níveis protéicos na dieta de girinos de rã-touro (Lithobates catesbeianus) e seus efeitos sobre o tecido hepático / Different protein levels in the diet of bullfrog tadpoles (Lithobates catesbeianus) and its effects on the liver tissue

Para verificação da ocorrência de alterações morfológicas no fígado, foram coletados dez animais de cada dieta, no 30º dia (1º período experimental) e no 60º dia (2º período experimental), sendo esse, o último dia do período experimental e início do clímax da metamorfose. Os girinos foram distribuídos em delineamento experimental inteiramente casualizado (DIC) com três tratamentos: dieta experimental com 32,68% de proteína bruta e duas dietas comerciais com 37,92% e 57,53% de proteína bruta. Os órgãos coletados foram fixados em solução de Bouin e depois submetidos às práticas da rotina histotecnológica e coradas com hematoxilina - Eosina (HE). Na avaliação microscópica do fígado foram encontradas diversas alterações morfológicas como: Desorganização e vacuolização de hepatócitos, infiltrado inflamatório mononuclear periportal, multifocal e difuso, infiltrado inflamatório eosinofílico, congestão, hemorragia, hemólise e necrose. As alterações hepáticas encontradas neste estudo sugerem que as dietas utilizadas para os girinos de rã-touro, não atenderam suas necessidades dietéticas, afetando a homeostasia dos mesmos, comprometendo assim, sua sanidade.(AU)

To verify the occurrence of liver morphological changes, bullfrog tadpoles were fed three diets: an experimental diet with 32.68% crude protein and two commercial diets with 37.92% and 57.53% crude protein. Tadpoles were distributed into a completely randomized design (CRD) with three treatments and four replications. Liver samples were collected twice, on the 30th and 60th day of the experiment. Tadpole livers were fixed in Bouin's solution, then subjected to routine histotechnology procedures, and stained with hematoxylin - eosin (HE). Microscopic evaluation of liver tissue showed several morphological changes like disorganization and vacuolization of hepatocytes; periportal, multifocal and diffuse mononuclear inflammatory infiltrate, eosinophilic inflammatory infiltration, congestion, hemorrhage, hemolysis and necrosis. The liver changes found in this study suggest that diets used for bullfrog tadpoles, did not meet their dietary needs, what affected their homeostasis, thus compromising their health.(AU)

Spatial and seasonal patterns in fish assemblage in Córrego Rico, upper Paraná River basin

The upper Paraná River basin drains areas of intensive industry and agriculture, suffering negative impacts. The Córrego Rico flows through sugar cane fields and receives urban wastewater. The aim of this work is to describe and to compare the fish assemblage structure in Córrego Rico. Six standardized bimonthly samples were collected between August 2008 and June 2009 in seven different stretches of Córrego Rico. Fishes were collected with an experimental seine and sieves, euthanized, fixed in formalin and preserved in ethanol for counting and identification. Data were recorded for water parameters, instream habitat and riparian features within each stretch. Non-metric multidimensional scaling, species richness and diversity analysis were performed to examine spatial and seasonal variation in assemblage structure. Fish assemblage structure was correlated with instream habitat and water parameters. The fish assemblage was divided in three groups: upper, middle and lower reaches. High values of richness and diversity were observed in the upper and lower stretches due to connectivity with a small lake and Mogi Guaçu River, respectively. Middle stretches showed low values of richness and diversity suggesting that a small dam in the middle stretch negatively impacts the fish assemblage. Seasonal differences in fish assemblage structure were observed only in the lower stretches.

A bacia do alto rio Paraná drena áreas caracterizadas pela agricultura e industrialização intensiva, sofrendo vários impactos negativos. O Córrego Rico é um tributário da bacia do alto rio Paraná que atravessa áreas de cultivo de cana-de-açúcar e recebe esgoto doméstico. O objetivo do presente trabalho é descrever e comparar a estrutura da assembleia de peixes no Córrego Rico. Foram realizadas amostragens padronizadas bimestrais, entre agosto de 2008 e junho de 2009, em sete trechos do rio com diferentes condições ambientais. Foram utilizadas redes de arrasto e peneiras. Os peixes coletados foram fixados, identificados, listados e quantificados. Caracterização ambiental e da qualidade da água foram realizadas nos trechos amostrados. Foram utilizados análise multivariada, estimadores de riqueza e diversidade para analisar os dados. A estrutura da assembleia de peixes foi relacionada com estrutura do leito do rio e pelas características físicas e químicas da água. A assembleia de peixes foi dividida em três grupos: trecho superior, médio e inferior. Altos valores de riqueza e diversidade foram observados nos trechos superior e inferior devido a conectividade com um pequeno lago e o rio Mogi Guaçu, respectivamente. Baixos valores de riqueza e diversidade foram observados nos trechos médios, sugerindo que uma barragem entre estes trechos causa impacto na assembleia de peixes do Córrego Rico. Diferenças sazonais na estrutura da assembleia de peixes foram observadas somente no trecho inferior.

Structural and ultrastructural characterization of the embryonic development of Pseudoplatystoma spp. hybrids.

The hybrid fish Pseudoplatystoma spp. has been raised on a large scale by several fish farmers, despite the fact that little is known about its biology. This is because it presents a number of zootechnical advantages over the parental species. In order to provide information about the early morphology of this important species, we analyzed the fertilization and embryonic development of the hybrid between spotted females and barred males of sorubim specimens by light microscopy and by scanning (SEM) and transmission electron microscopy (TEM) after induced spawning. Samples were collected at pre-established moments up to larval hatching. Seven distinct stages of hybrid embryonic development were identified: zygote, cleavage, morula, blastula, gastrula, histogenesis and organogenesis, and hatching. Under SEM, we observed spermatozoa at the micropyle entrance, the formation of a fertilization cone in the eggs, the differentiation of cephalic and caudal regions, the neural tube and embryo growth along the cephalo-caudal axis, as well as rudimentary optic vesicle and barbels. Under light microscopy, cytoplasmic movement was apparent with the consequent formation of animal and vegetative poles in eggs, in addition to epiboly movements and a small notochord portion. Under TEM, the oocyte chorion and eggs presented a sieve-like aspect in transversal cuts, coupled with the rupture of cortical alveoli and chorion elevation, thus enlarging the perivitelline space. Several mitochondria in the cortical cytoplasm were detected in both oocytes and eggs. Overall, we observed that the larvae hatched without visible morphological alterations, and seemed to be as viable in captive systems as they are in the natural environment.