Nilo Bazzoli

Ovarian follicular atresia in two teleost species: a histological and ultrastructural study

Follicular atresia is a common phenomenon in vertebrate ovaries involving the oocyte and the follicular wall degeneration. Female Astyanax bimaculatus lacustris and Leporinus reinhardti were kept in aquaculture cages inside tanks from February 1994 to January 1995 for the study of the characteristics of different stages of follicular atresia. Histological and ultrastructural analysis demonstrated similarities in the degenerative events and in the resorption of oocytes in both species. Degradation of organelles, such as mitochondria, cortical alveoli, and annulate lamellae occurred in the peripheral ooplasm during the initial stage of the process. Follicle cells showed marked phagocytic activity with digestive vacuoles, myelin figures, and lipofuscin granules during the intermediate and advanced stages of follicular atresia. Granulocytes were in activity during the final stage of follicle resorption. The duration of follicular atresia was 4 months in Leporinus reinhardti and 7 months in Astyanax bimaculatus lacustris. When submitted to induced reproduction in December 1995, 50-60% of the females of both species responded to induced spawning, indicating the recovery of gonadal activity. It is suggested that, in captive conditions, follicular atresia is shorter in total-spawning fishes when compared to those showing partial spawning, and that it has no apparent deleterious effects on induced reproduction in the subsequent cycle.

Cortical alveoli in oocytes of freshwater neotropical teleost fish

Abstract Depending on the species, the teleost cortical alveolus (CA) has from one to several layers of small to large cortical vesicles forming a continuous or discontinuous collar in the peripheral ooplasm. The histochemical composition of the CA, which also varies among species, is made of neutral glycoprotein, carboxylated glycocon‐jugate, neutral glycoprotein plus carboxylated glycoconjugate, sulfated glycoconjugate, neutral glycoprotein plus sialic acid‐rich glycoprotein. The CA was sudanophobic in all species analyzed. The morphology and contents of the CA seem to express common characters among many of the groups studies. Variations in the morphology and contents of the CA may be related to different mechanisms of polyspermy blockade.

Reproductive biology and feeding of Curimatella lepidura (Eigenmann & Eigenmann) (Pisces, Curimatidae) in Juramento reservoir, Minas Gerais, Brazil

Reproductive biology and feeding of Curimatella lepidura (Eigenmann & Eigenmann, 1889) were studied in Juramento reservoir, Sao Francisco River basin, Southeastern Brazil. Histological analyses and gonadosomatic indexes revealed females and males in reproductive activity from October to March and total spawning occurring from January to March coupled with the peak of spermiating males. In the dry season, the fishes accumulated energetic reserves for reproduction during a short rainy season. The species presented sexual dimorphism, being females larger than males and sexual maturation occurring close to 7.7 cm standard length for females and 7.1 cm for males. C. lepidura presented iliophagous feeding habit, ingesting mainly sediment/detritus and a small amount of acari, algae, Tricoptera insects and Ostracoda crustaceans, suggesting a probable role in nutrient recycling of the Juramento reservoir.

Reproduction of the catfish Iheringichthys labrosus (Lütken) (Pisces, Siluriformes) in Furnas reservoir, Minas Gerais, Brazil

The reproductive biology of Iheringichthys labrosus (Lutken, 1874) was studied in Furnas reservoir, Minas Gerais, Brazil. The fishes, 323 males and 817 females, were captured bimonthly from August 1993 to July 1994 by using gill nets with 3-10 cm mesh size. Gonadal maturation of the specimens was analyzed through macro and microscopical characteristics of the gonads. The secretory activity of the tubules of the caudal region of the testis was analyzed during the maturational testicular cycle. Females and males were in reproductive activity throughout the year in the reservoir. The peak of advanced maturation/mature stages occurred from October to January and of spawned/spent from February to May. The spawning of I. labrosus was identified as fractional or multiple type: occurring in the reservoir or in tributaries around it. The oocyte development of the species was asynchronous as different clusters of oocytes occurred simultaneously in the ovarian parenchyma. The epithelium of the tubules of the caudal region of the testis was in high secretory activity during advanced maturation/mature stage and this activity was absence in resting. The gonadosomatic index followed gonadal maturation, and the hepatosomatic index of females was lowest in advanced maturation/mature probably due the contribution of the liver in the vitellogenesis. The variations of the stomach repletion index, coelomic fat and condition factor indicated that the feeding activity was reduced and that the energetic reserves were consumed during the reproductive period.

Reproductive biology of Leporinus taeniatus Lütken (Pisces, Anostomidae) in Juramento Reservoir, São Francisco River basin, Minas Gerais, Brazil

A biologia reprodutiva do piau-jejo Leporinus taeniatus Lutken, 1875, especie endemica da bacia do rio Sao Francisco, foi estudada utilizando-se tecnicas biometricas, macroscopicas e microscopicas. Capturaram-se no reservatorio de Juramento, MG, em coletas trimestrais, 121 machos e 94 femeas, no periodo de marco de 2002 a fevereiro de 2003. Observou-se que femeas sao maiores do que os machos indicando dimorfismo sexual. Determinaram-se os estadios de maturacao gonadal atraves de analise histologica e do indice gonado-somatico. Os picos de maturacao/maduro e de peixes desovados/espermiados ocorreram no trimestre dezembro/janeiro/fevereiro. L. taeniatus apresentou desova total e desenvolvimento grupo-sincronico dos ovocitos. O indice gonadossomatico acompanhou a maturacao das gonadas e o indice de gordura celomica apresentou menores valores no estadio maturacao/maduro, indicando consumo de reservas graxas no periodo reprodutivo. O indice de replecao estomacal apresentou maiores valores no estadio desovado/espermiado, indicando que a especie alimenta-se mais apos a reproducao.

Influence of a large dam and importance of an undammed tributary on the reproductive ecology of the threatened fish matrinxã Brycon orthotaenia Günther, 1864 (Characiformes: Bryconidae) in southeastern Brazil

A total of 312 adults of matrinxa were captured bimonthly, between 2011-2012, in two sites of the rio Sao Francisco: immediately downstream of the Tres Marias Dam (site 1) and in the confluence with the rio Abaete (site 2). Specimens of Brycon orthotaenia from site 2 presented higher values of total length (32.24 ± 5.70 cm for females and 26.64 ± 3.79 cm for males) and body weight (506.66 ± 332.17 g for females and 267.36 ± 145.84 g for males), when compared with the site 1. In site 2 was registered the highest GSI means (9.97 ± 2.96 for females and 0.93 ± 0.52 for males), compared with the site 1 means. Reproduction period occurred from October to February. Unlike site 2, no spawned females or spent males were captured in site 1. Significant differences were found between females and males in site 2 (χ2 = 26.84, df = 1, P < 0.05). Physical-chemical parameters of the water presented higher values in site 2. The canonical correlation test indicated that the reproduction of males is less susceptible to environmental factors than that of females. These results show that B. orthotaenia finds favourable conditions to reproduction just in site 2.

Morphology of gonads, maturity and spawning season of Loricariichthys spixii (Siluriformes, Loricariidae) in a Subtropical Reservoir

A morfologia das gonadas e a epoca de desova de Loricariichthys spixii, no reservatorio de Lajes foi descrita baseada em 175 machos e 613 femeas, coletados de Janeiro-1996 a Dezembro-1997. Celulas de linhagem espermatogenica foram divididas em 4 fases: espermatogonias (primarias e secundarias), espermatocitos (primarios e secundarios), espermatides e espermatozoides, enquanto as celulas de linhagem ovocitaria tambem foram divididas em 4 fases, baseadas em caracteristicas do nucleo, ooplasma e foliculos dos ovocitos: ovocitos primarios (O1), ovocitos previtelogenicos (O2), ovocitos de vesicula cortical (O3) e globulos de vitelo ou vitelogenicos (O4). Cinco estadios gonadais foram descritos para machos/femeas de acordo com a distribuicao das celulas de linhagem ovocitaria / espermatogenicas: repouso (1); maturacao inicial (2a); maturacao avancada (2b); parcialmente esvaziado/desovado (4a); totalmente esvaziado/desovado (4b). Desova e parcelada, ocorrendo atraves do ano. O repouso/recuperacao ocorreu em Julho/Agosto para femeas coincidindo com menores temperaturas e pluviosidades, e diminuicoes do niveis da agua. O amplo periodo reprodutivo e parte da estrategia desenvolvida por esta especie para suportar as pressoes ambientais (bioticas e abioticas) e obter sucesso neste reservatorio oligotrofico e pobremente estruturado.

Relationship between bcl-2, bax, beclin-1, and cathepsin-D proteins during postovulatory follicular regression in fish ovary

In fish ovaries, postovulatory follicles (POFs) are key biomarkers of breeding and provide an interesting model for studying the relationship between autophagy and apoptosis. In this study, we investigated the immunohistochemical expression of autophagic and apoptotic proteins to improve the knowledge on the mechanisms regulating ovarian remodeling after spawning. Females from three neotropical fish species kept in captivity were submitted to hormonal induction. After ova stripping, ovarian sections were sampled daily until 5 days postspawning (dps). Similar events of POF regression were detected by histology, terminal transferase-mediated dUTP nick-end labeling (TUNEL), and electron microscopy in the three species: follicular cells hypertrophy, progressive disintegration of the basement membrane, gradual closing of the follicular lumen, theca thickening, and formation of large autophagic vacuoles preceding apoptosis of the follicular cells. Autophagic and apoptotic proteins were assessed by immunohistochemistry. Morphometric analysis of the immunolabeling revealed a more intense reaction for bcl-2 and beclin-1 (BECN1) in POFs at 0 to 1 dps and for bax at 2 to 3 dps (P < 0.001), the later period being the peak of apoptosis of the follicular cells. The immunostaining for cathepsin-D was more elevated until 2 to 3 dps and decreased significantly at 4 to 5 dps, when the POFs were in late stage of regression. Double labeling for BECN1 and caspase-3 indicated a shift in the relationship between autophagy and apoptosis at 2 to 3 dps, a critical period in determining the fate of follicular cells in POFs. Together, these results indicate that the bcl-2 family, BECN1, and cathepsin-D can be involved in the regulation of ovarian remodeling in teleost fish.

Observations on the seasonal breeding biology and fine structure of the egg surface in the white piranha Serrasalmus brandtii from the São Francisco River basin, Brazil

In the Juramento Reservoir, south-eastern Brazil, the white piranha Serrasalmus brandtii showed a prolonged reproductive season, with evidence for multiple spawning and a reproductive peak associated with seasonal rains. The egg surface exhibited a honeycomb-like pore canal arrangement and an adhesive apparatus surrounding the micropyle. Electron microscopic analysis suggests a role for the micropylar cell and neighbouring follicular cells in secretion of substances for egg attachment.

Reproductive plasticity of Hypostomus affinis (Siluriformes: Loricariidae) as a mechanism to adapt to a reservoir with poor habitat complexity

In this work we describe the gonad morphology and spawning season of Hypostomus affinis (Steindachner, 1877) in a tropical reservoir based on 55 males and 125 females. Our aim was to assess eventual adaptations in reproductive tactics developed by this riverine species inhabiting an oligotrophic reservoir with low habitat complexity, few rocks and few other preferred consolidated substrata. We described the stages of cells of reproductive lineage, gonadal development and some reproductive traits which were compared with information in the available literature. Cells from the spermatogenic lineage were spermatogonia, spermatocytes, spermatids and spermatozoa, and cells from the oocytarian lineage were primary oocytes, previtelogenic oocytes, cortical vesicle oocytes and yolk globules or vitellogenic. Five stages were described for the males/females according to the distribution of oocytes and spermatogenic lineage cells: resting; initial maturation; advanced maturation; partially spent/spawned; totally spent/spawn. Females outnumbered males and reached larger size. Synchronic ovary development in two groups was found with diameter of mature oocytes ranging from 2 to 3.35 mm. Indication of early maturation, a longer reproductive period and the production of smaller eggs in small clutches seems to be features of the reservoir population not found in riverine systems. Such changes in tactics may indicate a shift to an opportunistic strategy, helping the population to withstand environmental constraints and to succeed in this oligotrophic and poorly structured reservoir.