No abstract

Autophagy, a highly conserved catabolic program for degrading proteins and organelles, is essential for cell and tissue homeostasis. Primarily, this process has a cytoprotective role under nutrient deprivation, but several stress stimuli can induce autophagy and, thus, distinct programmed cell death (PCD) pathways can be actived when stress is not abolished. Fish ovaries are a suitable experimental model system for studying the mechanisms of PCD due to the presence of postovulatory and atretic (i.e., nonovulated) follicles, which follow different routes after spawning. Apoptosis of the follicular cells is the major mechanism responsible for the rapid resorption of the postovulatory follicles. Recently, we investigated the contribution of PCD during follicular atresia in two species of freshwater fish. In contrast to mammals, this study revealed that follicular apoptosis is not a major process for deletion of follicular cells in atretic follicles. Furthermore, we detected autophagic vacuoles containing degenerating organelles increasing through follicular atresia in both species. In this addendum, we propose a hypothesis for follicular cell removal during ovarian regression in oviparous fish. In this model, autophagy could have dual roles in follicular atresia. Thus, fish ovaries after breeding are suitable models for studying the interactions among the different cell death pathways.

We describe and compare the histology of liver and spleen of Geophagus brasiliensis (Perciformes), Hypostomus francisci (Siluriformes) and Hoplias aff. malabaricus (Characiformes), tropical freshwater fishes. In G. brasiliensis and H. aff. malabaricus the hepatocytes were arranged in tubular form whereas in H. francisci they cord-like. In all species, hepatocytes presented glycogen, but in G. brasiliensis and H. aff. malabaricus they showed strong stained for hemossiderin in the cytoplasm. In G. brasiliensis and H. aff. malabaricus, melanomacrophage centres (MMCs) were associated to hepatic structures and only in G. brasiliensis was observed intrahepatic exocrine pancreas. The spleen, in all species, was characterized by red and white pulp without boundary between the two regions, but only in H. francisci was recorded nodular organization in splenic parenchyma. The G. brasiliensis and H. aff. malabaricus presented in the white pulp MMCs linked mainly to ellipsoids. Besides, we observed large MMCs in the spleen in relation to liver of G. brasiliensis and H. aff. malabaricus. In liver, highest values of reticular fibers and collagen were observed in G. brasiliensis. In spleen, highest values of reticular fibers and collagen were recorded in H. aff. malabaricus and H. francisci, respectively. Histological differences confirm the hypothesis that the phylogenetic distance is reflected in liver and spleen.Keywords: Extracellular matrix, Hepatocytes, Intrahepatic exocrine pancreas, Melanomacrophage centres, Red and White pulp.Nós descrevemos e comparamos a histologia do fígado e do baço de Geophagus brasiliensis (Perciformes), Hypostomus francisci (Siluriformes) e Hoplias aff. malabaricus (Characiformes), peixes neotropicais de água doce. Em G. brasiliensis e H. aff. malabaricus os hepatócitos organizaram-se na forma tubular enquanto que em H. francisci eles apresentaram-se como cordões celulares. Em todas as espécies, os hepatócitos apresentaram glicogênio, mas em G. brasiliensis e H. aff. malabaricus, eles mostraram forte marcação para hemossiderina no citoplasma. Em G. brasiliensis e H. aff. malabaricus, centros melanomacrofágicos (CMMs) foram associados a estruturas hepáticas e somente em G. brasiliensis foi observado pâncreas exócrino intrahepático. O baço, em todas as espécies, foi caracterizado pela polpa vermelha e branca sem limites entre as duas regiões, mas somente em H. francisci foi registrado uma organização nodular no parênquima esplênico. G. brasiliensis e H. aff. malabaricus apresentaram na polpa branca CMMs associados principalmente a elipsoides. Além disso, nós observamos CMMs grandes no baço em relação ao fígado de G. brasiliensis e de H. aff. malabaricus. No fígado, valores altos de fibras reticulares e colágeno foram observado em G. brasiliensis. No baço, valores altos de fibras reticulares e colágeno foram registrados em H. aff. malabaricus e H. francisci, respectivamente. Diferenças histológicas confirmam a hipótese que a distância filogenética está refletida no fígado e no baço. Palavras-chave:...

Herein we determine for the first time the reproduction parameters and population structure of Hypostomus francisci in the Itapecerica River, São Francisco Basin. A total of 250 specimens was captured quarterly between March 2010 and February 2012. Body weight, total length and weight of the gonads were obtained in the laboratory. Gonad samples were submitted to histological and histochemical techniques. Females with spawning capable ovaries were used to determine the fecundity and relative fecundity. Sex ratio with 1:1.01 (female:male) was observed. Males were more numerous than females for individuals smaller than 170 mm, however the number of females was significantly greater for specimens larger than 330 mm. The length-weight relationship estimated for H. francisci indicates negative-allometric growth. Females spawning capable were observed mostly in November-December-January. Two cohorts of oocytes at a determined time evidencing the development type group-synchronic. The eggs reaching 3.4 mm and the fecundity ranged from 312-1,460 oocytes with an average of 585.81 ± 337.43 oocytes per female. The reproductive parameters and population structure of H. francisci from Itapecerica River suggested that this species showed singular reproductive tactics among congeners.

River damming and building of hydroelectric power plants interrupt the reproductive migration routes and change the major physicochemical parameters of water quality, with drastic consequences for populations of migratory fishes. The goal of this study was to evaluate proliferation and cell death during spermatogenesis and serum profiles of sex steroids in Prochilodus argenteus, from the São Francisco River, downstream from the Três Marias Dam. A total of 257 adult males were caught quarterly during a reproductive cycle in two sites: the first 34 km of the river after the dam (site 1) and the second 34-54 km after the dam (site 2), after the confluence with a tributary, the Abaeté River. Seasonal changes in the testicular activity associated with morphometric analyses of germ cells as well as proliferation and testicular apoptosis support a more active spermatogenesis in fish from site 2, where higher levels of sex steroids and gonadosomatic index (GSI) were also found. In site 1, fish presented low serum levels of testosterone, 17β-estradiol and 17α-hydroxyprogesterone and a low GSI during gonadal maturation. Spermatogonial proliferation (PCNA) and apoptosis (TUNEL) were more elevated in fish from site 1, but spermatocytes were mainly labelled in fish from site 2. Overall, these data demonstrate changes in testicular activity and plasma sex steroids in a neotropical teleost fish living downstream from a hydroelectric dam, supplying new data on fish reproduction in regulated rivers. Moreover, morphometric analyses associated with sex steroids profiles provide reliable tools to assess fish spermatogenesis under environmental stress conditions.