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Oocyte morphology, embryogenesis and early larval development were compared in Hoplerythrinus unitaeniatus, Hoplias lacerdae and Hoplias malabaricus (Characiformes: Erythrinidae) by macroscopical, histological, histochemical and ultrastructural analyses. The eggs of the three species were yellowish and adhesive, containing carboxyl and sulphate radicals in the glycoconjugates of the zona radiata. A complex surface arrangement was identified in oocytes of H. unitaeniatus and H. lacerdae, while H. malabaricus had a simple oocyte surface pattern. Lectin histochemistry revealed different carbohydrate terminal residues in cortical alveoli, outer zona radiata and follicular cells of the three species. At the animal pole, the oocyte surface topography surrounding the micropyle was species-specific. The micropylar cell was ConApositive, suggesting the presence of carbohydrates with mannose/glucose terminal residues that could have a role during fertilization. The erythrinids exhibited a prolonged embryonic and larval development compared to other Characiformes, a reproductive strategy used for increasing offspring protection. Early development proceeded most rapidly in H. unitaeniatus, followed by H. malabaricus and then H. lacerdae, which could have more developed parental care behaviour. An adhesive organ composed of secretory prismatic cells protruding from the cephalic region of the three erythrinid larva allowed them to attach to one another during development. Reproductive behaviour and early developmental strategies were similar in the three species, but the oocyte surface morphology suggests a close relationship between H. unitaeniatus and H. lacerdae.

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We studied the relationship between the morphology of the reproductive system and the reproductive strategies of six neotropical catfishes using macroscopic and microscopic analyses. The reproductive system of the examined Siluriformes showed diversified characteristics, but permitted their being grouped according to three reproductive strategies: pelagic spawning, demersal spawning, and internally fertilizing. The pelagic spawners Pseudoplatystoma corruscans and Conorhynchos conirostris have testes that are characterized by filiform lobes, absence of testicular secretion, full-grown oocytes of small diameter, thin zona radiata, and cuboidal follicular cells. Pimelodus maculatus is morphologically distinct from the other two pelagic spawners catfishes due to the presence of testicular secretion. The demersal spawners Lophiosilurus alexandri and Rhinelepis aspera possess homogeneous testicular secretion, large mature oocytes, and columnar follicular cells. The most specialized reproductive system was observed in the internally fertilizing Trachelyopterus galeatus, which possesses a seminal vesicle accessory to the testes, spermatozoa with elongated nuclei that form spermatozeugmata, and a secretory ovarian lamellar epithelium that is associated with sperm storage. The reproductive system observed in Neotropical catfishes showed a relationship associated with the type of fertilization and the reproductive strategies of the six species studied.

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.

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The increasing amounts of heavy metals entering aquatic environments can result in high accumulation levels of these contaminants in fi sh and their consumers, which pose a serious risk to ecosystems and human health. We investigated the concentrations of mercury (Hg), cadmium (Cd), zinc (Zn), chromium (Cr), and lead (Pb) in muscle, liver, and spleen tissues of Pseudoplatystoma corruscans specimens collected from two sites on the Paraopeba River, Brazil. The level of heavy metals concentrations in the tissues was often higher in viscera (i.e. liver and spleen) than in muscle, and thus, the viscera should not be considered for human consumption. Correlations between metal concentrations and fi sh size were not signifi cant. Although the levels of muscle bioaccumulation of Hg, Cd, Zn, Cr, and Pb, generally do not exceed the safe levels for human consumption, the constant presence of heavy metals in concentrations near those limits considered safe for human consumption, is a reason for concern, and populations who constantly consume fi sh from polluted rivers should be warned. Our fi ndings also indicate that in a river network where certain areas are connected to other areas with high rates of environmental pollutants, people should be cautious about the regular consumption of fi sh, even when the fi sh consumed are caught in stretches of the basin where contamination levels are considered low, since many of the freshwater fi sh with high commercial value, such as the catfi sh surubim, are migratory.

Summary To evaluate the reproductive cycle and fecundity of tucunaré (Cichla kelberi Kullander & Ferreira, 2006), 697 specimens were captured in Três Marias Reservoir, São Francisco River, Brazil during 1994–1995 and 2005–2006. Reproductive activity was recorded throughout the sampling periods, with females exhibiting asynchronous oocyte development and multiple spawnings with a peak in September–October. Vitellogenic oocytes of the tucunaré were elliptical in shape with the longest diameter approximately 1230 μm and the shortest 700 μm, yolk globules with ellipsoid inclusions, lipid vesicles, small cortical alveoli and thin zona radiata (9.3 ± 2.0 μm thickness). Follicular cells were prisma‐shaped (49.0 ± 16.4 μm) in the vegetative pole, progressively becoming cubic cells in the animal pole toward the micropyle. Histochemical analyses indicated the presence of mucosubstances in the outer zona radiata and follicular cells that could be contributors to egg adhesiveness. Batch fecundity ranged from 4450 to 13 900 oocytes for females 31.5–43.5 cm total length, respectively, and correlated to gonadal weight (r2 = 0.80) and body weight (r2 = 0.70). Mean relative fecundity was 10.6 vitellogenic oocytes per gram body weight. As tucunaré is an exotic piscivorous species well‐adapted to the Três Marias Reservoir, the present work may be considered a contribution toward future strategies for population control.