Biomarkers of exposure to metal contamination and lipid peroxidation in the benthic fish Cathorops spixii from two estuaries in South America, Brazil

Biomarkers as lipid peroxidation, metallothionein and delta-aminolevulinic acid dehydratase were determined in Cathorops spixii to compare the biological responses of this fish from estuaries with distinct anthropogenic influence. Three areas were selected in two estuaries in accordance with the levels of contamination for the polluted (Santos/So Vicente) and with the hydrodynamic characteristics for the non-polluted (Canan,ia) estuary. Water characteristics and mercury levels in C. spixii confirmed a high human influence in the polluted system. In general, the biomarkers showed differences between the estuaries, suggesting disturbances in the specific cell mechanisms due to the presence of multiple xenobiotics in the contaminated system. Therefore, these biomarkers are recommended to promote more accurate information about the exposure to pollutants. Additionally, the study of the effect of the multiple xenobiotics on resident species such as the benthic fish C. spixii can favor a better assessment of the environmental quality of these systems.

Population biology and diet of the puffer fish Lagocephalus laevigatus (Tetraodontiformes: Tetraodontidae) in Caraguatatuba Bay, south-eastern Brazil

This study describes the spatio-temporal distribution, population biology, and diet of the puffer fish Lagocephalus laevigatus in Caraguatatuba Bay, south-eastern Brazil. Monthly samples were taken between August 2003 and October 2004 by trawls in two areas, south and north, at depths of 1 to 4 m. The fish were measured and their sex and reproductive stage determined. The abundance of this species was compared between areas and among months, and the items in the diet were identified and quantified. Lagocephalus laevigatus was rare in Caraguatatuba Bay, where only 199 small individuals (4.8 to 15.4 cm) were obtained in the entire study period, suggesting that this species uses the estuary as a nursery. None of the specimens of L. laevigatus captured in Caraguatatuba Bay were sexually mature. Higher densities of L. laevigatus in the bay were recorded in the south area and between October and December 2003, i.e. in the spring, suggesting that spawning may occur from late winter to spring (August through to November). The diet items consumed by L. laevigatus in Caraguatatuba Bay were, as expected from the current literature, crustaceans, mainly amphipods, and fish. However, the most-consumed item was the sea whip Leptogorgia setacea (Cnidaria). This feeding habit may be related to the presence of toxins (tetrodotoxin and saxitoxin) that are frequently found in the skin and viscera of L. laevigatus, which may be sequestered from the sea whip, which possibility still needs to be specifically evaluated.

Antioxidant defenses and biochemical changes in the neotropical fish pacu, Piaractus mesopotamicus: Responses to single and combined copper and hypercarbia exposure

This study investigated the potentially detrimental effects of copper and elevated aquatic CO2 (hypercarbia), alone or in combination, on pacu, Piaractus mesopotamicus. Fish were exposed for 48 h to control (no copper addition in normocarbia), to 400 mu g Cu2+L-1, to hypercarbic (1% CO2; PCO2=6.9 mm Hg) water and to 400 mu g Cu2+L-1+ hypercarbia. In liver the single factors caused an increase in lipid hydroperoxide concentration that was not observed when the factors were combined. Copper exposure elicited increased hepatic superoxide dismutase activity, irrespective of aquatic CO2 level. On the other hand, the effects of copper on hepatic glutathione peroxidase activity were dependent on water CO2 levels. The two stressors combined did not affect hepatic catalase activity. Hypercarbic water caused a decline in plasma glucose concentration, but this was not observed when hypercarbia was combined with copper exposure. Copper caused a decrease in branchial Na+/K+-ATPase activity that was independent of water CO2 level. Copper caused an increase in branchial metallothionein concentration that was independent of water CO2 level. Thus, branchial metallothionein and Na+/K+-ATPase were effective biomarkers of copper exposure that were not affected by water CO2 level. (C) 2012 Elsevier Inc. All rights reserved.

Behavioral characterization of the alarm reaction and anxiolytic-like effect of acute treatment with fluoxetine in piaucu fish

In Ostariophysan fish, the detection of the alarm substance liberated into the water as a consequence of an attack by a predator elicits an alarm reaction or anti-predatory behavior. In this study, experiments were performed to: (i) describe and quantitatively characterize the behavioral and ventilatory responses in piaucu fish (Leporinus macrocephalus), individually and as part of a school, to conspecific alarm substance (CAS) and; (ii) test the effect of acute fluoxetine treatment on alarm reaction. Histological analysis revealed the presence of club cells in the intermediate and superficial layers of the epidermis. The predominant behavioral response to CAS was freezing for fish held individually, characterized by the cessation of the swimming activity as the animal settles to a bottom corner of the aquarium. Fish exposed to CAS showed decrease in the mean ventilatory frequency (approximately 13%) relative to control. In schools, CAS elicited a biphasic response that was characterized by erratic movements followed by increased school cohesion and immobility, reflected as an increased school cohesion (65.5% vs. -5.8% for controls) and in the number of animals near the bottom of the aquarium (42.0% vs. 6.5% for controls). Animals treated with single i.p. injections of fluoxetine (10 mu g/g b.w.) did not exhibit alarm behavior following CAS stimulation. These results show that an alarm pheromone system is present in piaucu fish, evidenced by the presence of epidermal club cells and an alarm reaction induced by CAS and consequently of a chemosensory system to transmit the appropriate information to neural structures responsible for initiating anti-predator behavioral responses. In addition, fluoxetine treatment caused an anxiolytic-like effect following CAS exposure. Thus, the alarm reaction in piaucu can be a useful model for neuroethological and pharmacological studies of anxiety-related states. (C) 2011 Elsevier Inc. All rights reserved.

The fish fauna in the fish passage at the Ourinhos Dam, Paranapanema River

The composition and abundance of the fish assemblage were evaluated in the fish ladder of Ourinhos Dam, the newest dam (closed in 2005) in the cascade of dams constructed on the Paranapanema River. Samplings were carried out three times on a diel cycle, in three sampling periods, two in the warm season and one in the cold season of 2008 - 2009. The ladder was closed and emptied and the entire fish assemblage was sampled and identified. Most individuals were released alive downstream of the dam. The assemblage found in the ladder was compared with the fish fauna sampled in the reservoir and in downstream sites, in the same period. Twenty seven species and a total of 4682 individuals were caught in the ladder. Pimelodus maculatus was the only migratory species, which was caught in low number in the ladder (0.04% of the total captured), where small sedentary species predominated. The most abundant species were the non-migratory Apareiodon affinis, Bryconamericus stramineus, Astyanax fasciatus and Parodon nasus. Individuals observed in the ladder's window were moving up-and down the passage. The fish ladder is a microhabitat inhabited by an abundant association of benthic organisms that is probably used as a food resource for the fish assemblage in the ladder. The similarity between the fish fauna in the ladder and that of the Ourinhos Reservoir was low (26%). The species richness of migrants in the stretch between the uspstream reservoir (Chavantes) and the downstream one (Salto Grande), before the Ourinhos dam closure (23 species) was reduced to 16 and 12 species in Salto Grande and Ourinhos reservoirs, respectively, after the dam closure, and to a single species in the ladder.

Aggressiveness Overcomes Body-Size Effects in Fights Staged between Invasive and Native Fish Species with Overlapping Niches

Approximately 50 years ago, Nile tilapia were accidentally introduced to Brazil, and the decline of pearl cichlid populations, which has been intensified by habitat degradation, in some locations has been associated with the presence of Nile tilapia. There is, however, little strong empirical evidence for the negative interaction of non-native fish populations with native fish populations; such evidence would indicate a potential behavioural mechanism that could cause the population of the native fish to decline. In this study, we show that in fights staged between pairs of Nile tilapia and pearl cichlids of differing body size, the Nile tilapia were more aggressive than the pearl cichlid. Because this effect prevailed over body-size effects, the pearl cichlids were at a disadvantage. The niche overlap between the Nile tilapia and the pearl cichlid in nature, and the competitive advantage shown by the Nile tilapia in this study potentially represent one of several possible results of the negative interactions imposed by an invasive species. These negative effects may reduce population viability of the native species and cause competitive exclusion.