Gobionellus oceanicus is a species widely distributed on the Atlantic coast and may be susceptible to anthropic effects. This study evaluated the morphology and the Na/K-ATPase activity of G. oceanicus gills considering the concentration of metals in the fish and Subaé River estuary. Although the metal concentrations detected in the water and sediment did not exceed certain limits, CONAMA (Brazilian Environment Council), TEL (Threshold Effect Level), and PEL (Probable Effect Level), the metals levels in gills plus muscle and skin of G. oceanicus were above the permitted setting of the Ministry of Health, Brazil. The pavement epithelial cells (PVC) of the gill filament was observed that there were long microridges either in the apical surface or in the lamella; especially, microridges degeneration was shown in some PVC from filament epithelium. The number of ionocyte and the volume density were (0.02 ± 0.001)/μm and (0.38 ± 0.27) %, respectively. The activity of Na/K-ATPase was 1.13 ± 0.76 μM Pi mg protein h. We describe the volume density and number of ionocytes and Na/K-ATPase enzymatic activity in G. oceanicus for the first time, which is useful for basic and comparative future studies to support aquatic biomonitoring.

Snakes are interesting examples of overcoming energy metabolism challenges as many species can endure long periods without feeding, and their eventual meals are of reasonably large sizes, thus exhibiting dual extreme adaptations. Consequently, metabolic rate increases considerably to attend to the energetic demand of digestion, absorption, and protein synthesis. These animals should be adapted to transition from these two opposite states of energy fairly quickly, and therefore we investigated mitochondrial function plasticity in these states. Herein we compared liver mitochondrial bioenergetics of the boid snake Boa constrictor during fasting and after meal intake. We fasted the snakes for 60 days, and then we fed a subgroup with 30% of their body size and evaluated their maximum postprandial response. We measured liver respiration rates from permeabilized tissue and isolated mitochondria. From isolated mitochondria, we also measured Ca2+ retention capacity and redox status. Mitochondrial respiration rates were maximized after feeding, reaching approximately a 60% increase from fasting levels when energized with complex I-linked substrates. Interestingly, fasting and fed snakes exhibited similar respiratory control ratios and citrate synthase activity. Furthermore, we found no differences in Ca2+ retention capacity, indicating no increase in susceptibility to mitochondrial permeability transition (MPT), and no changes in mitochondrial redox state, although fed animals exhibited increases in the release of H2O2. Thus, we conclude that liver mitochondria from B. constrictor snakes increase mitochondrial respiration rates during the postprandial period and quickly improve the mitochondrial bioenergetics capacity without compromising redox balance.

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This article describes the morphology of the respiratory surfaces, gills, and integument of the palate of the goby Gobionellus oceanicus (Pallas, 1770). We highlight the role of the palate integument's surface for air breathing in estuarine environments under probable hypoxia conditions. Such conditions can result from decreases in dissolved oxygen related to fluctuations in water level between tides, chemical composition, and increase in water temperature. Thus, a surface with respiratory characteristics can guarantee this fish's survival in environments that suffer constant variations.