Ritmos biológicos de parâmetros fisiológicos em peixes amazônicos

Abstract

The aim of this study was to evaluate the biological rhythms of physiological parameters in juvenile oscar (Astronotus ocellatus) and matrinxã (Brycon amazonicus). Chapter 1 shows that some physiological parameters that are indicators of energy expenditure and, therefore, related to stressful conditions, present circadian variation related to the light/dark cycle for both species. B. amazonicus showed a greater number of physiological parameters that showed daily rhythms (Htc, Hb, MCH, MCHC, glucose, triglycerides and total cholesterol) compared to A. ocellatus (Htc, MCV, triglycerides and total proteins). These results may contribute to a better adequacy of conditions that provide better welfare and productive performance for these animals when kept in artificial systems. Chapter 2 shows responses on the lunar cycle effect of the juvenile matrinxã, indicating that the concentrations of melatonin, cortisol, metabolic parameters and oxidative stress indicators are modulated by both light/dark and moon phases (full and new moon). Our research provides the first insight into the influence of the lunar cycle on physiological parameters in matrinxã, and these results highlighted that moonlight is relevant for investigating how fish deal with environmental cycles. Chapter 3 refers to the circadian rhythm of plasma and ocular melatonin and that luminosity (light/dark cycle and light pulse) acts as a modulator of this hormone levels. Plasma melatonin levels were higher in the dark period for A. ocellatus and B. amazonicus. In A. ocellatus, the rhythmic pattern of melatonin in the retina is independent of the dark period. However, for B. amazonicus, ocular melatonin levels showed marked changes in the light/dark cycle, with lower values during the light period and higher values in the dark. A reduction in plasma melatonin levels was observed on exposure to pulse light for A. ocellatus and B. amazonicus, indicating that plasma melatonin is highly sensitive to light. In summary, the results highlight the importance of evaluating biological rhythms (circadian and infradian) for physiological parameters in species of commercial interest and susceptible to stressful situations in rearing conditions. In addition, the information generated can support the advancement of new technologies that may be used by environmental management programs and, consequently, contribute to the well-being of fish, essential for sustainable aquaculture.