The objective of the present study was to investigate the influence of the establishment of dominance relationships and social stress on plasma cortisol and metabolite levels in Nile tilapia (Oreochromis niloticus). During the 30-day experiment, the fish weighing 236 ± 29 g were kept in individual aquaria, except for two pairings lasting 6 h each. Blood samples were taken from the animals before and after pairing. Display, approach, attack, rebuff, chase flight, and coloration were carried out on days 16 and 30. Activities and behaviors characteristic of the establishment of dominance relationships were described. It was possible to classify all experimental fish (N = 30) as dominant or subordinate. No differences were detected between dominant (N = 15) and subordinate (N = 15) fish during isolation or after pairing in cortisol (isolated: 5.76 ± 0.98 vs 5.42 ± 0.63; paired: 10.94 ± 1.62 vs 11.21 ± 2.45 µg/dl), glucose (isolated: 60.02 ± 4.9 vs 67. 85 ± 16.16; paired: 110.44 ± 15.72 vs 136.26 ± 22.46 mg/dl), triglyceride (isolated: 167.87 ± 5.06 vs 185.68 ± 7.24; paired: 210.85 ± 13.40 vs 221.82 ± 12.70 mg/dl) or total protein levels (isolated: 7.01 ± 0.42 vs 6.69 ± 0.59; paired: 9.21 ± 0.62 vs 9.51 ± 0.66 g/dl). However, when isolated (N = 30) and paired (N = 30) tilapia were compared, there were significant differences in cortisol and metabolite levels. The similar response presented by dominant and subordinate tilapia indicates that establishment of dominance relationships was a stressor for both groups.

Euacalyptus is part of the national economy. This is a natural source that provides pulp for papermaking, coal for the steel industry and bioactive compounds used in various medical and industrial areas. The essential oil extracted from leaves is an important product obtained from Eucalyptus. This work evaluated essential oil extracted from leaves of Eucalyptus resistant and susceptible to Glycaspis brimblecombei using thermal tools. Samples of essential oils were extracted from crushed leaves of E. pellita (resistant) and E. camaldulenses (susceptible) by Clevenger method. The oils were analyzed by physicochemical characterization, thermogravimetry and differential thermal simultaneous analysis (TGA-DTA) and differential scanning calorimetry (DSC). The TGA curves of the essential oil from E. camaldulensis and commercial showed similarity and show that the major constituent can be 1,8-cineole. However, the TGA curves of the E. pellita essential oil has different pattern. In DSC, changing the endothermic peak of the commercial oil indicates the presence of other components or additives. The results indicate that these Eucalyptus essential oils had different chemical composition and the 1,8cineole can be the reason of resistance and susceptibility to G. brimblecombei attack. Further studies will be performed to characterize these samples.