Stress response in silver catfish (Rhamdia quelen) exposed to the essential oil of Hesperozygis ringens

This study investigated the effects of prolonged exposure of silver catfish (Rhamdia quelen) to the essential oil (EO) of Hesperozygis ringens. Ventilatory rate (VR), stress and metabolic indicators, energy enzyme activities, and mRNA expression of adenohypophyseal hormones were examined in specimens that were exposed for 6 h to 0 (control), 30 or 50 µL L−1 EO of H. ringens in water. Reduction in VR was observed in response to each treatment, but no differences were found between treatments. Plasma glucose, protein, and osmolality increased in fish exposed to 50 µL L−1. Moreover, lactate levels increased after exposure to both EO concentrations. Plasma cortisol levels were not changed by EO exposure. Fish exposed to 30 µL L−1 EO exhibited higher glycerol-3-phosphate dehydrogenase (G3PDH) activity, while exposure to 50 µL L−1 EO elicited an increase in glucose-6-phosphate dehydrogenase (G6PDH), fructose-biphosphatase (FBP), and 3-hydroxyacyl-CoA-dehydrogenase (HOAD) activities compared with the control group. Expression of growth hormone (GH) only decreased in fish exposed to 50 µL L−1 EO, while somatolactin (SL) expression decreased in fish exposed to both concentrations of EO. Exposure to EO did not change prolactin expression. The results indicate that GH and SL are associated with energy reorganization in silver catfish. Fish were only slightly affected by 30 µL L−1 EO of H. ringens, suggesting that it could be used in practices where a reduction in the movement of fish for prolonged periods is beneficial, i.e., such as during fish transportation.This study was supported by research funds from the Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS/PRONEX), Ministério da Pesca/Ministério da Ciência e Tecnologia/FINEP, Conselho Nacional de Pesquisa e Desenvolvimento Científico (CNPq) and by project AGL2013-48835-C2-1-R (Ministerio de Economía y Competividad) to J.M. Mancera (Spain). B. Baldisserotto received a research fellowship from CNPq. C. Toni and C.G. Pinheiro received PhD fellowships from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and J.A. Martos-Sitcha is supported by a PhD fellowship (FPU, Reference AP2008-01194) from Ministerio de Educación (Spain).Peer reviewe