Abstract
Environmental hypoxia represents a major physiological challenge for Eriocheir sinensis and Palaemonetes sinensis and is a severe problem in aquaculture. Therefore, understanding the metabolic response mechanisms of E. sinensis and P. sinensis, which are economically important species, to environmental hypoxia and reoxygenation is essential. However, little is known about the intrinsic mechanisms by which E. sinensis and P. sinensis cope with environmental hypoxia at the metabolic level. Hypoxia–reoxygenation represents an important physiological challenge for their culture. In this study, respiratory metabolism and respiratory metabolic enzymes of E. sinensis and P. sinensis were evaluated after different hypoxia and reoxygenation times. The results showed that environmental hypoxia had a dramatic influence on the respiratory metabolism and activities of related enzymes. The oxygen consumption rates (OCR) significantly increased as hypoxia time increased, while the ammonia excretion rate (AER) was significantly lower than that in the control group after 8 h hypoxia. The oxygen to nitrogen ratio (O:N) in the control group was <16, indicating that all the energy substrates were proteins. After environmental hypoxia, the O:N significantly increased, and the energy substrate shifted from protein to a protein–lipid mixture. The OCR, AER, and O:N did not restore to initial levels after 2 h or 12 h reoxygenation and was still the same as after 8 h hypoxia. As environmental hypoxia time increased, succinate dehydrogenase (SDH) gradually decreased and lactate dehydrogenase (LDH) gradually increased. Both SDH and LDH were gradually restored to normal levels after reoxygenation. Therefore, environmental hypoxia should be avoided as much as possible during aquaculture breeding of E. sinensis and P. sinensis. Further, since OCR will significantly increase after a short period of reoxygenation, secondary environmental hypoxia due to rapid consumption of oxygen should also be avoided in aquaculture.
Highlights
The growth and development of crustaceans is regulated by the endocrine system, and aspects of the external environment, such as dissolved oxygen (DO), temperature, salinity, light, and pH (Castejón et al, 2015; Long et al, 2017)
The oxygen consumption rates (OCR) increased first and decreased as environmental hypoxia time increased, and there was a significant difference between the hypoxia and control groups (P < 0.05)
The OCR of E. sinensis and P. sinensis increased as environmental hypoxia time increased
Summary
The growth and development of crustaceans is regulated by the endocrine system, and aspects of the external environment, such as dissolved oxygen (DO), temperature, salinity, light, and pH (Castejón et al, 2015; Long et al, 2017). The level of DO is a key indicator of water quality, and partially determines the intensity of crustacean aquaculture. There are many factors that cause hypoxia in aquaculture, such as extreme weather changes, eutrophication, long-distance transportation, and human factors (Lehtonen and Burnett, 2016; Lund et al, 2017). Much research has focused on the negative effects of environmental hypoxia on crustaceans. Environmental hypoxia causes abnormal breathing and metabolic disorders in crustaceans, which leads to a decline in feeding and efficiency of food transformation and retarded growth (Han et al, 2017; Sun et al, 2018). Environmental hypoxia even affects the behavior, morphological characteristics, immunity, and reproduction of crustaceans (De Lima et al, 2015; Lara et al, 2017; Peruzza et al, 2018.)
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