Effects of hypoxia and subsequent recovery on turbot Scophthalmus maximus: hormonal changes and anaerobic metabolism

Abstract

Hormonal changes, substrate mobilization and energy metabolism were studied in turbot Scophthalmus maximus exposed to 3 hypoxic conditions (oxygen partial pressure in water, PwO 2 = 90, 60 and 30 mm Hg) followed by recovery under normoxia. Measurements of the blood pH, total CO 2 concentration, arterial oxygen partial pressure, hematocrit, glucose, lactate, and 'stress' hormones (cortisol, adrenaline and noradrenaline) plasmatic concentrations were performed. Highenergy phosphorylated compounds, glycogen, glucose and lactate concentrations were also determined in liver and white muscle tissues. Exposure to 90 or 60 mm Hg did not induce any major physiological change, as hyperventilation by itself could compensate for the decrease in water oxygen tension. At 30 mm Hg, marked increases in cortisol, adrenaline and noradrenaline concentrations, associated with a decrease in blood arterial oxygen partial pressure, were observed. During exposure to 30 mm Hg, turbot resorted to anaerobic metabolism, resulting in liver glycogen depletion and lactate production. This mechanism appeared to be efficient enough to produce energy, as no significant change in phosphorylated compounds and adenylate energy charges in muscle and liver could be observed. These results indicate an absence of metabolic depression in turbot down to 30 mm Hg and confirm the high capacity of this species to cope with low water oxygen tension.

CRF-related peptides contribute to stress response and regulation of appetite in hypoxic rainbow trout

“…Overall, the increases in plasma cortisol in this study were proportional to the severity of the hypoxic bout and its duration. These results are consistent with similar observations in different species acutely exposed to hypoxic levels ranging from moderate to severe (39,45,47,50) and suggest that plasma glucocorticoids are sensitive indicators of short-term hypoxia exposure in fish. Through its effects on intermediary metabolism, the hypoxia-associated increase in plasma cortisol may promote the mobilization of stored energy and increase fuel availability (36).…”

“…There is now some evidence in fish that stressors can elicit an increase in CRF expression in the NPO (1,20). Whether the brain's CRF system is recruited in response to a hypoxic stress in fish is not known, but exposure to severe hypoxia is associated with a marked increase in the final product of HPI axis activation, i.e., plasma cortisol (39,50).…”

Improving sneaky-sex in a low oxygen environment: reproductive and physiological responses of male mosquito fish to chronic hypoxia

“…Testosterone, oestrogen and triiodothyronine were reported to decrease in common carp Cyprinus carpio when acclimated to hypoxia, resulting in retarded gonadal development (Wu et al, 2003). Increases in stress hormones such as cortisol as a result of chronic exposure to hypoxia (Pichavant et al, 2002) may disrupt spermatogenesis and other hormone pathways involved in sperm production. Alternatively, it is also possible that lower sperm numbers could be a physiological response to hypoxic conditions.…”

The effect of hypoxia on ventilation frequency in startled common soleSolea solea

“…1). A higher F V and amplitude are mechanisms that help to compensate for the reduction in oxygen availability to limit hypoxemia (Maxime et al , 2000; Pichavant et al , 2002). The S. solea in hypoxia did not show any difference between pre‐ and post‐stimulus F V values.…”