Effects of hypoxia, anoxia, and endogenous ethanol on thermoregulation in goldfish,Carassius auratus

Abstract

Effects of hypoxia, anoxia, and endogenous ethanol (EtOH) on selected temperature (T(sel)) and activity in goldfish were evaluated. Blood and brain EtOH concentrations ([EtOH]) and brain oxygen partial pressure (PO(2)) were quantified at crucial ambient oxygen pressures. Below a threshold value near 31 Torr, T(sel) decreased as a function of environmental PO(2). T(sel) of 15 degrees C-acclimated fish was approximately 10 degrees C at the onset of anoxia and changed little over 2 h. Activity showed a similar response pattern. Brain [EtOH] was significantly elevated above control levels after 1 h anoxia. In normoxic water, T(sel) remained different in previously anoxic and normoxic control fish for approximately 20 min. Blood [EtOH] of previously anoxic fish remained significantly elevated ([EtOH] >4.0 micromol/g blood), and activity was significantly depressed at 20 min. Brain PO(2) reached normal levels in <3 min. We conclude that [EtOH] (brain or blood) and brain PO(2) are not proximal causes of either behavioral anapyrexia (hypothermia) or inactivity in goldfish exposed to oxygen-depleted environments.

Temperature Monitoring and Perioperative Thermoregulation

“…Behavioral regulation is most dramatic in reptiles and amphibians. These animals, often referred to as “cold-blooded,” actually regulate their temperatures remarkably well and even develop behavioral “fever.”86 Given access to a reasonable range of environmental temperatures, they will position themselves to maintain a central temperature within a few degrees of “normal.” Interestingly, the temperatures maintained as optimal by most reptiles is similar to that in mammals, near 37 C. Similarly, fish provided with a thermal gradient will position themselves to maintain a nearly constant central temperature 87. One investigator was even able to train a goldfish to maintain his water (and therefore body) temperature nearly constant by pushing a button!88 Even bacteria, given an opportunity, will position themselves to maintain optimal temperature.…”

Hypoxia Tolerance in Animals: Biology and Application

“…Endothermic species may also achieve metabolic rate depression by lowering the thermoregulatory set point (anapyrexia), slowing cellular processes and ultimately decreasing energy demand. Some ectotherms-for example, lizards (Hicks and Wood 1985), frogs (Wood and Malvin 1991), fish (Rausch and Crawshaw 1990), and crayfish (Dupre and Wood 1988)-actively seek out colder environments to reduce their body temperature, thereby reducing metabolic rate and their requirement for O 2 , a behavior known as hypoxia-induced behavioral hypothermia (HIBH; Wood 1991;Morris 2004).…”

Oxygen-limited thermal tolerance in Antarctic fish investigated by MRI and31P-MRS

“…On the warm side, for instance, high mitochondrial densities as found in Antarctic species may result in greater energy losses due to proton leak (15,33,34), which, with rising temperature, would soon lead to a situation in which oxygen demand surpassed oxygen availability. Limited oxygen availability to tissues might be the first manifestation of thermal intolerance and lead to lower optimum temperatures (35) before heat-induced damage at lower levels of complexity, i.e., organ or cellular functions, contributes to heat death of an animal (29,30).…”