How does the cold stenothermal gadoid Lota lota survive high water temperatures during summer?

Abstract

The cold-stenothermal freshwater gadid Lota lota inhabiting the potamic regions of lowland rivers in central Europe, is exposed to summer temperatures up to 25 degrees C, which is far above the thermal preferendum of this species. Oxygen consumption rates, determined in field catches sampled at different times of the year, revealed that the basal metabolic rate is depressed during summer when water temperatures are high (152+/-16 micromol O2 100 g(-1) h(-1)at 22 degrees C in July compared to 250+/-33 micromol O2 100 g(-1) h(-1) at 6 degrees C in November). This observation led us to investigate whether the observed depression of the metabolic rate is caused by oxygen limitation due to thermal impairment of the ventilatory system, as has been observed in other species. Determination of anaerobic end products (lactate and succinate) in the liver tissue of fish caught at different sampling dates did not show an accumulation of anaerobic end products during the summer, indicating no oxygen limitation. Measurements of enzyme activities in the white musculature and liver suggest that enzymes involved in aerobic metabolism were down-regulated during summer, which may have contributed to the observed reduction of metabolic rate.

Energy allocation in juvenile roach and burbot under different temperature and feeding regimes

“…1 (approach I) and Figs. 2 and 3 (approach II) Fish Physiol Biochem (2008) 34:103-116 111 However, the field data of Hardewig et al (2004) were in the same range as our data for food-deprived burbot displaying metabolic depression at 20°C (1.88 mg 25 g À1 h À1 ). The comparison of laboratory and field data indicates a restricted food intake in wild burbot during periods of high temperatures and supports the view of depressed basal metabolism in burbot during summer.…”

“…MO 2 of juvenile burbot caught in the River Oder (July, 22°C water temperature) were significantly lower (1.89 mg 25 g À1 h À1 ; Hardewig et al 2004) than rates of continuously fed burbot held at 20°C (3.80 mg 25 g À1 h À1 ) determined in this study. Fig.…”

“…The effects of starvation interfere with the dynamics of endogenous energy utilisation and contribute to a crucial reorganisation of body fuels (Black and Love 1986;Méndez and Wieser 1993;Collins and Anderson 1995;Guderley et al 1996;Hölker et al 2004;van Dijk et al 2005). For freshwater burbot, the combined effect of temperature and starvation on energy allocation is of particular interest, since previous studies revealed that high summer temperatures are linked to reduced food uptake and starvation (Pulliainen and Korhonen 1990;Hardewig et al 2004;Hölker et al 2004).…”

Antarctic fish can compensate for rising temperatures: thermal acclimation of cardiac performance in Pagothenia borchgrevinki

“…This is likely, as resting cardiac output was reduced at 4°C acclimated fish compared with -1°C acclimated fish. The stenothermal gadoid, Lota lota, can survive high summer water temperatures because it is able to downregulate its aerobic metabolism (Hardewig et al, 2004). Surprisingly, the thermal acclimation of resting metabolic rate has not been studied in P. borchgrevinki, although metabolic capacities (i.e.…”

Geographical variation in thermal tolerance within Southern Ocean marine ectotherms

“…Within the window bounded by critical temperatures, an even narrower window is bordered by pejus limits (pejus: getting worse) which indicate when temperatures move beyond the optimal range and functionality starts to be lost, which is paralleled by a shortfall in oxygen supply and demand until critical limits are reached and anaerobic metabolic pathways are recruited. Species tested this way include the boreal freshwater gadoid, Lota lota (Hardewig et al, 2004), the worms, Sipunculus nudus (Zielinski and Pörtner, 1996), several populations of Arenicola marina (Sommer et al, 1997), and several Antarctic species (e.g. Limopsis marionensis; Pörtner et al, 1999) including both L. elliptica and N. concinna (Pörtner et al, 1999) selected that measure the integrity of cellular systems and identify the temperature at which there is a departure from homeostasis (pHi and cCO 2 ), with the main focus on those that measure the aerobic status of the animal, circulation (heart rate), aerobic metabolism (O 2 consumption and citrate synthase activity), tissue energy status (balance of adenylates) and recruitment of anaerobic pathways (build up of organic acids).…”