. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 100 50 15 20 25 (Hour) Figure 4. Hourly heat dissipation rates of 5 Callinectes sapidus (A) and 5 Eurypanopeus depressus (B) at 25°C and 10%»S. Rates ex- pressed as J-g dry wr'-h"' ± (mean -^- and standard error limits — • —) for crabs exposed to consecutive 12 h periods of norm- oxia, hypoxia (25% air saturation), and normoxia. Dashed lines: per- cent air saturation values for ambient seawater. for Penaeus aztecus and ppm (22% air saturation or 34 Torr) for Penaeus setiferus (Renaud, 1986b). Juvenile shrimp ma
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 100 50 15 20 25 (Hour) Figure 4. Hourly heat dissipation rates of 5 Callinectes sapidus (A) and 5 Eurypanopeus depressus (B) at 25°C and 10%»S. Rates ex- pressed as J-g dry wr'-h"' ± (mean -^- and standard error limits — • —) for crabs exposed to consecutive 12 h periods of norm- oxia, hypoxia (25% air saturation), and normoxia. Dashed lines: per- cent air saturation values for ambient seawater. for Penaeus aztecus and ppm (22% air saturation or 34 Torr) for Penaeus setiferus (Renaud, 1986b). Juvenile shrimp may be able to alter their migration patterns to move around patches of hypoxic water (Rabalais et al., 1986a, b; Renaud, 1986a), provided the patches are spa- tially and temporally isolated. The values for metabolic rate depression observed in this study fall within the range of values reported in the literature and emphasize the need to consider this com- ponent of physiological adaptation in relation to the life cycle niche occupied by each species. It is not surprising that juvenile blue crabs, which are active swimmers, are intolerant of anoxia, and that their metabolic rate at 25% air saturation is depressed only to 32% of their normoxic metabolic rate. Although Eurypanopeus depressus is also intolerant of anoxia and exhibits metabolic rate depres- sion to 47% of its normoxic rate upon exposure to 25% air saturated seawater, its brackish water oyster reef habi- tat is not exposed to hypoxic water masses of the same duration as those that develop offshore (Rabalais et al., 1985). These crabs are exposed to diurnal variations in oxygen tension. In contrast, the copepod Cyclops abys- sorum. which lives in alpine ponds that become hypoxic in the winter, exhibits metabolic rate depression to 17% of the normoxic rate upon exposure to anoxia at 6°C (Gnaiger, 1981). The metabolic rate depression of molluscs exposed to anoxic seawater is also highly variable among species,
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
