Thermal dependence of locomotor capacity

The thermal dependence of locomotor performance capacity, particularly speed and endurance, in vertebrate ectotherms is examined. Most studies have found an optimal speed for performance at relatively high body temperatures, close to upper lethal limits. These performance capacities decrease markedly at low body temperatures and may be compensated by increments in aggressive or evasive behaviors. Relative ranking of performance is maintained among individuals across body temperatures. Acclimation of performance capacities is generally incomplete or entirely absent: most animals compensate locomotor performance rather poorly to cold exposure. Locomotor performance in different groups has been shown to possess the attributes (e.g., variability, repeatability, heritability, and differential survivorship) necessary for evolutionary adaptation, but interpretation of comparative data is complicated by phylogenetic differences among species studied. Controlled studies show partial but incomplete adaptation to environmental temperature.

Hepatic carbohydrate metabolism in Tilapia mossambica (Peters) acclimated to low environmental pH

Fresh water fish, Tilapia mossambica (Peters), were exposed to various pH media. O2 consumption of the fish was suppressed in the pH media on either side of neutrality. Lethal limits of pH were determined to be pHs 3.7 and 10.3. Fish were acclimated to sublethal acidic pH (pH 4.0) and hepatic carbohydrate metabolism was studied on exposure and acclimation. The hepatic tissue of acclimated fish exhibited inhibited glycolysis with an onset of gluconeogenesis. In general, acclimation to acidic pH seems to result in the elevation of the synthetic phase of hepatic carbohydrate metabolism.

Effects of Thermal Shocks on Drifting Aquatic Insects: A Laboratory Simulation

Effects of temperature shocks from thermal plumes on drifting Isonychia (Ephemeroptera: Baetidae) and Hydropsyche (Trichoptera: Hydropsychidae) larvae were examined in a laboratory simulation. Groups of both insects were collected at various seasons and acclimated in the laboratory at temperatures comparable to those in the field. Groups were exposed to thermal shocks of varying duration and observed for periods of 10 days afterward. Consistent statistically significant differences in mortality between treatment and control groups were not evident until shock temperatures neared the respective upper lethal limits for the two insects. While consistent treatment related differences in molting frequency in Isonychia were not obtained, changes in the patterns of molting were observed. Behavioral tests with Isonychia indicated no discernable treatment effects on rheotaxis, phototaxis, and substrate orientation. No discernable effects of treatment on susceptibility to predation of Isonychia by Cottus carolinae were observed.

Thermal Requirements of the Early Life History Stages of Walleye, Stizostedion vitreum vitreum, and Sauger, Stizostedion canadense

Walleye (Stizostedion vitreum vitreum) and sauger (Stizostedion canadense) eggs were exposed to temperatures ranging from 6 to 21 C to determine temperature effects on fertilization, incubation, and fry survival. Optimum fertilization temperatures were 6–12 C for walleye and 9 C for sauger. Optimum incubation temperatures were 9–15 C for both walleye and sauger. A sharp drop or rise in temperature had no great effect on walleye fry and juvenile survival. Optimum temperature for juvenile walleye and sauger growth was 22 C. When acclimated at 8–26 C, 96-h upper lethal temperatures for walleye juveniles were 27.0–31.6 C, with the lower acclimation temperatures producing the lower upper lethal limits and intermediate acclimation producing intermediate upper lethal limits in order as acclimation temperatures increased. When acclimated at 10–26 C, the 96-h upper lethal temperatures for sauger juveniles was 26.6–30.4 C, in order as with the walleye.