Meeting Abstract

48.1  Saturday, Jan. 5  Temperature effects and aerobic capacity in sedentary and migratory forms of the Mormon cricket CHAPPELL, MA*; BAILEY, NW; REDAK, RA; ZUK, M; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside; Univ. of California, Riverside mark.chappell@ucr.edu

A central premise of comparative and evolutionary physiology is that physiological functions reflect whole-animal performance, e.g., in species with high performance we expect to find corresponding increases in those sub-organismal attributes that support the performance trait in question. A striking example of contrasting locomotor performance occurs in the Mormon cricket Anabrus simplex, a flightless shield-backed katydid from western North America. Mormon crickets occur in two different forms: a small, cryptically colored �solitary� form that occurs at low density and moves < 1 m/day, and a large, dark-colored �gregarious� form that occurs in extensive roving bands that can move up to 1-2 km/day. We compared the body temperatures (T_b) of the two forms in natural habitats and measured resting metabolic rate (RMR) and maximal forced-exercise metabolic rate (MMR) across ambient temperatures (T_a) of 10-40 °C. Field T_b did not differ between forms and usually were between 30 and 40 °C during the day. RMR also did not differ between forms, showing a Q₁₀ of about 2.2 between 10 and 40 °C. Discontinuous gas exchange occurred in both forms at low to moderate T_a (10-30 °C). Despite the 1000-fold difference in daily movement distances between forms, there was no difference in MMR. MMR varied with a Q₁₀ of 1.75 between 10 and 30 °C, and with a lower Q₁₀ of roughly 1.2 between 30 and 40 °C. Factorial scope (MMR/RMR) declined with increasing T_a, but absolute scope (MMR � RMR; an index of metabolic power available for activity) was highest and roughly constant from 30-40 °C, the most frequent T_b in wild Mormon crickets. These results show that large differences in activity are not necessarily associated with divergence in subordinate physiological traits.