F. Roces et Ja. Nunez, THERMAL SENSITIVITY DURING BROOD CARE IN WORKERS OF 2 CAMPONOTUS ANT SPECIES - CIRCADIAN VARIATION AND ITS ECOLOGICAL CORRELATES, Journal of insect physiology, 41(8), 1995, pp. 659-669
Thermal sensitivity during brood care was analysed in two Neotropical
Camponotus ant species, related phylogenetically but disparate in ecol
ogy, Camponotus mus is dominant in temperate climates, whereas C. rufi
pes is dominant in subtropical climates, Sensitivity was assessed by f
irst allowing workers to manifest their preference along a thermal gra
dient, and thereafter increasing the temperature of the nest floor con
tinuously at a rate of 0.2 degrees C/min, The removal of brood by work
ers was recorded as an indicative response of upper thermal tolerance,
Along a thermal gradient, while C. mus nurse workers exhibited a bimo
dal circadian rhythm of temperature preference to locate the brood, C,
rufipes nurses selected an invariant temperature throughout the day,
Irrespective of their thermal preferences, sensitivity to temperature
changes in both species showed a conspicuous circadian rhythm. Its end
ogenous nature was supported by a free-run under constant darkness, In
C, mus, instantaneous resetting by the light:dark cycle could also be
demonstrated, and experiments suggest the involvement of one oscillat
or controlling thermal responses, At the middle of the light period wh
en extreme environmental temperatures are expected, C, mas nurses exhi
bited the highest sensitivity (brood removal after an increase of 0.2
degrees C), while C, rufipes showed the lowest (removal after an incre
ase of 6.7 degrees C), For both species, the time-course of thermal se
nsitivity during brood care suggests an adaptation to the wide and sli
ght daily fluctuations undergone by temperature in temperate and tropi
cal climates, respectively.