Not-adaptive behavior of isotropically heated, inert populations of Oxytricha bifaria (Ciliophora, Stichotrichia).
The physiological effects on isotropically heated populations of Oxytricha bifaria cultured at 24 degrees C were investigated. At 34.6 degrees C ciliates became inert, and did not adaptively react to either cold or warm microgradients; they neither moved towards the favorable cold thermal source nor escaped from the unfavorable warm one. The inert oxytrichas were only able to perform the Side-Stepping Reaction (SSR) on the same spot. However, mobile ciliates at 31.6 degrees C reacted to the cold microgradient by immediately orienting themselves towards its source, without accelerating but reducing their SSR frequency. Moreover, in a warm microgradient such ciliates immediately increased their SSR frequency, then moved away from the thermal source. At 34.6 degrees C the behavior of ciliates was not-adaptive--not acting to guide the organisms to more favorable conditions--whereas at 31.6 degrees C it was still clearly adaptive. Therefore, the locomotory inertness of the oxytrichas at 34.6 degrees C was the result of thermal stress rather than their behavioral response to the environmental isotropy, in contrast to populations of the same species made inert at 9 degrees C.
Barbanera
Filippo
F
Dipartimento di Etologia, Ecologia ed Evoluzione, Pisa, Italy. rbanchettilc@deee.unipi.it
Erra
Fabrizio
F
Banchetti
Rosalba
R
D000222:Adaptation, Physiological; D000818:Animals; D001522:Behavior, Animal; D003080:Cold Temperature; D006358:Hot Temperature; D008124:Locomotion / Q000502:physiology; D016813:Oxytricha / Q000502:physiology*; D011156:Population Density