Is the deep-sea crab Chaceon affinis able to induce a thermal stress response?

Fluctuations in the stress level of an organism are expressed in behavioural and molecular changes that can affect its ecology and survival. Our knowledge of thermal adaptations in deep-sea organisms is very limited, and this study investigates the critical thermal maximum (CTmax) and the heat-shock response (HSR) in the deep-sea crab Chaceon affinis commonly found in waters of the North East Atlantic. A mild but significant HSR in C. affinis was noted and one of the lowest CTmax known amongst Crustacea was revealed (27.5 °C at 0.1 MPa; 28.5 °C at 10 MPa). The thermal sensitivity of this species appears to be reduced at in situ pressure (10 MPa), given the slightly higher CTmax and the significant 3-fold induction of stress genes hsp70 form 1 and hsp70 form 2. Although C. affinis deep-sea habitat is characterized by overall low temperature this species appears to have retained its ability to induce a HSR. This capability may be linked with C. affinis' occasional exploitation of warmer and thermally instable hydrothermal vent fields, where it has been found foraging for food.

Western scrub-jays anticipate future needs independently of their current motivational state.

Planning for the future has been considered to be a uniquely human trait [1-3]. However, recent studies challenge this hypothesis by showing that food-caching Western scrub-jays (Aphelocoma californica) can relate their previous experience as thieves to the possibility of future cache theft by another bird [4], are sensitive to the state of their caches at recovery ([5] and S. De Kort, S.P.C.C., D. Alexis, A.D., and N.S.C., unpublished data), and can plan for tomorrow's breakfast [6]. Although these results suggest that scrub-jays are capable of future planning, the degree to which these birds act independently of their current motivational state is a matter of contention. The Bischof-Köhler hypothesis [1] holds that nonhuman animals cannot anticipate and act toward the satisfaction of a future need not currently experienced or cued by their present motivational state. Using specific satiety to control for the jays' current and future motivational states, here we specifically test this hypothesis by dissociating current and future motivational states. We report that Western scrub-jays anticipate the recovery of their caches, as well as their own future needs, by acting independently of their current motivational state and immediate needs. The fact that the birds act in favor of a future need as opposed to the current one challenges the hypothesis that this ability is unique to humans.

The control of food-caching behavior by Western scrub-jays (Aphelocoma californica).

Western scrub-jays (Aphelocoma californica) did not show extinction when caching behavior was never rewarded and they had no choice of where to cache the food. However, when the jays had the choice of caching items in 2 different locations or during 2 successive episodes, and only 1 of each was always rewarded at recovery, they rapidly learned to cache in the rewarded location or episode. When the jays had learned during training trials that their caches were always moved to 1 of 2 locations they did not cache in, then on the test trial they cached in the location that had been previously rewarded. To test whether these jays avoided the location in which their caches had been pilfered or chose the rewarded location, the procedure was repeated to include a 3rd location that was never rewarded. The jays avoided the pilfered location but cached equally in the rewarded and nonrewarded locations.