Meeting Abstract

103-2  Saturday, Jan. 7 13:45 – 14:00  Thermal constraints on microhabitat selection and mating opportunities in fiddler crabs. MUNGUIA, P; BACKWELL, P; DARNELL, MZ*; The University of Adelaide; The Australian National University; The University of Southern Mississippi zachary.darnell@usm.edu http://sites.usm.edu/zdarnell/

Hot tropical environments constrain ectotherm mating opportunities when mate selection occurs on the surface. Thus, microhabitats and refugia can become a qualitative trait in mate selection. In fiddler crabs, the enlarged claw of males can act as a heat sink, which becomes advantageous when surface temperatures reach 50°C during the day and crabs are actively seeking to mate. Uca mjoebergi females prefer male burrows found in the shade, therefore we asked what are the thermal constraints imposed on males and females in shaded and non-shaded habitats. Crab surface activity decreases and body temperature increases as the day progresses, with more crabs active in shaded microhabitats than in sunny microhabitats. Body temperature was lower in male crabs found in burrows relative to crabs on the surface. Male claw size explained 10% of body temperature. Results suggest thermal constraints imposed on males can be overcome by the large claw acting as a heat sink and the burrow acting as a refuge from heat. Classic sexually selected traits, including ornaments and behaviors, can have a secondary purpose in thermoregulation.