Meeting Abstract

69.3  Monday, Jan. 6 08:30  Autotomy-induced effects on the maximum locomotor performance of ghost crabs in the field PFEIFFENBERGER, J.A.*; HSIEH, S.T.; Temple University; Temple University jpfeiffe@temple.edu

Atlantic ghost crabs (Ocypode quadrata), as many arthropods, can voluntarily drop, or autotomize, limbs in response to aggressive inter- and intra-specific interactions. Although survival is the obvious short-term benefit for this response, long-term costs can include hampering locomotor performance. When running at high speeds, ghost crabs adopt a quadrupedal gait using their 1^st and 2^nd pair of legs while raising their 3^rd and 4^th pair of legs off the ground. This suggests that some limbs may be more important for achieving maximal locomotor performance than others. The goal of this study was to quantify the effects of limb loss on maximum locomotor performance and to determine whether crabs adjusted their gait in response to limb loss. Based on the observations above, we hypothesized that autotomizing the 3^rd and 4^th pair of legs will have less of an impact on locomotor performance as compared to loss of the 1^st and 2^nd pair of legs. To elicit maximum performance, we tested crabs in the field within 24 hours of capture at the Cape May National Wildlife Refuge in New Jersey. A total of 75 animals were collected at night and assigned to one of four autotomy treatments or the control group, then run in a sand trackway while filming at 500fps. The fastest, constant velocity run per individual was selected for analysis. In their natural environment, we were able to elicit very high running speeds in intact animals (2.23±0.04 m/s). Whereas autotomy of the 4^th pair of legs did not significantly impact running performance (2.06±0.10 m/s), removal of the other limbs significantly decreased running speeds (1^st: 1.70±0.03 m/s; 2^nd:1.67±0.07 m/s; and 3^rd: 1.58±0.11 m/s), as compared to the control runs. There was no significant effect of limb loss on pitch (23 – 30°) and roll (-0.8 – 2.5°) as these were highly variable within and among treatments.