Autotomy and the dorsoventral righting reflex in purple shore crabs (Hemigrapsus nudus)

Locomotion has been a well-studied avenue for questions regarding the costs of limb loss (autotomy).  However, most studies focus on “traditional” means of locomotion such as walking, running, swimming, etc. One unexplored aspect of locomotion as it relates to the costs of autotomy is the dorsoventral righting reflex (DVRR); intertidal crabs such as Hemigrapsus nudus are often flipped on to their carapace by challenging terrain or the advance/retreat of the tides, and the animals quickly use their legs to return to a dorsal side up position. Two factors that could affect the efficacy of the DVRR were explored in this study: the difference in righting time 1) terrestrially versus aquatically and 2) on a sand versus a gravel substrate. Moreover, to determine if certain legs were more crucial than others, we generated a comprehensive set of treatment groups, each missing a unique set of legs. Our results suggested that autotomy only affects the DVRR in terrestrial habitats and that the enlarged claws of males greatly impede the DVRR.  How these results affect the animals in natural conditions is currently unknown, but it is likely that increased time in the inverted position compromises fitness. Future work aims to explore how the regeneration of these appendages alters the effects of autotomy as it relates to the DVRR.