Doctor of Philosophy (PhD)
The study of pedestrian locomotion in crustaceans has largely focused on forward walking macrurans, or sideway walking brachyurans. The spider crab, Libinia emarginata is a brachyuran that, unlike its close relatives, preferentially walks forward. The phylogenetic position, behavioral preference, and amenability to experimental techniques make spider crabs an attractive model for comparative studies of crustacean locomotion. This dissertation looks at the neuroethology of forward walking in L. emarginata. I described the skeletal, muscular, and neural anatomy of the walking machinery of L. emarginata and found adaptations at each level that reflect its walking preference. The ranges of motion of leg joints aiding in forward locomotion were larger for spider crabs than for sideway walking crabs. The leg segments housing the musculature moving these joints were also larger. The proximal leg musculature consists of multiple muscle heads that can be activated independently during locomotion. The motor neurons innervating this musculature exhibited features of distantly related species that walk forward. Unlike many brachyurans, spider crabs use all ten legs during walking. Kinematic characterization of forward walking in L. emarginata showed that anterior and posterior limbs perform different functions during walking. Cross-correlation analysis among the leg joints of spider crabs revealed that distant joints have stronger coupling than adjacent ones. Neuroethology studies of pedestrian locomotion use multiple approaches. In order to understand how adaptive behavior is produced, it is necessary to study how the neural, muscular, and skeletal systems of an organism interact during its performance.
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Vidal Gadea, Andres Gabriel, "Comparative aspects of the control of posture and locomotion in the spider crab Libinia emarginata" (2008). LSU Doctoral Dissertations. 3617.