Angela M. Horner M.S. student
Address: Angela M. Horner Department of Biological Sciences, ML006 University of Cincinnati Cincinnati, Ohio 45221-0006 Telephone: (513) 556-5696 FAX: (513) 556-5299 Email: horneram@email.uc.edu

Terrestrial vertebrates have evolved numerous locomotion strategies for moving through habitats with variable environments. The resultant diversity of locomotor modes includes flight, saltation, brachiation, and cursoriality, among others. The first tetrapods, however, moved in much the same way that most fishes move-via lateral undulation. Additionally, their bodies were more like fish than tetrapods, with the majority of mass is in axial (trunk) musculature. How did these amphibious organisms use a body adapted for aquatic life to colonize land? Part of the answer might lie somewhere in between water and land - that is, in mud. Therefore I am studying the axial muscle motor pattern of the closest extant relative to early tetrapods, the lungfish (Sarcopterygii: Dipnoi), moving through a viscosity gradient representing variation in the "muddiness" that early tetrapods may have encountered. 

Despite their pivotal evolutionary position, no previous study has characterized either steady or rapid escape swimming of the Dipnoi.  I am studying an African species of lungfish (Protopterus annectens) to correlate variation in muscle activity with the amplitude and propagation of lateral bending. I am characterizing axial motor pattern during both steady and escape swimming.  To simulate the muddy environments I am experimentally manipulating viscosity. My muddiest medium will require the fish to move on, rather than through it. As axial muscles encounter increasing external resistance, motor pattern may differ from activity in a normal aqueous environment.