Meeting Abstract

57.1  Thursday, Jan. 6  Benthic Walking in the African Lungfish (Protopterus annectens) KING, Heather M*; SHUBIN, Neil H; COATES, Michael I; HALE , Melina E; Univ of Chicago; Univ of Chicago; Univ of Chicago; Univ of Chicago hking@uchicago.edu

Central questions in tetrapod evolution are how the transitions from water to land and fins to limbs occurred. Previous studies have looked to salamanders, fossil trackways, and fossil limb anatomy for evidence to inform these questions, but the lungfish (Protopterus annectens) is a living, benthic, non-tetrapod sarcopteryigian. We can look to P. annectens for important behavioral data that may inform these questions. Here we present the first quantified description of benthic, limbed locomotion in P. annectens. We found that unlike previous descriptions, P. annectens uses only the pelvic appendages, rather than all four limbs, in contact with the substrate during walking. Since P. annectens does not have anatomical feet, we were interested in how the pelvic fins interact with the substrate. We found that the pelvic fins form regions of support or ‘pivot points.’ These pivot points change in anatomical location along the limb from step to step. In addition, we found that the fish is able to raise its body clear of the substrate during pelvic fin locomotion. We hypothesize that the anterior lungs play a role in generating lift and may be an important feature to consider when studying early tetrapods. P. annectens can also rotate its pelvic fins dorsally and rostrally relative to the articulation with the pelvis, which is similar to the movements seen in sprawl-limbed tetrapods, but unlike the movements we would expect to see in fish. Here, we give an example of a system designed for underwater locomotion that may have been common in lunged sarcopterygians and aquatic early tetrapods, and may be useful for further investigation of the evolution of tetrapod locomotion. This material is based upon work supported by the National Science Foundation under IGERT Grant No. DGE-0903637