Meeting Abstract
P2.112 Saturday, Jan. 5 Differences in polychaete musculature lead to distinct burrowing behaviors LAW, CJ*; DORGAN, KM; ROUSE, GW; Scripps Institution of Oceanography, UCSD; Scripps Institution of Oceanography, UCSD; Scripps Institution of Oceanography, UCSD cjlaw9@gmail.com
Divergent morphologies between closely related species can give rise to distinct behaviors and habitat uses. Considerable morphological and behavioral differences are found between the two clades within the polychaete family Opheliidae; Thoracophelia mucronata burrows by peristalsis whereas Armandia brevis exhibits undulatory burrowing. We investigate the anatomical differences that allow for diverse burrowing behaviors within Opheliidae as well as broader phylogenetic (DNA-based) and morphological analyses of Opheliidae, Scalibregmatidae, and Polygordiidae, which share morphological characteristics including the presence of a ventral groove. Phylogenetic analyses reveal that the three families are monophyletic but further study is needed to resolve the relationships among them and taxonomic problems within Opheliidae. 3D histology (Amira 5.4) of A. brevis reveals bilateral longitudinal muscle bands acting as the salient musculature of the body. Circular muscles required for peristalsis are absent; instead thick bands of oblique muscle work antagonistically with longitudinal muscles for undulatory burrowing. Circular muscles are present, however, in the anterior of T. mucronata, extending away from the body wall to form oblique muscle bands and transitioning in the posterior to musculature similar to A. brevis. Whereas A. brevis has an open body cavity, a septum separates the anterior of T. mucronata and gives rise to the injector organ needed for the inflation of the head region while burrowing. These morphological differences between opheliids A. brevis and T. mucronata led to disparate forms of burrowing behavior. Linking differences in morphologies between related taxa to their behaviors and habitats will give us greater context to the evolution and function of burrowing animals.
