Meeting Abstract
P2.50 Friday, Jan. 4 Functional morphology of the musculoskeletal system in sessile and planktonic species of Collothecaceae and Flosculariaceae (Rotifera) BROWN, R*; HOCHBERG, R; Univ. Massachusetts Lowell; Univ. Massachusetts Lowell rick_hochberg@uml.edu
Rotifers of the orders Collothecaceae and Flosculariaceae hold an uncertain phylogenetic position within the Rotifera, but are hypothesized to be closely related based on characteristics of the jaw-like hardparts, or trophi. From a ecomorphological perspective, species of both orders exhibit some of the most unusual morphologies and lifestyles within the Rotifera, including planktonic species with mobile appendages, sessile tube- and jelly-dwelling species, sessile colonial forms, and planktonic colonial forms. Interestingly, the sessile form is rare within the Rotifera but prevalent within both orders; the colonial form is prevalent only within the Flosculariaceae. Past studies have hypothesized a possible evolutionary link between the sessile and colonial lifestyles. Here, we investigate the organization of the musculoskeletal system in several species from both orders that exhibit the sessile and colonial lifestyles: Acyclus inquietus, Stephanceros fimbriatus, Conochilus hippocrepsis and Floscularia conifera. Using phalloidin staining and confocal laser scanning microscopy, we attempt to answer three questions: 1) Do sessile and colonial forms share similar muscle organizations? 2) Are there any commonalities in muscle architecture that can serve as characters (synapomorphies) for demonstrating evolutionary relationships? 3) How much does the muscular organization of the sessile and colonial form differ from the presumed ground pattern of the Rotifera? Our investigations reveal that sessile and colonial species differ from their free-living planktonic counterparts in the degree of circular and longitudinal muscle development. We provide hypotheses on the functional implications of these differences and whether such differences might provide evidence of ancestry.
