Meeting Abstract
P3.74 Jan. 6 The Functional Morphology of Appendage Movement in Planktonic Rotifers ABLAK GURBUZ, O*; LEE, B; RITTER, S; HOCHBERG, R; University of Massachusetts Lowell; Westford Academy High School; Westford Academy High School; University of Massachusetts Lowell rick_hochberg@uml.edu
Planktonic rotifers possess a wide assortment of moveable appendages, from spines and bristle-covered arms to paddle-like limbs. Despite this structural diversity, species that possess appendages generally use them in a similar manner � sweeping them fore and aft � to generate thrust and move away larger zooplanktonic predators. In species of Hexarthra and Polyarthra, the appendages appear well-adapted for locomotion at low Reynolds numbers � being bristle-covered arms or flat paddles with broad surfaces, respectively � that function as hydrofoils during power and recovery strokes. In other species such as those of Filinia, the appendages appear more like classic defensive structures, being thin and elongate spines (setae) that function to both ward off predators and generate thrust. In an effort to understand the functions of these different appendages, and how they achieve similar forms of movement, we made observations on the musculature of three species of planktonic Rotifera with three different forms of movable appendages: Filinia with two spine-like appendages, Hexarthra with six bristle-covered arms, and Polyarthra with twelve blade-shaped paddle-like limbs. Results show that species of Filinia and Polyarthra rely on indirect muscle supply to control appendage movement, while species of Hexarthra have muscles that supply the appendages directly. Moreover, appendage movement in Filinia does not appear to contribute to locomotion, but is instead part of a defensive posture that precedes locomotion. The observed differences in muscle supply among species are suggestive of a separate evolutionary origin for the different appendages, and hence different selective pressures that led to their evolution and diversification.
