Meeting Abstract
P3.95 Saturday, Jan. 5 External anatomy and neuromuscular organization of the freshwater colonial rotifer Sinantherina socialis LILLEY, G*; HOCHBERG, R; Univ. Massachusetts Lowell; Univ. Massachusetts Lowell rick_hochberg@uml.edu
Most of the approximately 2000 species of rotifers are free living; however, several freshwater species in the order Flosculariaceae can form colonies. One particularly well-known species is Sinantherina socialis, a rotifer that forms colonies on submerged vegetation. The ecology of this rotifer has been explored in some detail, including aspects of substrate selection and experimental assessments of its susceptibility to predators. These latter studies hypothesized that the rotifer can secrete an unpalatable, chemical compound from two pairs of wart-like glands on its trunk. Upon mechanical stimulation of the colony, each member contracts, thus exposing the glands to the predator and thereby releasing the compound to ward off attack. To improve our knowledge of these wart-like glands, and gain a better appreciation for the colonial lifestyle, we explored this rotifer�s anatomy and neuromuscular organization using light microscopy, SEM and CLSM. Light microscopical observations reveal that the wart-like glands contain pigmented secretions; however, a lack of OsO4 staining indicates that the pigments probably lack lipid moieties. Under SEM, the glands of relaxed specimens are generally indistinguishable, but in contracted specimens, they appear as large, discernable bulges. There are no obvious external openings to the glands or any sensory cilia associated with them. Phalloidin staining and 5HT-immunohistochemistry further reveals that the glands lack both a muscle supply and serotonergic innervation, respectively, indicating that general body contraction is the likely method of chemical release. In addition to these findings, we provide new details on the general anatomy of the species and explore some functional aspects of movement in colony members.
