HOCHBERG, R; Smithsonian Marine Station, Fort Pierce, FL.: Functional morphology of jumping appendages in planktonic Rotifera: Ultrastructure and neuromuscular control of spines in Filinia longiseta

Filinia longiseta is a planktonic rotifer common in lentic systems. The species possesses paired, elongate lateral spines that function in saltatory sweeping motions in response to sheer disturbances by predators. The purpose of this investigation was to gain insight into the neuromuscular control of spine movement through the use of electron microscopy, confocal laser scanning microscopy, and immunohistochemistry. Bodywall musculature and neural innervation were visualized using CLSM in combination with phalloidin and antibodies to structural proteins (tubulins) and various neurotransmitters (serotonin, FMRFamide, etc). Computer generated three-dimensional models of the neuroanatomy were subsequently constructed. Results show that muscular supply to the lateral spines is indirect: paired, striated bodywall muscles insert on the syncytial integument around the spines and do not insert within the hollow spine interior. Dorosoventral movement of the spines appears to be produced by local distortions of the integument caused by antagonistic muscular contractions. A single neuron (non-immunoreactive to 5HT or FMRFamide) innervates the hollow spines and may have a propioreceptive function, relaying positional information to the cererbral ganglion about spinal movement. Additional neuroanatomical details are presented.