Meeting Abstract
108.5 Sunday, Jan. 6 Neuromuscular Facilitation in the Motor Networks of Cubomedusae EICHINGER, J.M.*; SATTERLIE, R.A.; Univ. of North Carolina Wilmington; Univ. of North Carolina Wilmington jme1463@uncw.edu
The first modern physiological analysis of cnidarian nerve nets was performed by Pantin, in which he provided the first detailed investigation of the “staircase” effect. He later coined the term “facilitation” to describe the process in which a train of sufficient stimuli affects the response to subsequent stimuli in the direction of augmentation. In the case of jellyfish, a succession of stimuli elicits a graded increase in the force of muscle contraction. This process is frequency dependent in that decreasing interpulse interval produces stronger contractions. Jellyfish swim via rhythmic contractions of the bell musculature and rely on frequency dependent neuromuscular facilitation (FDNF) as a mechanism to produce strong, periodic contractions and efficient swimming. Cubomedusae further rely on FDNF for the existence of a biphasic modulatory potential within the swim system where jellyfish swim at approximately 80% of maximum. These data were taken from the subumbrella of C. marsupialis, but recently it has been shown in this and another species (T. cystophora) that the subumbrellar network is sparsely innervated and relatively disorganized as is stereotypical of a nerve net. The velarium and frenulum exhibit significantly higher network densities, and neurons of the latter align with radial muscle fibers. Similar networks in the retractor muscles of some anemones exhibit rapid conduction velocities and faster times to maximal facilitation. Here we investigated the facilitation properties of the subumbrella, velarium and frenulum in two box jellyfish species (C. quadrumanus and T. haplonema) seasonally local to North Carolina. Differences in facilitation properties were found between muscle sheets as well as different size classes of the same species. These results may offer clues to the functioning of different muscle sheets in executing complex swimming behaviors.
