EARLY, M.D.*; GOAD, A.J.; PIRTLE, T.J.; Abilene Christian University; Abilene Christian University; Abilene Christian University: The Distribution of FMRF-amide, Serotonin, and Small Cardioactive Peptide b in the Cerata of Hermissenda crassicornis and Flabellina trilineata
The aeolid nudibranch molluscs Hermissenda crassicornis and Flabellina trilineata, like most members of the aeolid group incorporate the nematocysts of the cnidarian prey they consume into the distal ends of their cerata. While ceras structure and nematocyst incorporation have been described in several aeolid species little is known regarding the neuronal mechanisms involved in moving the nematocysts through the digestive tract to their final destination in the cerata. Additionally, little is known regarding the possible neuronal mechanisms underlying discharge of the nematocysts from the cerata during defensive behavior. Thus, the goal of our study was to describe the neuromuscular morphology of the cerata from two species of aeolid nudibranchs � Hermissenda crassicornis and Flabellina trilineata. Using immunohistochemistry labeling methods we examined the distribution of three neurotransmitters, FMRFamide, serotonin (5-HT), and small cardioactive peptide b (SCPb), in the cerata of the two study species. Both Hermissenda and Flabellina have similar distributions of FMRFamide, 5-HT, and SCPb in their cerata. FMRFamide and 5-HT were distributed in a way that suggests that these two neurotransmitters may innervate the circular and longitudinal muscles composing the cerata musculature. SCPb was distributed along the diverticulum of the digestive tract that runs the length of the ceras and distributed along the muscular cnidosac that contains nematocysts at the very distal end of the ceras. Our results suggest that FMRFamide and 5-HT control or modulate whole ceras movement while SCPb plays a role in movements of the digestive tract and cnidosac.
