Meeting Abstract

P1.49  Thursday, Jan. 3  Apical ganglion morphology: serotonergic and ampullary neurons of larval Neritimorph and Pulmonate gastropods KEMPF, Stephen C.*; PAGE, Louise R.; Auburn University; University of Victoria kempfsc@auburn.edu

The apical ganglion of gastropod mollusks is a sensory structure with multiple functions Previous research suggests that the AG represents a major component of the larval nervous system that not only initiates metamophosis, but also controls many other larval behaviors. The serotonergic cluster of neurons in the AG generally consists of 3 sensory and two interneurons; however, there is some variation among species. Similary the ampullary neuron group generally consists of 5 neurons, but again with some variation in number. Immunohistochemically labeled larvae were examined with a Bio-Rad 1024, laser-scanning confocal system. The AG of newly hatched, larval Nerita atramentosa possessed only two serotonergic interneurons. At 61 d post-hatch this species AG still lacked sensory serotonergic neurons, but had added additional interneurons. At hatching, larvae of this species lacked ampullary neurons, but by 61 d post-hatch veligers had added what appeared to be numerous ampullary neurons either in or close to the AG. These putative ampullary neurons were of two types, Type I had a tubular, cilia-filled invagination that appeared to extend to the pre-trochal surface. Type II had a spherical, cilia-filled chamber that was close, but unconnected to, the pretrochal surface. Larvae of Siphonaria denticulata and Williamia sp. exhibited the typical 5 serotonergic neurons in the AG and 4 associated ampullary neurons grouped in pairs on the left and right sides of the central serotonergic sensory neuron. Observed differences in the serotonergic and ampullary components of the AG in these species may relate to function and to relationships of these species within the Gastropoda.