Meeting Abstract

P2.114  Sunday, Jan. 5 15:30  Larviparity, metamorphosis, and neural architecture in species of Gnesiotrocha (Rotifera: Monogononta) HOCHBERG, A*; HOCHBERG, R; Univ. of Massachusetts, Lowell; Univ. of Massachusetts, Lowell adele_hochberg@student.uml.edu

Sessility is a rare lifestyle among species of Rotifera and one that demands unique adaptations relative to the more common freeliving (planktonic and benthic) lifestyle typical of rotifers. One exceptional adaptation is indirect development, which leads to the production of a short-lived larval stage that functions in dispersal. Indirect development is common among species in the superorder Gnesiotrocha, which includes sessile rotifers that produce larvae that undergo one of two forms of metamorphosis: 1) gradual metamorphosis that involves only allometric growth of the larva, and drastic metamorphosis that involves precocious development of the adult head with eventual replacement of the larval corona. In this study, we examine the neural architecture of two sessile species that display each of these conditions (gradual: Floscularia conifera; drastic: Stephanoceros fimbriatus) to determine how metamorphosis affects the serotonergic nervous system. As serotonin is likely to play a significant role in ciliary locomotion (as larvae) and ciliary feeding (as adults), we hypothesize that both species will show changes in the number and distribution of serotonergic neurons (and their connections) from larva to adult. We also hypothesize that neural patterns will differ between the species as a result of their considerably different adult body plans and feeding styles. We test these hypotheses using immunohistochemical protocols and confocal laser scanning microscopy. Our results show that all larvae have broadly similar neural patterns, but metamorphosis leads to a reorganization of serotonergic elements that produces distinctly different adult topologies.