Meeting Abstract

P3.86  Jan. 6  Physiological Examination of PPD1 in Armina californica SHERMAN, A.L.; Portland State University, Oregon shermana@pdx.edu

Organisms with common ancestors often have homologous morphological structures. The nudibranchs Tritonia diomedea and Armina californica are closely related, have similar natural histories and exist in similar ecological niches. Tritonia is studied extensively in neurobiology because of its large, accessible, reidentifiable neurons (Willows et al. 1973, Cain et al. 2005). One of these neurons, Pedal (Pd) 5 increases its electrical activity in response to the stimulus of magnetic field changes (Lohmann and Willows 1987). A morphologically similar neuron, PPD1 in Armina does not respond to rotations in a manipulated magnetic field. However, the cells may share a functional homology that both PPD1 and Pd5 are ciliary motor neurons (Cain et al. 2006 and Baltzley 2006). This study investigated synaptic connections between PPD1 and the similar large, pedal peptidergic cells PPV1 and PPD2 in addition to determining whether PPD1 is magnetically responsive. PPD1, PPD2 and PPV1 were recorded pairwise in an isolated brain to determine their synaptic connectivity. PPD1 and PPV1 receive common synaptic input and show simultaneous inhibition while PPD1 and PPD2 show opposing activity patterns. The synaptic relationships between the three largest, pedal peptidergic cells are similar to those between the three largest pedal peptidergic cells (Pd5, Pd6 and Pd7) found in Tritonia. Although PPD1 is not magnetically responsive, it remains a partially functional and morphological homologue to Pd5. It also exists in a network that resembles a closely-related network in Tritonia that controls ciliary locomotion. Further investigation into the electrical patterns of these cells may reveal the details involved in the evolution of these neural networks, and how they change over time in different organisms to support different functions.