The neuronal basis of behavior in Tritonia. I. Functional organization of the central nervous system

Abstract

An account is presented of the brain (paired cerebral, pleural, and pedal ganglia) of the nudibranch mollusc Tritonia diomedia. The major efferent nerve fibers are related to their nerve cell bodies and their functional roles identified as far as possible. The channels of sensory input relating to some of these neurons are given so as to provide an overall view of the organization of the brain.A standardized system of abbreviation and notation for the central ganglia, nerve trunks, and giant somata is propcsed. The system of reference is intended to provide a guide to the location in the ganglia of many of the smaller neurons of which the functional attributes are known, but which cannot be consistently recognized on visual criteria alone. A system of rectangular coordinates is proposed which is applied to the natural outline of the ganglia. I n addition, a system of cell notation is described which is independent of the co-ordinates used to define the position of the cell on the grid. Cells which by reason of their size, pigmentation, characteristic location and physiological attributes are consistently recognizable from animal to animal are numbered. Two principles were followed in numbering cells; (i) the series begins at unity in each ganglion; (ii) cell homologues in opposite ganglia are given the same number, but distinguished by prefixing the abbreviation for the ganglion in which they occur. It is considered that the system will facilitate the exchange of information between workers on the same species, and also benefit the comparison of neural organization of behavior in closely related forms. The brain is organized in an almost exactly bilaterally symmetrical manner. There are a few bilateral neural pathways, but the major functional routes are ipsilateral. A few motorneurons, which are uniquely identifiable anatomically, cause unique, discrete movements. Others are in small groups sharing overlapping or similar functions.

Odours detected by rhinophores mediate orientation to flow in the nudibranch mollusc,Tritonia diomedea

“…A combination of easily observed behaviours with a relatively simple and accessible nervous system has promoted a variety of neuroethological studies (e.g. Willows et al, 1973;Hume et al, 1982;Willows, 1978;Beck et al, 2000;Popescu and Frost, 2002). Field studies have reported the slugs' navigational behaviours, suggesting the importance of odours and water flow as navigational cues (Wyeth and Willows, in press; Wyeth et al, in press).…”

State-, Timing-, and Pattern-Dependent Neuromodulation of Synaptic Strength by a Serotonergic Interneuron

“…Physiological saline composition was (in mM): 420 NaCl, 10 KCl, 10 CaCl 2 , 50 MgCl 2 , 10 D-glucose, and 10 HEPES, pH 7.4. The cell bodies of the neurons were exposed by removing the connective tissue sheath from the surface of the ganglia (Willows et al, 1973). Suction electrodes, made from polyethylene tubing, were placed on pedal nerves including pedal nerves 3, 5, and 6.…”

One rhinophore likely provides sufficient sensory input for odour-based navigation by the nudibranch mollusc,Tritonia diomedea

“…To test the role of bilateral comparisons between rhinophores, we removed either the left or right rhinophore (Wyeth and Willows, 2006b). To test the role of the oral veil, we denervated it by combining procedures that have been explained in previous reports (Murray and Willows, 1996;Willows et al, 1973;Wyeth et al, 2009). Briefly, the brain was exposed and pinned by connective tissue to a waxcovered platform.…”