Yu Cheng Liao

Abstract

The decapod crustacean with a relatively well-defined visual system have contributed significantly to our understanding of visual neuron morphology and physiology. The general morphology of the optic lobes of several decapods were initially described by Parker (1897) and Hanstrom (1924). In the past few years, several light and electron microscope studies have been made on the lamina ganglionaris: the first optic ganglion, of the lobster (Hamori and Horridge, 1966a); the crayfish (Hafner, 1974; Nassel, 1976a), and the crab (Stowe et al., 1977; Rafuse et al., in preparation). As yet, no adequate description has been made of the visual neurons in the remaining optic ganglia, the medulla externa, medulla intermedia, and the medulla terminalis.

In this study, the gross structure and neural arrangement has been studied in the medulla externa of the crab Hemigrapsus nudus. Neurons were labeled using Golgi techniques, cobalt chloride staining, and procion dye fluorescence. Reconstruction of neurons was made from photomicrographs and camera lucida projections. The fine details of the ganglion were visualized by means of electron micrographs.

The medulla externa in Hemigrapsus nudus is composed of four horizontal plexiforms layers surrounded by a rind of cell bodies. Monopolar neurons with centripetal projection fibers form the main neuron type identified in the columns while five types of horizontal cells were described in the superficial layer, the most distal of the horizontal layers. Neurons projecting to the medulla externa and the centrifugal and centripetal neurons originating in the ganglion were identified and described. The distinct and replicative morphology of the neuron types in the medulla externa suggest a high degree of synaptic efficacy and integrative capability.

The description of neuronal morphology and architecture as described in this study contributes significantly to our understanding of the neuronal circuitry involved in visual processing. A map of the neurons and their pathways provides direction for the physiological studies which are needed to elucidate the integrative processes involved in sensory systems.

LLU Discipline

Physiology

Department

Physiology

School

Graduate School

First Advisor

Donald D. Rafuse

Second Advisor

Robert L. Schultz

Third Advisor

George Maeda

Degree Name

Master of Science (MS)

Degree Level

M.S.

Year Degree Awarded

1980

Date (Title Page)

9-1980

Language

English

Library of Congress/MESH Subject Headings

Vision -- physiology; Neurons -- physiology; Crabs -- physiology

Type

Thesis

Page Count

vi; 50

Digital Format

PDF

Digital Publisher

Loma Linda University Libraries

Usage Rights

This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.

Collection

Loma Linda University Electronic Theses and Dissertations

Collection Website

http://scholarsrepository.llu.edu/etd/

Repository

Loma Linda University. Del E. Webb Memorial Library. University Archives

Download

Share

COinS