Date of Award

Spring 2020

Document Type

Open Access Dissertation

Department

Biological Sciences

First Advisor

Joseph M. Quattro

Second Advisor

Roger Sawyer

Abstract

This study examined the histological aspects of the visual system of six species of fish. Menidia extensa and Fundulus waccamensis are found in Lake Waccamaw, which is a unique aquatic environment of the Atlantic coastal plain characterized by low turbidity, higher pH and clarity. Menidia beryllina, Menidia menidia, Fundulus diaphanus and Fundulus heteroclitus are found in the Waccamaw River, which is characterized by high turbidity. These species have undergone morphological changes likely related to inhabiting two ecological systems that differ in their environmental characteristics. We tested the hypothesis that fish modify their visual system to adapt to various environments.

The advantage of the present study was that all parts of the retina were examined using the modified method of Alsudani et al 2018. The number of rods and cones calculated in the whole retina. It was found that light availability has a significant influence on the quality of the visual system. The number of cones are higher in bright environment of both genera. It was observed that a higher number of rods across species in Waccamaw River found to have acclimatized to low light environments. Furthermore, these species are characterized by having a pattern of photoreceptors called double layers that are considered as a method of optimal exploitation of light available in improving vision. Also, the investigation was to evaluate the effects that the quantity of light available in a specific habitat has on the development of the optic nerve and optic tectum in six species of fish. The results suggest that light has a specific influence on the development of both optic nerve and tectum. The number of optic nerve fibers in clear water fish are higher than for vi dark water fish. The size of the optic tectum is smaller in fish that inhabit dark water compared to that for clear water fish.

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