Date of Award

2016

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

First Advisor

Jacqueline Webb

Abstract

The deep sea is characterized by extreme environmental conditions including limited light availability, which makes non-visual sensory capabilities quite important. In addition to the visual, auditory, olfactory and gustatory systems found in all vertebrates, all fishes have a mechanosensory lateral line system. This system is composed of neuromast receptor organs on the skin and in bony canals on the head and trunk and is sensitive to unidirectional water flows and low frequency vibrations. Our knowledge about the lateral line system (LL) in deep-sea fishes is limited. Of the taxa in which the LL has been described, there appears to be two morphologies: widened LL canals with large canal neuromasts, and a reduced LL canal system with a proliferation of superficial neuromasts (SNs). However, the one published description of the LL in a species of the prominent midwater order Stomiiformes, suggests that there is a third LL morphology defined by a reduction in canals on the head accompanied by just a few, small SNs. The goal of Chapter 1 was to use traditional and modern morphological methods to provide the first detailed description of the LL system in two groups of stomiiform fishes (Argyropelecus [Family Sternoptychidae] and Cyclothone [Family Gonostomatidae]) as well as other fishes in the Families Gonostomatidae, Phocichthyidae, and Stomiidae in order to test the hypothesis that reduced canals and a reduced number of SNs is a strategy in the evolution of the LL in stomiiform fishes. A total of 27 species in 17 genera in four families were studied using one or more morphological approaches (including histology and micro computed tomography, or µCT). In Chapter 2, specimens were imaged under different wavelengths of light as a new tool to distinguish SNs from both complex and simple photophores. A total of 34 stomiiform species (in four families) and representatives of two other deep-sea taxa (Myctophidae, Melamphaidae) were examined. Novel observations made in this study show 1) that the mechanosensory lateral line system needs to be included in any discussion of sensory biology of deep-sea fishes and 2) the diversity and distribution of photophores is much greater than previously described.

Cyclothone ID Key_11x17 format.pdf (30 kB)
Cyclothone ID Key

Available for download on Thursday, July 26, 2018

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