Date of Award

2019

Degree Type

Thesis

Degree Name

Master of Science in Biological and Environmental Sciences (MSBES)

Specialization

Evolution & Marine Biology

Department

Biological Sciences

First Advisor

Jacqueline F. Webb

Abstract

Chapter 1

Gobies (Family Gobiidae) have a complex mechanosensory lateral line system composed of reduced cranial and trunk canals and a proliferation of small superficial neuromasts, perched on the tips of “sensory papillae”, which occur in several linear series on the head, trunk and tail. Elacatinus lori is being used as a model species for larval orientation and dispersal and the ability to rear it in the lab has allowed the use of a suite of morphological methods to provide the first description of the post-embryonic development of the lateral line system from hatch through settlement and to adulthood for any goby species. The distribution of canal neuromasts (CNs) and superficial neuromasts (SNs) was described in adult E. lori using fluorescent imaging, revealing six cranial superficial neuromast series composed of 33 lines of neuromasts, reduced cranial lateral line canals (only the supraorbital, postotic, and preopercular canals are present), 31 lines on the trunk and three lines on the caudal fin. The total number of SNs on the head increases linearly through the larval period to settlement (at 35 dph) while all CNs are present on the surface of the skin by about 15 dph before becoming enclosed in canals. Both CNs and SNs are diamond-shaped at hatch, which along with the proliferation of neuromasts within lines may have interesting implications for the sensitivity and functional role of these neuromasts, especially during the larval period. This study also compares the adult lateral line morphology of E. lori to congeners and representatives of the sister genus, Tigrigobius. We found that among Elacatinus and Tigrigobius species there are significant correlations between SN number and microhabitat, which indicates small-scale environmental factors, like a sponge-dwelling habit versus a coral-dwelling habit, can have significant impacts on lateral line system morphology.

Chapter 2

For many years, researchers have been trying to determine how pelagic larvae navigate the water column and find settlement sites, but this still remains unclear. Elacatinus lori, an obligate sponge-dwelling goby native to Belizean reefs, is a model species for larval coral reef fish navigation and dispersal. This study looks at the ontogeny of the visual system (opsin gene expression and eye size and structure) using both morphological and genomic analyses to infer larval sensory capabilities that are likely to play a role in larval orientation and settlement site selection. Results showed that the morphology of the eye and retina in E. lori is very similar to those in other fish species studied. Some variation was found in the growth rate of the different retinal layers. The molecular portion of the study faced some challenges in that not all opsin sequences could be identified and so a gene expression analysis could not be completed. Alternative methods for future analysis of opsin expression in E. lori are presented and whole genome sequencing and transcriptomics are suggested as methods that will need to be used to identify all other opsin sequences.

Available for download on Monday, August 09, 2021

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