THE VISUAL OPSIN AND PHOTOTRANSDUCTION PATHWAY GENES ASSOCIATED WITH EYE REDUCTION AND LOSS IN BAT FLIES (STREBLIDAE, NYCTERIBIIDAE)

Atkins, Melissa Leigh

THE VISUAL OPSIN AND PHOTOTRANSDUCTION PATHWAY GENES ASSOCIATED WITH EYE REDUCTION AND LOSS IN BAT FLIES (STREBLIDAE, NYCTERIBIIDAE)

Files

Atkins_hawii_0085O_11157.pdf (3.57 MB)

Date

2021

Authors

Atkins, Melissa Leigh

Advisor

Porter, Megan L.

Department

Zoology

Abstract

Evolutionary reduction of visual sensing ability is common in troglobiont species where no light filters into the habitat. Independent of light environments, parasitism is also well-known to be associated with a reduction in eye structures. The combination of these two ecological features is exhibited in the aptly named bat fly, a parasitic arthropod that feeds on bat hosts, many of which are cave-roosting. In line with other parasitic arthropods, bat flies exhibit rudimentary development of their visual system. They are derived from fully visual, free-living ancestors, but the varying degrees of eye reduction observed throughout the clade make them a unique group of species to study. Although both parasitic and troglobitic species are well-known to be associated with a reduction in eye structures, the extent of gene loss and transcription attenuations that are accompanied with eye-loss are not well-studied. In insect compound eyes, visual perception is dependent on the number of ommatidia present and how light is focused onto the underlying receptors. Thus far, studies of bat fly macro-morphology from different species have described eyes containing from 0 to 57 facets. This diverse macro-morphology is thought to reflect microstructural changes associated with low light levels such as rhabdomere rearrangement of photoreceptor cells. In order to investigate changes in the molecular components associated with these anatomical changes, I assembled de novo transcriptomes from eight bat fly species and de novo genomes from seven bat fly species. These 15 samples represent a taxonomically diverse set of species with facet numbers ranging 0 to 12. All assemblies were annotated for opsin genes, which encode proteins that are responsible for light detection. Thus far, our analyses of genomes reveal that a common dipteran rhodopsin, Rh1, is present in all bat fly species, with an additional rhodopsin, Rh6, present in Cyclopodia dubia, though Rh1 was the only opsin to have expression at the transcriptome level. Multi-level analyses using both transcriptomes and genomes allows for confirmation of sequences and a more comprehensive understanding of the RNA transcript expression levels in reduced eyes. This work aims to elucidate the evolutionary trajectories of broader ectoparasite and troglobiont trends in visual system reductions through the absence of rhodopsin paralogs and phototransduction cascade genes.

Keywords

Molecular biology, Zoology, Bioinformatics, bat fly, evolutionary genetics, evolutionary loss, opsin, parasitic arthropod, transcriptomics

URI

http://hdl.handle.net/10125/76493

Extent

65 pages

Rights

All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.

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M.S. - Zoology

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