Insight into a Sexually Dimorphic Ostracod Crustacean by Mass Spectrometry and Microtomography

Author

Cindy D. Davis, University of the PacificFollow

Date of Award

2024

Document Type

Thesis

Degree Name

Master of Science (M.S.)

Department

Biological Sciences

First Advisor

Ajna Rivera

First Committee Member

Craig Vierra

Second Committee Member

Jane Khudyakov

Third Committee Member

Eric Thomas

Abstract

The importance of the central nervous system cannot be understated. An array ofmolecules associated with the brain regulate basic behaviors as well as sex specific behaviors. Describing the molecular background is not the only way that I can learn more of the central nervous system. Describing the anatomy of the central nervous system can be crucial in understanding what regions of the brain is particularly key to the animal. Euphilomedes carcharodonta is a small marine crustacean native to the subtidal zone of the California coast. This ostracod makes for a compelling candidate to explore these research interests as this organism displays not only drastic sexual dimorphism (in which males possess large complex lateral eyes and females lack such eyes), but also exhibit drastically different behaviors (females are almost entirely interstitial whiles males display diurnal swimming patterns). The potential neurochemical pathways driving the behavioral differences is unknown as characterization of the molecular processes are not well understood. Preliminary work has suggested that when females are treated with serotonin their behavior is masculinized. It is not hard to imagine that sexually dimorphic eye loss would also lend to dimorphism of the central nervous system of this organism, but this has not been established as the neuroanatomy of this species has not been previously studied. In this paper, I will study the neural anatomy utilizing microtomography and attempt to describe it’s proteome of the head by high-throughput shotgun mass spectrometry.

In part 1 of this study, I advance the understanding of the neurochemical pathways. Initially, I attempted this by treating the females with serotonin and observing their behavior. We expected that if serotonin plays a role in modulating swimming behaviors, then females would display male-like swimming patterns. I did not find that treatment changed female behavior. Secondly, I used LC-MS/MS in the efforts to describe the proteome of the head and compare how the proteome of the male and female. As this has not yet been performed with ostracod tissue, I trialed three different sample sizes of full body tissue to determine an appropriate sample size. I then performed LC-MS/MS from head tissue from both males and females. Most peptides were related to housekeeping functions. I found a larger number of peptides from the females. However, more experimentation would be required for an adequate review of the proteome. In part 2 of this study, animals were scanned by a micro-CT scanner, giving us CT scans of the entire ostracod body at a 1-micron resolution. These images were then processed using FIJI and 3-D Slicer software to render 2D and 3D imaging. This imaging allowed for locating and segmentation of the central nervous system and other internal structures (such as the lateral eyes, median eye, and gut). I were able to describe the central nervous system and compare the brain volume across the sexes.

Pages

59

Recommended Citation

Davis, Cindy D.. (2024). Insight into a Sexually Dimorphic Ostracod Crustacean by Mass Spectrometry and Microtomography. University of the Pacific, Thesis. https://scholarlycommons.pacific.edu/uop_etds/4280