Biomarkers that Could Explain Parasite-Induced Behavioral Alterations in the Golden Shiner (Notemigonus Crysoleucas) – Posthodiplostomum System

Author

Laura D. Nicolas, Nova Southeastern UniversityFollow

Defense Date

5-9-2025

Document Type

Thesis

Degree Type

Master of Science

Degree Name

Marine Science

First Advisor

Christopher Blanar, PhD

Second Advisor

Mary "Allie" Holschbach, PhD

Third Advisor

Lauren E. Nadler, PhD

Keywords

physiology, behavior, neural, endocrine, immune, cytokines, IL-1ß, serotonin, cortisol, parasites

Abstract

Trophically transmitted parasites require an intermediate host to be consumed and often manipulate host phenotype (i.e., morphology, physiology, and/or behavior) to increase predation risk by definitive hosts. Posthodiplostomum is a trematode with a complex life cycle involving snails as first hosts, fish as second intermediate hosts, and piscivorous birds as definitive hosts. In fish hosts, Posthodiplostomum infection has been linked to increased predation, suggesting suppression of antipredator behaviors. However, the specific physiological pathways remained unexplored and changes in the host’s neural, endocrine, and immune systems could be involved. Thus, I examined whether Posthodiplostomum infection intensity was associated with brain serotonin (neural), and whole-body interleukin-1ß (IL-1 ß immune) and cortisol (endocrine) levels in golden shiners (Notemigonus crysoleucas), and whether the parasite influenced the interactions among these systems. Microdissections and enzyme-linked immunosorbent assays (ELISAs) were employed to quantify serotonin in neurochemically relevant brain regions and systemic cortisol and IL-1ß. Fish with higher parasite load had less serotonin in the brainstem, which may be one way through which the parasite alters locomotor behaviors to increase predation. The relationship between IL-1β and cortisol was positive for fish harboring low levels of parasites and became negative for fish harboring high parasite intensities, which may reduce vigilance toward threats and thereby increase susceptibility predation. Overall, these findings revealed some candidate signaling pathways that parasites might manipulate to alter host behavior via phenotypic engineering and highlighted the value of a systems level approach to host-parasite interactions.

ORCID ID

https://orcid.org/0009-0002-4638-7506

NSUWorks Citation

Laura D. Nicolas. 2025. Biomarkers that Could Explain Parasite-Induced Behavioral Alterations in the Golden Shiner (Notemigonus Crysoleucas) – Posthodiplostomum System. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (209)
https://nsuworks.nova.edu/hcas_etd_all/209.