EFFECTS OF BACKGROUND RISK ON ASSOCIATIVE LEARNING OF ZEBRAFISH (DANIO RERIO)
Date
2025-02-18
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
0009-0001-2727-359X
Type
Thesis
Degree Level
Doctoral
Abstract
Predation is one of the important selective forces that influence morphology, life history traits, and behaviour of an individual. Under increased predation pressure, prey often exhibit generalized antipredator responses to novel stimuli, a phenomenon known as neophobia. It helps increase an individual’s chance to survive an initial predator encounter. Individuals with this high-risk phenotype have been reported to retain predator information longer than their low-risk counterparts. However, studies on learning performance of high-risk prey beyond predator recognition show inconsistent results. In this thesis, I demonstrate that background risk and the type of information learned influence the learning and retention of learned association in prey. Using zebrafish (Danio rerio), I first show that repeated exposures to high-risk conditions induce neophobia in a novel environment and towards a novel predator odour. To compare the cognitive ability of high-risk and low-risk phenotypes, I repeatedly (20 times) trained high- and low-risk zebrafish in a plus-maze to associate a reward with a visual cue, using either a social reward (the sight of conspecifics) or a food reward. When tested after 24 h, both groups showed successful learning. Another test was performed 45 days after the last training trial to test for memory. Only high-risk individuals trained with a social reward retained the learned association after 45 days. When trained with a food reward, neither group retained the information. To investigate the role of risk and reward type on the speed of learning, I trained high- and low-risk fish using a similar setup, except the fish only had 8 training trials rather than 20. I demonstrated that high-risk individuals trained with a social reward learned faster, while low-risk individuals trained with a food reward showed quicker learning than high-risk individuals. These results highlight how background risk and reward type impact learning and retention in zebrafish.
Description
Keywords
cognition, plus-shaped maze, predation, alarm cues, neophobia
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Biology
Program
Biology