Why are you so defensive? Investigating the correlation between risk-taking behaviors and defensive morphology of marine Three-Spined Stickleback, Gasterosteus aculeatus

Abstract

Defensive morphologies, spines and armor, are wide-spread across multicellular life and do not exist in a vacuum, but instead co-evolve with a host of other traits to form an overall “Armor Syndrome”. The evolution of armor systems has mainly been studied in plants and mammals. Our goal for this study is to look for armor syndrome traits in fish, focusing specifically on a marine population of the three-spine stickleback (Gasterosteus aculeatus). We measured various risk-taking behaviors ( activity, inspection, time inspecting, orientation, and time sheltering) and ventilatory response to predator cues and correlated these with defensive morphological traits, quantified via uCT scans. Contrary to our initial expectations, we found no significant correlation between behaviors and armor measurements, but found a significant negative correlation between spine aspect ratio and number of inspections. This lack of significant correlation is similar to observations of intra-population variance in freshwater populations.