| dc.description.abstract | Sphaeroma quadridentatum (Say 1818) is a coastal species of marine isopod common in the US East and Gulf coasts that can be found in the TAMUG Small Boat Basin. S. quadridentatum has been shown to employ a melanophore response mechanism which changes the isopod’s coloration in response to changes in light intensity, circadian rhythm, and substrate coloration. The aim of this study is to examine and observe the presence of a melanophore response system in S. quadridentatum as a response mechanism in the presence of Callinectes sapidus (Rathbun 1896) and to explore new alternative ways by which to quantify melanophore dispersal across a range of metazoan phyla. In similarity to many aquatic animals, S. quadridentatum employ a melanophore dispersal mechanism as a method for color change. Previous research examining the melanophore response in these isopods has found that the color change mechanism can be triggered in response to a variety of physiochemical cues, such as changes in salinity and lighting. For example, S. quadridentatum melanophore dispersal changes with the coloration of the substrate the isopod is placed on. These changes in coloration may facilitate camouflage which, in turn, decrease predation pressure and facilitates survival. In addition, other isopod species have demonstrated behavioral changes in response to predatory olfactory cues. I hypothesize that the melanophore response of S. quadridentatum is affected by the presence of olfactory cues from a predator. Callinectes sapidus (Rathbun 1896) was chosen as the predator due to its frequency in estuarine habitats and the opportunistic nature of its foraging behavior. To test for the presence of a melanophore response mechanism to predatory cues, isopods were collected and cultured in the laboratory. Isopods were exposed to four treatments: 1) exposure to predatory cues on white substrate, 2) exposure to predatory cues on black substrate, 3) control without predatory cues on white substrate, and 4) control without predatory cues on black substrate. Isopods were photographed before and after exposure to treatments. Mean melanophore dispersal was quantified and variance analyzed. Melanophore dispersal response was variable across experimental and control isopods on both white and black substrates. Total mean melanophore data before and after treatment varied insignificantly but may suggest the presence of a melanophore response to hydrodynamic changes. Analysis of variance demonstrated that variations in substrate coloration are significant predictors of melanophore response in isopods relative to predatory olfactory cues. This represents a possible continuous and adaptable melanophore response adaptation which may enhance predator avoidance. Further research could focus in investigating the potential of a melanophore response to hydrodynamic cues and behavior modifications as a predator avoidance strategy. | |
