Meeting Abstract
Butterflyfishes (Family Chaetodontidae) are iconic coral reef inhabitants. Their beautiful and striking color patterns belie a potent set of structural defenses against predators, featuring an unusually deep-bodied shape and numerous, long and strong spines in the dorsal and anal fins. Both a deep body and spines discourage gape-limited predators. We explored the impact of social grouping and trophic niche on defensive morphology across 97 butterflyfish species. Grouping increases vigilance for predators, while feeding in close proximity to reef structures may keep refuges close at hand. Nine morphological traits that function to defend against, or detect and avoid predation were measured and analyzed in a phylogenetic context. Phylogenetic least squares analysis revealed no relationship between body depth and spine length, as had been found in a survey that spanned teleosts. We found no effect of grouping behavior on defensive morphology. However, we did find a significant trend of shorter spines in more corallivorous species. The decoupling of spine length from body depth suggests that a high body-depth alone may adequately protect most butterflyfish species from gape-limited predators, or they may rely on other sources of protection. The reduction of spine length in coral feeders suggests that their close association with live corals may afford them additional protection from predation, or, shorter spines may facilitate movement in dense coral microhabitats where long spines would catch on coral branches.
