Alimentary tract morphology and diet in three coral reef fish families

Alimentary tract morphology and its relationship with diet was examined in three coral reef fish families: Labridae, Chaetodontidae and Pomacentridae. Convergent patterns of dietary‐related morphological variation were evident across the three families, with corallivores possessing long and narrow intestines, carnivores relatively short and wide intestines and herbivores relatively long and wide intestines. Between‐family differences were also evident: chaetodontids typically possessed long and narrow intestines, pomacentrids long and wide intestines and labrids generally possessed short and wide intestines. Overall, intestinal length variation was most strongly attributable to diet, whilst intestinal diameter varied most widely among families. Relative intestinal length appears as a useful predictor of dietary variation, particularly within families. Relative intestinal diameter appears as a less reliable measure, but rather, a useful adjunct to intestinal length comparisons.