Abstract :
[en] Coral reefs act as catalysts for morphological diversification, producing extreme body shapes like trumpetfish and boxfish, or unique adaptations such as the beak of parrotfish. Goatfishes (Mullidae) provide another example of morphological innovation with their hyoid barbels, which are articulated finger-like structures covered of sensory cells organized into taste buds. Commonly categorized as benthic invertivores, goatfish use their barbels to detect and extract prey from soft sediments or coral crevices. While similar types of barbels were studied in catfishes, little is known about the morphological diversity of goatfish barbels especially concerning the characteristics and the distribution of taste buds. The proximity of barbels to the mouth and their role in feeding behavior suggests a link between barbel morphology and goatfish trophic ecology. Thus, we first checked the relationship between barbel morphology (i.e. size and distribution of taste buds, and barbel length) and trophic ecology of 14 species from the Toliara Reef (Madagascar) assessed by using stable isotopes of carbon, nitrogen, and sulfur. Surprisingly, Phylogenetic Generalized Least Squares (PGLS) analysis revealed no significant relationships between stable isotopes and barbel morphology, except between 15N and barbel length. Then, we aimed to explore the diversification of barbel morphology across the family by studying 34 species from major genera. A moderate phylogenetic signal (Kmult = 0.63, P < 0.05) suggested some conservatism of barbel traits within the family. The mapping of barbel morphology onto the evolutionary tree revealed that a monophyletic subclade within the Upeneus genus exhibited a unique barbel morphology, made of a high density of small taste buds. While barbel morphology is relatively conserved throughout goatfish evolution, some variation exists deeper in the phylogeny. However, the facet of trophic ecology grasped by stable isotopes appears to play a limited role in driving this diversification.
