Taxonomic review of Western Indian Ocean goatfishes of the genus Mulloidichthys (Family Mullidae), with description of a new species and remarks on colour and body form variation in Indo-West Pacific species

Abstract

The taxonomy of the goatfish species of the genus Mulloidichthys from the Western Indian Ocean is reviewed. Four species are recognized: M. ayliffe sp. nov., M. flavolineatus, M. pfl uegeri and M. vanicolensis. As colour may vary considerably in live fish and fades in preserved fish, and meristic characters are rather conservative in this genus, a large set of 41 morphometric characters was also examined. All seven valid Mulloidichthys species are included in the comparisons. The Western Indian Ocean M. ayliffe sp. nov. differs from its Pacific sister species M. mimicus in number of lateral-line scales, several morphometric features, the position of the conspicuous bluish dorso-midlateral body stripe in relation to the lateral line, and the width of the yellow mid-lateral body stripe. The new species can also be distinguished from the other congenerics by colour, meristic and morphometric characters. A key is provided for the Western Indian Ocean species, which includes the South Pacifi c species, M. mimicus. The fi rst evidence for geographic variation in body form among Mulloidichthys species with marked differences between the Pacific and Indian Ocean is presented. These results complement earlier findings of interoceanic divergence in the number of gill rakers in M. vanicolensis. The implications of these fi ndings are discussed with respect to the need for DNA–based comparative studies on population differentiation and the ecological functions of colour patterns in Mulloidichthys species.