Ontogeny and homology of the skeletal elements that form the sucking disc of remoras (Teleostei, Echeneoidei, Echeneidae)



The sucking disc of the sharksuckers (Echeneidae) is one of the most remarkable and most highly modified skeletal structures among vertebrates. In this issue of the Journal of Morphology, Britz and Johnson (pp. 1353–1366) report about their study of the development of the sucking disc based on a series of larval, juvenile, and adult echeneids. They aim at answering the question of the homology of the different skeletal parts that form the disc. The cover image shows the head and sucking disc of a 26.7 mm long juvenile marlinsucker, Remora osteochir, in frontal view. Remoras use their sucking disc to attach to larger marine animals and several remora species are host specific. Remora osteochir prefers spearfishes as hosts, in particular sailfish and white marlin. The striking sucking disc of remoras is homologous to the spinous dorsal fin of other spiny-rayed fishes. The skeleton of the disc is formed in development through the enormous expansion of both the bases of the fin spines and the distal radial elements of the fin supports.