A rare discovery: a new Loimos species (Monocotylidae: Loimoinae) from the gills of Rhizoprionodon taylori (Carcharhinidae) off the southern Great Barrier Reef, Australia.

A new species of Loimos MacCallum, 1917 is described more than half a century after the last species was described in 1972. The new species was collected from the gills of Rhizoprionodon taylori (Ogilby, 1915) off the Central Queensland coast, Australia, and is the first Loimos species and the first representative of the Loimoinae Price, 1936 known from Oceania. A detailed morphological description and 28S rDNA molecular sequences are provided for the new species. In the molecular phylogeny based on available 28S rDNA sequences for relevant Monocotylidae, the new species grouped together with the only other Loimos sequence available in GenBank, that of the nonugen Loimos sp. from China (OM060238), sister to Loimosina wilsoni Manter, 1944. The estimated genetic divergence between the new species and the nonugen Loimos sp. sequence is low, between 0.0452 and 0.0737, suggesting that the nonugen sequence may represent the new species, or a very closely related congener. Host identity was confirmed by comparing COI sequences with those of known sharks in GenBank. We also provide the first 12S and 16S molecular sequences for this shark species.