Review of the genus Loimia Malmgren, 1866 (Annelida, Terebellidae) from China seas with recognition of two new species based on integrative taxonomy

Specimens of the genus Loimia (Annelida, Terebellidae) deposited in the Marine Biological Museum of the Chinese Academy of Sciences (MBMCAS) together with materials newly collected from China seas were examined. Based on morphological comparisons and molecular analysis, some specimens collected from the coasts of Shandong province and Guangxi province were confirmed as two new Loimia species respectively (Loimia borealis sp. n. and Loimia macrobranchia sp. n.). Morphologically, L. borealis sp. n. is distinguished from previously known species of this genus by having seven equal sized ventral shields, with length five times the width; this species was retrieved as sister to the clades of Loimia arborea Moore, 1903 and Loimia bandera Hutchings, 1990 in the phylogenetic tree, which was reconstructed based on mitochondrial COI gene. Loimia macrobranchia sp. n. differs from congeners by the large size of its first pair of branchiae with a thick main stem and about 18 dendritic branches arranged in two levels. A key to identifying Loimia species found in Chinese seas is given.