DIFFERENCES OF MAXILLULA AND HINGEMENT AMONG THREE PHYLOGENETIC GROUPS IN THE SPECIES OF GENUS LOXOCONCHA SARS, 1866 (CRUSTACEA, OSTRACODA, PODOCOPIDA)

Abstract

A total of 27 species of the genus Loxoconcha, in which 21 species living in the coast of Japan, two species in the European and Mediterranean coasts and four species from Vietnam were presented in the present study. The data set of 6 species was referred from the previous literatures and of 21 species was shown here for the first time. Sampling was carried out in a variety of locations from Japan and Vietnam in period of 2012 to 2015. Species of genus Loxoconcha was divided into three phylogenetic groups based on the distributional pattern of the pore system below eye tubercle. The difference of the chaetotaxy on three endites of maxillula and the difference of length of posterior tooth of left valve’s hingement were consistent with three phylogenetic groups. The total number of setae of three endites on the maxillula was lowest in the Group A, highest in the Group C, but the length of posterior tooth in hingement of the left valve was largest in the Group A and smallest in the Group C. On the other hand, the numbers of setae of exopodite and outer 1st podomere of the endopodite as well as the length of other hinge elements (posterior socket, anterior tooth) on the left valve did not show any remarkable relationships.

Keywords: Loxoconcha, chaetotaxy, maxillula, taxonomy, phylogeny