Phylogeny of the genus Chrissia (Ostracoda: Cyprididae) with description of a new species from China

Abstract

A new species of the genus Chrissia Hartmann, 1957 is described from Dongqian Lake, East China. Chrissia dongqianhuensis n. sp. is characterized by short swimming setae on the second antenna. This character state is very rare in the genus, and besides the new species the feature is found only in Chrissia ceylonica (Daday, 1898). The two species can be distinguished from each other based on the shell shape: C. ceylonica has distinctly protruding posterior end with sinusoid postero-dorsal margin, while in C. dongqianhuensis the postero-dorsal margin is evenly rounded and the posterior end is not protruding. In addition, C. dongqianhuensis has only 5 swimming setae. Chrissia presently contains 35 living species. In order to assess the position of the new species within the genus and the position of Chrissia within Cyprididae, we analyzed morphological data and nucleotide sequences for 18S rDNA. A total of 18 morphological characters for 32 species were used. Molecular data include sequences from 29 species (18 from the GenBank, 11 newly obtained) belonging to several lineages of Cyprididae and Ilyocyprididae. Analysis of the morphological characters resulted in 16 equally parsimonious trees with several well-supported lineages, such as the African-Indian lineage of Chrissia with pointed extensions on their shells, and a predominantly Asian lineage with low shells with rounded margins. The molecular phylogeny suggests that Herpetocypridinae is polyphyletic and in need of revision, and also indicates that some sequences from the GenBank are probably misidentified. High bootstrap values support Cypridopsinae, Cypricercinae, and Dolerocypridinae, while Cyprinotinae seems to be polyphyletic.