Australian Ceriodaphnia (Cladocera: Daphniidae) are examined using morphological attributes and two mitochondrial DNA (COI and 16s) and one nuclear DNA (28s) gene fragments to differentiate the species. The sequence data supports the existence of three species, that is, C. dubia, one reinstated species C. spinata Henry, 1919, and one new species C. sp. 1. Morphological characteristics were also able to accurately separate the three species. Furthermore, genetic analysis of COI sequences from Ceriodaphnia supported three clades. The high degree of correlation between morphological and molecular identification in this study indicates that mitochondrial markers, COI and 16s, are appropriate molecular markers for species discrimination and identification of Ceriodaphnia. 1. Introduction Ceriodaphnia Dana, 1853 (Cladocera: Daphniidae), displays little diversification in terms of species richness and morphological disparity, with the genus currently comprising 14 “valid” species worldwide, predominantly based on morphology . In addition, there are 21 species inquirenda and 24 species that are probably junior synonyms of previously described species . There is limited morphological and genetic evidence to support this proliferation of the large number of proposed names. According to Smirnov and Timms (1983) , there are only five Ceriodaphnia species from Australia which includes one beaked species (‘beak’ = a rostral projection) i.e. C. cornuta Sars, 1885, and four non-beaked species C. dubia Richard, 1894, C. laticaudata Müller, 1867, C. quadrangula (Müller, 1785) and C. rotunda Sars, 1862. One further, non-beaked species, C. pulchella Sars, 1862, has been recorded since . In addition to these, two more non-beaked species, C. planifrons Smith, 1909 and C. spinata Henry, 1919 were re-instated by Berner , thereby increasing the total number of recorded species from Australia to eight. The literature on Ceriodaphnia sp. generally points towards the absence of divergent morphological characters for this group. Additionally, the historical taxonomic descriptions are incomplete and primarily focused on the head, antennule, antennae, postabdomen, carapace, reticulation, and rarely trunk appendages of Ceriodaphnia. Where morphological evidence is unclear, molecular techniques can be used to improve our understanding of taxonomic divergence and speciation. Barnett et al.  emphasised that genetics has become an increasingly important parameter in the classification and identification of organisms in comparison to more traditional morphological
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