Study of Ephemeroporus Frey, 1982 populations from Peninsular Malaysia revealed a new species. Ephemeroporus malaysiaensis sp. nov. is characterized by the presence of four-five large denticles on anal margin of postabdomen instead of two-three, and five distinctive pigmented spots on each valve. Pigmented spots on the valves were never recorded for any species of family Chydoridae. E. malaysiaensis sp. nov. seems to be another endemic Chydoridae species of South-East Asia. E. malaysiaensis sp. nov. is a rare species, associated with emergent macrophytes in the littoral zone of shallow lake. Most of Ephemeroporus populations from Peninsular Malaysia belong to eurybiotic Paleotropical species Ephemeroporus barroisi (Richard, 1984).
A new species of Ovalona Van Damme & Dumont, 2008 (Cladocera: Anomopoda) related to the rare Australian species Ovalona archeri (Sars, 1888), is described from the Mekong Delta, South Vietnam. Ovalona garibiani sp. nov. differs from O. archeri in morphology of antenna, postabdomen, and proportions of setae on thoracic limbs II-III. Both species differ from other species of the genus Ovalona in the postabdomen with a narrow and sparsely spaced group of lateral setulae, the distance between the postanal groups being slightly greater than the width of the group. O. garibiani sp. nov. is a rare phytophilous species, known from a few localities in continental Malaysia, Southern Thailand and Vietnam.
During recent years, many taxa of water fleas (Crustacea: Cladocera) with wide distribution ranges were revised and finally accepted as groups of cryptic species. Here we provide a redescription of Ilyocryptus raridentatus Smirnov, 1989 (Anomopoda: Ilyocryptidae). Our study clearly confirms that I. raridentatus belongs to the sarsi-group based on incomplete moulting, absence of dorsal keel, structure of antennule, thoracic limb I and postabdomen. The species is widely distributed in Australia and East Asia (Malaysia, Thailand, Vietnam, Central China, Japan, South Korea) and penetrates north to the Far East of Russia. A morphological variability among different populations of I. raridentatus does not exceed an intrapopulational level. I. raridentatus seems to be a relatively rare species with a benthic lifestyle similar to its congeners.