A review of the systematics and distribution of Chydorus ventricosus Daday, 1898, with the first description of the male and redescription of the species

Based on the study of the type series and material from Sri Lanka, a comprehensive description of Chydorus ventricosus Daday is given including the first description of the male. The detailed morphology of all instars of females and males, population structure, and some biological notes are also provided. This species was considered a tropicopolitan species based on previous records from Asia, America, and Africa. However, a detailed study of populations from a wide area of the Oriental region and material previously designated as Chydorus ventricosus from America and Africa, and a critical review of the literature indicates that it is very probably restricted to the Oriental region. Chydorus ventricosus closely resembles an undetermined number of taxa. Only a detailed study will determine their status. We have compared it with the only two well-described, closely related species. The present study has characterized all stages of Chydorus ventricosus. This will enable accurate diagnosis of this species.