Coronatella (Coronatella) rectangula

22. Coronatella (Coronatella) rectangula (Sars, 1862) Localities and specimens found: 16 – 1♀; 25 – 1♀ em; 97 – 1♀. Distribution and ecology. Coronatella rectangula (formerly most often recognized as Alona rectangula Sars, 1862) is a very confusing taxon with a complicated taxonomic history and many synonyms (Van Damme & Dumont 2008; Van Damme et al. 2010, 2013; Sinev 2017; Korovchinsky et al. 2021b; WoRMS Editorial Board 2024). Until recently, it was supposed that it has an almost global distribution (Kotov et al. 2013a). According to modern concepts, the distribution of the typical form of this chydorid seems to be limited to the Palearctic and Oriental regions (Sinev 2017; Korovchinsky et al. 2021b), although the Southeast Asian populations have some differences and require additional research (Sinev & Yusoff 2015; Sinev et al. 2015; Sinev 2016, 2017). The findings of C. rectangula -like specimens are rather common in the Oriental and adjacent areas (Chiang & Du 1979; Rajapaksa & Fernando 1982a; Idris 1983; Michael & Sharma 1998; Sanoamuang 1998; Tanaka & Ohtaka 2010; Maiphae et al. 2005, 2008; Rane 2011; Chatterjee et al. 2013; Korovchinsky 2013; Kotov et al. 2013b; Ji et al. 2015; Sinev & Yusoff 2015; Sinev et al. 2015; Sinev 2016; Sharma & Sharma 2017; Gogoi et al. 2018; Tiang-nga et al. 2020; Choedchim & Maiphae 2023). In Vietnam, this crustacean is well known as well (Shirota 1966; Dang et al. 1980, 2002; Dang & Ho 2001; Duong et al. 2008; Gusakov et al. 2014; Zhdanova 2014). Coronatella rectangula is considered one of the most eurybiont representatives of the Aloninae. It occurs in almost all types of water bodies of any trophic level, in a wide range of environments. The species is found both in plankton and benthos. In big water bodies, it prefers littoral habitats, usually with aquatic vegetation (Van Damme et al. 2010; Sinev 2016; Korovchinsky et al. 2021b). In our samples, the species was rare and in low concentrations.