Biapertura affinis

19. Biapertura cf. affinis (Leydig, 1860) Localities and specimens found: 41 – 17♀, 3♀ ov, 1♀ em, 2♂, 8j; 42 – 5♀, 7♀ ov, 5♀ em, 10j; 59 –3j; 92 – 1♀ ov, 1♀ em. Distribution and ecology. Biapertura affinis s. lat. is a nearly cosmopolitan group of closely related species (Sinev 1997, 2017, 2020; Van Damme et al. 2010; Chatterjee et al. 2013; Kotov et al. 2013a; Korovchinsky et al. 2021b). There are numerous reports of findings of B. affinis -like populations (mainly as Alona affinis (Leydig, 1860), A. cf. affinis or Biapertura affinis, B. cf. affinis) in the Oriental and surrounding areas (Chiang & Du 1979; Idris & Fernando 1981; Idris 1983; Michael & Sharma 1998; Sanoamuang 1998; Rane 2005, 2011; Tanaka & Ohtaka 2010; Chatterjee et al. 2013; Korovchinsky 2013; Kotov et al. 2013b; Van Damme et al. 2013; Ji et al. 2015; Sinev 2016; Lopez et al. 2017; Sharma & Sharma 2017; Gogoi et al. 2018; Sinev et al. 2020; Tiang-nga et al. 2020; Choedchim & Maiphae 2023; Dadykin et al. 2023). In Vietnam, these crustaceans were designated as Alona affinis (Shirota, 1966; Sinev & Korovchinsky 2013), Biapertura affinis vietnamica Dang, 1967 (Dang et al. 1980, 2002; Dang & Ho 2001), Alona cf. affinis (Zhdanova 2014), A. affinis var. ornata Stingelin, 1895 (Gusakov et al. 2014). Biapertura affinis is a littoral cladoceran occurring in the bottom sediments and among the vegetation thickets. Throughout the world, its populations live in a wide variety of water bodies and biotopes, in a wide range of environments (Fryer 1968; Sinev 2020; Korovchinsky et al. 2021b). In Southeast Asia, this crustacean was recorded in floodplain and oxbow lakes, reservoirs, ponds, rice fields, marshes, peat swamps, rivers, streams (Idris 1983; Dang & Ho 2001; Sinev & Korovchinsky 2013; Zhdanova 2014; Sinev 2016; Gogoi et al. 2018; Choedchim & Maiphae 2023). In our samples, specimens corresponding to this taxon were most numerous in overgrown acidified ponds, but they were also found in a mountain river (see Appendix 1). Remarks. This chydorid has a complicated taxonomic history with many synonymized names (Van Damme et al. 2010; Kotov et al. 2013a; Sinev 2020; Korovchinsky et al. 2021b; WoRMS Editorial Board 2024). At the present time, it is considered that the B. affinis s. str. is a Palearctic inhabitant, with similar worldwide populations represented by a complex of sibling species. The analogous Oriental populations still need careful revision and possibly include more than one allied species (Van Damme et al. 2010, 2013; Chatterjee et al. 2013; Kotov et al. 2013b; Sinev 2016, 2017; Lopez et al. 2017; Sinev 2020; Korovchinsky et al. 2021b).