Alona intermedia Sars, 1862

15. Alona intermedia Sars, 1862 View in CoL

Localities and specimens found: 41 – 12♀, 4♀ ov, 3♀ em, 2j; 95 – 1♀, 1♀ ov, 1♀ em, 1j.

Distribution and ecology. Alona intermedia has an almost cosmopolitan distribution ( Kotov et al. 2013a; Sinev 2016, 2017). It is relatively widely known (mainly as A. intermedia or as a synonym, Biapertura intermedia (Sars, 1862)) in the Oriental region ( Fernando 1974; Chiang & Du 1979; Idris & Fernando 1981; Idris 1983; Michael & Sharma 1988; Maiphae et al. 2008; Tanaka & Ohtaka 2010; Chatterjee et al. 2013; Korovchinsky 2013; Van Damme et al. 2013; Ji et al. 2015; Sinev 2016; Lopez et al. 2017; Sharma & Sharma 2017; Choedchim & Maiphae 2023), not excluding Vietnam ( Dang et al. 1980, 2002; Dang & Ho 2001; Sinev 2017; present study).

The lifestyle and ecology of this crustacean are still not fully understood. According to Korovchinsky et al. (2021b), its northern populations usually live in the open sandy littoral of lakes and ponds of various trophic levels and are not generally found in the thickets of aquatic plants. However, it is also present in swamps, including among sphagnum. In Southeast Asia, A. intermedia is positioned as a littoral species, associated with vegetation (Sinev 2016). In this region, it is recorded in lakes, streams, ponds, rice fields, swamps ( Idris 1983; Dang & Ho 2001; Choedchim & Maiphae 2023). We detected these chydorids in a densely plant-filled, acidified small man-made pond and in a clean mountain stream in the dry season (see Appendix 1). Thus, it is obvious that A. intermedia can inhabit a wide spectrum of habitats.

Remarks. Globally, A. intermedia populations most likely represent a group of cryptic species in need of comprehensive revision (Van Damme et al. 2010, 2013; Sinev 2016, 2017; Korovchinsky et al. 2021b).