Camptocercus vietnamensis Dang, 1967

20. Camptocercus vietnamensis Dang, 1967 View in CoL

Localities and specimens found: 17 – 5♀, 2♀ ov, 1j; 45 – 1♀; 48 – 1♀ ov; 51 – 1♀.

Distribution and ecology. This is a rare species originally found and described in the Northern Vietnam ( Dang 1967 cited by Phan et al. 2015; Dang et al. 1980, 2002; Dang & Ho 2001). Later, it was noted in the Southern part of the country (Sinev, 2011; Sinev & Korovchinsky 2013; Phan et al. 2015; Gusakov et al. 2014). Now, C. vietnamensis has already been indicated in India, Laos, Thailand, China and South Korea ( Kotov et al. 2012; Kotov et al. 2013b; Jeong et al. 2014, 2015; Sinev et al. 2015; Sinev 2016, 2017; Sharma & Sharma 2017; Tiang-nga et al. 2020; Dadykin et al. 2023; Padhye et al. 2023). In addition, previous records in the regions of some other congeners (see Remarks for details) need to be revised and should be attributed at least partially to C. vietnamensis as well (Sinev 2011, 2016, 2017; Kotov et al. 2013b; Lopez et al. 2017). Thus, the established current range of C. vietnamensis covers, as a minimum, Southern, Southeastern and part of Eastern Asia.

The species lifestyle and ecology are not yet fully understood. It often occurs in rivers and streams, which, together with specific morphological adaptations, may indicate its rheophilicity (Sinev 2011; Sinev & Korovchinsky 2013; Korovchinsky et al. 2021b). However, C. vietnamensis was also repeatedly found in different stagnant water bodies: lakes, reservoirs, rice fields, swamps, pools ( Dang et al. 2002; Dang & Ho 2001; Kotov et al. 2012; Jeong et al. 2015; Phan et al. 2015; Sinev et al. 2015; Dadykin et al. 2023; Padhye et al. 2023). In our material, a few individuals of this crustacean were encountered only in vegetation-rich natural lakes, on the bottom and in the rhizosphere of floating moss (see Appendix 1).

Remarks. Camptocercus vietnamensis is very close to C. uncinatus Smirnov, 1971 , which is also present in the Оriental region. It is noted (Sinev 2011, 2016, 2017; Kotov et al. 2013b; Lopez et al. 2017) that at least some earlier records of C. uncinatus in this area may in reality refer to C. vietnamensis . The records of C. rectirostris Schödler, 1862 ( Shirota 1966; Chiang & Du 1979; Tanaka & Ohtaka 2010; Kotov et al. 2012; Korovchinsky 2013) and C. australis Sars, 1896 ( Idris & Fernando 1981; Idris 1983; Korovchinsky 2013) in Southeast and East ( South Korea, China) Asia are also apparently erroneous and in most (if not all) cases should be attributed to C. vietnamensis as well (Sinev 2011, 2016; Kotov et al. 2012, 2013b).