Ilyocryptus yooni Jeong, Kotov et Lee, 2012

9. * Ilyocryptus yooni Jeong, Kotov et Lee, 2012

Localities and specimens found: 8 − 4♀, 3♀ ov, 4♀ em; 12 −1j; 25 −2j.

Distribution and ecology. Ilyocryptus yooni is a recently described member of the genus distributed in East and Southeast Asia. Today, the ascertained range of the species extends from the Russian Far East and Japan, through Korea and China, to Vietnam and Malaysian Borneo ( Jeong et al. 2012, 2014; Sinev & Yusoff 2015; Sinev et al. 2015; Xiang et al. 2015; Korovchinsky et al. 2021b; Dadykin et al. 2023; Kotov et al. 2024). Before the present studies on meiobenthos, I. yooni was not known in Vietnam ( Gusakov et al. 2024; Kotov et al. 2024).

Ilyocryptus yooni is a benthic species that apparently prefers permanent lentic and lotic water bodies. To date, it has been recorded in large lakes with broad shallow areas rich in aquatic vegetation, in the backwater of a small river and in its channel with a slow current, in a small stream, in ponds and in rice fields ( Jeong et al. 2012; Sinev & Yusoff 2015; Sinev et al. 2015; Dadykin et al. 2023). In Vietnam, we found it in the open littoral of three reservoirs on clay and silty-sandy sediments (see Appendix 1).

Remarks. In East Asia ( China and further south), prior to its description I. yooni was usually identified as its close congener I. agilis Kurz, 1878 ( Jeong et al. 2012, 2014; Xiang et al. 2015; Kotov et al. 2024). Our initial findings of I. yooni individuals in Vietnam (samples Nos. 8 and 12; see Appendix 1) were also documented as I. cf. agilis ( Gusakov et al. 2014) .