Morimotobathynella undetermined

Morimotobathynella sp. Material examined. Pocheon-si (38°6'56.21"N, 127°15'46.38"E), South Korea. Collected by S.-J. Ji and C.-W. Lee on 31 May 2020. Remarks. This specimen was included in the phylogenetic analysis to mitigate potential long-branch attraction issues that could affect the phylogenetic placement of M. koreana sp. nov. The inclusion of this closely related species provides a more robust phylogenetic framework for the genus Morimotobathynella in East Asia. Although a detailed morphological examination suggests that this specimen represents another potentially new species, a formal description requires additional material. CO 1 and 18 S rRNA gene sequencing In this study, 597 bp of CO 1 (PQ 790059 – PQ 790061) and 1,713 bp of 18 S sequences (PQ 789943, PQ 789944) were obtained from M. koreana sp. nov. The three CO 1 and two 18 S sequences obtained from M. koreana sp. nov. showed no intraspecific variation. Additionally, 597 bp of CO 1 (PQ 790062) and 1,210 bp of 18 S sequences (PQ 789945) were obtained from Morimotobathynella sp. collected in Pocheon, South Korea. Genetic divergence analysis revealed that the two Korean Morimotobathynella species had p - distances of 10.4 % for CO 1 and 1.2 % for 18 S sequences. Phylogenetic analysis ML and BI analyses were performed using a concatenated 1,002 bp dataset comprising CO 1 (615 bp) and 18 S rRNA (387 bp) sequences from the new species and 18 other Bathynellidae species available in GenBank (Fig. 7, Suppl. material 2: table S 2). Allobathynella danyangensis Ji & Min, 2023 from South Korea (Family Parabathynellidae) was used as outgroup, and the analysis confirmed the monophyly of Bathynellidae. Both the ML and BI analyses produced congruent tree topologies. Our results also support the separation of three distinct subfamilies within Bathynellidae, corroborating previous studies (Camacho et al. 2013, 2020). Phylogenetic trees revealed that M. koreana sp. nov. and Morimotobathynella sp. from South Korea formed a distinct monophyletic lineage within the subfamily Bathynellinae, with strong support (bootstrap support: 100 %, posterior probability: 1.0). They showed a close relationship with species of the genus Altainella from Mongolia and Russia (bootstrap support: 68 %, posterior probability: 0.95). This phylogenetic relationship may suggest a historical biogeographic connection among bathynellid taxa in Northeast Asia.