Sillago ingenuua McKay 1985

Sillago ingenuua McKay, 1985 Figure 6 A & B Sillago ingenuua McKay, 1985: 44 (Chantaburi, Gulf of Thailand). Bay sillago Materials examined. India: FL_ JNU uncat. [CH121911, CH121915 – CH121918, CH121920, CH121922 and CH121923], 9 specimens, 122.9–141.4 mm SL, Chennai, December 2019. Comparative material: Sillago ingenuua: FEL_OUC 176002, 122.5 mm SL, China, Fujian, Dongshan. Brief description: Dorsal-fin rays XI+I,17; anal-fin rays II,16–17; scales in lateral line 66–71; scale rows above lateral line 4–5; vertebrae: 13–14+9–10+9–12=32–34. Swimbladder with a short median anterior extension, a single posterior extension and about 5 small, pointed anterolateral projections. Body color is pale yellowish brown. The general body shape and swimbladder are shown in Figure 6A–C. Geographical distribution: According to the phylogenetic analysis and species delimitation approaches Sillago ingenuua is divided into two (ASAP and PTP) or three (ABGD) genetic lineages (Fig. 7): Sillago ingenuua A from the Gulf of Thailand (type locality), Indonesia, Vietnam, China, and Malaysia (BOLD number MUHD 029-15, private sequences as S. sihama); S. ingenuua B from Western Australia, eastern Australia (BOLD number FOAL 889-10) and Taiwan (both lineages were recognized by Gao et al. 2023); and S. ingenuua from Chennai, India. Sillago ingenuua was also reported from Sri Lanka (De Bruin et al. 1994) but no genetic material was available from that area. Remarks: Two separate lineages with 4.9 % and 6.9 % genetic divergence were previously detected in S. ingenuua, based on COI sequences and 13 concatenated protein coding gene sequences in the absence of significant morphological differences (Tikochinski et al. 2013; Cheng et al. 2020; Gao et al. 2023). One is Sillago ingenuua A from China, Vietnam, Thailand and Indonesia, and Malaysia, another is Sillago ingenuua B from Australia and Taiwan. Because there is insufficient distance (1.6 %) between S. ingenuua from India and S. ingenuua A, the former was included as the member of that lineage. In this study, we first report S. ingenuua A from the Indian Ocean, specimens of which form a monophyletic group within S. ingenuua A and are recognized as a potential separate species by the ABGD approach for species delimitation only, whereas PTP and ASAP do not suggest a separation from their western Pacific Ocean conspecifics. In this species, an integrative taxonomic study is needed to resolve the actual species boundaries.