Sillago ingenuua McKay, 1985

Saha, Shilpi, Bogorodsky, Sergey V., Baki, Mohammad Abdul, Gao, Tianxiang, Mckay, Roland J., Alpermann, Tilman J. & Song, Na, 2024, Assessment of the diversity of the family Sillaginidae in the Indian Ocean with emphasis on the taxonomic identity of Sillago sihama, Zootaxa 5493 (5), pp. 451-485 : 471

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.

Figures

FIGURE 6. A: Sillago ingenuua A, FL_JNUCH121922, 130.1 mm SL, Chennai, India; B & C: Swimbladder of Sillago ingenuua A, Chennai, India; D: Swimbladder of Sillago ingenuua, Dongshan, China (Xiao 2018); E: Swimbladder of Sillago ingenuua B, Taiwan (Xiao 2018).

FIGURE 7. Phylogenetic tree using COI gene sequences of 45 species of Sillaginidae based on maximum likelihood method. Three species of the suborder Percoidei, Callanthias japonicus, Dicentrarchus labrax and Pempheris schwenkii, were selected as outgroup species. Findings from species delimitation approaches on the basis of COI gene sequences using the PTP, ABGD and ASAP methods are presented as vertical bars that link extreme taxa in the tree if allocated to the same hypothetical species.