A New Species of Thrissina from the Andaman Sea and Re-assessment of the Taxonomic Status of Thrissina cuvierii (Swainson, 1839) and Thrissina malabarica (Bloch, 1795) (Teleostei: Clupeiformes: Engraulidae: Coiliinae)

Abstract

Examination of the original description of Thrissina malabarica (Bloch, 1795), a name previously applied to an Indian Ocean species with a distinctly deep body, revealed that the former nominal species was actually a senior synonym of Thrissina hamiltonii (Gray, 1835), a slender-bodied Indo-West Pacific species. The applicable name for the species previously treated as T. malabarica is Thrissina cuvierii (Swainson, 1839). To stabilize the taxonomic status of these three nominal species, a neotype for T. cuvierii is designated. In addition, Thrissina aurora, new species, is described from a specimen collected from the Andaman Sea near Phuket, Thailand. Although both the new species and T. cuvierii share a deep body, the former is distinguished by lower counts of gill rakers and anal-fin rays than the latter. The mitochondrial cytochrome oxidase I (COI) haplotype network of 11 specimens of T. cuvierii and three specimens (including the holotype) of T. aurora, new species, revealed 22 nucleotide differences between the two species, corresponding to 3.4% mean uncorrected genetic distance.

Resurrection and redescriptions of nominal species previously regarded as synonyms of Thrissina mystax (Bloch and Schneider, 1801) (Teleostei: Clupeiformes: Engraulidae)

“…Furthermore, T. mystax , T. porava , and T. valenciennesi differ from T. dayi and T. stenosoma in having fewer branched anal‐fin rays (40 or fewer in the former vs. 40 or more in the latter). The remaining species, T. splendida , is separated from T. mystax and T. porava by a lower number of branched anal‐fin rays (37–43 in T. splendida vs. 30–35 in T. mystax and T. porava ) and double dark lines on the dorsum (vs. no dark lines on dorsum) (Hata, 2022; Hata et al, 2020, 2021, 2022a; Hata, Lavoué, Bogorodsky, et al, 2023; Hata, Lavoué, Chunthanawong, & Motomura, 2023; Hata & Motomura, 2019; Whitehead et al, 1988; Wongratana et al, 1999). Comparisons of T. mystax with T. porava and T. valenciennesi are given in “Comparisons” under each species.…”

“…Kottelat (2013) regarded E. poorawah (Bleeker, 1872) as a junior synonym of T. mystax , the former having been based on 35 specimens (100–210 mm total length) collected from Singapore and various localities in Indonesia (Java, Sumatra, Bintang [currently Bintan Island, Riau Archipelago], Bangka, Borneo, Celebes, Batjan, and Ceram). According to Whitehead et al (1966), the probable type specimens of the nominal species are shared with those of Engraulis grayi (Bleeker, 1851) (regarded as a junior synonym of Thrissina hamiltonii Gray, 1835, both nominal species currently being regarded as junior synonyms of Thrissina malabarica Bloch, 1795, a species with the maxilla posterior tip reaching only slightly beyond the opercular margin, and short of the pectoral‐fin insertion; Whitehead et al, 1988; Hata et al, 2022a; Hata, Lavoué, Chunthanawong, & Motomura, 2023), and labeled as “ E. poorawah ” in the RMNH collection. Although Bleeker (1872: p. 132) described E. poorawah as having the maxilla just reaching to the pectoral‐fin insertion, the key to E. poorawah on p. 129 described the maxilla tip as not reaching the pectoral fin.…”

“…In fact, no figures in Bleeker (1872) were captioned as “ E. poorawah ,” Bleeker (1872) apparently treating E. poorawah as a junior synonym of T. hamiltonii and E. grayi . It is now believed that Bleeker's (1872) E. poorawah was conspecific with T. hamiltonii (currently regarded as a junior synonym of T. malabarica ; Hata, Lavoué, Chunthanawong, & Motomura, 2023). Because the type specimens of E. poorawah are thought to include the lectotype and paralectotypes of E. grayi , future nomenclatural stability is served by designating herein RMNH.PISC.7068 (159.6 mm SL, collected from Riau Island or Jakarta, Java, Indonesia; Hata et al, 2022a, Figure 1g), also designated as the lectotype of E. grayi by Whitehead et al (1966), as the lectotype of E. poorawah , the latter becoming a junior objective synonym of E. grayi Bleeker, 1851.…”

“…T. valenciennesi further differs from T. mystax in having a shorter maxilla (24.4%–27.9% of SL in T. valenciennesi vs. 28.1%–31.1% in T. mystax ; Figure 7d) and a lower number of 4TGR (14–17 [rarely 18] vs. 19–22 [18]; Figure 6d). In fact, the gill raker numbers on each gill arch are an important diagnostic character in various clupeiform fishes (Agostinho et al, 2022; Gangan et al, 2020; Kimura et al, 2009; Singh et al, 2021; Whitehead et al, 1988), and even 4TGR numbers (gill rakers on innermost gill arch) can be a distinguishing character in some cases (Hata et al, 2022b; Hata, Lavoué, Bogorodsky, et al, 2023; Hata, Lavoué, Chunthanawong, & Motomura, 2023). However, it appears to be rare that two apparently closely related species differ significantly in 4TGR number, even though no differences exist in GR numbers on other gill arches.…”

“…Although the genus was reviewed by Whitehead et al (1988), who recognized 24 valid species, taxonomic research of the genus has progressed in recent years by the authors' research group. Because the recent studies described many new species and reassessed taxonomic status of various nominal species related to the genus, there are currently 35 valid species in this genus (Gill et al, 2018; Hata, 2020, 2022; Hata et al, 2020, 2021, 2022a; Hata & Koeda, 2020; Hata, Lavoué, Bogorodsky, et al, 2023; Hata, Lavoué, Chunthanawong, & Motomura, 2023; Hata, Mandagi, & Masengi, 2023; Hata & Motomura, 2019; Hata & Nakae, 2019; Roberts, 1978; Whitehead et al, 1988; Wongratana, 1983, 1987; Wongratana et al, 1999).…”