A new species of anchovy, Encrasicholina auster (Clupeiformes: Engraulidae) from Fiji, southwestern Pacific Ocean

Description of three new species previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933 and a re-description of S.bengalensis (Chordata, Osteichthyes, Clupeiformes, Engraulidae)

Examination of numerous specimens characterised by predorsal scute, long maxilla, indented preopercle and pelvic scute lacking a spine and previously identified as Stolephorusbengalensis (Dutt & Babu Rao, 1959) or Stolephorusinsularis Hardenberg, 1933, revealed four distinct species, true S.bengalensis (distributed from the Bay of Bengal to Pakistan) and three new species, viz., Stolephoruseldorado sp. nov. (Taiwan to Java, Indonesia), Stolephorusdiabolus sp. nov. (Strait of Malacca, from Penang , Malaysia, to Singapore) and Stolephoruseclipsis sp. nov. (Bintan Island, Riau Archipelago, Indonesia). Characters separating the four species include numbers of gill rakers on each gill arch and vertebrae and pelvic fin and dorsal-fin ray lengths. Two molecular markers (mitochondrial cytochrome b and cytochrome oxidase I genes) demonstrated the distinction of three of the species examined morphologically and enabled a reconstruction of their phylogenetic relationships. Each species was genetically divergent from the others by 3.5%-7.7% mean uncorrected distance in the mitochondrial cytochrome oxidase I gene.

Redescription of Stolephorus ronquilloi Wongratana, 1983 and Description of Stolephorus hindustanensis, a New Anchovy from the Western Coast of India (Teleostei: Clupeiformes: Engraulidae)

The new anchovy Stolephorus hindustanensis n. sp., described on the basis of 11 specimens collected from Mumbai, western coast of India, closely resembles Stolephorus ronquilloi Wongratana, 1983 in sharing an indented preopercle posterior margin, long maxilla extending beyond the preopercle posterior margin, double pigmented lines on the dorsum behind the dorsal fin, and lacking a predorsal scute. However, the new species differs from S. ronquilloi in having lower counts of gill rakers on the first and second gill arches, higher counts of total vertebrae, a deeper body, greater distances between the snout tip and anal-fin origin, origins of the dorsal and anal fins, and pelvic-fin insertion and anal-fin origin, and longer pelvic fin, third dorsal-fin ray, third anal-fin ray, and postorbital length.

Stolephorus grandis, a new anchovy (Teleostei: Clupeiformes: Engraulidae) from New Guinea and Australia

The new anchovy Stolephorus grandis n. sp., described on the basis of 10 specimens collected from Papua, Indonesia, and Australia, closely resembles Stolephorus mercurius Hata, Lavou Motomura, 2021, Stolephorus multibranchus Wongratana, 1987, and Stolephorus rex Jordan Seale, 1926, all having double pigmented lines on the dorsum from the occiput to the dorsal-fin origin, a long maxilla (posterior tip just reaching or slightly beyond the posterior margin of preopercle), and lacking a predorsal scute. However, the new species clearly differs from the others in having fewer gill rakers (3539 total gill rakers on the first gill arch in S. grandis vs. > 38 in the other species), a greater number of vertebrae (total vertebrae 4243 vs. fewer than 41), longer caudal peduncle (21.923.7% SL vs. 20.8%), and the depressed pelvic fin not reaching posteriorly to vertical through the dorsal fin-origin (vs. reaching beyond level of dorsal-fin origin).

Multigene barcoding and phylogeny of selected Engraulidae species

Anchovies (Engraulidae) are one of the ecologically important groups and often difficult to identify due to their small size and overlapping morphological characters. In the present study, reference DNA barcodes were generated for 82 individuals representing 13 species of Engraulidae family using mitochondrial Cytochrome c oxidase subunit I (COI) and 16S rRNA genes. The average genetic distance value of COI gene for conspecific, congeneric and confamilial is 0.25, 20.45 and 22.28%, respectively. Mitochondrial 16S rRNA showed an average divergence value of 0.60, 10.28 and 14.37% for within species, between species and within families, respectively. Comparison of the present study reference barcodes with the reported sequences revealed high frequency of misidentification of species and possible occurrence of cryptic species in this family. Phylogenetic tree reconstructed using different methodologies revealed monophyletic nature of genus Stolephorus and the evolutionary relationship within genus Stolephorus is defined as ([S. insularis: S. tamilensis] S. dubiosus (S. waitei [S. commersonnii: S. indicus])).

Molecular systematics of the anchovy genus Encrasicholina in the Northwest Pacific

The anchovy genus Encrasicholina is an important coastal marine resource of the tropical Indo-West Pacific (IWP) region for which insufficient comparative data are available to evaluate the effects of current exploitation levels on the sustainability of its species and populations. Encrasicholina currently comprises nine valid species that are morphologically very similar. Only three, Encrasicholina punctifer, E. heteroloba, and E. pseudoheteroloba, occur in the Northwest Pacific subregion of the northeastern part of the IWP region. These species are otherwise broadly distributed and abundant in the IWP region, making them the most important anchovy species for local fisheries. In this study, we reconstructed the phylogeny of these three species of Encrasicholina within the Engraulidae. We sequenced 10 complete mitochondrial genomes (using high-throughput and Sanger DNA sequencing technologies) and compared those sequences to 21 previously published mitochondrial genomes from various engraulid taxa. The phylogenetic results showed that the genus Encrasicholina is monophyletic, and it is the sister group to the more-diverse "New World anchovy" clade. The mitogenome-based dating results indicated that the crown group Encrasicholina originated about 33.7 million years ago (nearby the limit Eocene/Oligocene), and each species of Encrasicholina has been reproductively isolated from the others for more than 20 million years, despite their morphological similarities. In contrast, preliminary population genetic analyses across the Northwest Pacific region using four mitogenomic sequences revealed very low levels of genetic differentiation within Encrasicholina punctifer. These molecular results combined with recent taxonomic revisions are important for designing further studies on the population structure and phylogeography of these anchovies.