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Author: search.filters.author.Klangnurak, WanladaSubject: search.filters.subject.Gulf of Thailand

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    Morphological and molecular insights into diversity of Brevitrygon (Elasmobranchii, Myliobatiformes, Dasyatidae) in Thai waters
    (2026-01-01)
    Wongmanee, Phiphat
    ;
    Khudamrongsawat, Jenjit
    ;
    Krajangdara, Tassapon
    ;
    Senanan, Wansuk
    ;
    Panithanarak, Thadsin
    Stingrays of the genus Brevitrygon in Thailand are captured as bycatch in fisheries, and a proportion of the catch is used for local consumption, but information on their biodiversity remains limited. This study examines the diversity of Brevitrygon species collected from the Gulf of Thailand and the Andaman Sea. A total of 148 specimens were morphologically identified as either Brevitrygon heterura (Bleeker, 1852) or Brevitrygon cf. imbricata, based on diagnostic characters. Morphometric analysis revealed that all specimens more closely resembled B. heterura, with no significant differences between morphotypes or sexes. Genetic analysis based on COI sequences from 39 samples further supported these results. All samples grouped within the B. heterura clade with strong bootstrap support and formed two distinct genetic subgroups corresponding tothe Gulf of Thailand and the Andaman Sea. The mean intraspecific divergence (1.08%) fell within the expected range for population-level variation in elasmobranchs, with interspecific divergence from other Brevitrygon species exceeding 9%. These results indicate that B. heterura in Thai waters likely represents a single species. While both morphometric and genetic data suggest regional differentiation, the observed variation falls within the normal range for a single species, providing no evidence of cryptic diversity. This study underscores the value of integrating morphological and molecular data to better understand population structure and taxonomy in stingrays.
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    Resolving Species Identification and Distribution Patterns of Neotrygon spp. in Thai Waters: Inefficiency of Morphometric Analysis and the Power of COI Gene Barcoding and Phylogenetics
    (2025-01-01)
    Panithanarak, Thadsin
    ;
    Karuwanjaroen, Ratima
    ;
    Utama, Chanapa
    ;
    Laongmanee, Penchan
    ;
    Meejan, Titirat
    Three species of maskrays in the genus Neotrygon have previously been reported in Thai waters. However, the high morphological similarity among species within the blue-spotted maskray complex (Neotrygon spp.) makes accurate identification challenging. This study aimed to confirm species identification in Neotrygon spp. using morphometric and genetic data and to further examine their phylogenetic relationships in Thai waters by analyzing mitochondrial COI (cytochrome c oxidase subunit I) sequences. Multivariate analysis (PCA) of 37 morphometric characters from 55 specimens proved insufficient for species-level discrimination. However, molecular phylogenetic analysis of 14 unique COI sequences from Thai waters, combined with 61 reference sequences from previously documented related species and closely related species, identified two monophyletic clades. These clades corresponded to two species: N. varidens, found exclusively in the Gulf of Thailand, and N. malaccensis, recorded for the first time in Thailand, occurring in both the Gulf of Thailand and the Andaman Sea. This DNA-based identification provides clear evidence for species boundaries within Thai Neotrygon species and highlights the importance of molecular tools for distinguishing morphologically similar marine species in the Indo-Pacific region.