Tropical Natural History

Her Royal Highness Princess Maha Chakri Sirindhorn: Princess of Taxonomy and Biodiversity of Thailand

Parin Jirapatrasilp, Chirasak Sutcharit, Sumonta Promboon, Somsak Panha — Tue, 14 Oct 2025 00:00:00 +0700

Her Royal Highness Princess Maha Chakri Sirindhorn (hereafter HRH Princess Sirindhorn) has demonstrated a lifelong dedication to the study of nature, biodiversity, and environmental conservation. Her initiatives have made significant impacts both in Thailand and internationally. Through her leadership, numerous projects have been championed including botanical gardens, school botanical garden-based education, plant genetic conservation, seed preservation programs, organic farming, natural history museums and the Flora of Thailand project. The Princess’s contributions extend beyond institutional development to inspire and support new generations of taxonomists and biologists. Her comprehensive understanding of biodiversity, coupled with the ability to recognize both its inherent beauty and practical applications, has guided her approach to sustainable development. Moreover, her work exemplifies how scientific knowledge can be applied for the benefit of humanity while preserving natural heritage. Through her decades-long commitment to this field, HRH Princess Sirindhorn serves as a powerful role model, inspiring children and youth to develop their own appreciation for nature and commitment to environmental conservation.

Review of the Flat Back Millipede Genus Yuennanina Attems, 1936 (Polydesmida: Paradoxosomatidae), with the Description of a New Species from Thailand

Natdanai Likhitrakarn, Sergei Golovatch, Somsak Panha — Tue, 14 Oct 2025 00:00:00 +0700

The millipede genus Yuennanina Attems, 1936 has been known so far only from Yunnan Province, southwestern China. Currently, it comprises three species: Y. ceratogaster Attems, 1936, Y. aceratogaster Zhang & Li, 1977, and Y. petalolobodes Chang & Zhang, 1989. Herein, we describe Y. sirindhornae sp. nov., from Huai Nam Dang, Chiang Mai Province, northern Thailand, representing the first formal record of this genus not only from Thailand, but also from entire Southeast Asia. The new species is characterized by its unique gonopodal solenophore the shape of which resembles a young fern frond with fimbriate edges. A detailed redescription of the type species, Y. ceratogaster, is provided based on a revision of type material. An updated identification key to all four presently known Yuennanina species is also provided.

Camponotus (Tanaemyrmex) sirindhornae sp. nov., a New Cave-dwelling Ant (Hymenoptera: Formicidae) from Thailand, with Its Ecological Notes

Tue, 14 Oct 2025 00:00:00 +0700

A newly cavernicolous ant species was discovered from cave environments and a man-made underground tunnel in Kanchanaburi Province, western Thailand based on worker and dealate queen. This represents the first record of the genus Camponotus nesting in subterranean habitats. The new species, described herein as Camponotus sirindhornae Jaitrong, Jantarit & Pitaktunsakul, sp. nov. is specialized to the subterranean lifestyle, displaying a set of troglobiotic traits i.e. reduced pigmentation, elongated antennae and appendages, and a slender head and body. It can be distinguished from its closely related congeners by a distinct combination of the following characters: 1) head of minor worker in full-face view, narrowed and prolonged behind eye, narrowest just in front of posterior margin, occipital carina forming distinct flange; 2) entire body (head, mesosoma and metasoma) reticulate with smooth and shiny interspaces; 3) head, mesosoma and petiole bright yellowish; 4) anterior half of each matasomal segments III–VI yellowish brown, while posterior half dark brown. The new species was observed prying on other cave-dwelling arthropods such as crickets, cockroaches, moths, and beetles. The ecology traits of this new species, along with its troglobiotic adaptation is also discussed.

A New Thai Millipede Species of the Genus Coxobolellus Pimvichai, Enghoff, Panha & Backeljau, 2020 (Diplopoda: Spirobolida: Pseudospirobolellidae)

Piyatida Pimvichai, Pongpun Prasankok, Thierry Backeljau — Tue, 14 Oct 2025 00:00:00 +0700

A new millipede species of the genus Coxobolellus is described from Mae Hong Son Province, Thailand: Coxobolellus sirin-dhornae sp. nov. The new species is defined by its gonopod morphology and COI DNA barcodes. These latter place the new species within the well-supported Coxobolellus clade. The new species exhibits four gonopod synapomorphies that are diagnostic for the genus: (1) a protruding process on the coxae of the 3^rd (and sometimes 4^th) pair of male legs, (2) large, triangular coxae on the 4^th and 5^th pairs of legs, (3) a short process on the preanal ring extending to or slightly beyond the anal valves, and (4) the posterior gonopod telopodite divided into two parts, with a conspicuous pore opening at the mesal margin at the end of the coxal part. The new species is included in an updated morphological identification key for all currently recognized Coxobolellus species.

A New Species of the Pill Millipede Genus Rhopalomeris Verhoeff, 1906 (Diplopoda, Glomerida) from Southern Thailand

Pichsinee Sapparojpattana, Ekgachai Jeratthitikul, Natdanai Likhitrakarn — Tue, 14 Oct 2025 00:00:00 +0700

A new species of pill millipede, Rhopalomeris sirindhornae sp. nov., is described from southern Thailand based on morphological characteristics and genetic barcoding. This species is distinguished from its congeners by light yellowish body with pale pink lateral margins on each tergum, a pair of black obtuse subtriangular patches on the dorsum, a pair of faded black dots on the lateral side of the thoracic shield, a light yellowish venter with faded light brown spots on pleurites 3–11, and a roundly triangular to spatulate syncoxital lobe of the telopod. Phylogenetic trees based on a fragment of the mitochondrial COI gene confirmed the entity of the new species and revealed a close relationship with R. carnifex and R. nigroflava. Interspecific genetic distances between R. sirindhornae sp. nov. and other Rhopalomeris species ranged from 9.97–14.36%, with the shortest distance to R. carnifex. Intraspecific genetic distances within each Rhopalomeris species ranged from 0–6.16%. A new distribution map of the presently known Rhopalomeris is also provided.

Phylogenetic and Morphological Evidence for Two New Species of Terrestrial Micro Snail Genus Georissa Blanford, 1864 (Neritimorpha: Hydrocenidae) from Central Thailand

Tue, 14 Oct 2025 00:00:00 +0700

This paper introduces two newly discovered endemic micro snails, Georissa chatra Buathanom & Pholyotha, sp. nov. and G. principalis Buathanom & Tongkerd, sp. nov., from limestone hills of Uthai Thani and Nakhon Sawan Provinces in central Thailand. These findings expand the number of Georissa species recorded in Thailand to seven. The taxonomic status and species boundaries of these new species were determined through a comprehensive analysis of comparative morphology and mitochondrial genetics. Georissa chatra sp. nov. is distinguished by a conical shell with tall and prominent carinas. Georissa principalis sp. nov. is characterized by an elongate conical or turreted shell with prominent cord-like spiral ridges, and an operculum with two layers. The cytochrome c oxidase subunit I (COI) phylogeny supports the monophyly of both lineages, but the relationships with other congeners remain unresolved. The analysis also revealed interspecific genetic distances among examined species ranging from 6.8% to 18.6%. Additionally, intraspecific genetic distances are surprisingly high, with 6.1% for G. chatra sp. nov. and 7.5% for G. principalis sp. nov. The observed high intraspecific genetic divergences are likely due to the significant endemism and fragmented distribution of populations within karst ecosystems. As a result, the discovery of these two new species significantly advances our understanding of micro snail diversity and represents a crucial first step in establishing a comprehensive DNA barcode reference library for micro snails in Thailand.

Integrative Taxonomy Reveals Two New Dragon Millipede Species in the Genus Desmoxytes Chamberlin, 1923 from Thailand (Diplopoda: Polydesmida: Paradoxosomatidae)

Ruttapon Srisonchai, Khanet Srikampha, Theemaporn Benchapong, Somsak Panha — Tue, 14 Oct 2025 00:00:00 +0700

Recent field surveys in northern Thailand led to the discovery of two remarkable new species of dragon millipede in the genus Desmoxytes Chamberlin, 1923. Using an integrative approach that combined morphological and molecular data, we confirmed the validity of these species, herein described as Desmoxytes chaofa Srisonchai, sp. nov. from Mae Hong Son Province and Desmoxytes sirindhornae Srisonchai, sp. nov. from Tak Province. To assess their systematic position and relationships, we conducted morphological examinations and reconstructed the phylogeny based on three gene fragments (COI, 16S rRNA, and 28S rRNA). Phylogenetic analysis supports the validity of these two new species, with genetic divergence in the COI gene clearly distinguishing them from congeners, ranging from 10.67–18.67% for D. chaofa Srisonchai, sp. nov. and 10.05–17.91% for D. sirindhornae Srisonchai, sp. nov. (mean = 14.71%). Notably, the phylogenetic tree aligns well with morphological characters, particularly those of the gonopod. Desmoxytes chaofa Srisonchai, sp. nov. is closely related to D. octoconigera Srisonchai, Enghoff & Panha, 2018, while D. sirindhornae Srisonchai, sp. nov. clusters together with D. des Srisonchai, Enghoff & Panha, 2016, both pairs exhibiting similarities in body colouration and gonopod telopodite. Based on current data, these two species are considered as narrow endemics and are restricted to limestone rock wall habitats. Complete morphological illustrations of the two new species and a distribution map of all Desmoxytes species are provided.

Integrative Taxonomy of a New Thyropygus Pocock, 1894 Species from Thailand (Diplopoda: Spirostreptida: Harpagophoridae)

Piyatida Pimvichai, Pongpun Prasankok, Thierry Backeljau — Tue, 14 Oct 2025 00:00:00 +0700

A new juliformian millipede species, Thyropygus sirindhornae sp. nov., is described from Chiang Rai Province, Thailand and assigned to the Thyropygus allevatus group based on two diagnostic gonopodal characters: (1) the gonopod telopodite with both tibial and femoral spines, and (2) a notably long tibial spine recurved toward the femoral spine. Despite its affiliation with the informal T. allevatus group, T. sirindhornae sp. nov. cannot be assigned to one of the four informal subgroups of the T. allevatus group because it lacks any of the diagnostic characters of these subgroups. Similarly, while the COI DNA barcode data support the distinctiveness of T. sirindhornae sp. nov. from other Thyropygus species within the T. allevatus group (mean interspecific sequence divergence of 0.16 ± 0.02, range: 0.12–0.19), they do not provide information about the sister group relationships or subgroup assignment of the new species. As a result, T. sirindhornae sp. nov. is tentatively assigned to the T. allevatus group, but is labelled as “incertae sedis” with respect to its sister group relations and subgroup classification. In fact, as the COI phylogeny only included species of the T. allevatus group, the assignment of T. sirindhornae sp. nov. to this informal species group needs to be confirmed by including representatives of other informal Thyropygus species groups.

Discovery of a New Helicarionoidean Land Snail Genus Siamopotaxis gen. nov. (Eupulmonata: Helicarionidae) from Thailand Based on Molecular Phylogenetic and Morphological Evidence

Arthit Pholyotha, Piyoros Tongkerd, Somsak Panha, Chirasak Sutcharit — Tue, 14 Oct 2025 00:00:00 +0700

The new helicarionoidean land snail genus Siamopotaxis Pholyotha, gen. nov. is described for two new species, Siamopotaxis principalis Pholyotha, sp. nov. and Siamopotaxis thailandensis Pholyotha, sp. nov., both from Thailand. The new genus is characterised by a medium-sized, globose, high-spired, cream-coloured shell, with one or two supraperipheral bands, a rounded last whorl, a short epiphallic caecum, an elongated dart apparatus, and many radular teeth with pectiniform cusps. Siamopotaxis principalis sp. nov. differs from S. thailandensis sp. nov. by the presence of one spiral band, whereas the latter species has two spiral bands. A DNA sequence analysis of mitochondrial COI and 16S DNA, and nuclear 28S DNA gene fragments, supports the systematic placement of these new taxa and confirms that Siamopotaxis gen. nov. as a distinct clade within the Helicarionidae.

Debaratania Pinkaew (Lepidoptera: Tortricidae: Olethreutinae), A New Gorgeous Genus from Thailand with Description of Its Type Species

Nantasak Pinkaew — Tue, 14 Oct 2025 00:00:00 +0700

Debaratania gen. nov. is described from Thailand, with Debaratania bellula sp. nov. designated as the type species. The new genus is characterized by its colorful forewing pattern, sexual dimorphism in the shape of both the fore- and the hindwing, and distinctive male hindwing venation, where M₃ and CuA₁ are short-stalked both proximally and distally, with three distinct anal veins. The male genitalia feature a prominent leaf-like uncus and a large tubular phallus with long, narrow cornuti. In the female genitalia, a conspicuous sclerotized plate with a strongly developed thorn-like process is present at the anterior end of ductus bursae. Living and pinned specimens, wing venation, and genitalia are illustrated. Structural features support placement in the tribe Enarmoniini.

A Second Species of the Rogadine Genus, Batothecoides Watanabe, 1958 (Hymenoptera: Braconidae) from Thailand

Avinjikkattu Parambil Ranjith, Donald Quicke, Buntika Areekul Butcher — Tue, 14 Oct 2025 00:00:00 +0700

A second species of the rogadine braconid wasp genus, Batothecoides Watanabe, 1958 is described from Thailand, the genus having been known only from the type species for the past 66 years. The new species, Batothecoides sirindhornae Ranjith, Butcher & Quicke, sp. nov., is distinguished from the type species of the genus, B. yakushimensis (Watanabe, 1938), by morphology, color and DNA sequence data. The type species is redescribed based on images of the holotype. A molecular phylogeny of all members of the subtribe Spinariina for which barcode data are available is presented.

Integrative Taxonomy Reveals a New Species of Freshwater Mussel, Pseudodon septuaginta sp. nov. (Unionidae: Pseudodontini), from the Mekong River Basin in Northeastern Thailand

Tue, 14 Oct 2025 00:00:00 +0700

This study investigated the taxonomy and phylogenetic relationships of the freshwater mussel genus Pseudodon Gould, 1844, with a specific focus on Indochinese populations, using a comprehensive molecular dataset and morphometric analyses. Our findings confirm the valid status of seven among the nine currently recognized extant Pseudodon species, and include the discovery of a new cryptic species, P. septuaginta sp. nov., from the Mekong River Basin in northeastern Thailand. The new species is characterized by a compressed, sub-trigonal shell outline, the presence of a posterior wing, weakly developed pseudocardinal teeth, and obsolete lateral teeth. Phylogenetic analysis revealed this new species as the sister taxon to the adjacent allopatric P. vagulus, which is distributed in Mekong River tributaries in the upper Khorat Plateau, exhibiting a 6.71% uncorrected COI p-distance. Despite some morphological overlap, these two species are distinguishable by pseudocardinal tooth structure and overall shell shape. Furthermore, phylogenetic analyses support a potential Bornean origin for Pseudodon, followed by dispersal into Myanmar and Indochina, with paleo-drainage isolation driving diversification within the Indochinese lineages.

Curcuma princeps (Zingiberaceae), A New Species from Southwestern Thailand

Tue, 14 Oct 2025 00:00:00 +0700

Curcuma princeps, a new species from the Curcuma subgen. Curcuma (Zingiberaceae: Zingiberoideae) from southwestern Thailand is described and illustrated. For the diagnostic purpose it is compared to the morphologically closest species Curcuma petiolata. Detailed description based on living flowering material, colour plates, notes on the distribution, habitat and phenology are provided. The provisional IUCN conservation status is proposed as Endangered for this species, based on the IUCN guidelines and criteria.

A New Species and New Records of the Dobsonfly Genus Protohermes van der Weele, 1907 (Megaloptera: Corydalidae: Corydalinae) from Thailand

Tue, 14 Oct 2025 00:00:00 +0700

The dobsonfly genus Protohermes van der Weele, 1907 is the most diverse genus within the family Corydalidae of the order Megaloptera. In the present study, we describe a new species of Protohermes, namely Protohermes sirindhornae Piraonapicha, Chomphuphuang & Liu, sp. nov., and report three additional species newly recorded from Thailand: P. cangyuanensis Yang & Yang, 1988, P. impunctatus Liu, Hayashi & Yang, 2008, and P. striatulus Navás, 1926. These findings are based on an integrative approach that combines both morphological and molecular data. A key to the males of Thai Protohermes species is provided.

Caridina sirindhornae sp. nov., A New Landlocked Atyid Species (Decapoda: Atyidae) from the Middle Mekong Basin, Thailand

Tue, 14 Oct 2025 00:00:00 +0700

A new species of landlocked and geographically restricted freshwater shrimp, Caridina sirindhornae sp. nov., is described from tributaries of the Mekong River in northeastern Thailand. The new species is morphologically similar to C. sumatrensis and C. maeklongensis by sharing characteristics such as a short antennular peduncle, the presence of epipods on the first four pereiopods, similar appendix interna on the male first pleopod, and a prominent subtriangular preanal carina without a spine. However, they can be distinguished by characteristics of the rostrum and egg size. Phylogenetic analyses based on partial sequences of the mitochondrial 16S rRNA and cytochrome oxidase subunit I (COI) genes (540 bp and 1,242 bp, respectively) robustly support the distinctiveness of C. sirindhornae sp. nov. Additionally, the findings show that the new species shares a sister relationship with C. lanceifrons, with a significant 16S rRNA p-distance of 6.74%, remarkably exceeding established species delimitation thresholds within the genus Caridina. This discovery represents the second landlocked Caridina species endemic to the Middle Mekong Basin in Thailand.

A New Species of Strobilanthes Blume (Acanthaceae) from Thailand

Pornchai Kladwong, Naphat Modsang, Pranom Chantaranothai — Tue, 14 Oct 2025 00:00:00 +0700

A species new to science, belonging to Strobilanthes from Thailand is described. Strobilanthes sirindhorniae Kladwong & Chantar., sp. nov. is found on limestone in northern Thailand. It is morphologically similar to S. maxwellii J.R.I.Wood and S. rosea Nees. A comparison table with similar and closely related species and a distribution map, and an illustration of S. sirindhorniae sp. nov. are provided.

Ephoron debaratana sp. nov., A New Species of Burrowing Mayfly (Ephemeroptera: Polymitarcyidae) from Thailand

Tue, 14 Oct 2025 00:00:00 +0700

A new species of burrowing mayfly, Ephoron debaratana sp. nov., is described based on the larval stage. The morphological characteristics distinguished the new species from other known Ephoron species are the followings: 1) pigmented lateral tracheal branches on the abdominal gills, 2) number of tubercles on the tusk, and 3) triangular frontal process. The morphological evidence presented in this study is strongly supported by cytochrome c oxidase subunit I (COI) gene data. This new species was found in a headwater stream in Kanchanaburi Province, Thailand. The habitat information and a comparison to the known species of Thai larvae are also presented.

Teloganopsis sirindhornae sp. nov. (Ephemeroptera: Ephemerellidae), A New Species of Thai Mayfly Revealed by the Integrative Taxonomy

Tue, 14 Oct 2025 00:00:00 +0700

In the present study, a new species of the genus Teloganopsis Ulmer, 1939, T. sirindhornae sp. nov., is described based on specimens collected and reared in Thailand. The new species is distinguished from other Thai Teloganopsis species by its abdominal color pattern, which is consistent across all developmental stages. Both morphology characteristics and molecular analysis support its designation as a new species. A concatenated phylogenetic tree based on COI and 28S rDNA confirms its monophyly and clearly separates it from other Teloganopsis species. Additionally, a description of the chorionic structure of T. sirindhornae sp. nov., a distribution map of known Teloganopsis species in Thailand and a dichotomous key for both larval and imaginal stages of known Oriental Teloganopsis species are provided.

A New Caruncle-bearing Limnonectes (Anura: Dicroglossidae) from the Phu Phan Mountain Range in Northeastern Thailand

Tue, 14 Oct 2025 00:00:00 +0700

We describe a new species of dicroglossid frog in the genus Limnonectes from the Phu Phan Mountain Range, Sakon Nakhon Province, northeastern Thailand. Molecular phylogenetic analyses, based on the mitochondrial 16S ribosomal RNA gene, revealed that Limnonectes sirindhornae Rujirawan, Yodthong & Aowphol, sp. nov. is closely related to L. lauhachindai but has mean uncorrected pairwise genetic divergences of 4.25%. The new species can be distinguished from its congeners by having the combination of SVL 36.7–44.7 mm (n = 8) in adult males, 40.2–45.6 mm (n = 8) in adult females; adult males with hypertrophied heads; adult males with interorbital caruncle weakly developed, low-profiled, U-shaped, without free posterior margin; two enlarged odontoid processes on anterior margin of lower jaw, larger in males than in females; vocal sac opening in males absent; and yellowish coloration in life on ventral surfaces absent.

The Ant Genus Temnothorax Mayr, 1861 (Formicidae: Myrmicinae) in Thailand, with a Description of a New Species

Netnapa Phosrithong, Kaewpawika Jitthamma Ignatius, Yudthana Samung — Tue, 14 Oct 2025 00:00:00 +0700

Temnothorax Mayr, 1861, a large ant genus with 502 valid species, 33 valid subspecies, and one valid fossil species (inclu-ding the new species), is predominantly found in temperate regions of the Old and New Worlds. The genus is represented in Thailand by two named species: Temnothorax barrettoi Hamer & Guénard, 2023, and T. sirindhornae Phosrithong, Ignatius & Samung, sp. nov. Herein, Temnothorax sirindhornae sp. nov. is described based on worker and dealate queen castes from the highlands of western Thailand, and T. barrettoi is newly recorded from the country's lowlands. Notably, both species nest in dead twigs on trees.

A New Species of the Ant Genus Tetraponera Smith, 1852 (Hymenoptera: Formicidae: Pseudomyrmecinae) from Thailand

Mon, 20 Oct 2025 00:00:00 +0700

Tetraponera Smith, 1852, a large ant genus comprising 87 extant and seven fossil species, is primarily distributed in the Afrotropical, Oriental, and Australasian regions. A new species, T. sirindhornae Yodprasit, Tasen & Jaitrong, sp. nov., is described from southern Thailand based on worker, dealate queen, and male castes. The new species exhibits worker dimorphism and is morphologically similar to T. binghami (Forel, 1902), T. connectens Ward, 2001, and T. notabilis Ward, 2001 in possessing an elongated head, but differs by the presence of a distinct mandibular gap between masticatory margins when the mandibles are closed (in the case of major worker and queen). The new species was found nesting in a dead rubber tree branch on a tree within a rubber plantation near a stream.

Ceratocombus sirindhornae sp. nov. (Hemiptera: Heteroptera: Dipsocoromorpha: Ceratocombidae): A New Species of the Minute Litter Bugs from Thailand

Mon, 20 Oct 2025 00:00:00 +0700

A new species of the minute litter bug, Ceratocombus sirindhornae sp. nov. is described from Thailand. Detailed morpho-logical information including description, diagnosis, and brief biology of the new species are presented.

Description of Two New Earthworm Species (Oligochaeta: Megascolecidae) from the Mekong River, Thailand

Ueangfa Bantaowong, Ratmanee Chanabun, Nattawadee Nantarat, Somsak Panha — Mon, 20 Oct 2025 00:00:00 +0700

Two new earthworm species are described from the Mekong River, Thailand, namely Amynthas septuaginta Bantaowong & Panha, sp. nov. and Metaphire fidelis Bantaowong & Panha, sp. nov. The former is a small Mekong earthworm in the A. aeruginosus species group with two pairs of spermathecal pores in 7/8-8/9. It is mainly distinguished from other Amynthas from the Mekong River by its small size (less than 50 mm), and with no genital markings at the male pore region. The latter is distinguished by having four pairs of spermathecal pores in 5/6-8/9, genital markings paired on xvii, ampulla paddle-shaped, and with diverticulum as a slender tube with a loose loop. Morphological description, taxonomic comments, illustrations, and distribution are provided.

A Revision of Brachylophon Oliv. (Malpighiaceae) Based on Morphology, Phylogenetics, and Palynology Reveals a New Species Endemic to Thailand

Mon, 20 Oct 2025 00:00:00 +0700

We present a taxonomic revision of Brachylophon (Malpighiaceae) in Thailand, Southeast Asia, based on herbarium collections and a field trip conducted in 2024. Two previously accepted species, B. anatomosans Craib and B. curtisii Oliv., are reported, alongside the new species, B. sirindhorniae Chaisongkram & Ruchis., described and illustrated for the first time. The new species is characterized by having white petals, pedicels 2–5 mm long; filaments 1.5–2.5 mm long; and mericarp 6–7 mm long. A detailed description, illustrations, and a comparison with closely related species are provided to aid in its identification. The discovery of this new species highlights the ongoing need for further exploration and taxonomic study of the genus in Southeast Asia to fully understand its diversity and distribution.

A Second Unicorn Darwin Wasp Species Gilen principissa sp. nov. (Hymenoptera: Ichneumonidae, Ctenopelmatinae) from Thailand

Mon, 20 Oct 2025 00:00:00 +0700

A new species of the genus Gilen Reshchikov & van Achterberg, 2018 (Hymenoptera, Ichneumonidae, Ctenopelmatinae), G. principissa Chansri, Kerkig & Reshchikov, sp. nov., from Thailand is described and illustrated based on female specimens collected with Malaise traps. A molecular phylogenetic tree is presented based on DNA barcode sequences of representative Ctenopelmatinae, including sequences from both known Gilen species. The new species was recovered as sister to G. orientalis Reshchikov & van Achterberg, 2018 with 100% bootstrap support, but on a long branch. Comparison of the sequences revealed that they differ at 88 positions out of 658 (13.4%) possibly indicating that their lineages diverged between six and 13 million years ago.

Tropodiaptomus sirindhornae sp. nov., A New Diaptomid Copepod (Copepoda: Calanoida) from Thailand

Thanida Saetang, Supiyanit Maiphae — Mon, 20 Oct 2025 00:00:00 +0700

Tropodiaptomus sirindhornae sp. nov. is described and illustrated based on materials collected from both permanent and temporary habitats across several regions of Thailand. This new species can be distinguished from its congeners by the following morphological characters of adult male antennule and fifth leg: the antepenultimate segment of right antennule with straight spinous process reaching between 1/2 and 3/4 of next segment; the inner margin of exopodal segment of left fifth leg with two lobes, and with uniform serration; the basis of right fifth leg has one triangular process and one longitudinal hyaline lamella; and second exopodal segment of right fifth leg is rectangular, posterior surface ornamented with one semicircular hyaline knob on middle close to inner margin and one triangular apophysis on distal outer margin. This species is widely distributed both spatially and temporally.

Paralona sirindhornae sp. nov. and Karualona cambodiaensis sp. nov., Two New Species of Cladocera (Crustacea: Cladocera: Chydoridae) from Southeast Asia

Artem Y. Sinev, La-orsri Sanoamuang — Mon, 20 Oct 2025 00:00:00 +0700

Two new cladocera species of the family Chydoridae (Crustacea: Cladocera) are described from Southeast Asia. Populations of Paralona sirindhornae sp. nov. were found in Thailand and Cambodia, while Karualona cambodiaensis sp. nov. was detected in Cambodia only. Paralona sirindhornae sp. nov. differs from the only other species of the genus Paralona Šramek-Hušek, Strašcraba et Brtek, 1962, namely, Holarctic P. pigra (Sars, 1862), in its smaller size, different position of the head pores, and the morphology of thoracic limbs III–V. Our data suggest that the populations of Paralona from South America and Africa also belong to independent species rather than P. pigra. Karualona cambodiaensis sp. nov. differs from other species of the genus in the unique morphology of the posteroventral angle of the valves, as well as in the body shape and morphology of the antenna. The morphology and taxonomic position of two new species are discussed. Both new species appear to be extremely rare in Southeast Asia, and their discovery is a result of recent intensive sampling efforts.

A New Species of Megachile (Callomegachile) Michener, 1962 (Hymenoptera: Megachilidae) Described from Thailand

Mon, 20 Oct 2025 00:00:00 +0700

During the revision of the resin bees subgenus Callomegachile Michener, 1962 in Thailand, we have identified and illustrated a novel species, Megachile (Callomegachile) sirindhornae Chatthanabun & Warrit, sp. nov. This discovery is based on three female specimens collected from northeastern and western regions of Thailand. The species exhibits an association with Akschindlium godefroyanum (Kuntze) H. Ohashi (Fabaceae), which serves as a floral resource. Additionally, the barcode sequence derived from the COI region of this new species has been submitted to GenBank, with the accession number PX354073.

Cryptic Diversity within the Endemic Mekong Giant Earthworm, Amynthas mekongianus (Cognetti, 1922) (Clitellata: Megascolecidae) Across the Lower Mekong River Basin with Descriptions of a New Species

Mon, 20 Oct 2025 00:00:00 +0700

The Lower Mekong Basin is recognized as a region of remarkable biodiversity. However, it is currently experiencing severe degradation due to rapid economic development and the intensifying effects of climate change. Numerous species, including earthworms, are under increasing threat. In addition, Amynthas mekongianus (Cognetti, 1922) exhibits considerable intraspecific morphological variability, making its identification challenging. Therefore, the study aims to clarify species boundaries within the A. mekongianus complex in the Lower Mekong River Basin using both morphological and molecular approaches. Specimens were collected from multiple sites in the basin, and analyses revealed at least two putative species. Phylogenetic reconstructions (NJ, ML, and BI) together with species delimitation methods (ASAP, GMYC, and bPTP) consistently supported the recognition of two distinct lineages. These lineages differ primarily in body length, segment number, and spermathecae morphology. Accordingly, they are recognized as A. mekongianus sensu stricto and A. sirindhornae Nantarat & Bantaowong, sp. nov., which is formally described herein. This study enhances understanding of the evolutionary complexity and taxonomic status of the group, providing a foundation for future conservation and management strategies in the region.

Discovery of a New Discartemon Species (Eupulmonata: Streptaxidae) from Peninsular Thailand

Mon, 20 Oct 2025 00:00:00 +0700

Discartemon sirindhornae Artsamart & Siriboon, sp. nov. is described and illustrated based on specimens collected from Chumphon Province in Peninsular Thailand. The new species possesses a flattened shell with a slightly convex spire, a weakly angular last whorl, and an intermediately expanded whorl. The apertural dentition consists of one parietal lamella, one ridge-like and one small lower palatal, one small basal, and one small columellar lamella. The penis is long, slender and twisted distally, with penial hooks separated by elevated longitudinal folds. The current study advances knowledge of the streptaxid land snail species in Thailand and emphasizes the value of limestone habitats for preserving biodiversity.

A New Species of Wishbone Spider Genus Damarchus from Doi Inthanon National Park, Thailand (Mygalomorphae: Bemmeridae)

Mon, 20 Oct 2025 00:00:00 +0700

The wishbone spider genus Damarchus, belonging to the family Bemmeridae, encompasses four recognized genera: Atmeto-chilus, Damarchus, Homostola, and Spiroctenus. Current distribution records indicate that Atmetochilus and Damarchus are exclusively found in Asia. To date, ten species of Damarchus have been documented, with three species reported in Thailand. However, our field surveys conducted since 2015 have identified multiple undescribed species within the genus that remain unclassified. Through detailed morphological analyses, we describe a new species, Damarchus sirindhornae Kunsete & Warrit, sp. nov., discovered in Doi Inthanon National Park. This species is classified within the workmani-group but can be distinguished from other members of the group by the absence of spines on the male coupling spur and the absence of secondary receptacles on the female spermathecae.

Three Novel Ascomycetous Yeast Species Isolated from Plant Leaves and Wild Mushrooms Collected in Thailand

Mon, 20 Oct 2025 00:00:00 +0700

Four yeast strains representing three novel species were isolated from two sources in Thailand, one from the leaf surface of a tall-stilt mangrove (Rhizophora apiculata, strain DMKU-RG45) and three from the fruiting bodies of wild mushrooms (strains DMKU-TM03, DMKU-SM11, and DMKU-SM28) collected in Thailand. Sequence analysis of the D1/D2 domain of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) region revealed that these four strains differed by 0.87–8.68% and 2.07–13.55% in their nucleotide divergence from their closest described species in the sequences of the D1/D2 domain of the LSU rRNA gene and the ITS region, respectively. In phylogenetic analyses, the strain DMKU-RG45 belonged to the genus Cyberlindnera and was distinct from other recognized species in this genus, whereas the strains DMKU-TM03, DMKU-SM11, and DMKU-SM28 were members of the genus Blastobotrys. However, they were in two different positions, each of which was distinct from closely related species. Based on molecular analyses and phenotypic characteristics, the strain DMKU-RG45 is proposed as Cyberlindnera sirindhorniae f.a., sp. nov. (the holotype is TBRC 19863^T; MycoBank No. is MB 858763). The other three strains (DMKU-TM03, DMKU-SM11, and DMKU-SM28) are proposed as two novel Blasto-botrys species. Blastobotrys princeps f.a., sp. nov. is proposed to accommodate the strain DMKU-TM03 (the holotype is TBRC 19382^T; MycoBank No. is MB 858764). Blastobotrys siamensis f.a., sp. nov. is proposed to accommodate both strains DMKU-SM11 and DMKU-SM28 (the holotype is TBRC 19380^T; MycoBank No. is MB 858765).

Coeliccia sirindhornae sp. nov., A New Damselfly (Odonata: Platycnemididae) from Northwest Thailand

Mon, 17 Nov 2025 00:00:00 +0700

A new species of the genus Coeliccia Kirby, 1890, C. sirindhornae sp. nov., is described based on specimens of both sexes collected from Kanchanaburi Province, Thailand. This species can be differentiated from its congeners by its unique combination of morphological characters, including the shape of antehumeral stripe, the structure and pattern of prothorax, and the shape of anal appendages in both sexes, and the markings on the terminal abdominal segments in female.

The Ant Genus Vombisidris Bolton, 1991 (Hymenoptera: Formicidae) in Thailand, with a Description of a New Species

Tadsanai Jeenthong, Yudthana Samung, Netnapa Phosrithong, Weeyawat Jaitrong — Mon, 17 Nov 2025 00:00:00 +0700

Vombisidris Bolton, 1991, a small ant genus comprising 20 extant species (including the new species), is distributed in India, China, various countries in Southeast Asia, New Guinea, and Queensland of Australia. Two species of the genus, V. satunensis Jeenthong, Jaitrong & Tasen, 2023 and V. sirindhornae Jeenthong, Samung & Jaitrong, sp. nov. are known in Thailand. Vombisidris satunensis inhabits lowland habitats (ca. 100–200 m a.s.l.), while V. sirindhornae is found in highland habitats (1,000 m a.s.l.). Both species were found nesting in dead twigs on trees at forest edges.

Metschnikowia sirindhorniae f.a., sp. nov. and Moniliella princeps sp. nov., Two Novel Yeasts Species Isolated from Toddy Palm (Borassus flabellifer L.) Inflorescence Sap in Thailand

Mon, 17 Nov 2025 00:00:00 +0700

Two strains, YSP-519 and YSP-478, respectively representing novel ascomycetous and basidiomycetous yeast species, were obtained from toddy palm inflorescence sap collected in Thailand. The ascomycetous yeast strain YSP-519 was closely related to Metschnikowia agaves CBS 7744^T. There were 1.6% nucleotide substitutions (9 nucleotide substitutions and 2 gaps out of 555 nt) in the D1/D2 domains of the LSU rRNA gene and 0.7% nucleotide substitutions (3 nucleotide substitutions out of 454 nt) in the ITS regions. The basidiomycetous yeast strain YSP-478 was closely related to Moniliella pollinis CBS 461.67^T. It had 0.5 % nucleotide substitutions (3 nucleotide substitutions out of 554 nt) in the D1/D2 domains of the LSU rRNA gene and 2.0% nucleotide substitutions (9 nucleotide substitutions out of 473 nt) in the ITS regions. Phylogenetic analysis based on the concatenated sequences of the ITS regions and the D1/D2 domains confirmed that the two strains represent two new species. The name Metschnikowia sirindhorniae f.a., sp. nov. is proposed for YSP-519^T), and Moniliella princeps sp. nov. is proposed for YSP-478^T. The holotypes of M. sirindhorniae and Mo. princeps are TBRC 10642^T and TBRC 10641^T, respectively and the ex-type are CGMCC 2.6079^T and CGMCC 2.6078^T, respectively. The MycoBank numbers of M. sirindhorniae and Mo. princeps are MB858878 and MB858879, respectively.

The Lepidonella sirindhornae sp. nov. (Entomobryidae: Paronellinae), A New Collembola species from Southern Thailand

Areeruk Nilsai, Ronnaphon Engchuan, Sopark Jantarit — Mon, 17 Nov 2025 00:00:00 +0700

The genus Lepidonella is widely distributed across Southeast Asia, South Asia, Papua New Guinea, the Melanesian region, Australia, Africa, and the Americas. To date, only a single species of the genus has been formally recorded from Thailand. However, numerous undescribed species, particularly from southern Thailand, have been reported, indicating a greater diversity than currently recognized. This study presents the first formal description of a Lepidonella species from a cave habitat in the country. Lepidonella sirindhornae Nilsai & Jantarit, sp. nov. is described and illustrated from Tham Phraya Bangsa in Satun Province. The new species is distinguished from its congeners by a unique combination of morphological characters, including labial chaetotaxy formula (M1m2rEL1L2), elongation of antennal length (3.5–5.1 antenna: head ratio), presence of 6+6 eyes and a distinctive number of chaetae on both the anterior and posterior surfaces of the ventral tube. Additionally, this study provides a distribution map of the genus Lepidonella found in Thailand, underscoring the diversity of cave-dwelling species in the region and the need for further taxonomic investigation.

Calathella sirindhorniae (Agaricales, Basidiomycota), A New Cyphelloid Fungus from Thailand

Mon, 17 Nov 2025 00:00:00 +0700

A novel cupulate basidiomycete fungus was discovered during a survey of mangrove-associated fungi in Chanthaburi and Phetchaburi Provinces, Thailand. This species, found exclusively on decaying Rhizophora mucronata hypocotyls in intertidal zones, forms minute fruiting bodies and shows close morphological and molecular resemblance to Calathella mangrovei Jones & Agerer, 1992. Phylogenetic analyses of ITS and LSU rDNA regions confirmed its placement within Calathella, as a distinct sister lineage to C. mangrovei. Therefore, these isolates represent a novel species, for which the name Calathella sirindhorniae sp. nov. is proposed.

A New Species of Quadrimaera (Amphipoda: Maeridae) from Coral Reefs of Chon Buri Province, Thailand

Chaichat Boonyanusith, Sumaitt Putchakarn, Koraon Wongkamhaeng — Mon, 17 Nov 2025 00:00:00 +0700

Quadrimaera sirindhornae sp. nov. was described from specimens collected from algae in a coral reef in Chon Buri Province, Thailand. The new amphipod species can be distinguished from its closest relative by its accessory flagellum with seven articles, gnathopod 2 propodus 1.8x longer than wide, uropod 3 ratio of outer ramus and peduncle is 1.2. The illustration and comparison of diagnostic charac-teristics in male Quadrimaera reported in Southeast Asia were provided.

Sirindhornea siamensis, A New Sequestrate Boletoid Genus of Boletaceae from Thailand

Mon, 17 Nov 2025 00:00:00 +0700

This study investigates sequestrate boletes from southern Thailand and presents a morphologically distinctive specimen with a strong cantaloupe-like odor. Detailed morphological and molecular phylogenetic analyses, utilizing the internal transcribed spacer (ITS), large subunit ribosomal RNA (LSU) and RNA polymerase II second largest subunit (RPB2) genes were performed to determine its taxonomic position. Nonetheless, the new sequestrate bolete exhibited a distinctive morphological features, including a scaly peridium, a characteristic cantaloupe-like odor at maturity. Together with molecular evidence, these characteristics clearly distinguish it from other sequestrate boletoid (Chamonixia, Durianella, Octaviania, Rossbeevera, and Turmalinea). These findings support the recognition of a novel genus within the subfamily Leccinoideae. Therefore, we propose a new genus and new species, Sirindhornea siamensis, for this sequestrate bolete species.

Morphology and Molecular Phylogeny of a New Species, Macrobrachium debaratae sp. nov. (Caridea, Palaemonidae) from Songkhram River, Northeast Thailand

Mon, 17 Nov 2025 00:00:00 +0700

The recognized diversity of Macrobrachium prawns in Thailand has increased recently due to taxono-mic investigation using integrative approaches, i.e. from morphology and DNA barcoding. The freshwater habitats in northeast Thailand such as riparian wetland ecosystems provide diverse ecological conditions that promote adaptive diversification among organisms. The varying condition of the freshwater bodies can support the existence of cryptic species among the aquatic animal fauna, including in prawns of the genus Macrobrachium. Several Macrobrachium species have previously been reported in association with the vast network of tributaries that form the Mekong River basin. Newly described species and unidentified morphospecies have particularly been reported from this area in previous systematic studies, which indicates that the current known diversity of the aquatic fauna is likely to be largely incomplete. In this study, a new species of the genus Macrobrachium from the Songkhram River, one of the Mekong tributaries, is described and named as Macrobrachium debaratae Siriwut, sp. nov. This new species contains several distinct morphological characters from its congeneric and co-existing species group, such as the rostral teeth formula, the size and the shape of second pereiopods, and the tooth present on the cutting edge of the fingers of the chelae of the second pereiopods. Genetic distance analysis among the known Macrobrachium species supported this morphological classification as a new species with an interspecific COI divergence of 13%. The COI phylogenetic tree indicated that M. debaratae Siriwut, sp. nov. was monophyletic and was placed close to M. sirindhorn, a member within the M. pilimanus species group. This study highlights the need for a detailed morphological inspection to examine the variability in the taxonomic characters of Macrobrachium, particularly in the M. pilimanus species group found in mainland Southeast Asia tributaries. Further taxonomic review based on intensive sampling is required to provide a more adequate understanding of the diversity of Macrobrachium in the Mekong basin.