A new terrestrial talitrid genus, Kachinorchestia, with a new species from Myanmar (Crustacea, Amphipoda, Arcitalitridae)

Biodiversity Data Journal 13: e162403 doi: 10.3897/BDJ.13.e162403 Taxonomy & Inventories A new terrestrial talitrid genus, Kachinorchestia, with a new species from Myanmar (Crustacea, Amphipoda, Arcitalitridae) Yan Tong , Zeyu Liu , Hongguang Liu , Zhonge Hou ‡ State Key Laboratory of Animal Biodiversity Conservation and Integrated Pest Management, Institute of Zoology, Chinese Academy of Sciences, Beijing, China § University of Chinese Academy of Sciences, Beijing, China Corresponding author: Zhonge Hou ([email protected]) Academic editor: Denis Copilas-Ciocianu Received: 18 Jun 2025 | Accepted: 25 Sep 2025 | Published: 13 Oct 2025 Citation: Tong Y, Liu Z, Liu H, Hou Z (2025) A new terrestrial talitrid genus, Kachinorchestia, with a new species from Myanmar (Crustacea, Amphipoda, Arcitalitridae). Biodiversity Data Journal 13: e162403. https://doi.org/10.3897/BDJ.13.e162403 ZooBank: urn:lsid:zoobank.org:pub:53F6B160-5FE8-47FB-A3E7-B6E18EB1043E Abstract Background The Arcitalitridae (Amphipoda, Senticaudata, Talitrida, Talitroidea) is a diverse family containing 15 genera, of which Myanmarorchestia Hou, 2017 and Solitroides Suzuki, Nakano, Nguyen, Nguyen, Morino & Tomikawa, 2017 were reported in Southeast Asia. During research of terrestrial amphipods in Myanmar, we found character traits of some specimens did not match any existing genus of the family Arcitalitridae. These specimens should belong to a new genus. New information This new genus Kachinorchestia Hou, gen. nov. with one new species Kachinorchestia putao Hou, sp. nov. is described from terrestrial habitats in Myanmar. This new genus is characterised by mandible left lacinia mobilis with four teeth, gnathopod II propodus of ‡,§ ‡ ‡ ‡ © Tong Y et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. male enlarged, oval and subchelate, with hook posteriorly, simplidactylate pereopods, complex and lobed gills and telson uncleft. Photos, molecular and morphological descriptions of new genus are provided. Keywords landhopper, morphology, DNA barcodes, new genus, taxonomy Introduction Myers & Lowry (2020) recently published a revision of the Talitroidea, which erected two epifamilies, the Talitroidae and Protorchestoidae. The Protorchestoidae includes three families, Arcitalitridae, Protorchestiidae and Uhlorchestiidae (Myers and Lowry 2020). The Arcitalitridae is characterised by maxilliped palp article 2 without distomedial lobe, article 4 small, distinct; pereopods III–VII simplidactylate, uropod I outer ramus without marginal robust setae and uropod 3 ramus shorter than peduncle. Currently there are 15 genera in the family Arcitalitridae, of which two terrestrial genera have been recorded in the Southeast Asia. The genera Solitroides Suzuki, Nakano, Nguyen, Nguyen, Morino & Tomikawa, 2017 were recorded in Vietnam (Suzuki et al. 2017), while Myanmarorchestia Hou, 2017 were found in Myanmar. Here, we assign a new genus Kachinorchestia to Arcitalitridae, due to its maxilliped palp article 2 without distomedial lobe, article 4 small, distinct; pereopods III–VII simplidactylate and uropod III ramus shorter than peduncle. The detailed relationships amongst these morphological groups need to be assessed with molecular evidence. The landhopper genus Myanmarorchestia Hou in Hou and Zhao (2017) is most recognisable by coxal gills convoluted, with or without marginal filamentous projections and has a well-defined distribution. The new genus Kachinorchestia is most similar to the genus Myanmarorchestia in coxal gills convoluted. The convoluted gills might be some of the adaptations to terrestrial habitat (Liu et al. 2025). It is mainly recorded in Southeast Asia (Liu et al. 2023). The genus Myanmarorchestia currently includes four species, of which three species have been recorded in high altitude forests of Mt. Victoria, Myanmar and show some vertical distribution patterns. For example, M. victoria Hou in Zheng and Hou (2017) occurs above 2600 m above sea level, M. peterjaegeri Hou in Hou and Zhao (2017) occurs above 2000 m, while M. seabri Hou in Hou and Zhao (2017) inhabits understorey leaf litter around 1500 m. The last species M. nunomurai (Nakano et al. 2018 ) was recorded in the mountainous habitat (elevation 1900 m) of Yunnan, China, near the border of Myanmar (Fig. 1). During a field survey of terrestrial amphipods in Myanmar, landhoppers were collected from mountain forest habitats. In this paper, these landhoppers are described as a new genus Kachinorchestia Hou, gen. nov. and a new species, Kachinorchestia putao Hou, sp. nov. The barcode sequence of the new species is presented and the genetic 2Tong Y et al distances between the new species and known species are calculated to affirm the species delimitation. Materials and methods Morphological observation The specimens were collected by sweeping rotten wood with a fine-meshed hand net. Samples were preserved in 95% ethanol in the field and deposited under -20°C refrigeration for long-term preservation. The amphipod’s body length was recorded by holding the specimen straight and measuring the distance along the dorsal side of the body from the base of the first antenna to the base of the telson (Suzuki et al. 2017, Wang et al. 2024). Photographs were taken using an Olympus C7070 wide zoom digital camera. Helicon Focus version 6.0 software was used for digital stacking, while the final images were edited and polished using Adobe’s Photoshop cc 2020 and Illustrator 2021 software. Appendages were drawn using a Leica DM2500 compound microscope, equipped with a drawing tube. Terminology and taxonomic descriptions follow literature (Hou and Zhao 2017, Zheng and Hou 2017). The terms “setae” and “spines” are used to distinguish between thin or fine and more robust setal structures. All types and other materials are lodged in the Institute of Zoology, Chinese Academy of Sciences (IZCAS), Beijing. Figure 1. Type localities of Kachinorchestia and Myanmarorchestia species from Myanmar and China. 1. K. putao sp. nov. 2. M. nunomurai Nakano & Morino, 2018; 3. M. victoria Hou, 2017; 4. M. peterjaegeri Hou, 2017; 5. M. seabri Hou, 2017.  A new terrestrial talitrid genus, Kachinorchestia, with a new species from ... 3 DNA sequencing and phylogenetic analyses Genomic DNA was extracted from appendages of the specimens using a TIANamp Genomic DNA Kit (TIANGEN). The fragments of the 28S and COI were amplified and sequenced following published protocols (Hou et al. 2022). The new sequences and reference sequences downloaded from GenBank were aligned using MEGA v.7.0.26 (Kumar et al. 2016). The GenBank accession numbers and pairwise distances are presented in Table 1 and Table 2. In total, 24 specimens belonging to 17 talitrid species, were used in molecular phylogenetic analyses. The Hyalella tiwanaku Gonzalez & Watling, 2003 and Hyalella franciscae Gonzalez & Watling, 2003 were selected as outgroup taxa. Phylogenetic relationships were inferred using Maximum Likelihood (ML) and Bayesian Inference (BI) on concatenated sequences. ML phylogenies were conducted using RAxML v.8.2.12 (Stamatakis 2014) with 1000 rapid bootstrap replicates followed by a thorough tree search. Bayesian analyses were carried out using MrBayes v.3.2.7 (Ronquist et al. 2012), implementing two independent runs of five million generations. Species Locality COI 28S Kachinorchestia putao sp. nov. (IZCAS-I-A2096-2) Myanmar PV764417 PV987539 Kachinorchestia putao sp. nov. (IZCAS-I-A2096-3) Myanmar PX315801 PX316576 Myanmarorchestia nunomurai 1 Myanmar OQ512653 OQ514792 Myanmarorchestia nunomurai 2 Myanmar PV760292 OQ514791 Myanmarorchestia peterjaegeri 1 Myanmar OQ512620 OQ514768 Myanmarorchestia peterjaegeri 2 Myanmar OQ512619 OQ514876 Myanmarorchestia seabri 1 Myanmar OQ512626 OQ514773 Myanmarorchestia seabri 2 Myanmar OQ512630 OQ514776 Myanmarorchestia Victoria 1 Myanmar OQ512624 OQ514771 Myanmarorchestia Victoria 2 Myanmar OQ512623 OQ514770 Platorchestia monodi Australia OQ512228 OQ514574 Platorchestia pacifica Russia OQ512217 OQ514566 Floresorchestia thienemanni Indonesia OQ512301 OQ514373 Floresorchestia hanoiensis Singapore OQ512304 OQ514620 Talorchestia martensii Indonesia OQ512422 OQ514419 Talorchestia qeshm Iran MG655858 MG655800 Nipponorchestia curvatus 1 Japan - LC566566 Nipponorchestia curvatus 2 Japan LC566563 LC566562 Minamitalitrus zoltani 1 Japan LC566559 LC566558 Table 1. Samples used for the phylogenetic analyses, with locality information accompanied by sequence accession numbers. 4Tong Y et al Species Locality COI 28S Minamitalitrus zoltani 2 Japan LC566555 LC566554 Mysticotalitrus cryptus Australia OQ512596 OQ514482 Arcitalitrus sylvaticus Australia OQ512532 OQ514451 Arcitalitrus dorrieni New Zealand OQ512551 OQ514460 Solitroides motokawai Vietnam LC223808 LC223807 Hyalella tiwanaku Xinjiang, China OM513861 MW047142 Hyalella franciscae Beijing, China OM513891 MW047137 Species 28S 1 2 3 4 5 6 COI OQ514781 OQ514791 OQ514768 OQ514776 OQ514771 LC223807 1 K. putao sp. nov. PV764417 0.055 0.044 0.048 0.051 0.069 2 M. nunomurai PV760292 0.255 0.044 0.046 0.041 0.072 3 M. peterjaegeri MF663279 0.268 0.231 0.013 0.030 0.078 4 M. seabri MF663278 0.270 0.255 0.188 0.031 0.078 5 M. victoria MF969263 0.255 0.222 0.175 0.148 0.069 6 S. motokawai LC223808 0.268 0.266 0.233 0.244 0.230 Taxon treatments Kachinorchestia Hou, gen. nov. • ZooBank 157F7226-7246-4D6A-AD0E-29A8FB615215 Type species Kachinorchestia putao Hou, sp. nov. Diagnosis Body size medium. Eyes rounded. Antenna I reaching mid-point of peduncular article V of antenna II, flagellum a little shorter than peduncle. Antenna II flagellum a little longer than peduncle. Mandible left lacinia mobilis with four teeth; right lacinia mobilis bifurcate. Maxilla I outer plate with one small articulate palp present. Maxilliped palp article 4 reduced, small, but distinct. Gnathopod I sexually dimorphic; merus and carpus of male protuberant medioposteriorly, propodus distally expanded and subchelate, merus and carpus of Table 2. GenBank accession numbers and uncorrected pairwise distances of the COI and 28S partial sequences between Kachinorchestia and Myanmarorchestia species. A new terrestrial talitrid genus, Kachinorchestia, with a new species from ... 5 female without protuberance, propodus simple. Gnathopod II sexually dimorphic; propodus of male enlarged, oval and subchelate, with hook posteriorly and spines, propodus of female expanded, with protuberance posteriorly. Pereopods simplidactylate, with two spines at hinge of unguis. Coxal gills present on gnathopod II and pereopods III–VI; each gill lobed and convoluted, without ridged margins or filamentous projections. Oostegites slender, present on gnathopod II and pereopods III–V. Epimeral plates acuminate posterodistally, distal margins without armature. Pleopods well-developed, peduncles with plumose setae on exterior margins. Uropod I peduncle with distolateral spine, outer ramus marginally bare. Uropod III ramus narrower and shorter than peduncle. Telson uncleft, with one terminal spine each side. The general morphology is stable across all examined male specimens, with variations only in quantitative characters like the number of spines. Etymology The generic name is derived from “Kachin” the State of type locality, in combination with the Orchestia stem. Kachinorchestia putao Hou, sp. nov. • ZooBank E43793A0-B3CB-4AE5-A1C3-73C334D3C275 Materials Holotype: a. scientificName: Kachinorchestia putao Hou, sp. nov.; order: Amphipoda; family: Arcitalitridae; genus: Kachinorchestia; country: Myanmar; stateProvince: Kachin State; county: Putao; locality: Hponkanrazi Wildlife Sanctuary; verbatimElevation: 1447 m; verbatimCoordinates: 27°35.526'N 97°01.303'E; decimalLatitude: 27.59; decimalLongitude: 97.02; individualCount: 1; sex: male; lifeStage: adult; recordedBy: Wu Jiang-lang, Chen Zhi-gang; institutionCode: IZCAS-I-A2096-1; occurrenceID: A3361FE6-5E9B-5DFB-BCE6-5593D45D01A2 Paratypes: a. scientificName: Kachinorchestia putao Hou, sp. nov.; order: Amphipoda; family: Arcitalitridae; genus: Kachinorchestia; country: Myanmar; stateProvince: Kachin State; county: Putao; locality: Hponkanrazi Wildlife Sanctuary; verbatimElevation: 1447 m; verbatimCoordinates: 27°35.526'N 97°01.303'E; decimalLatitude: 27.59; decimalLongitude: 97.02; individualCount: 1; sex: female; lifeStage: adult; recordedBy: Wu Jiang-lang, Chen Zhi-gang; institutionCode: IZCAS-I-A2096-2; occurrenceID: 307A74BD-DC01-51D9-9612-461615F2D222 b. scientificName: Kachinorchestia putao Hou, sp. nov.; order: Amphipoda; family: Arcitalitridae; genus: Kachinorchestia; country: Myanmar; stateProvince: Kachin State; county: Putao; locality: Hponkanrazi Wildlife Sanctuary; verbatimElevation: 1447 m; verbatimCoordinates: 27°35.526'N 97°01.303'E; decimalLatitude: 27.59; 6Tong Y et al decimalLongitude: 97.02; individualCount: 1; sex: male; lifeStage: adult; recordedBy: Wu Jiang-lang, Chen Zhi-gang; institutionCode: IZCAS-I-A2096-3; occurrenceID: DE312ECB-DFA1-5419-80E9-AB2451719CC4 Description Based on holotype male (IZCAS-I-A2096-1), 8.0 mm (Fig. 2). Head. Eyes rounded (Fig. 2). Antenna I (Fig. 3A): reaching mid-point of peduncular article V of antenna II, flagellum a little shorter than peduncle. peduncle articles 1–3 in length ratio 1.0: 1.0: 1.1, with distal spines; flagellum with five articles, last article tiny, each article with short distal setae. Antenna II (Fig. 3B): peduncle articles 3–5 in length ratio 1.0: 2.3: 3.2; flagellum with 10 articles. Upper lip (Fig. 3C): ventral margin rounded, bearing minute setae. Mandible (Fig. 3D and E): left mandible incisor with five teeth; lacinia mobilis with four teeth; spine row with four plumose setae; molar well developed and with a plumose seta; right mandible incisor with five teeth, lacinia mobilis bifurcate. Lower lip (Fig. 3H): inner lobes indistinct, outer lobes covered with fine setae. Maxilla I (Fig. 3F): inner plate thin, with two terminal plumose setae; outer plate with nine terminal serrate setae; one small articulate palp present. Maxilla II (Fig. 3G): inner plate narrower and shorter than outer plate, with one plumose seta and numerous simple setae on medial margin; outer plate with two rows of apical Figure 2. Kachinorchestia putao sp. nov. holotype male, 8.0 mm and paratype female, 9.0 mm.  A new terrestrial talitrid genus, Kachinorchestia, with a new species from ... 7 setae. Maxilliped (Fig. 3I): inner plate with three stout spines distally; outer plate with apical setae; palp article 4 reduced, small, but distinct. Pereon. Gnathopod I (Fig. 4A and B): sexually dimorphic; coxal plate ventral margin rounded, with four small spines; basis anterior and posterior margins with short setae; merus, carpus and propodus in length ratio 1.0: 1.9: 1.1; merus protuberant medioposteriorly, bearing two spines on the base of the protuberance; carpus anterior and posterior margins with setae; propodus distally expanded, with a row of spines on both faces, palm margin well developed exceeding dactylus length, with two spines medially; dactylus with two setae at hinge of unguis. Gnathopod II (Fig. 4C and D): sexually dimorphic; coxal plate wider than that of gnathopod I, with a short posterior cusp, ventral margin spinose; basis stout, posterior margin with a minute spine; propodus enlarged and oval, 1.3 times as long as wide, with hook posteriorly and spines; palmar margin smoothly convex, fringed with spines; dactylus as long as propodus palm. Figure 3. Kachinorchestia putao sp. nov. holotype male A antenna I; B antenna II; C upper lip; D left mandible; E right mandible; F maxilla I; G maxilla II; H lower lip; I maxilliped.  8Tong Y et al Pereopods III–VII (Fig. 5A–E), simplidactylate. Pereopod III (Fig. 5A and F): coxal plate with a posterior cusp, ventral margin with short spines; basis longest, with spines on anterior and posterior margins; merus, carpus and propodus in length ratio 1.0: 0.7: 0.9; carpus and propodus with spines on posterior margins; dactylus with two spines at hinge of unguis. Pereopod IV (Fig. 5B and G): shorter than pereopod III; coxal plate with a shorter posterior cusp, ventral margin with setae; merus, carpus and propodus in length ratio 1.0: 0.7: 1.1, dactylus with two spines at hinge of unguis. Pereopod V (Fig. 5C and H): coxal plate bilobed, anterior lobe larger than posterior lobe, bearing one seta on anterior lobe; basis suboval, with spines on both margins; merus, carpus and propodus in length ratio 1.0: 1.2: 1.7, with spines on both margins; dactylus with two spines at hinge of unguis. Pereopod VI (Fig. 5D, I): coxal plate bilobed, anterior lobe much smaller than posterior lobe, bearing two setae on posterior lobe; basis suboval, with seven spines on anterior margin and many setae on posterior margin; merus, carpus and propodus in length ratio 1.0: 1.1: 1.6, with Figure 4. Kachinorchestia putao sp. nov. holotype male A gnathopod I; B propodus of gnathopod I; C gnathopod II; D propodus of gnathopod II; E uropod I; F uropod II; G uropod III; H pleopod I; I telson; J epimeral plate I; K epimeral plate II; L epimeral plate III.  A new terrestrial talitrid genus, Kachinorchestia, with a new species from ... 9 Identification keys Key to species of Kachinorchestia and Myanmarorchestia 1 Male gnathopod II propodus massively enlarged, subchelate K. putao sp. nov. – Male gnathopod II mitten-shaped (parachelate) 2 2 Uropod III peduncle with a single long posterodistal robust seta 3 –Uropod III peduncle with two unequal length posterodistal robust setae M. seabri Hou, 2017 3 Pereopod VII much shorter than pereopod VI M. nunomurai Nakano & Morino, 2018 – Pereopod VII subequal with or longer than pereopod VI 4 4Uropod II outer ramus only a little short than inner ramus, with three or four apical robust setae and no marginal setae M. peterjaegeri Hou, 2017 –Uropod II outer ramus much shorter than inner ramus, with one marginal and one apical robust seta M. victoria Hou, 2017 Acknowledgements We are grateful to Jianglang Wu and Zhigang Chen for their assistance in the field. This study was supported by the International Partnership Program of Chinese Academy of Sciences (Grant No. 073GJHZ2024043MI), National Natural Science Foundation of China (Grant No. 32470474) and the Institute of Zoology, Chinese Academy of Sciences (2024IOZ0108). References • Hou Z, Li S (2010) Intraspecific or interspecific variation: delimitation of species boundaries within the genus Gammarus (Crustacea, Amphipoda, Gammaridae), with description of four new species: delimitation of Gammarus species boundar ies. Zoological Journal of the Linnean Society 160: 215‑253. https://doi.org/10.1111/j. 1096-3642.2009.00603.x • Hou Z, Zhao S (2017) A new terrestrial talitrid genus, Myanmarorchestia, with two new species from Myanmar (Crustacea, Amphipoda, Talitridae). ZooKeys 705: 15‑39. https:// doi.org/10.3897/zookeys.705.15045 • Hou Z, Jin P, Liu H, Qiao H, Sket B, Cannizzaro A, Berg D, Li S (2022) Past climate cooling promoted global dispersal of amphipods from tian shan montane lakes to 16 Tong Y et al circumboreal lakes. Global Change Biology 28 (12): 3830‑3845. https://doi.org/10.1111/ gcb.16160 • Kumar S, Stecher G, Tamura K (2016) MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for bigger datasets. Molecular Phylogenetics and Evolution 33: 1870‑1874. https://doi.org/10.1093/molbev/msw054 • Lefébure T, Douady C, Gouy M, Gibert J (2006) Relationship between morphological taxonomy and molecular divergence within Crustacea: Proposal of a molecular threshold to help species delimitation. Molecular Phylogenetics and Evolution 40: 435‑447. https:// doi.org/10.1016/j.ympev.2006.03.014 • Liu H, Zheng Y, Zhu B, Tong Y, Xin W, Yang H, Jin P, Hu Y, Huang M, Chang W, Ballarin F, Li S, Hou Z (2023) Marine-montane transitions coupled with gill and genetic convergence in extant crustacean. Science Advances 9: eadg4011. https://doi.org/10.1126/ sciadv.adg4011 • Liu H, Wang X, Liu Z, Li S, Hou Z (2025) Osmoregulatory evolution of gills promoted salinity adaptation following the sea–land transition of crustaceans. Marine Life Science & Technology 7 (2): 205‑217. https://doi.org/10.1007/s42995-025-00298-6 • Lowry JK, Coleman CO (2012) A new terrestrial talitrid genus from the philippine islands (Crustacea, Amphipoda, Talitrida, Talitridae) and the designation of two informal subgroups. Zootaxa 25 (3400): 64‑68. https://doi.org/10.1002/cne.23080. • Myers AA, Lowry JK (2020) A phylogeny and classification of the Talitroidea (Amphipoda, Senticaudata) based on interpretation of morphological synapomorphies and homoplasies. Zootaxa 2: 281‑310. https://doi.org/10.11646/zootaxa.4778.2.3. • Nakano T, Tomikawa K, Hou Z, Morino H (2018) A new landhopper species of Myanmarorchestia (Crustacea: Amphipoda: Talitridae) from Yunnan, China. Journal of Natural History 52 (17-18): 1181‑1199. https://doi.org/10.1080/00222933.2018.1453098 • Ronquist F, Teslenko M, van der Mark P, Ayres D, Darling A, Höhna S, Larget B, Liu L, Suchard M, Huelsenbeck J (2012) MrBayes 3.2: Efficient Bayesian Phylogenetic Inference and Model Choice Across a Large Model Space. Systematic Biology 61 (3): 539‑542. https://doi.org/10.1093/sysbio/sys029 • Stamatakis A (2014) RAxML version 8: a tool for phylogenetic analysis and post-analysis of large phylogenies. Bioinformatics 30: 1312‑1313. https://doi.org/10.1093/bioinformatics/ btu033 • Suzuki Y, Nakano T, Nguyen S, Nguyen A, Tomikawa K (2017) A new landhopper genus and species (Crustacea: Amphipoda: Talitridae) from annamite range, vietnam. Raffles Bulletin of Zoology 65: 304‑315. • Wang Y, Sha Z, Ren X (2024) One new species of Stegocephalus Krøyer, 1842 (Amphipoda, Stegocephalidae) described from a seamount of the Caroline Plate, NW Pacific. ZooKeys 1195: 121‑130. https://doi.org/10.3897/zookeys.1195.114209 • Zheng Y, Hou Z (2017) Myanmarorchestia victoria sp. nov. (Crustacea, Amphipoda, Talitridae), a new species of landhopper from the high altitude forests in Myanmar. Zoological Research 38: 281‑290. https://doi.org/10.24272/j.issn.2095-8137.2017.067 A new terrestrial talitrid genus, Kachinorchestia, with a new species from ... 17