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| Theosbaena loko Jantarit, Promdam & Wongkamhaeng, 2020 |
Abstract
Background:
Thermosbaenaceans are subterranean crustaceans, widespread and occur in freshwater, oligohaline or anchialine caves or thermal springs. Currently, four families, seven genera, and 45 species are recognised worldwide. During our studies of the isolated karst, Tham Loko (Loko Cave) in Khao Chaison District, Phatthalung Province, we found an undescribed thermosbanacean species in the genus Theosbaena. Theosbaena is the only genus reported from freshwater in the Oriental Region. Previously, there were only two known species, Theosbaena cambodjiana Cals & Boutin, 1985 from Kampot Province, southern Cambodia and Khon Kaen, Thailand and T. kiatwongchai Rogers & Sanoamuang, 2016 discovered in a cave of Takhli District, Nakhon Sawan, central Thailand. Our new species is the third species recorded in the Oriental Region.
New information:
Theosbaena loko sp. n. differs from its congeners by having a telson 1.8x longer than its breadth, maxilla 1 palp distal segment 4x longer than the proximal palpomere and the maxillopodal exopod twice as long as its basal width. This microshrimp is the third described species of the genus. A key to the species is given and suggestions for the conservation status of the new species are discussed.
Keywords: new species, peninsular Thailand, subterranean habitats, taxonomy
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| Figure 1. Distribution of Theosbaena in the Oriental Region. T. cambodjiana in red circle, T. kiatwongchai in blue circle and Theosbaena loko sp. n. in green circle. |
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| Khao Chaison isolated karst system extracted from Google Earth. |
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| Figure 2. Theosbaena loko sp. n. แมงกุ้งถ้ำลอกอ A: Habitus in situ at Tham Loko. B: Lateral view of a female with brood pouch. C: General cave environment with the pools where the new species was collected. |
Theosbaena loko, sp. n.
Diagnosis: Theosbaena loko sp. n. is the third species of the genus reported from Thailand. Theosbaena loko sp. n. can be distinguished from its congeners in having a telson 1.8x longer than its breadth, maxilla 1 palp distal segment 4x as long as proximal palpomere and a maxillopodal exopod twice as long as its basal width. It shares some characteristics with T. cambodjiana in having: mandibular palp segment 1:2:1 ratio 9:1.5:7/ segment 2 with 6 plumose setae; ocular scale evenly arcuate and rounded; gnathopod dactylus subrectangular, with 3 long, stout, arcuate macrosetae, each bearing a ventral membrane and uropod distal segment of the exopod and the distal margin of the endopod both bearing elongate, plumose macrosetae and endopod lateral edge is margined with a row of scaliform macrosetae. However, T. loko sp. n. differs from T. cambodjiana in the absence of pleopod 1. Theosbaena loko sp. n. is similar to T. kiatwongchai in having: a mandibular palp segment 1:2:1 ratio 9:1.5:7/ segment 2 with 6 plumose setae (vs. palp segment 1:2:3 ratio 9:1.5:7/ segment 2 with 6 microsetae); pereopod 1-4 exopod contains more than 2 segments (vs. 2 segments); ocular scale evenly arcuate and rounded (vs. transverse); and uropod endopod lateral edge is margined with a row of scaliform macrosetae (vs. endopod medial margin is inerm, except for 2 filiform macrosetae, midway along its length). Diagnostic morphological characters and their variation for each population/species are given in Table 1 and the identification key of the genus Theosbaena is provided.
Nomenclature: The specific epithet "loko" is the name of the type locality [
isolated limestone of Tham Loko (Loko Cave), Khao Chaison, Phatthalung Province
]. It is used here as a noun in apposition. The gender is masculine.Distribution: Theosbaena loko sp. n. is only known from the freshwater pool in the dark zone of Loko Cave, Khao Chaison District, Phatthalung Province. The Cave is 352 metres long. The Cave contains three pools, with T. loko sp. n. found in all three pools, although two of the pools dry out during the dry season.
Sopark Jantarit, Rueangrit Promdam and Koraon Wongkamhaeng. 2020. Theosbaena loko sp. n. A New Stygobiotic Microshrimp (Thermosbaenacea: Halosbaenidae) from southern Thailand. Biodiversity Data Journal. 8: e59528. DOI: 10.3897/BDJ.8.e59528
