Research Article |
Corresponding author: Zhonge Hou ( houze@ioz.ac.cn ) Academic editor: Charles Oliver Coleman
© 2017 Zhonge Hou, Shuangyan Zhao.
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.
Citation:
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
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Myanmarorchestia Hou, gen. n. with two new species is described from terrestrial habitats in Myanmar. This new genus is characterised by 4-dentate lacinia on left mandible, simple gnathopod I in both sexes, weakly chelate gnathopod II in male, simplidactylate pereopods and complex and lobed gills. Myanmarorchestia peterjaegeri Hou, sp. n. closely resembles M. seabri Hou, sp. n. in gnathopod II merus and carpus protuberant on posterior margin; however, the former is distinguished from the latter by palp of maxilla I with two articles, coxal gills convoluted, and telson with nicks on surface. Additionally, DNA barcodes of the new species are obtained to confirm their distinctiveness.
taxonomy, Myanmarorchestia , COI, Indo-West Pacific, leaf litter
The amphipod family Talitridae Rafinesque, 1815 includes two groups, the Orchestia group and the Talitrus group (
For Southeast Asian talitrid fauna, most recorded species were collected near the beach, such as Talorchestia morinoi Othman & Azman, 2007 from Tioman Island, Malaysia, Floresorchestia hanoiensis Hou & Li, 2003 from Vietnam, and Floresorchestia samroiyodensis
Mt. Victoria is located in the southwest of Myanmar, known for endemics of montane species (
The specimens were collected by sieving forest floor litter. Samples were preserved in 95% ethanol in the field, and then deposited at -20°C refrigerator for long preservation. Type specimens are lodged in the Senckenberg Museum, Frankfurt am Main (
The 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. Photos of whole animal were taken with an Olympus C7070 wide zoom digital camera (7.1 megapixels) mounted on an Olympus SZX12 microscope, and they were montaged using Helicon Focus image stacking software. All dissected appendages were mounted on slides in glycerol according to the methods described by
A partial fragment of the mitochondrial cytochrome oxidase subunite I (COI) was proposed as a crustacean barcode (
The COI sequences were manually aligned, because no indels were observed. Pairwise comparison of uncorrected p-distances for two COI sequences obtained in this study was calculated using MEGA7.0.16 (
Myanmarorchestia peterjaegeri Hou, sp. n.
The generic name is derived from “Myanmar” in combination with the Orchestia stem.
Body size medium. Eyes rounded or sub-rounded, approximately 1/3 of head length. Antenna I reaching mid-point of peduncular article V of antenna II, flagellum a little shorter than peduncle. Antenna II 28% of body length, flagellum a little longer than peduncle. Mandible left lacinia mobilis 4-dentate. Maxilliped palp with four articles, first two articles broad; article III not lobate distomedially, article IV distinct, short, with apical spine and setae.
Gnathopod I coxal plate with anterior process prominent, carpus lacking pellucid lobe, propodus simple, narrowed distally in both sexes. Gnathopod II sexually dimorphic; propodus of male transitional form, weakly chelate, with tumescence, propodus of female mitten-shaped. Pereopods simplidactylate, with two spines at hinge of unguis. Coxal gills present on gnathopod II and pereopods III–VI; each gill lobed and convoluted, one or two lobes with ridged margins or filamentous projections. Oostegites slender, present on gnathopod II and pereopods III–V.
Epimeral plates acuminate posterodistally, ventral margins without armature, lacking submarginal pits. Pleopods well-developed, peduncles with plumose setae on exterior margins. Uropod I peduncle with large distolateral spine, outer ramus marginally bare. Uropod III ramus shorter than peduncle. Telson subtriangular shaped, apically notched, each lobe with one or two apical spines.
Myanmarorchestia Hou, gen. n. is quite unique in having complex coxal gills which bears filamentous projections, simple gnathopod I in both sexes, and weakly chelate, transitional gnathopod II in male.
The new genus belongs to the Orchestia group. It is most similar to the genus Bousfieldia Chou & Lee, 1996 in left lacinia 4-dentate, well-developed pleopods and bare outer ramus in uropod I. It can be distinguished from Bousfieldia by the following characters (Bousfieldia in parentheses): gnathopod II in male subtriangle, with tumescence (strongly subchelate, oval in shape); pereopods simplidactylate (cuspidactylate); coxal gills of gnathopod II and pereopods III–VI lobed and convoluted, with ridged margins or filamentous projections (coxal gills lobed at middle, no filamentous projections).
The new genus can be distinguished from other terrestrial Orchestia groups from Indo-West Pacific margins (Lanorchestia Miyamoto & Morino, 2010, Mizuhorchestia Morino, 2014 and Nipponorchestia Morino & Miyamoto, 2015) by gnathopod II subtriangle (oval); pereopods simplidactylate (cuspidactylate); and pleopods well-developed (reduced).
This new genus shows morphological similarities to one landhopper genus from the Philippines, Curiotalitrus Lowry & Coleman, 2012 in sharing antenna I shorter than peduncular article V of antenna II; mandible left lacinia mobilis 4-dentate; article IV of maxilliped palp very short, well defined; uropod III ramus shorter than peduncle. It can be distinguished from Curiotalitrus by the following characters (Curiotalitrus in parentheses): gnathopod I carpus slightly expended near distal end, propodus stout (subchelate; posterior margins of carpus and propodus with palmate lobes); gnathopod II sexually dimorphic, propodus of male subtriangle, with tumescence (not sexually dimorphic, mitten-shaped); pleopods rami with numerous articles (fused 1-articulate); uropod I of male similar to that of the female (sexual dimorphism in uropod I); telson with 1–2 apical spines on each lobe (with 3–6 robust setae).
The new genus Myanmarorchestia is similar to landhopper genera Arcitalitrus Hurley, 1975, Keratroides Hurley, 1975 and Mysticotalitrus Hurley, 1975 in sharing following characters: left mandible lacinia mobilis 4-dentate; maxilliped palp article II unlobed, article IV distinct and small; gnathopod I simple; pereopods III–VII simplidactylate; and uropod I peduncle with distinct distolateral spine, outer ramus marginally bare. However, genera Arcitalitrus, Keratroides and Mysticotalitrus with more or less reduced pleopods, the peduncle lacking plumose setae; and telson not subtriangular in shape. Solitroides female is also similar to that of the new genus, but coxal gills not lobed, reduced pleopod III are distinguishing characters. The genus Talitriator Methuen, 1913 shares most features with the new genus, but gnathopod II in male is mitten-shaped and the telson is wider in middle. The peculiar gnathopod II in male of the new genus Myanmarorchestia is also exhibited in Puhuruhuru patersoni (Stephensen, 1938), Parorchestia lesliensis (Hurley, 1957), and Platorchestia zachsi (Derzhavin, 1937), but they can be distinguished from the new genus by cuspidactylate pereopods III–VII.
Holotype: female (
The specific name honours Peter Jäger, the collector of specimens used in this study and an excellent scientist supporting the diversity research in Myanmar; noun (name) in genitive case.
Eyes sub-rounded (Fig.
(
Head. (Fig.
Antenna I (Fig.
Antenna II (Fig.
Upper lip (Fig.
Mandible (Fig.
Lower lip (Fig.
Maxilla I (Fig.
Maxilla II (Fig.
Maxilliped (Fig.
Pereon.Gnathopod I (Fig.
Gnathopod II (Fig.
Myanmarorchestia peterjaegeri Hou, sp. n., female holotype. A gnathopod I B dactylus of gnathopod I C gnathopod II D propodus of gnathopod II E oostegite of gnathopod II F oostegite of pereopod III G oostegite of pereopod IV H oostegite of pereopod V I coxal gill of gnathopod II J coxal gill of pereopod III K coxal gill of pereopod IV L coxal gill of pereopod V M coxal gill of pereopod VI.
Pereopod III (Fig.
Pereopod IV (Fig.
Pereopod V (Fig.
Pereopod VI (Fig.
Pereopod VII (Fig.
Coxal gills (Fig.
Oostegites (Fig.
Pleon.Epimeral plates (Fig.
Pleopods I–III (Fig.
Urosome.Uropods I–III (Fig.
Myanmarorchestia peterjaegeri Hou, sp. n., A–F female, holotype; G–N male, paratype. A pleopod I B pleopod II C pleopod III D uropod I E uropod II F uropod III G uropod I H uropod II (right) I uropod III J telson K coxal gill of gnathopod II L coxal gill of pereopod III M coxal gill of pereopod V N coxal gill of pereopod VI.
Telson (Fig.
(SMF50714), head missing, 7.0 mm.
Pereon.Gnathopod I (Fig.
Gnathopod II (Fig.
Pereopods III–VII (Fig.
Coxal gills (Fig.
Urosome. As is the female except: Uropod I (Fig.
Telson (Fig.
This species was collected from a disturbed primary forest of the Nat Ma Taung National Park (Fig.
The new species is characterised by the complex lobed gills with filamentous projections. This structure may be related to its terrestrial habitats at high elevations. The convoluted feature can increase the surface area of the gills to keep respiration.
Holotype: male (
The specific name is derived from abbreviation of the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (CAS-SEABRI); noun in apposition.
Eyes rounded; maxilla I palp with one article; male gnathopod II merus and carpus protuberant on posterior margin, propodus with tumescence, sub-triangular; coxal gills convoluted; telson bare on surface.
Holotype (
Head. (Fig.
Antenna I (Fig.
Antenna II (Fig.
Upper lip (Fig.
Mandible (Fig.
Lower lip (Fig.
Maxilla I (Fig.
Maxilla II (Fig.
Maxilliped (Fig.
Pereon.Gnathopod I (Fig.
Gnathopod II (Fig.
Pereopod III (Fig.
Pereopod IV (Fig.
Pereopod V (Fig.
Pereopod VI (Fig.
Pereopod VII (Fig.
Coxal gills (Figs
Myanmarorchestia seabri Hou, sp. n., male holotype. A pereopod III B pereopod IV C pereopod V D pereopod VI E pereopod VII F dactylus of pereopod III G dactylus of pereopod IV H dactylus of pereopod V I dactylus of pereopod VI J dactylus of pereopod VII K coxal gill of pereopod III L coxal gill of pereopod IV M coxal gill of pereopod V N coxal gill of pereopod VI.
Pleon.Epimeral plates (Fig.
Pleopods I–III (Fig.
Urosome.Uropods I–III (Fig.
Telson (Fig.
(SMF50716), head and gnathopod I missing, 10.0 mm.
Pereon.Gnathopod II (Fig.
Pereopods III–VII (Fig.
Coxal gills (Fig.
Oostegites (Fig.
Urosome.Uropods I–III (Figs
Telson (Fig.
Myanmarorchestia seabri Hou, sp. n. can be distinguished from M. peterjaegeri Hou, sp. n. by the following characters (M. peterjaegeri Hou, sp. n. in parentheses): palp of maxilla I with one fused article (with two small articles); gnathopod II of male subtriangle, with bigger tumescence than that of M. peterjaegeri Hou, sp. n., palm margin with a row of spines on interior and exterior sides (with setae), dactylus elongate (short); coxal gills with one or two lobes ridged (with more filamentous projections or ridged margins); uropod III peduncle with two posterodistal spines (with one posterodistal spine); telson surface bare (with nicks). In addition, M. peterjaegeri Hou, sp. n. and M. seabri inhabit separate habitats, with up to 500 m elevation difference.
The uncorrected p-distance between M. peterjaegeri Hou, sp. n. and M. seabri Hou, sp. n. is 18.8% for COI. This significant differentiation confirmed that they are two different new species, in comparison with previous molecular threshold used for crustacean species delimitation (
We are grateful to Dr Peter Jäger for his donation of specimens. We thank Prof. Hiroshi Morino and Prof. Azman Abdul Rahim for their constructive comments. The study was supported by the Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences (2015CASEABRI005, Y4ZK111B01), the National Natural Sciences Foundation of China (NSFC-31422048/31372156), and a grant for Science and Technology Basic Research (2014FY210700).