Research Article |
Corresponding author: Xiao-Yong Chen ( chenxy@mail.kiz.ac.cn ) Corresponding author: La-orsri Sanoamuang ( la_orsri@kku.ac.th ) Academic editor: Pavel Stoev
© 2018 Shu-Sen Shu, D. Christopher Rogers, Xiao-Yong Chen, La-orsri Sanoamuang.
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:
Shu S-S, Rogers DC, Chen X-Y, Sanoamuang L (2018) Streptocephalus diversity in Myanmar, with description of a new species (Branchiopoda, Anostraca). ZooKeys 734: 1-12. https://doi.org/10.3897/zookeys.734.21153
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The diversity of anostracans in Myanmar is poorly known. A series of biodiversity surveys had been conducted in Myanmar, and two species of Streptocephalus were collected in the central dry zone. Streptocephalus sirindhornae Sanoamuang et al., 2000 is reported in Myanmar for the first time, and Streptocephalus shinsawbuae sp. n. is described as new. Streptocephalus shinsawbuae sp. n. belongs to the S. dichotomus group and is similar to S. simplex Bond, 1934 and S. sahyadriensis Rogers & Padhye, 2014, but can be distinguished by the form of the male antennal posterior primary ramus and anterior primary ramus apex and egg ornamentation. Streptocephalus dichotomus has been reported from Myanmar in the past but was not found in this survey.
Diversity, new record, Southeast Asia, Streptocephalus shinsawbuae sp. n.
The monogeneric Streptocephalidae Daday, 1910 is the largest anostracan family, composed of 65 species (
The Southeast Asia Biodiversity Research Institute (Chinese Academy of Sciences) and the Forest Research Institute, Myanmar, conducted a series of biodiversity surveys in Myanmar from 2015 to 2017. Two Streptocephalus species were collected during these efforts: the first records of S. sirindhornae Sanoamuang et al., 2000 from Myanmar and a species new to science.
Specimens were collected by a hand held dip net and preserved in 95% alcohol in the field. Specimens were examined under a stereo microscope (Zeiss Stemi 508) and a compound microscope (Olympus CX31) in the laboratory. All drawings were made using a camera lucida and images were taken by ToupCam microscope digital camera inside the compound microscope, the egg image (Fig.
KIZ–CR 2016001, male, collected from type locality on 29 December 2016: SS Shu, XY Chen, T Qin, KM Myint and TS Tin. Type deposited in the Kunming Natural History Museum of Zoology, Kunming Institute of Zoology (KIZ), Chinese Academy of Sciences (CAS).
KIZ–CR 2016002, female, same data as holotype.
One male (SEABRI–CR 2016001) and one female (SEABRI–CR 2016002) deposited in Freshwater Biodiversity Laboratory, Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences, Myanmar, same data as holotype.
MYANMAR: Mandalay region: Pyawbwe Township: near Yanaung Village: a pond in the southern side of the road from Pyawbwe to NO. 1 Highway, 20°33'46.9"N, 95°58'53.70"E, altitude 242 m, 25 males and 18 females. Zayetkon Township: a pond near the road from Kyaukpadaung to Nay Pyi Taw, 20°48'51.63"N, 95°26'58.88"E, altitude 430 m, 11 males and 24 females. SAGAING REGION: Monywa and Chaung-U Townships: a pond near Bawditataung Nature Reserve (Laykyun Sekkya Buddha), 22°5'26.47"N, 95°16'30.85"E, altitude 141 m, 6 males and 22 females. Myo Thar Township: a pond near the road from Gway Kone to Myo Thar, 21°43'37.31"N, 95°46'40.34"E, altitude 172 m, 15 males and 8 females. MAGWAY REGION: Yesagyo Township: a pond near the road from Yesagyo to Lingadaw, 21°38'46.22"N, 95°10'56.00"E, altitude 90 m, 10 males and 8 females. Htammakauk Township: a pond near the road from East Kan Dwinn to Ohnbin, 21°4'13.33"N, 94°43'21.61"E, altitude 105 m, 4 males and 3 females. Kyuntaw Township: a pond near the road from Ywathitkyi to Htanpinchaung, 21°0'16.17"N, 94°41'18.05"E, altitude 128 m, 15 males and 22 females. Chaung Kauk Township: a pond near the road from Koebin to Egayit, 19°38'22.09"N, 95°20'25.40"E, altitude 153 m, 6 males and 12 females. Lelu Township: a pond near the road from Taungdwingyi to Magway, 20°11'55.78"N, 95°22'0.62"E, altitude 145 m, 15 males and 13 females. Yenangyaung City, Gyae Gone Township: a pond near the road from Gyae Gone to Wetchok, 20°24'31.38"N, 95°2'57.32"E, altitude 200 m, 5 males and 17 females. All specimens except the type series were collected by SS Shu, XY Chen, T Qin, P Zaw in June and July, 2017, and the locations are marked in Fig.
Streptocephalus shinsawbuae sp. n. is a member of the “S. dichotomus” species group, and can be distinguished from its congeners by the following characters: base of second antenna distal antennomere expanded, subquadrate, basal projection absent; antennal appendage with long peduncle, with one (rarely two) fleshy papilla(e), distal geniculations with 5–7 spines; anterior primary ramus with a digitiform basoposterior spine, ending distally as a triangular, lamellar projection, anterior ramus posterior branch with a subdistal and shallow notch; posterior ramus biramous, posteriolateral branch with two groups of crenulations, posterior primary ramus with two longitudinal rows of spines, distal tenth slightly curved anteriorly; egg with large, basically pentagonal polygons, separated by vertical ridges.
Male. (Fig.
Head round, subcylindrical. Cephalic appendage (Fig.
Antennal appendage (Fig.
Anterior primary ramus (Figure
Posterior ramus (“finger”) biramous and longer than anterior ramus. Posterior margin in lateral view near rami confluence with a shallow emargination. Posteriolateral branch (“lower finger” in
Labrum large, triangular, middle compress, apex directed posteriorly. Mandible, first and second maxillae as typical for the genus.
Eleven pairs thoracopods, increasing in size from the first pair to the fifth pair, then decreasing posteriorly. The structures of praeepipodites and epipodites typical for genus. Fifth thoracopod endite I and II with closely set, long plumose marginal setae. Endite I submargin with three widely spaced spines, the distal two are single, the proximal one with a basal spinule. Endite II submargin with two closely spaced spines, distal spine short, proximal spine long. Endite III–V with 3, 2, 2 long plumose setae and 2, 2, 1 spine(s), respectively, with small setae in proximal half. Endopodite broad, margin distal half with sparse plumose setae, each with 1–6 basal spinulae. Exopodite linguiform, margins with closely set plumose setae, longest distally, most setae with basal spinule. Epipod oval, without setae and spines, prae-epipod broadly oval, margins with small hooks.
Genital segments smooth, with lateral linguiform outgrowths. Gonopod (Fig.
Abdomen and cercopods as typical for the genus.
Female. Body smaller than male, body length from 14.0 to 17.5 mm, average 15.4 mm (Fig.
First antennae 2.2 times length of eye plus peduncle and 1.6 times length of second antennae, apex blunt, with three subequal long setae. Second antennae (Fig.
Brood pouch (Fig.
Egg (Fig.
The specific epithet shinsawbuae refers to Queen Shin Sawbu (1453–1460) who facilitated more than 50 years of peace in Myanmar.
During the sampling at the type location in June, 2017, the pond had a water temperature of 37.6 °C, a pH of 8.3, conductivity of 117μS/cm, and the dissolved oxygen was 5.9 mg/L. One species of clam shrimp, Cyzicus pilosus Rogers, Thaimuangphol, Saengphan, and Sanoamuang, 2013 was also collected.
Streptocephalus shinsawbuae sp. n. is a member of the “S. dichotomus” species group, which includes S. dichotomus Baird, 1860, S. echinus Bond, 1934, S. longimanus Bond, 1934, S. sahyadriensis Rogers & Padhye, 2014, S. simplex Gurney, 1906, and S. sirindhornae Sanoamuang et al., 2000. This group is separated from all other Streptocephalus in that the posterior ramus (finger) is biramal. Of the six species in this group, S. shinsawbuae sp. n. is readily separated from other congers by the single papilla on the antennal appendage peduncle. Of approximately 120 male specimens of S. shinsawbuae sp. n., only one male from Magway (20°11'55.78"N, 95°22'0.62"E) had two papillae. This papilla in all other species of group is absent, or numbers three or more.
Streptocephalus shinsawbuae sp. n. is most similar to S. sahyadriensis. Both species have two longitudinal rows of spines on the antennal appendage posterior ramus (finger), and the anterior primary ramus (thumb) bears a small basoposterior spine. However, they can be separated by: (1) the shape of the posterior primary ramus (upper finger), which is straight in the proximal nine tenths, with the apex arcing anteriorly in S. shinsawbuae sp. n. vs. arcing distolaterally in the distal third 90° in S. sahyadriensis; (2) the posterior ramus posteriolateral branch (lower finger) has two groups of crenulations along the anterior margin in S. shinsawbuae sp. n. vs. only one group subdistally in S. sahyadriensis; (3) the anterior primary ramus apex shoulder is triangularly acute in S. shinsawbuae sp. n. vs. rounded in S. sahyadriensis; (4) the anterior primary ramus (thumb) basoposterior spine is digitiform in S. shinsawbuae sp. n. vs. triangular in S. sahyadriensis.
Streptocephalus shinsawbuae sp. n. is similar to S. simplex in having unbranched posterior primary ramus (upper finger), and acute anterior primary ramus (shoulder) apex, but they can be separated by: (1) the posterior ramus posteriolateral branch (lower finger) having two crenulated areas along anterior margin in S. shinsawbuae sp. n. vs. smooth in S. simplex; (2) the anterior primary ramus (shoulder) apex is triangular in S. shinsawbuae sp. n. vs. parallel sided in S. simplex; (3) anterior primary ramus (thumb) bearing a basal digitiform spine in S. shinsawbuae sp. n. vs. absent in S. simplex.
The eggs of S. shinsawbuae sp. n. have pentagonal polygons, which are very similar to those of both S. echinus and S. longimanus. From S. simplex it can be readily distinguished by the triangle polygons. In addition, the egg ridges are broad and deep in S. shinsawbuae sp. n. vs. narrow and shallow in S. sahyadriensis.
Streptocephalus sirindhornae is the most widely distributed member of the genus in Southeast Asia, with previous records from: Thailand, Laos, Cambodia, and China (
Our materials were collected from the central dry zone of Myanmar including Mandalay, Magway, and Sagaing regions (Fig.
MYANMAR: MANDALAY REGION: Nyaung Lunt Township: rice field near the road from Nyaung Lunt to Yamethin, 20°18'9.26"N, 96°9'51.08"E, altitude 189 m, 12 males and 22 females. Hlaingdet Township: a pond near the road from Meiktila to Yin Mar Bin, 20°46'53.80"N, 96°11'30.24"E, altitude 162 m, 8 males and 15 females. SAGAING REGION: Kanbalu Township: Kaing Taw Village: rice field near the road from Kanbalu to Chatthin Wildlife Sanctuary, 23°15'22.53"N, 95°30'54.45"E, altitude 169 m, 5 males and 3 females. Kanbulu Township, Bugon Township and Ywa Zin Township: a pond near the road from Kanbulu to Shwebo, respectively, 23°13'21.22"N, 95°31'55.57"E, altitude 181 m, 3 males and 5 females; 22°55'1.54"N, 95°41'56.33"E, altitude 160 m, 9 males and 15 females; 22°46'30.75"N, 95°42'39.15"E, altitude 152 m, 14 males and 8 females. Saye Township: rice field near Saye Lake, 22°2'14.29"N, 95°55'46.90"E, altitude 86 m, 14 males and 11 females. MAGWAY REGION: Aunglan Township: a pond near the road from Pyay (Prome) to Taungdwinggyi. All specimens were collected by S.S. Shu, X.Y. Chen, T. Qin, P. Zaw in June and July, 2017, and the locations are marked in Fig.
= Branchipus bengalensis Alcock, 1896, fide Gurney, 1906.
Streptocephalus dichotomus is widely distributed in the Indian subcontinent, Sri Lanka, and Pakistan (Selvarajah and Costa 1979;
Streptocephalus shinsawbuae sp. n. is the seventh species described from the S. dichotomus species group. The number of antennal peduncle papillae was used to separate some Indian species of Streptocephalus (
6(5) | Antennal peduncle papillae three or more; antennal appendage posterior ramus (“finger”) with lateral sickle shaped lateral subramus inerm on proximal half, crenulate on distal half | 7 |
6’ | Antennal peduncle papillae absent; antennal appendage posterior ramus with lateral sickle shaped lateral subramus with a longitudinal row of spines, at least proximally with crenulations (immatures); India | Streptocephalus echinus Bond, 1934 |
6’’ | Antennal peduncle papillae one (rarely two); antennal appendage posterior ramus (“finger”) with lateral sickle shaped lateral subramus inerm on proximal half, crenulate on distal half; Myanmar | Streptocephalus shinsawbuae sp. n. |
We are grateful to Mr. Paing Zaw for assistance in collecting and for checking the spelling of the local names. We thank to Mr. Tao Qin, Mrs. Khin Mar Myint, and Ms. Thinn Su Tin for helping in collecting the material. This study was supported by the Southeast Asia Biodiversity Research Institute, the Chinese Academy of Sciences (Y4ZK111B01), the National Natural Science Foundation of China (31702011) and the Yunnan Provincial Science and Technology Program (2014FB178).