Danio htamanthinus, Kullander, Sven O. & Norén, Michael, 2016

Kullander, Sven O. & Norén, Michael, 2016, Danio htamanthinus (Teleostei: Cyprinidae), a new species of miniature cyprinid fish from the Chindwin River in Myanmar, Zootaxa 4178 (4), pp. 535-546 : 536-543

Danio htamanthinus , new species

( Figs. 1 a–c)

Holotype. NRM 69502, adult male, 22.9 mm SL. Myanmar, Sagaing Division, stream outside Htamanthi village , 1 km W Chindwin River; 25°20′4″N 95°16′39″E. 1 Dec 2013. S.O. Kullander, M. Norén and B. Kajrup, field no. SOK-2013-029.

Paratypes. NRM 11997. 8, 17.1–22.1 mm SL; 42621, 1, not measured; NRM 69503, 10, 15.9–18.3 mm SL.

Same data as holotype. — NRM 11998. 3, 19.5–20.5 mm SL; 19, 15.0– 20.5 mm SL; NRM 42613, 1, 16.8 mm SL; NRM 42636, 1 not measured; NRM 42638, 1, not measured; NRM 42639, 1 , not measured. Myanmar: Sagaing Division, swamp and small stream 5 km W Htamanthi village ; 25°19′44″N 95°14′26″E. 1 Dec 2013. S.O. Kullander, M. Norén and B. Kajrup, field no. SOK-2013-028.

Diagnosis. Similar to Danio choprae and D. flagrans in general colour pattern with several vertical bars on side of abdomen; red interstripe below P+2 stripe in life, and presence of well-developed tubercles on infraorbital ossicles. Distinguished from D. choprae and D. flagrans by absence of P+1 stripe (vs. presence) and P stripe expressed as row of spots posteriorly on side and caudal peduncle (vs. P stripe entire). Distinguished also from D. flagrans by deeper body (26.5% SL vs. 22.5–26.6% SL), shorter caudal peduncle (17.1–20.5% SL vs. 20.5–24.7% SL), and longer anal-fin base (19.0–21.8% SL vs.14.2–18.3% SL); from D. choprae by longer maxillary barbel (16.6–23.0% SL, vs. 9.3% SL, reaching to below pectoral-fin base adults vs. not reaching pectoral-fin base. Distinguished from all other species of Danio by characters in combination: rostral barbel present (absent in D. erythromicron , D. margaritatus , D. nigrofasciatus , D. tinwini , variable in D. rerio ); mandibular barbel present (absent in D. erythromicron and D. margaritatus ); lateral line absent (complete in D. absconditus , D. annulosus , D. assamila , D. catenatus , D. concatenatus , D. dangila , D. feegradei , and D. meghalayensis ; abbreviated in D. aesculapii , D. albolineatus , flagrans , D. jaintianensis , D. kerri , D. kyathit , D. quagga , and D. roseus ; abbreviated or absent in D. choprae ), colour pattern consisting of vertical bars or spots anteriorly on side (vertical bars also posteriorly on side in D. erythromicron ; light spots on dark ground in D. annulosus , D. assamila , D. catenatus , D. concatenates , D. dangila , D. sysphigmatus , and D. margaritatus ; dark spots on light ground in D. kyathit and D. tinwini ; horizontal stripes only in D. albolineatus , D. jaintianensis , D. kerri , D. meghalayensis , D. nigrofasciatus , D. quagga , D. rerio , and D. roseus ; bars anteriorly, two horizontal rows of spots posteriorly in D. aesculapii ); branched dorsal-fin rays 7½ (6½ in D. aesculapii and D. tinwini ); circumpeduncular scale rows 10 (12 in D. aesculapii , D. albolineatus , D. erythromicron , D. kerri ; 14 in D. absconditus , D. annulosus , D. assamila , D. catenatus , D. concatenatus , D. dangila , D. feegradei , and D. meghalayensis ).

Description. General body features and pigmentation are illustrated in Figures 1 a–c. Proportional measurements are summarized in Table 1 . Counts from up to 12 specimens (NRM l1997, NRM 11998, NRM 69502). Holotype count marked with asterisk.

Body compressed, elongate (body depth 26.5–32.0% SL), sexes isomorphic, except for males with tubercles on pectoral fin; two specimens dissected, 16.6 and 17.9 mm SL, are females with large ovaries with ripening ova. Head laterally compressed, slightly deeper than wide. Snout short, obtuse, shorter than eye diameter. Mouth terminal, oblique in profile, jaws about equal in anterior extension. Small projection at dentary symphysis fitting into depression in upper jaw. Maxilla reaching to slightly beyond vertical from anterior margin of orbit. Lower jaw ending anteriorly slightly below middle of eye. Dentary with anterior lateral lobe with pointed tubercles; laterally a distinct band of 2–3 dense rows of pointed tubercles; sparse pointed tubercles medially on dentary. Holotype with row of minute tubercles in single row on adocular margin of interorbitals 2 and 3. Rostral barbel long, reaching to posterior margin of orbit or slightly beyond; maxillary barbel long, reaching to or slightly beyond insertion of pectoral fin.

Many specimens with scales abraded so that accurate counts could not be made. Lateral line absent; about 28 (6), 29 (1), 30* (1), 31 (2) scales in a row representing expected lateral line course. Scales in a row along middle of side about 28*–30. Median predorsal scales 15 (2), 16* (4), 17 (4). Body lateral scale rows 7* (9) between dorsalfin origin and pelvic-fin insertion. Circumpeduncular scale rows 10* (7). A row of scales along anal-fin base.

Dorsal-fin rays ii.7 ½* (12); anal-fin rays iii.11 ½ (2), iii.12 * (8), iii.13 ½ (2); pectoral-fin rays i.10 (6), i.11 * (5), i.12 (1); pelvic-fin rays i.6 * (6), i.7 (6). Principal caudal-fin rays, 10+9 (6), 10+10* (1). Dorsal fin inserted at highest point of dorsum, at about midway distance from head to caudal-fin base, at vertical from anal-fin origin. Pectoral-fin insertion at about vertical through posterior margin of opercle; extending to pelvic-fin insertion. Pectoral-fin axial lobe well developed. Bands of minute tubercles present on lateral aspect of first two or three branched rays of pectoral fin in holotype and 19.5 mm specimen (NRM 11998); pectoral-fin tubercles absent in all other specimens. Pelvic-fin origin situated slightly anterior to middle of body, well anterior to dorsal-fin origin; pelvic fin reaching to or almost to anal-fin origin, usually slightly shorter. Pelvic axillary scale present. Caudal fin forked, lobes with rounded tips, lobes equal or upper lobe slightly longer than lower lobe; lower lobe slightly wider than upper lobe.

Vertebrae 15+18=33* (4), 16+17=33 (13), 16+18=34 (3); predorsal vertebrae 13* (3), 14 (7); vertebrae contained within caudal peduncle 7 (2), 8* (8). Pharyngeal bone with tooth formula 2,3,5-5,3,2.

Colouration in preservative. Sexual dimorphism absent in colour pattern. Ground colour white to pale yellowish white. Dark markings brown or grey. Head dorsally pale brownish grey. Sides of head sparsely pigmented. Dorsum light brown with dark brown middorsal stripe anterior to dorsal fin; scale row adjacent to middorsal stripe conspicuously lighter. Next to it scales bearing narrow brown P+2 stripe from near gill cleft caudad. P+1 stripe absent. Sides anteriorly diffusely pigmented; from about distal part of pectoral fin caudad a number of dark vertical bars, extending vertically from level of hypothetical P+1 stripe level to about level of pectoral-fin base. Number of distinct bars (excluding spots) in measurement series of specimens 17.1–22.9 mm SL, 6 (3), 7* (5), 8 (2); bars gradually shorter caudally, becoming a row of more or less distinct small dark spots representing P stripe, and terminating with small spot at middle of base of caudal fin. Pectoral and pelvic fins hyaline. Dorsal fin hyaline with dark brown or blackish grey D stripe from middle of anterior margin obliquely across rays to tips of posterior rays; beyond that stripe hyaline. Anal fin basally grey, margined by black A stripe from middle of anterior margin caudad across rays to tip of posterior rays; distal to that stripe hyaline. Caudal fin hyaline or slightly pigmented; dark grey or black stripe along upper rays, dorsal margin white; ventral margin white.

Colour in life. A specimen photographed alive ( Fig. 1 c) with yellow margins to caudal fin lobes, anterior rays of dorsal fin, and yellow stripe distal to black A stripe. Red pigment patches on eye and dorsally on gill cover. Brilliant red interstripe stripe from caudal-fin base rostrad to anterior side, continued very narrow to gill cleft; red colour reaching fainter ventrally between black bars and blotches on caudal peduncle.

DNA. The COI sequences of two specimens of D. htamanthinus are identical, and differ from that of D. choprae and D. flagrans by 4.3% and 7.5% uncorrected p -distance. Danio choprae and D. flagrans differ by 7.0%.

Etymology. The specific name htamanthinus is an adjective formed on the name of the village near which the type series was collected.

Geographical distribution and habitat. Danio htamanthinus is so far only known from two small streams near Htamanthi on the right bank of the Chindwin River ( Fig. 2 ) and probably also in Shin Bway Yang further upstream in the Chindwin river basin. The type locality ( Fig. 3 ) was a small, shallow stream with clear water, margined by low vegetation, coming out of the forest and crossing a dirt road under a bridge. Associated species were Paracanthocobitis cf. rubidipinnis ( Nemacheilidae ), Channa gachua (Channidae) , Pethia meingangbii and P. thelys (Cyprinidae) , and undetermined species of Badis and Dario (Badidae) , Danio and Esomus (Cyprinidae) . A second locality near Htamanthi was a flooded cleared area with stagnant clear water over grasses and a small trickle of stream feeding it ( Fig. 4 ). Associated species here were Danio cf. quagga , Puntius chola , Pethia meingangbii , Rasbora ornata (Cyprinidae) , and undetermined species of Amblyceps (Amblycipitidae) and Dario .

Comparative morphometry. Proportional measurements of D. htamanthinus are similar to those of D. choprae , and they differ in the same way from D. flagrans in anal-fin base length and caudal peduncle length, but D. choprae stands out with shorter barbels than D. htamanthinus and D. flagrans ( Table 1 ). Size variation within species samples is small, and significant allometries could not be detected. Although the examined specimens of D. htamanthinus are smaller than those of D. flagrans and D. choprae , allometries may thus not influence the ratios significantly, and comparison of ratios may be useful for identification. The Principal Component Analysis ( Fig. 4 ; Table 2 ) also shows separation mainly on barbel length, but also detects the short anal fin and long caudal peduncle in D. flagrans , compared with the other two species.

Phylogenetic relationships. The close relationship of D. choprae , D. flagrans , D. margaritatus and D. erythromicron has already been indicated ( Collins et al., 2012; Fang et al. 2009; McCluskey et al., 2015; Tang et al., 2010), although we here present the first analysis of all species together. A Bayesian analysis of relationships based on the mitochondrial COI gene and with Danio dangila and D. rerio (Hamilton, 1822) as outgroup ( Fig. 6 ) confirms the sister-species relationship of D. margaritatus and D. erythromicron from the Thanlwin drainage near Lake Inle; and recovers D. choprae , D. flagrans and D. htamanthinus as sister group of the Thanlwin species. Danio htamanthinus shows as sister species of the pair D. choprae and D. flagrans , which is unexpected given that D. choprae and D. htamanthinus are more similar in colour pattern and shape. On the other hand, the probability for the latter grouping is low. Inclusion of more data may show that the clade D. choprae + D. flagrans + D. htamanthinus represents a trichotomy, or that the similarities between D. choprae and D. htamanthinus are plesiomorphies.

Figures

FIGURE 1. Danio htamanthinus: a, holotype, NRM 69502, male, 22.9 mm SL; Myanmar: Sagaing Division, stream close to Htamanthi village; b, paratype, NRM 42613. 16.8 mm SL; Myanmar: Sagaing Division: 5 km W Htamanthi village; c, paratype, NRM 42613, 16.8 mm SL, live colours immediately after capture.

FIGURE 2. Map of northern part of Myanmar showing collecting localities of Danio choprae, D. flagrans, and D. htamanthinus.

FIGURE 3. Myanmar, Sagaing Division, small stream near Htamanthi, type locality of Danio htamanthinus.

FIGURE 4. Myanmar, Sagaing Division, small, flooded stream near Htamanthi, habitat of Danio htamanthinus, 1 December 2013.

FIGURE 6. Phylogram of relationships from a Bayesian phylogenetic analysis of D. htamanthinus and related species, based on a 655 bp fragment of the mitochondrial COI gene. Internode values are Bayesian posterior probabilities. Sequences are tagged with Swedish Museum of Natural History voucher catalogue numbers (prefix NRM), GenBank sequence accession numbers (prefixed KT, KU, EF), or Barcode of Life identifier (prefix BOLD).

Tables

TABLE 1. Morphometry of Danio choprae, D. flagrans (đata from Kullanđer, 2012), anđ D. htamanthinus (NRM 11997, N = 7; NRM 11998, N = 2; NRM 69502, holotype). Measurements are in percent of stanđarđ length, except for stanđarđ length anđ total length (in mm). SD, stanđarđ đeviation. Values separating species are highlighteđ in bolđface. HT = holotype.

	Danio choprae			Danio flagrans			Danio htamanthinus
	N min max	mean	SD	n min max	mean	SD	HT n min	max	mean	SD
Stanđarđ length (mm)	20 19.8 29.9	23.9	3.6	21 18.4 33.0	25.3	4.8	22.9 10 17.1	22.9	20.6	1.6
Total length (mm)	20 25.8 38.6	31.6	4.4	20 26.2 43.3	33.8	6.0	31.0 9 23.1	31.0	27.0	2.4
Bođy đepth	20 26.6 31.6	28.6	1.4	21 22.5 26.5	24.9	0.9	29.7 10 26.5	32.0	29.8	1.5
Heađ length	20 23.3 27.3	24.5	0.9	21 23.5 26.8	25.1	1.0	24.5 10 23.5	26.1	24.7	0.9
Snout length	20 5.2 7.1	6.3	0.4	21 5.5 6.7	6.2	0.3	5.7 10 5.6	7.0	6.1	0.4
Heađ đepth	20 17.2 19.8	18.6	0.7	21 16.6 19.6	18.1	0.7	17.0 10 17.0	19.8	18.6	1.0
Heađ wiđth	20 13.3 15.2	14.2	0.6	21 12.6 15.5	13.9	0.5	13.5 10 13.5	15.3	14.2	0.6
Upper jaw length	20 8.6 10.6	9.4	0.6	21 8.7 10.9	10.0	0.5	10.0 10 9.0	10.8	9.9	0.6
Lower jaw length	20 9.9 13.1	11.3	0.8	21 11.1 13.0	12.0	0.4	11.4 10 11.0	12.7	11.8	0.5
Orbital điameter	20 8.0 9.9	9.0	0.5	21 7.7 9.8	8.7	0.5	9.2 10 8.6	9.9	9.2	0.5
Interorbital wiđth	20 10.7 13.1	11.7	0.6	21 10.3 11.9	11.1	0.4	10.5 10 10.5	12.2	11.4	0.5
Cauđal peđuncle length	20 16.1 19.1	17.7	0.8	21 20.5 24.7	22.2	1.2	19.2 10 17.1	20.5	19.0	1.1
Cauđal peđuncle đepth	20 11.8 15.1	13.6	0.9	21 11.4 13.3	12.2	0.5	13.1 10 11.7	13.3	12.5	0.6
Dorsal-fin base length	20 10.3 13.8	12.0	0.8	21 9.8 12.8	11.3	0.9	11.8 10 10.7	12.3	11.5	0.6
Anal-fin base length	20 19.2 23.9	21.3	1.3	21 14.2 18.3	16.2	1.1	21.8 10 19.0	21.8	20.3	1.1
Pređorsal length	20 60.3 66.7	63.7	1.9	21 57.6 63.3	61.1	1.6	64.6 10 62.0	66.2	63.9	1.4
Preanal length	20 59.6 65.8	62.7	1.7	21 59.3 64.4	62.2	1.4	61.1 10 59.0	64.3	61.6	1.5
Prepelvic length	20 44.1 49.4	46.8	1.7	21 44.7 49.1	46.8	1.2	46.7 10 44.5	48.9	46.8	1.3
Pectoral-fin length	20 20.1 27.8	22.8	1.9	20 20.9 25.9	22.9	1.3	23.1 9 23.0	27.4	25.3	1.6
Pelvic-fin length	20 13.3 18.1	15.5	1.4	21 13.8 17.1	15.2	1.0	15.7 10 14.9	18.3	16.2	1.1
Rostral barbel length	20 5.9 10.1	8.2	1.1	21 10.3 18.7	14.7	3.1	9.2 10 9.2	14.4	11.7	1.5
Maxillary barbel length	20 9.3 15.7	13.2	1.5	21 14.2 23.1	18.4	2.7	16.6 10 16.6	23.9	19.9	2.2

TABLE 2. Component loadings from Principal Component Analysis of morphometric data from Danio choprae (N = 20), D. flagrans (N = 20), and D. htamanthinus (N = 9); data from D. choprae and D. flagrans from Kullander (2010); the three highest loadings for each component are highlighted in boldface.

Standard length	PC I 0.208	PC II -0.092	Sheared PC II -0.069	PC III 0.101	Sheared PC III 0.115	PC IV -0.009	Sheared PCIV -0.011
Body depth Head length Snout length	0.171 0.192 0.203	-0.223 -0.058 -0.093	-0.202 -0.037 -0.071	-0.244 0.189 0.139	-0.234 0.203 0.153	0.272 0.093 0.041	0.271 0.091 0.039
Head depth Head width Upper jaw length	0.192 0.189 0.226	-0.116 -0.107 -0.012	-0.095 -0.086 0.012	0.076 0.110 0.050	0.089 0.123 0.065	0.12 0.166 0.082	0.118 0.164 0.080
Lower jaw length Orbital diameter Interorbital width	0.202 0.156 0.187	0.006 -0.078 -0.128	0.027 -0.060 -0.107	0.121 0.010 0.052	0.135 0.020 0.065	0.122 0.020 0.157	0.119 0.018 0.155
Caudal peduncle length Caudal peduncle depth Dorsal-fin base length	0.222 0.213 0.221	0.148 -0.255 -0.168	0.170 -0.230 -0.143	0.513 0.043 -0.134	0.530 0.057 -0.120	-0.172 -0.193 -0.580	-0.175 -0.195 -0.582
Anal-fin base length Predorsal length Preanal length	0.162 0.212 0.215	-0.376 -0.132 -0.108	-0.355 -0.108 -0.084	-0.473 -0.015 0.134	-0.465 -0.002 0.149	-0.191 0.130 0.142	-0.193 0.128 0.140
Prepelvic length Pectoral-fin length Pelvic-fin length	0.207 0.168 0.200	-0.095 -0.014 -0.108	-0.072 0.004 -0.085	0.136 -0.095 -0.041	0.150 -0.084 -0.028	0.196 0.238 -0.375	0.194 0.236 -0.377
Rostral barbel length Maxillary barbel length Eigenvalue	0.406 0.299 0.6398	0.639 0.408 0.1385	0.677 0.436 N/A	-0.033 -0.532 0.0199	-0.007 -0.515 N/A	-0.240 0.238 0.0073	-0.244 0.234 N/A
Cumulative variance	76.8%	93.4%	N/A	95.8%	N/A	96.7%	N/A