Paracanthocobitis putaoensis, Lin & Chen & Myint & Chen, 2023

Lin, Feng, Chen, Zhi-Ying, Myint, Khin Mar & Chen, Xiao-Yong, 2023, Paracanthocobitis putaoensis, a new loach species (Cypriniformes: Nemacheilidae) from the Irrawaddy basin in northern Myanmar, Zootaxa 5227 (2), pp. 265-278 : 268-272

Paracanthocobitis putaoensis sp. nov., Lin, Chen & Chen

( Figs 1–4 )

Holotype. KIZ 2015006395 ( SEABRI 20151117 ), 55.7 mm standard length (SL), male; Tanjar Stream , passing Lone Shar Yan Village, Putao District, Kachin State, Myanmar (approx. 27°08'18.92"N, 97°33'34.38"E; ~ 422 m a.s.l.); col. Xiao-Yong Chen, Tao Qin, Shu-Sen Shu, and Yunn Mi Mi Kyaw, 26 December 2015.

Paratypes. SEABRI 20140216–17 , 19 , 21–22 , 25 , 27–29 , 9 ex., 42.5–74.5 mm SL, tributary of Mali Hka River in NaungMun , Putao District, Kachin State, Myanmar (approx. 27°30'15.3"N, 97°48'48.2"E; ~ 543 m a.s.l.), col. Tao Qin; 30 November 2014 to 7 December 2014. SEABRI 20151113 , 20151116 , 20151118 , 3 ex., 36.6–66.0 mm SL, same data as holotype. KIZ 2015006396–98 ( SEABRI 20151247–49 ), 3 ex., 41.2–72.3 mm SL, Chan Khaung Stream , Putao District, Kachin State, Myanmar (approx. 27°24'32.09"N, 97°18'57.05"E; ~ 405 m a.s.l.), col. XiaoYong Chen, Tao Qin, Shu-Sen Shu, and Yunn Mi Mi Kyaw; 28 December 2015 .

Additional material. SEABRI20151114 , 1 ex., 55.1 mm SL, same data as holotype, used for physical dissection .

Material used in molecular genetic analysis. SEABRI-QT 20170096, 1 ex., 62.8 mm SL, Putao District : a stream of Mali Hka River, 27°40'20.69"N, 97°23'2.70"E (GenBank accession numbers: OP723460 ) .— SEABRIQT 20170116-117, 132-133, 4 ex., 54.3–66.3 mm SL, Putao District : a stream of Mali Hka River, 27°41'57.54"N, 97°24'7.29"E (GenBank accession numbers: OP723461 - OP723464 ) .

Diagnosis: Paracanthocobitis putaoensis can be readily distinguished from all other species of Paracanthocobitis by the combination of horizontally oriented suborbital groove in males; incomplete lateral line, with 39–54 pores, extending to anus but not surpassing origin of anal-fin; axillary pelvic lobe present; 9½–10½ (usually 10½) branched dorsal-fin rays; 11–12 (usually 12) pectoral-fin rays; and caudal fin with 5 dark bands.

Description: General appearance is shown in Figures 1–2 . Morphometric data for the holotype and 15 paratypes are shown in Table 2 . Body moderately elongated and robust, largest known specimen 74.5 mm SL. Body cylindrical anteriorly (between pectoral-fin and dorsal-fin origin) and slightly compressed posteriorly, especially caudal peduncle. Dorsal profile continuous with no hump between head and body, except the inconspicuous slight depression on occipital margin. Deepest and widest point of body at or just anterior to dorsal-fin origin; body depth slowly increasing to dorsal-fin origin and then appreciably decreasing to end of dorsal-fin base, postdorsal body depth almost uniform to caudal-fin base. Ventral profile almost flat to anal-fin origin, then slightly rising to caudalfin base.

Head moderately depressed and triangular when viewed dorsally, snout obtusely rounded. In lateral view, cheeks slightly swollen, snout slightly pointed. Anterior nostril pierced in front of a flap-like tube; posterior nostril adjacent to anterior nostril. Eye relatively small, eye diameter 14.7–26.9% HL. Mouth inferior, moderately large and strongly arched, gape about twice as wide as long. Lips thick and fleshy with well-developed papillae; upper lip with 3–4 rows of papillae, contiguous with lower lip, and a small median incision on upper lip; large thick pad with dense bulbous papillae on sides of lower lip; pads separated by a narrow median interruption ( Fig. 3 a ). Processus dentiformis on upper jaw present, and no median notch on lower jaw. Three pairs of barbels; maxillary barbels longest, reaching vertical of posterior rim of eye; inner rostral barbels reaching anterior margin of nostril, outer rostral barbels almost reaching vertical of anterior margin of orbit.

Body entirely covered with scales. Dorsal-fin origin anterior to pelvic-fin origin, and slightly closer to snout tip than to caudal-fin base; dorsal-fin with 4 simple and 9½ (6) or 10½ (10) branched rays, the 1 st or 2 nd branched ray longest; posterior margin of dorsal-fin truncate and distal margin above vertical of anus. Pectoral-fin margin slightly convex, with 1 simple and 10 (13) or 11 (3) branched rays; tip of adpressed fin reaching about 1/2 to 3/5 distance from pectoral-fin origin to pelvic-fin origin. Pelvic-fin origin at vertical line of third branched ray of dorsal fin, and slightly closer to pectoral-fin origin than to anal-fin origin or at midpoint of them. Pelvic fin with 1 simple and 7 branched rays, and tip of adpressed fin not reaching anus. Axillary pelvic lobe present ( Fig. 3 b ). Anus closer to anal-fin origin than to pelvic-fin tip. Anal-fin origin closer to caudal-fin base than to pelvic-fin origin. Anal fin small with convex margin, with 3 simple and 5½ branched rays, not reaching caudal-fin base. Caudal fin slightly emarginate, with 8+8 branched rays. Caudal-peduncle length 1.1–1.2 times its depth.

Lateral line incomplete, with 39–54 pores (6), extending at vicinity of anus and not surpassing anal-fin insertion. Cephalic sensory system (6) with 4+9–11 infraorbital pores, 7–8 supraorbital pores, 3 supratemporal pores, and 8 preoperculo-mandibular pores. Intestine with a loop behind stomach, extending forward to anterior extremity of stomach ( Fig. 3 c ).

Colouration: In preservative, yellowish brown on background of head and body, whitish on belly; head with 2–3 brown transverse blotches, snout, and cheeks with many small dark spots. Body with 3 rows of large blotches and 1 row of small, irregular paler spots close to ventral side. The 1 st row is 10–15 brown saddles across dorsum (3–4 predorsal, 3–4 subdorsal and 4–7 postdorsal). The 3rd row composed of 8–10 large brown irregular blotches centered along lateral line and extending to ventral side, some becoming slightly slanted, shape of blotches variable from elongated oval, oval, heart-shaped to triangular; 2 nd row composed of irregular different-sized blotches or spots inserted above lateral line at interspace between 1 st and 3rd rows (saddles and the blotches along lateral line). Black ocellus close to dorsal margin of caudal peduncle. Dorsal fin hyaline, with 3–4 longitudinal rows of dark brown spots. Caudal fin with 3–5 (usually 4) almost vertical rows of dark bands on rays, other fins hyaline.

In life ( Fig. 4 ), body and head light brown; belly paler; 2–3 dark brown transverse blotches on head; many dense and diverse dark brown blotches on body; subrotund black ocellus on upper 1/3 of caudal peduncle; pectoral, anal, pelvic, and caudal fins pale yellow; several light black spots on pectoral-fin and caudal-fin rays.

Sexual dimorphism: Adult males distinguished by presence of well-defined suborbital groove, extending from lower rim of eye to upper base of inner rostral barbel ( Fig. 3 d ). Females without suborbital groove or with a shallower, less defined groove in similar position.

Distribution and habitat: Paracanthocobitis putaoensis is known from the type locality, Tanjar Stream, Chan Khaung Stream and a tributary of the Mali Hka River in Naung Mun, all of which are tributaries of the Mali Hka River, Myanmar ( Fig. 5 ). This species inhabits slow flowing streams with a substrate of small gravel and stones ( Fig. 6 ). Other fishes collected with P. putaoensis include Psilorhynchidae : Psilorhynchus brachyrhynchus ; Cyprinidae : Danio flagrans , Tor yingjiangensis , Neolissochilus compressus , Opsarius barinoides , Poropuntius burtoni , Pethia tiantian , Pethia thelys , Garra qiaojiensis and Garra bispinosa ; Nemacheilidae : Schistura sikmaiensis ; Amblycepitidae: Amblyceps murraystuarti ; Bagridae : Batasio procerus ; Mastacembelidae : Mastacembelus armatus ; Badidae : Badis pyema ; Channidae : Channa burmanica .

Etymology: The specific name “ putaoensis ” refers to Putao District, Kachin State, Myanmar.

Figures

FIGURE 1. Paracanthocobitis putaoensis sp. nov. after fixation. KIZ 2015006395, holotype, male, 55.7 mm SL. a. lateral view; b. dorsal view; c. ventral view.

FIGURE 2. Paracanthocobitis putaoensis sp. nov. after fixation, paratypes; a. SEABRI 20140229, 65.5 mm SL; b. SEABRI 20151113, 42.3 mm SL; and c. SEABRI 20151249, 41.2 mm SL.

FIGURE 3. Morphological characteristics of Paracanthocobitis putaoensisis; a. lower lip (KIZ 2015006395, holotype, male, 55.7 mm SL); b. lateral view of the axillary pelvic lobe (SEABRI 20151118, paratype, 66.0 mm SL); c. ventral view of the digestive tract (SEABRI 20151114); d. lateral view of the suborbital groove in males (SEABRI 20151113, paratype, male, 42.3 mm SL).

FIGURE 4. Live individual of Paracanthocobitis putaoensis, from a small stream on the way from Zeyar Dan to Hponkanrazi on Dec., 15, 2015. Photo by Chen Xiao-Yong.

FIGURE 5. Distribution map of Paracanthocobitis putaoensis; star for locality of holotype, triangle for those of paratypes, circle for locality of specimens used in molecular genetic analysis.

FIGURE 6. Habitat of Paracanthocobitis putaoensis; Myanmar: Chan Khaung Stream, Dec. 28, 2015.