Mystus celator, Ng & Kottelat, 2023

Ng, Heok Hee & Kottelat, Maurice, 2023, Mystus celator, a new species of catfish from northern Myanmar (Actinopterygii: Siluriformes: Bagridae), Vertebrate Zoology 73, pp. 981-990 : 981

Mystus celator sp. nov.

Figure 2

Chresonymy.

Mystus pulcher (in part) - Chaudhuri (1911: 20).

Holotype.

MHNG 2790.082, 80.6 mm SL; Myanmar: Kachin State: Thein Lin Chaung at Thein Lin village, E of Bhamo, 24°11′1″N 97°15′30″E; M. Kottelat and Nyein Chan, 24 June 2017.

Paratypes.

CMK 26781 (1), 62.4 mm SL; Myanmar: Kachin State: Moe Sit Chaung, a small stream entering Irrawaddy River from the N opposite Shwegu, about 35 km downstream of Bhamo, about 1.5 km from mouth, ca. 100 masl, 24°12′35″N 96°50′5″E; Nyein Chan, 9 February 2017. CMK 26981 (1), 77.3 mm SL; ZRC 64887 (1), 74.5 mm SL; Myanmar: Kachin State: Nant Sa Ri Chaung at Kaung Jar Xan village, E of Bhamo, 24°12′33″N 97°15′35″E; M. Kottelat and Nyein Chan, 24 June 2017.

Additional Material.

ZSI F4718/1 (1), 51.5 mm SL; ZSI F4719/1 (1), 51.4 mm SL; Myanmar: Bhamo; J. Coggin--Brown, 1909-1910 (photographs examined).

Diagnosis.

Mystus celator sp. nov. is distinguished from congeners except for M. pulcher and M. rufescens in having a combination of three equally dark longitudinal stripes separated by pale interspaces on the sides of the body, a round, dark tympanic spot, and an ovoid, dark spot on the caudal peduncle (vs. at least one of these three features absent; Table 1 ). It differs from M. pulcher and M. rufescens in having a shorter adipose-fin base (18.0-23.3% SL vs. 27.5-49.1), with the following combination of characters further distinguishing it from congeners: angle between body axis and predorsal profile 21-24°, posterior cranial fontanel not reaching base of supraoccipital process, 25-30 rakers on the first branchial arch, and 35-36 vertebrae.

Description.

Biometric data in Table 2 . Head depressed; predorsal profile slightly convex and making angle of 21-24° with body axis, ventral profile almost straight; snout acutely rounded when viewed dorsally. Bony elements of dorsal surface of head covered with thin skin; bones readily visible, especially on posterior half of neurocranium, and ornamented with numerous fine, radial grooves. Midline of cranium with elongate fontanel extending from behind snout to just beyond level of posterior orbit margin. Supraoccipital process elongate, with gently converging sides and pointed tip; extending to anterior nuchal plate. Eye ovoid, horizontal axis longest, with free margin; located entirely in dorsal half of head. Gill openings wide, extending from posttemporal to beyond isthmus. Gill membranes free from isthmus, with 8 (4) branchiostegal rays.

Mouth subterminal, fleshy upper lip extending anteriorly beyond upper jaw. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band curved, of equal width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Vomerine tooth band unpaired, continuous across midline; smoothly arched along anterior margin; band width narrower than premaxillary band at midline, widening laterally and then tapering to a sharp point posterolaterally.

Barbels in four pairs. Maxillary barbel long and slender, extending to vertical through middle of anal-fin base. Nasal barbel slender, extending to midway between posterior orbital margin and dorsalmost point of gill opening. Inner mandibular-barbel origin close to midline; barbel thicker and longer than nasal barbel and extending beyond level of last pectoral-fin ray base. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to two-thirds of distance between base of last pectoral-fin ray and pelvic-fin origin.

Body subterete, slightly compressed, becoming more so toward caudal peduncle. Dorsal profile rising evenly, not steeply, from tip of snout to origin of dorsal fin, sloping gently ventrad from origin of dorsal fin to end of caudal peduncle. Ventral profile slightly convex to anal-fin base, then sloping slightly dorsally to end of caudal peduncle. Skin smooth. Lateral line complete, midlateral in position. Vertebrae 19+16=35* (2) or 19+17=36 (2).

Dorsal fin with spinelet, spine, and 7 (4) rays. Origin of dorsal fin at about one-third of body. Dorsal-fin margin convex, with anterior branch of fin rays longer than other branches. Dorsal-fin spine moderately long, straight, slender, posterior edge with 4*-5 retrorse serrae. Nuchal plate triangular and narrow.

Pectoral fin with stout spine, sharply pointed at tip, and I,7* (2) or I,8 (2) rays. Anterior margin of spine smooth; posterior margin of spine with 11-15* large, retrorse serrae along entire length. Pectoral-fin margin straight anteriorly, convex posteriorly. Cleithral process in form of narrow triangle with concave dorsal margin and extending for half of pectoral-spine length.

Pelvic-fin origin at vertical through posterior end of dorsal-fin base, with i,5 (4) rays, its distal margin slightly convex; tip of adpressed fin just reaching anal-fin origin. Anus located at vertical through middle of adpressed pelvic fin; urogenital opening located immediately anterior to base of first anal-fin ray, at vertical through posterior quarter of adpressed pelvic fin. Males with an elongate conical genital papilla.

Adipose fin with convex margin for entire length, with deeply-incised posterior portion; adipose-fin base moderate, spanning nearly half of postdorsal distance. Anal-fin origin posterior to vertical through origin of adipose fin; anal fin with iii,5,i (1), iii,7* (1), iii,8,i (1), or iv,6,i (1) rays and convex distal margin.

Caudal peduncle moderately deep. Caudal fin deeply forked, with i,7,8,i (4) principal rays; both lobes acutely rounded, upper lobe more slender and longer than lower. Procurrent rays extending anterior to caudal-fin base.

Coloration.

Fixed in formalin, stored in 70% ethanol: Dorsal and lateral surfaces of head brown, fading to cream ventrally. Body predominantly brown on dorsal and lateral surfaces, fading to cream ventrally. Three brown longitudinal stripes on dorsal and lateral surfaces of body: dorsal stripe originating from supraoccipital and epiotic area, middle stripe originating from posterolateral corner of head, and ventral stripe originating from tip of cleithral process. All three stripes extending posteriorly to caudal-fin origin and separated by narrow, pale interspaces. Dark gray to black, round tympanic spot on body above cleithral process. Dark gray to black ovoid spot, about eye size, at mid-height of posterior extremity of caudal peduncle. Adipose fin largely hyaline, with brown melanophores scattered along base. All fins with hyaline interradial membranes and dusting of brown melanophores along fin rays. Nasal and maxillary barbels brown dorsally, cream ventrally. Mandibular barbels cream.

Distribution.

Known from the middle Irrawaddy River drainage in Myanmar, upstream of Mandalay (Fig. 3 ).

Etymology.

The specific name comes from the Latin noun Mystus celator , meaning a concealer or hider, and is used in allusion to its close similarity to (and misidentification with) M. pulcher .

Figures

Figure 2. Mystus celator sp. nov., MHNG 2790.082, holotype, 80.6 mm SL; Myanmar: Thein Lin Chaung at Thein Lin village. Dorsal, lateral and ventral views.

Figure 3. Map showing collection localities for Mystus celator sp. nov. Each point may represent more than one collection locality.