Acantopsis spectabilis ( Blyth, 1860 )

Boyd, David A., Nithirojpakdee, Patchara, Deein, Gridsada, Vidthayanon, Chavalit, Grudpan, Chaiwut, Tangjitjaroen, Weerapongse, Pfeiffer, John M., Randall, Zachary S., Srisombat, Tippamas & Page, Lawrence M., 2017, Revision of the horseface loaches (Cobitidae, Acantopsis), with descriptions of three new species from Southeast Asia, Zootaxa 4341 (2), pp. 151-192 : 167-169

Acantopsis spectabilis ( Blyth, 1860)

Spectacular Horseface Loach ( Fig. 9 )

Prostheacanthus spectabilis Blyth, 1860: 167 (type locality: Burma: Tenasserim proVinces; types: none knoWn, possibly at ZSI but cannot be located [L. Kosygin, pers. comm., 6 Feb. 2017])

Acantopsis spectabilis .— Kottelat 2012:22

Acantopsis multistigmatus VishWanath and Laisram, 2005: 433 , fig. 1 (type locality: India: Manipur: ChindWin RiVer basin, Lokchao stream, tributary of Yu RiVer ; holotype: MUMF 3044 )

Diagnosis. Acantopsis spectabilis differs from all other species of Acantopsis ( Table 4) by combination of 3–4 black spots along upper lobe, 2–3 larger, often darker, black spots on lower lobe of caudal fin (smaller black spots in middle of fin); 1–2 bands on anal and paired fins; 2–3 pairs of labial barbels, 9½ branched dorsal rays; 10 pectoral rays; 9–12 dark saddles along dorsal midline; 9–15 black spots along side of body; 2–3 rows of large dark spots on side of head, 43–44 total vertebrae, body depth 9.0–11.6% SL, body width 6.8–9.4% SL, caudal-peduncle length 12.9–16.6% SL.

Comparisons. The unique color pattern on caudal fin distinguishes A. spectabilis from all other species of Acantopsis . It is most similar to A. thiemmedhi , which differs in having 1 large black blotch on each lobe of caudal fin. All other species of Acantopsis have no or dusky bands on caudal fin. It further differs from A. thiemmedhi by having 2–3 (vs. 1) pairs of labial barbels and in having usually 9½ (vs. 10½) branched dorsal rays and in lacking large black blotch on tip of anterior rays of dorsal fin. It further differs from A. dinema by having dark large spots on side of head, no row of black specks beneath midlateral row of black spots, usually 9½ (vs. 10½) branched dorsal rays, smaller body depth (9.0–11.6 vs. 12.0–14.5% SL). It further differs from A. rungthipae and A. ioa by having 2–3 (vs. 0) pairs of labial barbels, from A. rungthipae in lacking distinct small black spot on upper margin of caudal-fin base, and from A. ioa in having 9–12 (vs. 15–23) dark saddles along dorsal midline, 9–15 (vs. 13–21) black spots along side of body, large dark spots on side of head, 43–44 (vs. 46–48) total vertebrae. It further differs from A. dialuzona by lacking a well developed ocellus on the upper margin of the caudal-fin base and having usually 9½ (vs. 10½) branched dorsal rays.

Description. As in description of genus; Tables 1, 2, 4. Head long (21.8–25.7% SL); snout long (60.1–70.3% HL); 2–3 pairs of labial barbels; 9½, rarely 8½, branched dorsal rays; 10, rarely 11, pectoral rays; 31–32 abdominal + 12 caudal = 43–44 total vertebrae (N=3). Maximum SL = 212.5 mm, TL = 242.5 mm (NIFI 2456).

Color. Dark spots in 1 row on top of head, scattered or in 2–3 rows on side of head. Black line from eye to tip of snout. Nine–12 dark saddles along dorsal midline; 9–15 dark spots or blotches along to slightly below lateral line from head to caudal fin, varying from large and rounded to flattened and elongate; dark spots and blotches on upper side of body, none on lower side. Two–3 bold, irregular bands of blotches on caudal fin, darkest at extremity of lower lobe and along margins. One–2 dark bands on anal and paired fins. Small black spot near tip of anterior rays of dorsal fin. No small black spot or ocellus near upper margin of caudal-fin origin.

Distribution. Acantopsis spectabilis is known from the Irrawaddy River basin of Myanmar and India, the Salween River basin of Thailand and Myanmar, and the Tenasserim provinces region (Dawei River, and presumably the Ataran River basin) of Myanmar ( Fig. 10 ).

Figures

FIGURE 9. Acantopsis spectabilis. (A) Lateral and dorsal VieWs, CAS 238298, 163.0 mm SL. (B) Lateral VieWs, CAS 88783, 112.9 mm SL and 56.2 mm SL.

FIGURE 10. Localities of specimens examined of Acantopsis spectabilis, including the type locality of A. multistigmatus.