Acantopsis octoactinotos Siebert, 1991

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 : 170-171

Acantopsis octoactinotos Siebert, 1991

Dwarf Horseface Loach ( Fig. 11 )

Acantopsis octoactinotos Siebert, 1991b: 910 , fig. 2 (type locality: Malaysia: Borneo: Sabah: Kinabatangan District: tributary of Kinabatangan RiVer in loWlands near Deramakot RiVer , approx. 5°18'N 117°33'E; holotype: FMNH 68148 )

Diagnosis. Acantopsis octoactinotos differs from all other species of Acantopsis ( Table 4) by having usually 8½ branched dorsal rays. It also differs by combination of 2 pairs of labial barbels, black spot on upper margin of caudal-fin base, no black spot on tip of anterior rays of dorsal fin, no large dark spots on side of head, no row of black specks beneath midlateral row of black spots, usually 9 pectoral rays, 11–17 dark saddles along dorsal midline, 8–13 large dark spots along side of body, 40–44 total vertebrae, body depth 9.6–11.2% SL, body width 6.8–7.9% SL, caudal-peduncle length 16.1–17.2% SL.

Comparisons. Acantopsis octoactinotos is distinguished from all other species of Acantopsis by having 8½ (vs. 9½ or 10½) branched dorsal rays, and all species except A. dinema by lacking large dark spots on side of head. It differs from A. dialuzona , A. spectabilis , A. rungthipae , and A. ioa in having 9 (vs. 10) pectoral rays, and from A. spectabilis and A. thiemmedhi in having black spot on upper margin of caudal-fin base and no conspicuous black spots, blotches, or bands on caudal fin. It further differs from A. thiemmedhi in lacking large black blotch on tip of anterior rays of dorsal fin, and in having 2 (vs. 1) pairs of labial barbels, 11–17 (vs. 7–9) dark saddles along dorsal midline, longer caudal-peduncle 16.1–17.2 vs. 12.5–14.7% SL. It further differs from A. rungthipae in having 2 (vs. 0) pairs of labial barbels; from A. ioa in having 2 (vs. 0) pairs of labial barbels, 8–13 (vs. 13–21) dark spots along side of body, 40–44 (vs. 46–48) total vertebrae; and from A. dinema in having a small black spot on upper margin of caudal-fin base, no row of black specks beneath midlateral row of black spots, smaller body depth 9.6– 11.2 vs. 12.0–14.5% SL, longer caudal-peduncle 16.1–17.2 vs. 12.1–14.3% SL.

Description. As in description of genus; Tables 1, 2, 4. Head long (22.5–24.6% SL); snout long (53.7–58.4% HL); 2 pairs of labial barbels; 8½ (rarely 7 or 9; Siebert 1991b) branched dorsal rays; 9, rarely 10, pectoral rays; 28–29 abdominal + 12–13 caudal = 41–42 total vertebrae ( Table 1); Siebert (1991b) reported 40–44 total vertebrae. Maximum SL = 96.0 mm (FMNH 68150, caudal fin damaged).

Color. Dark spots in 1– 2 rows on top of head; no large dark spots on side of head. Black line from eye to tip of snout. Eleven–17 dark saddles along dorsal midline to origin of caudal fin; 8–13 dark spots or blotches along lateral line from head to caudal fin; small dark spots and reticulations on upper side of body; no dark spots on lower side of body below midlateral row of dark spots. Dorsal and caudal fins without bands; no dark margins on caudal fin. Small bold black spot near upper margin of caudal-fin origin; faint black spot on lower margin of caudal-fin origin. Inger and Chin (1962) reported pale yellowish coloration in live A. octoactinotos .

Sexual dimorphism. Males have a longer, ramified first branched pectoral-fin ray ( Siebert 1991b).

Distribution. Acantopsis octoactinotos is known from the Kinabatangan River and Segama River (Martin- Smith and Tan 1998) basins, Sabah, Malaysia ( Fig. 7 ).

Figures

FIGURE 7. Localities of specimens examined of Acantopsis dialuzona, including type locality of Cobitis choirorhynchos, and A. octoactinotos.

FIGURE 11. Acantopsis octoactinotos. Lateral and dorsal VieWs, FMNH 68150, 72.3 mm SL.