Acantopsis dialuzona van Hasselt, 1823

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 : 163-167

Acantopsis dialuzona van Hasselt, 1823

Piglet Horseface Loach

( Fig. 6 )

Acantopsis Dialuzona Van Hasselt, 1823: 133 (type locality: Indonesia: JaVa: BataVia [present-day Jakarta]; syntypes: RMNH 2707 [1]; unpublished Van Hasselt's figure reproduced in Roberts, 1993: fig. 25)

Acanthopsis biaculeata Rüppell, 1852:28 (nomen nudum, Kottelat 2012)

Cobitis choirorhynchos Bleeker, 1854:95 . (type locality: Indonesia: Sumatra: Palembang: at confluence of Lematang and Enim RiVers; lectotype: RMNH 4977, designated by Alfred 1961a:33)

Cobitis macrorhynchos Bleeker, 1854:95 (unnecessary replacement name for Acantopsis dialuzona Van Hasselt, 1823: 133 )

Diagnosis. Acantopsis dialuzona differs from all other species of Acantopsis ( Table 4) by combination of usually 3 pairs of labial barbels, well developed ocellus on upper margin of caudal-fin base, 0–1 row of large spots on side of head, no large black spots on dorsal or caudal fins, rarely black specks beneath midlateral row of black spots, usually 10½ branched dorsal rays and 10 pectoral rays, 11–17 dark saddles along dorsal midline, 7–13 black spots along side of body, 42–43 total vertebrae, body depth 8.9–11.9% SL, body width 6.4–9.1% SL, caudal-peduncle length 12.5–16.2% SL.

Comparisons. Acantopsis dialuzona is distinguished from all species of Acantopsis by having a well developed ocellus on the upper margin of the caudal-fin base, and from all species except A. spectabilis by having 3 (vs. 0–2) pairs of labial barbels. Acantopsis dialuzona differs from A. spectabilis and A. thiemmedhi in lacking conspicuous black spots, blotches, or bands on the caudal, anal, and paired fins, and from A. thiemmedhi in lacking a large black blotch on the tip of the anterior rays of the dorsal fin. It further differs from A. dinema in having large black spots on side of head, a less deep body (8.9–11.9 vs. 12.0–14.5), and lacking many black specks beneath midlateral row of black spots. It further differs from A. spectabilis , A. rungthipae , and A. ioa by having usually 10½ (vs. 9½) branched dorsal rays, from A. ioa by having 42–43 (vs. 46–48) total vertebrae, and from A. octoactinotos by having usually 10½ (vs. 8½) branched dorsal rays, usually 10 (vs. 9) pectoral rays, large dark spots on side of head.

Description. As in description of genus; Tables 1, 2, 4. Head long (22.9–29.7% SL); snout long (59.5–71.8% HL); 3, rarely 0–2, pairs of labial barbels; 10½, rarely 9½ or 11½, branched dorsal rays; 10, rarely 9 or 11, pectoral rays; 28–31 abdominal + 11–14 caudal = 42–44 total vertebrae ( Table 1; Roberts 1989, 1993). Maximum SL = 183.6 mm, TL = 221.8 mm (UF 235414).

Color. Dark spots in 1 or 2 rows on top of head, scattered or in 1 poorly defined row on side of head. Eleven– 17 dark saddles along dorsal midline; 7–13 large dark spots or blotches along lateral line from head to caudal fin; dark spots or reticulations on upper side of body. Dark pigment on lower side highly variable; usually absent, but rarely with many dark specks. Four–5 faint bands on dorsal and caudal fins; other fins with no or faint bands; caudal fin sometimes with dark lower margin. Bold black spot in center of ocellus near upper margin of caudal-fin origin.

Bleeker (1860) described A. dialuzona as having irregular, diffuse, violet-colored spots in a longitudinal row or more or less united into a stripe along the side of the body, a small black spot at the upper edge of the caudal-fin base; and 3–4 dusky bands on the caudal fin.

Distribution. Acantopsis dialuzona occurs in Java, Borneo, Sumatra, and the Malay Peninsula as far north as southern Thailand ( Fig. 7 ). This distribution primarily encompasses the Southern Sumatra-Western Java and Malay Peninsula Eastern Slope ecoregions of Abell et al. (2008). It has been reported from areas of Southeast Asia outside its range, including as A. choirorhynchos (e.g., Seibert 1991b, Sontirat 1999, and Vishwanath and Laisram 2005), because of the lack of taxonomic resolution in Acantopsis .

Remarks. Cobitis choirorhynchos , treated by Kottelat (2012) and here as a synonym of A. dialuzona , was described by Bleeker (1854) based on three specimens 170–178 mm in total length from Sumatra. Alfred (1961a) re-examined these specimens and designated a lectotype (RMNH 4977, Fig. 8 ) with a total length of 166 mm and SL of 142 mm (the shorter TL recorded by Alfred is presumably due to shrinkage). A more detailed description of C. choirorhynchos by Bleeker (1860) is reproduced in English in van Oijen and Loots (2012:75–76, fig. 3) along with an illustration from the “Atlas Ichthyologique” ( Bleeker 1863 –1864). The only characters used by Bleeker (1854, 1860) to distinguish C. choirorhynchos from A. dialuzona was a slightly longer head, going 4⅔ to slightly more than 5 times in length of the body vs. 5 to 5⅓ times in A. dialuzona ; dark spots on the head, back, and side of the body vs. no dark spots on head and back; and anal fin with 5–6 rays vs. 6–7 rays. Head length increases with standard length, and the proportionally longer head in the type of C. choirorhynchos is a function of the fact that the type of C. choirorhynchos is larger than the type of A. dialuzona ( Fig. 3 ). Presence/absence of dark pigment on the back and side of the body is highly variable and likely related to water clarity and the color of the substrate on which specimens were collected.

Figures

FIGURE 3. Snout length / head length relatiVe to standard length in (A) Acantopsis dialuzona (Y = 0.141 X + 51.887; r 2 = 0.813), and (B) A. rungthipae (Y = 0.136 X + 49.056, r 2 = 0.722). Dots represent specimens measured. RMNH 2707 is the Value for the syntype of Acantopsis dialuzona, and RMNH 4977 is the Value for the lectotype of Cobitis choirorhynchos.

FIGURE 6. Acantopsis dialuzona. (A) Lateral VieW, syntype, RMNH 2707, 96.2 mm SL. (B) Lateral and dorsal VieWs, UF 235416, 120.5 mm SL. (C) Lateral VieW, UF 166886, 93.6 mm SL. (D) LiVe VieW, UF 236150, 73.7 mm SL.

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

FIGURE 8. Lectotype of Cobitis choirorhynchos, RMNH 4977, 139.2 mm SL.