Lasiancistrus volcanensis Dahl, 1942

Poveda-Cuellar, José Luis, Conde-Saldaña, Cristhian Camilo, Villa-Navarro, Francisco Antonio, Lujan, Nathan K. & Santos, Jorge Abdala Dergam dos, 2023, Phylogenetic revision of whisker-cheeked suckermouth catfishes (Loricariidae: Lasiancistrus) from east of the Andes: five species where once there were two, Zoological Journal of the Linnean Society 199 (3), pp. 688-712 : 706-707

Lasiancistrus volcanensis Dahl, 1942

( Fig. 9 ; Tables 4 and 5 )

Lasiancistrus volcanensis Dahl, 1942: 83 (type locality: Volcán River near its confluence with San Bartolomé River , less-bank tributary of Magdalena River between Nare and Ité rivers, Remedios Municipality, Antioquia Department, Colombia; holotype unique: ZMUL L936 /3702). Ferraris (2007: 264): remarks on holotype deposited at ZMUL.

Diagnosis: Lasiancistrus volcanensis differs from all trans-Andean congeners except L. guacharote by having the dorsal rim of the orbit co-equal with the interorbital space (vs. dorsal rim of orbit slightly elevated above interorbital space), abdominal region rectangular (vs. pyriform; Fig. 6 ) and eight ribs (vs. seven ribs), and from L. guacharote by lacking abdominal plates (vs. abdomen with patch of plates medial to pectoral-fin spine insertion). Moreover, L. volcanensis differs from L. mayoloi by having the head with a dark brown reticulated colour paưern (vs. head with small light brown spots) and the snout rounded (vs. acute; Fig. 5 ), from L. caucanus by having the suture between the parieto-supraoccipital and compound pterotic concave (vs. straight; Fig. 5 ), from L. wiwa by having the parieto-supraoccipital posterior margin posteromedially projected (vs. not posteromedially projected; Fig. 5 ) and the posterior margin of urohyal rounded (vs. V-shaped; Fig. 7 ).

Description: Morphometrics are provided in Table 4 , meristics in Table 5 . Abdomen naked; some specimens with one plate located medial to insertion of pectoral-fin spines. Body broadest anteriorly, narrow (depressed), with greatest body width at cleithrum. Dorsal profile gently ascending from snout to supraoccipital, flat to dorsal fin, gently descending in a straight line to dorsal procurrent caudal-fin rays, then slightly ascending to dorsal caudal-fin insertion. Body depth greatest at dorsal-fin origin. Ventral profile flat from snout to base of caudal-fin insertion. Robust caudal peduncle, almost triangular in cross-section: flaưened ventrally, with flaưened flanks converging to slightly acute dorsum.

Twenty-four median plates (mode = 24); three predorsal plates; six plates along dorsal-fin base; seven plates between dorsal and adipose fins; five plates between adipose and caudal fins; 10 or 11 plates between anal and caudal fins (mode = 10); three horizontal series of lateral plates on caudal peduncle. Parieto-supraoccipital level with nuchal region. Nuchal plate small and curved posterolaterally. Snout slightly rounded. Eye small (orbit diameter 17.3 ± 1.1% of head length); dorsal rim of orbit level with interorbital space. Interorbital space flat. Iris operculum present. Frontals, infraorbital, nasals, opercles, pterotics, sphenotics and supraoccipital supporting odontodes. Cheek odontodes occasionally moderately hypertrophied, robust and sharp (mode = 21, N = 49).

Whisker-like odontodes present among cheek odontodes and occasionally at the anterolateral corner of the snout and oriented ~90° from head. Distal pectoral-fin spine odontodes slightly hypertrophied. Odontodes on lateral plates not enlarged to form keels. Lips covered with minute hemispherical papillae; papillae larger near mouth. Lower lip wide, reaching almost to pectoral girdle; upper lip narrow. Maxillary barbel short, not reaching gill opening. Teeth bicuspid; 39–76 less dentary teeth (mode = 70); 39–72 less premaxillary teeth (mode = 56).

Dorsal-fin origin positioned slightly anterior to vertical through pelvic-fin insertion. Dorsal-fin spine shorter than snout length; last dorsal-fin ray reaching first or second preadipose plate when depressed. Adipose-fin spine curved, stout, not embedded; membrane present and easily visible beneath spine. Pectoral-fin spine reaching almost one-third length of pelvic fin when adpressed; pectoral-fin spine reaching middle of pelvic fin in larger specimens. Pelvic-fin spine reaching to middle of anal fin when adpressed. Unbranched anal-fin ray slightly shorter than first branched ray. Caudal fin slightly forked; ventral lobe longer than dorsal lobe. Tiny odontodes present on body plates. All fin spines with small odontodes, more developed on first two pelvic-fin rays in larger males. All fin rays with tiny odontodes. Dorsal fin i,7; caudal fin i,14,i; pectoral fin i,6; pelvic fin i,5; anal fin i,5. Twenty-six vertebrae (N = 4). Eight ribs (N = 4).

Coloration in life: Head and body with light brown base colour; head with darker moưling, wavy lines and reticulations; body flanks with darker transverse saddles and moưling. Abdomen uniformly light brown.All fins with darker brown bands.Adipose fin uniformly light brown.

Coloration in alcohol: As in life but faded, with less distinct paưerning.

Distribution: Lasiancistrus volcanensis is distributed across tributaries of the middle and upper Magdalena River basin and lower Cauca River basin in Colombia. These include Volcán Creek (type locality), La Tebaida Creek, Samaná River, Nare River, Guarinó River, Santo Domingo Creek, Gualanday Creek, Alvarado River, Cunday River and Suaza River ( Fig. 1 ).

Comments: Lasiancistrus volcanensis was found to be a synonym of L. caucanus by Armbruster (2005); however, that study examined only a single specimen from the Magdalena River basin. Here, both L. caucanus and L. volcanensis are treated as valid, allopatrically distributed species, with L. caucanus being restricted to the upper Cauca River basin and L. volcanensis being restricted to the lower Cauca River basin and most of the Magdalena River basin. In addition to morphological characters described above, COI sequence divergence> 3.5% supports the recognition of L. caucanus and L. volcanensis as distinct species.

Material examined: Colombia, upper Magdalena River drainage, Tolima Department: CZUTIC 82, nine individuals, 16.7–83.6 mm SL, Gualanday Creek , 4°18 ʹ 18.0 ″ N, 75°02 ʹ 16.0 ″ W ; CZUTIC 1889, four,18.6–78.3 mmSL, AlvaradoRiver , 4°31 ʹ 14.0 ″ N, 74°59 ʹ 16.0 ″ W ; CZUTIC 5898 (c&s), 10, 16.7–83.6 mm SL, Santo Domingo Creek , 5°00 ʹ 13.0 ″ N, 74°54 ʹ 14.0 ″ W ; CZUTIC 10763, five, 21.3–74.6 mm SL, Alvarado River , 4°31 ʹ 11.0 ″ N, 74°59 ʹ 14.0 ″ W . Huila Department: CZUTIC 13202, five, 35.1–48.6 mm SL, Suaza River , 2°10 ʹ 03.0 ″ N, 75°40 ʹ 02.0 ″ W ; CZUTIC 13206, five, 44.7–101.9 mm SL, Suaza River , 2°10 ʹ 03.0 ″ N, 75°40 ʹ 02.0 ″ W ; CZUTIC 13185, four, 35.1–48.6 mm SL, Suaza River , 2°10 ʹ 03.0 ″ N, 75°40 ʹ 02.0 ″ W . Middle Magdalena River drainage, Antioquia Department: ZMUL L936 /3702 (ph, xr), one, 82.4 mm SL, holotype (unique), Volcán River .

Figures

Figure 1. Geographical distributions of trans-Andean species of Lasiancistrus individuals and species examined in this study. Key:purple stars, Lasiancistrus caucanus; orange triangles, Lasiancistrus guacharote; green circles, Lasiancistrus mayoloi; red diamonds, Lasiancistrus volcanensis; yellow squares, Lasiancistrus wiwa.

Figure 5. Dorsal view of anterior portion of body.A, Lasiancistrus caucanus, CZUTIC12434, 98.83 mm standard length (SL). B, Lasiancistrus volcanensis, CZUTIC5898, 83.59 mm SL. C, Lasiancistrus mayoloi, CZUTIC21345, 91.68 mm SL.D, Lasiancistrus wiwa, CZUTIC17449, 79.55 mm SL. Abbreviations: F, frontal; PT, compound pterotic; SO, parieto-supraoccipital; SP, sphenotic. Scale bars:10 mm.

Figure 6. Ventral view of abdominal region.A, Lasiancistrus caucanus, CZUT-IC 12434, 98.83 mm standard length (SL). B, Lasiancistrus volcanensis, CZUT-IC 5898, 83.59 mm SL.C, Lasiancistrus mayoloi, CZUT-IC 21345, 91.68 mm SL. D, Lasiancistrus wiwa, CZUT-IC 17449, 79.55 mm SL. Scale bars: 1 mm.

Figure 7. Urohyal (UH) and hypohyals (HH) in ventral view. A, Lasiancistrus wiwa, CZUTIC17449, 79.55 mm standard length (SL). B, Lasiancistrus caucanus, CZUTIC12434, 98.83 mm SL. C, Lasiancistrus volcanensis, CZUTIC5898, 83.59 mm SL. D, Lasiancistrus mayoloi, CZUTIC21345, 91.68 mm SL. Scale bar: 1 mm.

Figure 9. Lasiancistrus volcanensis Dahl, 1942, 12.5 mm standard length, from ºuebrada Gualanday, tributary of Coello river, Upper Magdalena River basin.Scale bar:10 mm.Photographs by Jorge Garcia Melo.