Ancistrus centrolepis Regan 1913

Taphorn, Donald C., Armbruster, Jonathan W., Villa-Navarro, Francisco & Ray, C. Keith, 2013, Trans-Andean Ancistrus (Siluriformes: Loricariidae), Zootaxa 3641 (4), pp. 343-370 : 351-354

Ancistrus centrolepis Regan 1913

( Figs. 5 and 6 )

Images of syntype BMNH 1913.10.1.58 are available at the All Catfish Species Inventory website: http://acsi.acnatsci.org/base/image_list.html?mode=genus&genus= Ancistrus

Ancistrus centrolepis, Regan 1913:470 . Type locality: Colombia: Chocó, San Juan River. Syntypes: BMNH 1910.7.11.122 (1), 1913.10.1.58 (1). Eigenmann 1922 lists them from the Chocó region, Río San Juan and relegates A. melas Eigenmann 1916 to the synonymy of A. centrolepis . He also stated that A. spinosus might also prove to be a synonym of A. centrolepis .

Ancistrus melas, Eigenmann 1916: 83 . Type locality: Condoto [San Juan basin, Colombia]. Holotype: FMNH 58339 [ex CM 7335]; Isbrücker, 1980, 2001, 2002 (lists); Burgess 1989 (lists).

Ancistrus spinosus, Meek & Hildebrand, 1916:252 . Type locality: Río Calobre, tributary of the Río Bayano, Panama. Holotype FMNH 8942, length 135 mm (but specimen currently identified as holotype is 171 mm SL). Eigenmann 1922:87 western slopes of southern Panama, said it may prove to be a synonym of A. centrolepis Regan. Breder 1927:109 described five specimens from Río Chico, Pacific coast of Panama, and comments on growth and food. Smith & Bermingham 2005:1840, list in table. Ibarra & Stewart 1987 list in type catalog; Ferraris 2007; Meek & Hildebrand 1916; Isbrücker 1980; Burgess 1989; Isbrücker, 2001; Isbrücker, 2002; Fisch-Muller 2003; holotype said to be doubtful; Ferraris 2007 (lists).

Pristiancistrus eustictus, Fowler 1945: 121 , fig. 32. Type locality: Alto Río Baudó, Pacific slope at 914 masl, Colombia. Holotype: ANSP 71710. Isbrücker, 1980,2001, 2002 (list); Burgess 1989 (list); Fisch-Muller 2003 (list); Ferraris 2007 (list).

Ancistrus baudensis, Fowler 1945: 122 , fig. 34. Type locality: Alto Río Baudó, Pacific slope at 914 masl feet elevation, Colombia. Holotype: (unique) ANSP 71709. Isbrücker, 1980, 2001, 2002 (list); Burgess 1989 (list).

Diagnosis. Ancistrus centrolepis can be diagnosed from all other trans-Andean Ancistrus by the presence of one to three rows of greatly enlarged odontodes (some nearly equal to the width of the supporting plate) on the lateral plates (vs. odontodes enlarged only along the posterior margin of the plate, and never greater than half the width of the plates); and by having the body either entirely dark or lighter with dark spots (vs. white spots). Ancistrus centrolepis is further distinguished from the potentially sympatric A. chagresi by the pectoral-spine length/dorsaladipose distance: 1.90–3.68 vs. 1.24–1.90 ( Fig. 2 D); from A. galani by having fully developed eyes and pigment (vs. eyes reduced and pigment absent or reduced); from A. tolima and A. vericaucanus by usually having one preadipose plate (vs. 2 or more); and from A. tolima by having a well-developed, stout adipose-fin spine at a 45° to the dorsum (vs. adnate).

Description. N = 64. Size range this study: 54–187 mm SL. Morphometric data in Table 2 . Body anteriorly broad, robust, greatest body width between opercles and pectoral-fin origins, then narrowing progressively to end of caudal peduncle robust. Head and body somewhat depressed, greatest body depth between level of pectoral-fin insertions and dorsal-fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile of head and body convex from tip of snout tip to dorsal-fin origin, from there, gently concave and sloping gradually down to just posterior to tip of adipose-fin spine, then angled dorsally ~45° to caudal fin. Ventral profile flat from tip of snout to pelvic-fin insertions, abdomen slightly concave to pelvic-fin insertions, from there, straight and sloping gently ventrally towards caudal fin.

Head broad, interorbital width about equal to depth of head. Snout broadly rounded with large broad naked margin in males, less wide in females and juveniles. Snout length greater than one-half head length. Eye relatively large, dorsal margin of orbit not elevated above dorsal profile of head, interorbital area flat to slightly convex. Oral disk ovate, slightly wider than long. Lips covered with minute papillae, larger near mouth. Lower lip moderate in size, not reaching gill aperture, its border covered with very small papillae. Maxillary barbel short, its length less than orbit diameter. Dentary tooth row slightly curved, about same size as premaxillary tooth row. Teeth numerous (50–120), asymmetrically bifid, medial cusp much larger and spatulate, lateral cusp minute and pointed, usually not reaching more than half length of medial cusp, but equal in worn teeth. Premaxillary tooth cup about as long as that of dentary. Hypertrophied cheek odontodes five to 19, usually eight to 13, stout with tips hooked anteriorly, strongly evertible, bases encased in thick fleshy sheaths. Exposed part of opercle roughly triangular with short stout odontodes. Head smooth, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates usually clearly visible. Lateral plates not carinate.

Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small and curved posterolaterally. Lateral plates with the middle two or three series of enlarged odontodes, ending in quite strong odontodes at the posterior edge of each plate. Five series of lateral plates anteriorly, three on caudal peduncle, mid-dorsal and mid-ventral plate series ending near vertical through adipose-fin origin. Last plate in median series slightly smaller than penultimate plate, base of caudal fin with vertical column of about four small platelets after main series, and about eight roughly triangular platelets covering bases of caudal-fin rays.

Dorsal-fin origin situated anterior to vertical through pelvic-fin insertion. Dorsal fin variable in shape and length, its first ray not quite as long as head length; last dorsal-fin ray sometimes reaching adipose fin when depressed, sometimes not, as Eigenmann (1922) noted. Dorsal-fin base length greater than dorsal-adipose distance. Adipose fin large and very well developed, with stout spine projecting at 45o angle from body, adnate adipose-fin membrane that adheres to penultimate plate anterior to first procurrent caudal-fin ray. Pectoral spine elongate, reaching well past pelvic-fin insertions to anterior third to middle of pelvic fins. Anal fin well developed but short; base of first anal-fin pterygiophore covered by skin, its origin posterior to vertical through base of penultimate to last ray of dorsal fin. Pelvic fins reaching well past anal-fin origin, inserted posterior to vertical through first branched dorsal-fin ray. Caudal fin obliquely truncate, lower rays longest.

Tiny odontodes present on body plates, largest on posterior margins of plates. All fin spines with small odontodes, more developed in pectoral-fin spine of males. All fin rays with tiny odontodes on rays.

Mid-dorsal plates 17(2), 18(3), 19(19), 20(19), 21(20), 22(1); median plates 22(2), 23(51), 24(10), 25(1); midventral plates 17(2), 18(8), 19(23), 20(20), 21(10), 22(1); plates bordering dorsal-fin base 7(12), 8(51), 9(1); plates between dorsal and adipose fins 5(2), 6(51), 7(11); preadipose plates: 0(1), 1(61), 2(2). Fin-ray formulae: dorsal i,7; pectoral i,6; pelvic i,5; anal i,2(1) i,4 (63); caudal i,14,i. Caudal procurrent spines: dorsal: 3(1). 4(5), 5(58), ventral: 3(56), 4(6) 5(2).

Color in alcohol. Plain black, gray or dark brown, sometimes with darker spots. Degree of spotting or vermiculations varies among populations, and among individuals of same population. Specimens from Panama and Atrato River ( Fig. 6 ) have very few dark spots and those from Baudó River in Pacific Colombia most heavily spotted ( Fig. 5 ). Spots on fins more conspicuous than those on body in many specimens. Spots on the dorsal fin often consist of oblique dashes on membranes. See ‘Remarks’.

Distribution. Pacific drainages of southeast Panama (Bayano and Tuira river drainages) and Colombia (Chocó Region San Juan, Dagua, and Baudó rivers), and the Atrato River basin, which empties into the Caribbean Sea in northwest Colombia ( Fig. 4 ).

Remarks. Besides differences observed among specimens from different drainages, age, method and state of preservation also contribute to variability observed in pigmentation patterns that led to several species being described. For example, although Eigenmann (1916) described A. melas as uniformly blackish, the holotype today has faint dark spots on the abdomen. Fowler (1945) described two new species from the Baudó River, a small river which drains a coastal mountain range that lies between the San Juan River basin to the south (type locality of A. centrolepis ) and the Atrato River to the north where A. centrolepis is also present ( Fig 4 ). Fowler’s descriptions were mostly based upon differences in spotting: Pristiancistrus eustictus was the name erected for the more heavily spotted and spiny individuals and Ancistrus baudensis for the plain form. In collections with larger series of individuals, we find some fish are uniformly blackish, but others with obscure spots on the fins and sometimes the abdomen. Fishes from the Baudó River fish have a brown or gray base color, and are everywhere covered with dark spots that range from round to oblong, with some running together to form short lines. Specimens from the Atrato can be plain black, or dark with darker spotting ( Fig. 6 ).

Etymology. Although no explanation for the derivation of the name centrolepis was given in the original description we believe that this species was so named to call attention to the unusually spiny lateral plates, a notable feature of this species, and one that led Fowler (1945) to erect a distinct genus, Pristiancistrus for them. In Latin centrum means “a prickle or sharp point”, and lepis refers to the plates (Crane 2011).

Figures

FIGURE 2. Live coloration of Ancistrus caucanus, CP-UCO 1443, collected and photographed by Juan Guillermo Ospino Pabon from a creek, tributary to the Nare River, middle Magdalena River drainage, Município de San Rafael, Antioquia, 6.402694 º, - 74.921833 º, 694 masl.

FIGURE 4. Distributions of trans-Andean Ancistrus. Symbols may represent more than one collection. Open symbols indicate type localities.

FIGURE 5. Ancistrus centrolepis IMCN 1445 Río San Juan, Colombia (type locality).

FIGURE 6. Ancistrus centrolepis CIUA 227 in dorsal view from the Atrato River, a Caribbean drainage of northern Colombia; shows dark color phase.