Ancistrus chagresi Eigenmann & Eigenmann 1889

Taphorn, Donald C., Armbruster, Jonathan W., Villa-Navarro, Francisco & Ray, C. Keith, 2013, Trans-Andean Ancistrus (Siluriformes: Loricariidae), Zootaxa 3641 (4), pp. 343-370 : 354-357

Ancistrus chagresi Eigenmann & Eigenmann 1889

( Fig. 7 ).

Images of syntypes MCZ 8026 available at the All Catfish Species Inventory website: http://acsi.acnatsci.org/base/image_list.html?mode=genus&genus= Ancistrus

Ancistrus (Hypostomus) cirrhosus (non Valenciennes), Kner & Steindachner 1864:61, one male specimen reported from Río Chagres, misidentification.

Chaetostomus cirrhosus, Günther 1867:478 , listed for Río Chagres, misidentification.

Ancistrus chagresi, Eigenmann & Eigenmann 1889: 47 . Type locality: Río Chagres, Panama [a drainage of the northeastern Caribbean slope of Panama]. Syntypes: MCZ 8026 (2). Eigenmann 1905 lists from only Caribbean slopes of Panama; Meek & Hildebrand 1916, lists from Río Chagres Basin and Río Chorrera, Pacific slope, Panama; Eigenmann 1922, lists from both slopes of Panama; Kramer and Graham 1976, air breathing; Graham 1997, air breathing; Hildebrand 1938, reports from both slopes of central Panama; Evans 1952, behavior and color notes. Smith & Bermingham 2005, list in table.

Xenocara chagresi, Regan 1904, 1905 , 1906, 1908, Río Chagres.

Ancistrus spinosus, Power 1983, 1984a , b, c, ecology, misidentification.

Diagnosis. Ancistrus chagresi can be diagnosed from the potentially sympatric A. centrolepis by having white spots on the dorsum, sides, ventrum and fins (vs. usually plain black, brown, or dark gray, but sometimes has black spots on the dorsum, sides or ventrum) by the presence of moderately enlarged odontodes along posterior edge of plates only (vs. one to three rows of greatly enlarged odontodes); and by a pectoral-fin spine length/dorsal-adipose distance ratio of 1.2%–1.9% (vs. 1.9%–3.7% in all specimens of A. centrolepis examined except one, which is 1.4%) Fig. 3 D. Ancistrus chagresi can be diagnosed from other white-spotted trans-Andean Ancistrus by having well-developed white spots on the caudal fin in life (vs. dark spots; white spots are often faded on A. chagresi , but dark spots on the other species always present); 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); from A. tolima by having the adipose-fin spine at a 45° to the dorsum (vs. adnate).

Description. N = 30. Morphometric data in Table 3 . Size range in this study: 51–171 mm SL, maximum length: 195 mm SL (Fisch-Muller 2003).

A. chagresi (n=30) A. martini (n=48) Body anteriorly broad, widest in region posterior to pectoral-fin insertions. Body somewhat depressed, deepest at or just anterior to dorsal-fin origin. Caudal peduncle posteriorly compressed. Dorsal profile of head and body convex from tip of snout tip to dorsal-fin origin, from there, gently convex and sloping gradually down to just posterior to tip of adipose-fin spine, flat to tip of adipose spine then angled dorsally ~45o to caudal fin. Ventral profile flat to caudal peduncle, then sloping gently ventrally towards caudal fin.

Head broad, interorbital width about equal to depth of body. Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length greater than one-half head length. Eye large, upper margin of orbit not protruding from dorsal profile of head. Oral disk ovate, 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 straight, about same size as premaxillary tooth row. Teeth numerous (60–140 per jaw ramus), slender, 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. Hypertrophied cheek odontodes strongly evertible, seven to 18 odontodes of various lengths hooked anteriorly bases encased in thick fleshy sheaths. Head smooth, bones on back of head not carinate. Ventral surface of head and abdomen mostly naked, some specimens with small platelets covered with odontodes near base of pectoral-fin spine. Nuchal plate small and curved posterolaterally. No enlarged odontodes at edge of lateral plates. Five series of lateral plates anteriorly, three series on caudal peduncle, middorsal and mid-ventral plate series end on caudal peduncle beneath adipose fin. Last plate in median series slightly smaller than penultimate plate, base of caudal fin with about four small platelets after main series, then 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 elongate, just slightly longer than snout length; last dorsal-fin ray usually not reaching adipose fin when depressed. Dorsal fin moderately elevated; dorsal-fin base length greater than dorsal-adipose distance. Adipose fin with stout spine and well developed adnate membrane that adheres to plate just anterior to first procurrent caudal-fin ray. Pectoral fins reaching past base of pelvic fins, but failing to reach the middle of these fins, the spine notably shorter than head. Anal fin small, its origin posterior to vertical through base of last ray of dorsal. Pelvic fins reaching well past anal-fin origin, inserted posterior to vertical through first branched dorsalfin ray. Caudal fin with straight oblique or slightly concave margin, the lower rays the 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. Abdomen without exposed platelets anterior to anal-fin spine.

Mid-dorsal plates 18(10), 19(6), 20(8), 21(3); median plates 23(9), 24(18); mid-ventral plates 18(9), 19(10), 20(3), 21(5); plates bordering dorsal-fin base 6(6), 7(14), 8(7); plates between dorsal and adipose fins 5(5), 6(9), 7(12), 8(1); preadipose plates: 1(26), 2(1). Fin-ray formulae (N=27): dorsal i,7; pectoral i,6; pelvic i,5; anal i,3(2) i,4 (25); caudal i,14,i. Caudal procurrent spines: dorsal: 4(4), 5(23), ventral: 3(8), 4(19).

Color in alcohol. ( Fig. 7 ) The syntypes (MCZ 8026) are now completely depigmented. Some preserved specimens are uniformly dark on dorsum, but many still have light spots visible over dark background. Flanks dark with large, light rounded spots. Abdomen tan or brown with light spots which vary in size, shape and number among individuals. Fins brownish with distinct light spots. In newer material, dorsal, caudal, pelvic and pectoral fins have dark spots on spine and fin rays. Pale spots observed in preserved specimens said to be light green in life (Meek & Hildebrand 1916, Hildebrand 1938), but specimens collected by JWA were white. Smaller individuals may have four or five lighter tan saddles.

Distribution. Central America on both slopes of Central Panama ( Fig. 4 ). Along the Caribbean slope it has been found in the Chagres and Gatun River basins. On the Pacific side it is known only from the Chorrera River drainage (also called Caimito River on modern maps), just west of Panama City. Its current distribution has been affected by the construction of the Panama Canal. This species has penetrated further into Central America than any other Ancistrus .

Remarks. This species was named for the Chagres River (Caribbean Sea drainage) of north central Panama, which was largely impounded to form the Panama Canal.

Figures

FIGURE 3. Diagnostic biplots for species of Ancistrus.

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

FIGURE 7. Ancistrus chagresi, AUM 32114, 73.3 mm SL, Río Frijoles, tributary of Río Chagres, Panama (type locality).

Tables

TABLE 3. Selected morphometrics of Ancistrus chagresi and A. martini.

	A. chagresi (n=30)	A. martini (n=48)
	Mean SD Range	Mean SD Range
SL (mm)	95.7 50.5–170.7	61.1 44.0–110.8
%SL
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