Ancistrus amaris, De & Taphorn & Armbruster, 2019

De, Lesley S., Taphorn, Donald C. & Armbruster, Jonathan W., 2019, Review of Ancistrus (Siluriformes: Loricariidae) from the northwestern Guiana Shield, Orinoco Andes, and adjacent basins with description of six new species, Zootaxa 4552 (1), pp. 1-67 : 9-14

Ancistrus amaris new species

( Fig. 6 )

Holotype. MCNG 56679 (1, 103.4 mm SL) Venezuela, Estado Portuguesa, Orinoco/ Apure drainage, río Las Marías , 9.402778, -69.7375, J. Alexander, G. Galbreath, A. Seitz, H. López-Fernández, 19-Feb-1998.

Paratypes. All from Orinoco / Apure River Basin , Venezuela. AUM 71043 (2, 63.2–75.2) and MCNG 5280 (2, 64.9–66.1 mm SL) Estado Portuguesa, río Boconó , 9.052778, -70.094444, 2-June-1983, D. Taphorn ; CUMV uncataloged (2, 115.9–107.4) and MCNG 28904 (3, 93.3–115.7 mm SL), Estado Barinas, río La Yuca , 8.766667, -70.25, 31-Dec-1993, D. Taphorn; AUM 71044 (2, 102.0– 106.7 mm SL) and MCNG 41858 (1, 114.9 mm SL) same data as holotype ; MCNG 51925 (1, 71.2 mm SL), Estado Barinas, río Masparro , 8.844651, -70.083963, 23- Jan-2005, D. Taphorn ; INHS 27991 (2, 46.0– 113.5 mm SL), Estado Barinas, río Michay, La Esmeralda at Hwy. 5, 8.161762, -70.870009, 7-Jan-1992, L.Page, B. Burr, P.Ceas, C.Taylor, S. Walsh & A. Barbarino ; INHS 31835 (1, 69.9 mm SL) Estado Barinas, río Masparro and río La Yuca ( Masparro ) 14 km NE of Barinas, 8.77056, -70.25833 31-Dec-1993, D. Taphorn, L. Page, K.Cummings, C.Mayer, J. Armbruster, C. Laird, M.Sabaj, C. Johnston, S. Phelps & G. Mottesi ; INHS 31858 (2, 105.1– 106.4 mm SL) Estado Barinas, río La Yuca ( Masparro River drainage) 17 km NE of city of Barinas, 8.46, -70.15, 31-Dec-1993, D. Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps & G. Mottesi ; INHS 61274 (1, 77.0 mm SL) Estado Barinas, río Santa Bárbara 3 km NE Santa Barbara, 7.83567, -71.18567, 7-Jan-1992, L. Page, B. Burr, P. Ceas, C. Taylor, S. Walsh & A. Barbarino-Duque .

Diagnosis. Ancistrus amaris differs from all other Ancistrus in the region by having males with very short tentacles that are all smaller than orbit diameter (vs. some larger than orbit diameter) and from all except A. patronus and a few specimens of A. triradiatus from the Río Orotoy by having very long dentaries (dentary length/ cleithral width 23.8–28.4% in specimens greater than 69 mm SL and minimal interorbital width divided by dentary length less than 2.1 vs. usually greater than 2.1 but less than 23.7%; a few specimens overlap, but they do so because their bodies are narrow and not because their jaws are long). Several described species from the southern Andean piedmont upper Amazon River Basin tributaries also have long jaws, and A. amaris differs from these ( A. bolivianus ( Steindachner 1915) , A. bufonius ( Valenciennes 1840) , A. greeni ( Isbrücker 2001) , A. heterorhynchus ( Regan 1912) , A. marcapatae ( Regan 1904) , A. megalostomus Pearson 1924 , A. occloi Eigenmann 1928 (in Myers 1928), A. sericeus ( Cope 1872) , and perhaps A. jelksii (Steindachner 1876)) by having the dorsal fin reaching the preadipose plate (vs. well short), by having the pectoral-fin spine when adpressed below pelvic fin reaching beyond the pelvic-fin base (vs. barely or not reaching pelvic fin), and by having the body relatively deep (vs. very depressed). Ancistrus amaris differs from the other long-jawed Ancistrus from rivers of the Guiana Shield ( A. yutajae ) by the short snout tentacles mentioned above and by having large light spots and blotches on the body and fins (vs. with small white dots in unfaded specimens).

Description. Morphometrics in Table 1. A large sized Ancistrus , largest specimen examined 115.7 mm SL. Body broadest anteriorly, greatest body width at cleithra, then narrowing progressively to end of caudal peduncle. Head and body depressed, greatest body depth near posterior margin of supraoccipital. Caudal peduncle deep, compressed posteriorly. Dorsal profile of head ascending steeply to above eye, then ascending in convex arc to dorsal-fin origin. From the dorsal-fin origin descending straight or in slightly concave arc to caudal fin. Ventral profile flat from tip of snout to pelvic-fin insertions, from there, in concave arc to base of caudal fin.

Head wide, interorbital width equal or slightly less than head depth, slightly less than half of head length. Snout rounded with large broad naked margin in males, less wide in females and juveniles. Snout length more than one-half head length. Eye moderate in size, interorbital area convex. Oral disk round, just 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 very short, its length less than orbit diameter. Jaws long with premaxillary tooth rows forming gentle arc and dentary tooth rows forming angle of>135°. Dentary and premaxillary tooth rows slightly curved medially, most lateral dentary tooth lateral to most lateral premaxillary tooth. Teeth numerous (58–120 per jaw ramus), asymmetrically bifid, medial cusp larger and spatulate, lateral cusp smaller, pointed, usually not reaching more than half length of medial cusp but variable, almost equal in worn teeth. Hypertrophied cheek odontodes strongly evertible, nine to 17, stout with tips hooked anteriorly, bases encased in

thick fleshy sheaths. Exposed part of opercle small, roughly triangular with larger odontodes along free edge. Head without conspicuous ridges, bones on back of head not carinate; supraoccipital with margins between surrounding bones and plates usually clearly visible. Lateral plates not carinate, lateral line pores not easily visible except anteriorly.

Ventral surface of head and abdomen naked, no exposed platelets anterior to anal-fin spine. Nuchal plate small

and curved posterolaterally. Odontodes enlarged along edges of lateral plates. Five series of lateral plates anteriorly, three series on caudal peduncle, mid-dorsal plate series variable in length, often ending below third or fourth plate posterior to dorsal-fin base; mid-ventral plate series usually to preadipose plate or adipose spine. Last plate in median series about same size as penultimate plate, and median plate below end of adipose fin about twice as high as wide. Base of caudal fin with up to six small platelets covering bases of caudal-fin rays. Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray elongate, longer than snout length nearly as long as head; last dorsal-fin ray reaching first preadipose plate when depressed. Adipose-fin spine curved, stout, not embedded, oriented at angle to horizontal axis of body, membrane present, easily visible beneath spine. Pectoral spine long and stout, when adpressed ventrally reaching between posterior margin of pelvic-fin bases and the cloaca. Anal fin small but well developed; first anal-fin pterygiophore covered by skin, its origin well posterior to vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, about halfway out length of fin, inserted posterior to vertical through base of first branched dorsal-fin ray. Caudal fin truncate, lower lobe longer than upper. 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.

Meristics (N=20). mid-ventral plates 16– 19, x 18 ̃; median plates 22–24, x= ̃ 23; mid-dorsal plates 10–18, x =13; plates bordering dorsal-fin base four to eight, x= ̃seven; plates between dorsal and adipose fins four to eight, x= ̃seven; preadipose plates one to two, x= ̃one. Fin-ray formulae: dorsal II,7; pectoral I,6; pelvic i,5; anal i,3–4, x = i,4; caudal i,14,i. Caudal procurrent spines: dorsal: four to five, x= ̃five; ventral: three to four, x= ̃three.

Sexual dimorphism. Snout tentacles of nuptial males short, longest less than eye diameter. Posteromedial tentacles diverging in V- shape along anteriorly triangular snout plates. Naked areas of snout without tentacles not rugose, separated from naris by several wide plates.

Color in alcohol. ( Fig. 6 ) Dorsum of body base color light brown with medium-sized white spots on plateless area of snout, head and body. Males with relatively short tentacles on snout. Spines of dorsal, pectoral, pelvic, adipose and caudal fins with five or six alternating light and dark sections with similar markings mirrored on all fin rays, to form rows of dark and light spots. Spines of pectoral and pelvic fins darker overall. Ventral surface of head and abdomen tan to yellowish tan with no spots, oral disk yellow, plates on ventral surface of caudal peduncle with posterior margins dark brown, forming alternating light and dark pattern.

Life colors. Color in life unknown.

Distribution. Known from Andean piedmont streams of the Río Apure /Río Orinoco drainage of Venezuela ( Fig. 7 ).

Etymology. From the Latin maris for masculine or virile and the prefix a meaning without. In reference to the short tentacles in nuptial males.

Figures

FIGURE 6. Holotype of Ancistrus amaris in dorsal, lateral, and ventral views, MCNG 41858, 103.4 mm SL. Scale = 1 cm. Photos by J.W. Armbruster.

FIGURE 7. Distribution of species of Ancistrus from the northwestern Guiana Shield and neighboring regions.