Ancistrus nudiceps ( Müller & Troschel 1849 )

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 : 35-39

Ancistrus nudiceps ( Müller & Troschel 1849)

( Figs. 1 and 18 )

Hypostomus nudiceps Müller & Troschel, 1848: 631 . Type locality: dem Takutu, Britisch-Guiana. Holotype: ZMB 3180 .

Specimens examined. Guyana, Amazon River Basin: ANSP 185301 (1, 120.0 mm SL), Takutu River ca 2.75 km W of Saint Ignatius 3.35500, -21.30093, 5-Nov-2002, M. Sabaj, J. Armbruster, M. Thomas, D. Werneke, C. Allison, C. Chin, D. Arjoon, L. Atkinson; AUM 35628 (2, 93.8-113.5 mm SL), Takutu River ca. 2.75 km W Saint Ignatius, 3.35500, -59.83077, 5-Nov-02, J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, Atkinson; AUM 44666 (1, 118.2 mm SL), Pirara River, at Pirara Ranch, 3.62517, -59.67688, 26-Nov-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 44701 (5, 55.8-126.0 mm SL), Takutu River, near Lethem, 3.47043, -59.80993 27-Nov-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 47720 (2, 74.2-91.1 mm SL), Takutu River, rock beach; 3.47058, -59.80990 11-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 47793 (4, SL unrecorded) Takutu River, Garlic landing, beach N of Lethem, 3.42147, -59.81253, 17-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 48095 (1, 81.8 mm SL), Takutu River, N of Sand Creek; 2.95817, -59.95913 15-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 50795 (not measured), Takutu River, Tom’s beach, 3.41058, -59.81935, 11-Nov-200, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan. Guyana, Essequibo River Basin: ANSP 175917 (2, 54.5-55.3 mm SL), Stream effluent from Turtle Pond, 4.75417, -58.75333, 26-Jan-1997, W. Saul, N. Liley, G. Watkins, D. Torres, D. Allicock, E. McBirney, C. Watson; ANSP 177307 (1, 103.7 mm SL), Potaro/Siparuni River drainage, Pakatnu Falls Creek; 4.74972, -59.02694, 6-Dec-1997, W. Saul, N. Liley, G. Watkins, D. Torres, D. Allicock, E. McBirney, C. Watson; ANSP 39739 (1, 86.8 mm SL), Rupununi River, 3.29488, -59.34911 1911–1912, J. Ogilvie; AUM 35625 (3, 66.1-89.5 mm SL), Rupununi River 3.7 km SSE Massara, 3.86228, -59.28439 27-Oct-2002, J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, S. Mario; AUM 35627 (not measured) Stream 10.3 km NW Karanambo, 3.80758, -59.38490 28-Oct-2002, J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, M James; AUM 35623 (2), 81.8-138.4 mm SL), Rupununi River 4.6 km NW Massara, 3.92603, -59.28037, 26-Oct-2002, J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, M James; AUM 38929 (not measured), backwater and mainstem of Kuyuwini River 19.5 km W of Kuyuwini River mouth, 2.24098, -58.50093, 11-Nov-2003, J.W. Armbruster, M.H. Sabaj, M. Hardman, D. Arjoon, N.K. Lujan, L.S. de Souza; AUM 44511 (10, 48.0- 81.7 mm SL), Bununi Creek, 9.8 miles W of Massara, on the way to Toka, 3.86947, -59.43380, 25-Nov-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 45092 (1, 51.0 mm SL), Pond at Surama, 4.14845, -59.04015, 3-Dec-2005, L.S. de Souza, N.K. Lujan, D.C. Taphorn, J.A. Hartsell, E. Liverpool, S. Lord; AUM 47882 (2, 90.1-97.0mm Rupununi River at Kwatamang landing; 0 3.91798, -059.10053, 5-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 48397 Bununi Creek, 0.5 miles S of Massara, 3.87080, -59.31630, 7-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 49800 (1, 102.0 mm SL), Rupununi River at Massara Landing, 3.89500, -59.29370 6-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; AUM 50295 (not measured), Rupununi River at Kwaimatta landing, 3.84112, -59.30450, 7-Nov-2007, L.S. de Souza, D.C. Taphorn, J.N. Baskin, T. Geerinckx, J.L. Hwan; FMNH 53086 (1, 42.3 mm SL), Essequibo River at Gluck Island, 5.98303, -58.58174, 1908, C. Eigenmann; FMNH 53093 (1, 44.0 mm SL), Essequibo River at Gluck Island, 5.98303, -58.58174 1908, C. Eigenmann; FMNH 53144 (3, 53.5-83.9 mm SL), Essequibo /Rupununi Pan, 1908, C. Eigenmann; FMNH 53556 (1, 74.0 mm SL), Essequibo River at Packeoo Falls, 6.03715, -58.58438 1908, C. Eigenmann; FMNH 7412 (1, 74.0 mm SL), Rupununi Pan opposite Massara Landing, 3.89584, -59.29296 1908, C. Eigenmann; INHS 49273 (1, 100.3 mm SL), Essequibo River (Long Lake, 1.54 miles S of Rockstone, 5.96686, -58.56322, 20-Oct-1998, M. Sabaj, J. Armbruster, M. Hardman, J. Knouft, W. Prince, I. Peterson; USNM 372570 (2, 46.6-52.8, Rupununi River, Taraqua Creek, 3.75949, -59.28371, 31-Oct-2001, D. Arjoon. Venezuela, Bolivar state, Essequibo River Basin, Cuyuni River drainage: ANSP 168173 (1, 85.2 mm SL), Rio Macaruma on Guasipati-El Miamo Rd, ca 4 km SW of El Miamo, 7.44394, -61.87115, 24-Jan-1991, S. Schaefer, W. Saul, F. Provenzano; ANSP 168175 (2, 75.3-79.0 mm SL), Rio Corumo, 10 km E of Tumeremo on road from Tumeremo to Bochinche (just after Fort Terembay), 7.33053, -61.43732, 21-Jan-1991, S. Schaefer, W. Saul, F. Provenzano; ANSP 168176 (1, 49.3 mm SL), Caño Curumito, tributary of Botanamo River, 7.42381, -61.23843, 22-Jan-1991, S. Schaefer, W. Saul, F. Provenzano; AUM 36609 (3, 49.9-67.4, Río Macaruma, 134 km SE.of Cuidad Guiana, 5 km SE. of Guasipati, at old bridge just W of the main road, 7.43773, -61.87554, 11-Jun-2003, J.W. Armbruster, D.C. Werneke, T.P. Pera, N.K. Lujan, O León; INHS 31566 (1, 58.2 mm SL), Rio Oronata, S of town of Upata, (Rio Yuruari drainage), 7.54660, -62.24342, 9-Jan-1994, D.Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps, G. Mottesi; INHS 31582 (1, 77.4 mm SL), Rio Oronata, between Upata & El Manteco, (Rio Yuruari drainage, 7.54660, -62.24342, 9-Jan-1994, D.Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps, G. Mottesi; INHS 31732 (1, 55.0 mm SL), Essequibo/Cuyuni/ Rio Guanare (Yuruari River drainage, El Miamo, 7.64139, -61.77750, 11-Jan-1994, D.Taphorn, L. Page, K. Cummings, C. Mayer, J. Armbruster, C. Laird, M. Sabaj, C. Johnston, S. Phelps, G. Mottesi; MCNG 1068 (1, 82.7 mm SL), Creek of Botanamo River, 2.5 Km upstream of the confluence of Botanamo and Cuyuni Rivers, Bolivar state, 6.96667, - 61.20000, 28-Aug-1979, D. Taphorn, E. Salas; MCNG 10488 (1, 77.2 mm SL), Botanamo River, just downstream of the mouth of the Gurampin in the forest, Bolivar state, 7.08611, -60.97222, 15-Jul-1983, B. Stergios, G. Aymard; MCNG 16040 65.0 mm SL), Corumo River, at the bridge on highway Bochinche, 7.316667, -61.4, 21-Feb-1980, D. Taphorn, G. Feo, G. Ríos.

Diagnosis. Ancistrus nudiceps differs from all other Ancistrus in the region except A. patronus , A. leoni , A. lithurgicus , A. macrophthalmus and A. maximus by having an entirely black body with tiny white to golden dots; it differs from A. maximus by usually having II,7 dorsal-fin rays (vs. II,8; two specimens of A. nudiceps are also II,8) and by having smaller dots with no change in dot size with SL (vs. considerably larger spots in juveniles); from A. patronus by reaching a much greater maximum size (138 mm SL vs. 86 mm SL), by having the plated region of the snout forming a long, rounded triangle such that the area between the plates and the tip of the snout is much smaller than the distance between the tip of the plated area and a line drawn between the anterior margins of the orbits (vs. plated areas forming a broad arc and the distance from the plates to the tip of snout equal to the distance from the tip of the plates to a line drawn between the anterior margin of the orbits), and by having the tentacles of the snout bifurcating at the start of the snout plates in a V (vs. tentacles bifurcating in a U); and from A. leoni , A. lithurgicus , and A. macrophthalmus by being deep bodied (vs. flattened), by having the median plate below the posterior edge of the adipose-fin membrane about twice as tall as wide (vs. just slightly taller than), and by the eyes being laterally placed (vs. dorsolaterally placed in A. lithurgicus and almost completely dorsally placed in A. leoni and A. macrophthalmus .

Description. Morphometrics given in Table 5. Size range of specimens examined 42–138 mm SL. A relatively large Ancistrus , body broadest anteriorly, greatest body width near opercles, then narrowing progressively to end of caudal peduncle. Head and body somewhat depressed, greatest body depth just anterior to dorsal-fin origin. Caudal peduncle deep, robust, compressed posteriorly. Dorsal profile of head and body ascending at about a 45 degree angle to above eyes, then ascending gently in convex arc to dorsal-fin origin, from there, descending in straight line or gently convex arc sloping gradually down to beneath adipose-fin, then angled dorsally to caudal fin. Ventral profile flat to beneath pectoral-fin insertions, then slightly convex to pelvic-fin insertions, then descending straight to caudal-fin spine.

Head wide, interorbital width greater than head depth, much more 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 large, interorbital area slightly convex. Oral disk round, about as wide as 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 short with premaxillary tooth rows forming strong arc and dentary tooth rows forming angle of>135°. Dentary and premaxillary tooth rows strongly curved medially, lateralmost dentary tooth medial to lateralmost premaxillary tooth. Teeth numerous (44–62 per jaw ramus), 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, eight –13, stout with tips hooked anteriorly, bases encased in thick fleshy sheaths. Exposed part of opercle roughly an elongate diamond with rounded tips, covered with odontodes that are larger along its margins. 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, one exposed platelet present (tip of first pterygiophore) anterior to anal-fin spine. Nuchal plate small and curved posterolaterally. Enlarged odontodes present along edges of lateral plates. Five series of lateral plates anteriorly, three series on caudal peduncle, mid-dorsal plate series ending on caudal peduncle beneath first preadipose plate; mid-ventral plate series ending on caudal peduncle beneath

adipose-fin spine. Last plate in median series slightly same size as penultimate plate, and median plate below end of adipose fin about twice as high as wide. Base of caudal fin with eight to 13 small platelets covering bases of caudal-fin rays.

Dorsal-fin origin situated notably anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not elongate, longer than snout length; last dorsal-fin ray reaching adipose-fin spine when depressed. Dorsal-fin base length greater than dorsal–adipose distance. Adipose fin stout, angled up from body, membrane visible beneath spine. Pectoral spine stout, moderately long, reaching past pelvic-fin base but not to cloaca. Anal fin small but well developed; base of first anal-fin pterygiophore exposed, anal-fin origin posterior to vertical through base of last dorsal-fin ray. Pelvic fins reaching well past anal-fin origin, inserted at vertical through second branched dorsal-fin ray. Caudal fin truncate, lower lobe slightly 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=60). Mid-dorsal plates 16–18, x= ̃16; median plates 22–24, x= ̃23; mid-ventral plates 17–18, x= ̃ 18; plates bordering dorsal-fin base seven to eight, x= ̃eight; plates between dorsal and adipose fins six to seven, x = six; preadipose plates 1. Fin-ray formulae: dorsal II,7–8, xĨI,7; pectoral I,6; pelvic i,5; anal i,3–4, x= ̃i,4; caudal i,14,i. Caudal procurrent spines dorsal: three to five, x= ̃5; ventral: three to four, x= ̃three.

Sexual dimorphism. ( Fig. 5a ) Snout tentacles of nuptial males long, largest 1.5 times eye diameter. Posteromedial tentacles diverging in V- shape along anteriorly triangular snout plates. Naked areas of snout without tentacles rugose, separated from naris by several, wide plates; naked area narrow, distance from anteromedial plate to snout less than distance from anteromedial plate to line formed between anterior edges of nasal apertures.

Color in alcohol. ( Fig. 18 ) Base color of all fins, dorsum, sides and ventrum of body black, brown or gray, with tiny white dots; dots often lost in preservative. First dorsal-fin membrane dark black near its base.

Life colors. ( Fig. 1 ) Body and fins jet black with tiny white dots. First dorsal-fin membrane dark black near its base.

Distribution: Present in Guyana in both the Essequibo River Basin and tributaries of the Amazon River Basin (such as the Takutu) as well as the Cuyuni River of Venezuela ( Fig. 7 ).

Remarks. This fish can reach a very large size for an Ancistrus , over 138 mm SL. The largest species known, A. maximus reaches around 200 mm SL ( Oliveira et al., 2015), shares a similar color pattern, and is likely closely related to A. nudiceps . Oliveira et al. imply that the species differ by A. maximus having eight branched dorsal-fin rays (vs. seven). Eight is rare in other Ancistrus , but two specimens of A. nudiceps from the Cuyuni River were found to have eight branched dorsal-fin rays. Preliminary results of DNA analysis detected no significant differences among populations of A. nudiceps from rivers of the Essequibo and Amazon basins in Guyana or the Cuyuní River in Venezuela. Although there is about 12% divergence between A. nudiceps and A. patronus new species based on these preliminary Cyt b analysis.

Figures

FIGURE 1. Ancistrus nudiceps, lateral and anterior views, AUM 35623, 138.4 mm SL. Photos by M.H. Sabaj.

FIGURE 5. Heads, dorsal view, of A. Ancistrus nudiceps AUM 35623, 140.2 mm SL and B. A. patronus, holotype, AUM 39876, 83.6 mm SL demonstrating differences in head shape and tentacle pattern. Ancistrus nudiceps has a longer, more spatulate snout with the point from the edge of medial snout plates to the end of the snout (turquoise line) much shorter than the distance from the edge of the medial snout plates to a line through the anterior margins of the orbits (yellow line, dashed line is the line that demarks the anterior borders of the orbits) while the two lengths are approximately equal in A. patronus. In addition, the anterior margin of the snout plates form a rough V in A. nudiceps and a U in A. patronus (solid white line). Scale = 1 cm. Photos by J.W. Armbruster.

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

FIGURE 18. Ancistrus nudiceps in dorsal, lateral, and ventral views, AUM 35623, 140.2 mm SL. Scale = 1 cm. Photos by J.W. Armbruster.