Ancistrus trinitatis ( Günther, 1864 )

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 : 48-51

Ancistrus trinitatis ( Günther, 1864)

( Figs. 23–24 )

Chaetostomus trinitatis Günther, 1864: 246 . Type locality: Trinidad. Syntypes: based on specimens reported on by Gill (1858: 409) as Ancistrus guacharote , possibly deposited at USNM, but whereabouts unknown. See Comments below. Ancistrus maracasae Fowler, 1946: 2 , figs. 1–4. Type locality: Maracas River, Trinidad.

Neotype: ANSP 71723 (1, 82.0 mm SL), Maracas River , 29-Jun-1930, L. Wehekind, also holotype of A. maracasae . Neotype of Chaetostomus trinitatis Günther , by present designation.

Other specimens examined. All from Trinidad. INHS 40105 (1, 78.8 mm SL), Cumuto River , 5 km S Brazil on road to Talparo, St. George County, 29-Jan-1997 , L. Page, C. Ronto; MCNG 8202 (2, 73.8–81.1 mm SL, Guanapo River , 23-Jun-1983 ; MCNG 8260 (1, 56.1 mm SL), Caño Antigua, 23-Jun-1983 ; ROM 87569 (3, 62.2– 64.0 mm SL), Arima River , just downstream of Verdant Vale by Blachiseusse Rd., about 150 m of stream; 10.68022, -61.2903723, 23-Apr-2010 ; ROM 88768 (7, 68.3–96.8 mm SL), Maracas River , upstream of bridge at Maracas; 10.68427, -61.41032, 21-Apr-2010 , H. Lopez-Fernandez, J. Gilliam, D. Bloom, D. Taphorn, E. Holm; ROM 88881 (4, 38.6–75.3 mm SL), Maracas River at El Tucuche, #1 Acono junction by playground; 10.69475, - 61.40714, 21-Apr-2010 , H. Lopez-Fernandez, J. Gilliam, D. Bloom, D. Taphorn, E. Holm, D. Phillips.

Diagnosis. Ancistrus trinitatis can be separated from all other species in the region except A. brevifilis , A. leucostictus , and A. saudades by having large light spots or blotches on the dorsal and caudal fins; from all Ancistrus in the region by having black spots centered on the caudal-fin rays basally and white spots centered on the rays distally (vs. tiny white or yellow spots randomly placed, or large white spots centered on the membranes); from A. brevifilis by having the spots on the caudal fin generally smaller and better organized into rows (vs. at least some spots on the caudal fin combining across rows and running about half the length of the caudal fin); and from A. brevifilis , A. leucostictus , A. saudades , and A. triradiatus by lacking spots only on the dorsal fin rays (vs. spots centered on membranes).

Description. Morphometrics given in Table 4. A large-sized Ancistrus , largest specimen examined 96.8 mm SL. Body broadest anteriorly, greatest body width just posterior to opercles, 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 in arc to just behind supraoccipital and then descending to dorsal fin. From the dorsal-fin origin descending straight or in slightly concave arc to caudal fin. Ventral profile flat to 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 small, 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 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 (40–110 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 almost equal in worn teeth. Hypertrophied cheek odontodes strongly evertible, nine to 15, 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 smooth, 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.

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 reaching first 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 twelve small platelets covering bases of caudal-fin rays.

Dorsal-fin origin situated slightly anterior to vertical through pelvic-fin insertion. First dorsal-fin ray not elongate, much 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, which we categorize as medium distance. 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 half way 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=19). Mid-ventral plates 16–21, x= ̃19; median plates 22–25, x= ̃23; mid-dorsal plates 16–21, x= ̃ 18; plates bordering dorsal-fin base five to nine, x= ̃eight; plates between dorsal and adipose fins four to nine, x= ̃ seven; preadipose plates one. Fin-ray formulae invariable: dorsal II,7; pectoral II,6; pelvic i,5; anal i,4; caudal i,14,i. Caudal procurrent spines: dorsal: five; ventral: two to four, x= ̃three.

Sexual dimorphism. Snout tentacles of nuptial males long, largest greater than two times eye diameter. Posteromedial tentacles diverging in broad U- shape along anteriorly rounded snout plates. Naked areas of snout without tentacles rugose, separated from naris by several, wide plates; naked area wide, distance from anteromedial plate to snout greater than distance from anteromedial plate to line formed between anterior edges of nasal apertures.

Color in alcohol. ( Fig. 23 ) Body dark brown, slightly lighter ventrally. Medium white spots on the sides very obscure. Alternating dark and light spots centered on all fin rays. In the dorsal fin, the dark spots may extend onto the membranes as chevrons posteriorly. Dark spots on a light background present at the base of the caudal fin progressing into light spots on a light background about one third length of fin. Medium-size light spots generally visible on abdomen, dark insterpaces more than twice width of spots.

Life colors. ( Fig. 24 ). Body almost black, covered with medium-size light spots on all surfaces. Spots on sides very diffuse, starting behind eye, spots more intense on fins. Alternating black and white spots centered on all fin rays. Membranes generally hyaline, but dark spots extend as chevrons posterodistally on dorsal fin, and may extend onto rays in pelvic fin. Spots diffuse on anteroproximal portion of dorsal fin; dark spot present at base of dorsal-fin spine and first branched ray. Caudal fin with black spots on light background anteriorly progressing to light spots on dark background at about one third length of fin. Abdomen charcoal with light abdominal spots intense, random in shape, not circular; dark insterspaces more than twice width of spots.

Distribution. Distributed in the northwest corner of the island of Trinidad ( Fig. 7 ).

Comments. There is confusion over the name to apply to the Ancistrus from Trinidad. Günther (1864) described Chaetostomus trinitatis based on Ancistrus guacharote sensu Gill (1858) , but there is little in either description to readily identify what the species is. Ancistrus guacharote is now recognized as Lasiancistrus guacharote , and it was determined that the original locality of the type ( Puerto Rico) was in error and the species was from the Maracaibo Basin of Venezuela ( Armbruster, 2005). Specimens were potentially available of C. trinitatis at USNM, but the only loricariids deposited by Gill from the island of Trinidad are specimens of Hypostomus robinii Valenciennes, 1840 , which is the only other species of loricariid known from the island. Günther’s (1864) description does indicate that the cheek region has evertible odontodes, which means that the species cannot be H. robinii . Fowler (1946) described A. maracasae from the Maracas River of Trinidad, and we believe that this and A. trinitatis are synonymous. In order to solve the taxonomic confusion, we have chosen to recognize the holotype of A. maracasae as the neotype of A. trinitatis .

Figures

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

FIGURE 23. Ancistrus trinitatis in dorsal, lateral, and ventral views, MCNG 8202, 73.8 mm SL. Scale = 1 cm. Photos by J.W. Armbruster.

FIGURE 24. Live coloration of Ancistrus trinitatis in dorsal and anterodorsal views, ROM 88768, 97 mm SL. Photo by D.C. Taphorn.