Ancistrus brevifilis Eigenmann 1920

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 : 14-16

Ancistrus brevifilis Eigenmann 1920

( Fig. 8 )

Ancistrus brevifilis Eigenmann, 1920: 7 , pl. 1. Type locality: El Concejo, río Tiquirito [Tuy River Basin of Caribbean coast], Venezuela. Holotype: CAS 64609.

Specimens examined. All from Venezuela, Tuy River Basin. CAS 64610 (paratypes, 2, 73.3–102.0 mm SL) Aragua State, Tiquirito River at El Concejo, tributary of the Tuy River, 2040 masl, 10.24018, -67.26484. MCNG 14095 (1, 68.9 mm SL), Miranda State, District Guicaipuro, Guiare de Tácata River, approximately 5 km upriver of Tácata, 10.21274, 67.00551, 30-Jul-1985, D. Taphorn. MCNG 14304 (3, 61.2–68.0 mm SL) Miranda State, bridge near Araguita al Sur, District Acevedo, 10.21737, -66.45007, 29-Jul-1985, D. Taphorn. FMNH 84621 (6, 44.0– 102.8 mm SL), (ex MBUCV 2757), Miranda State, Guira River, 24-Apr-1966, F. Mago-L., & J. Moscó.

Diagnosis. Ancistrus brevifilis can be separated from all other Ancistrus in the region by having elongate light spots in the overall dark caudal fin with the spots irregular and often fusing with spots from other rows (vs. spots generally minuscule and usually lost in preservation or large, but round to only about twice as long as high and arranged relatively uniformly on the fin and not combining across rows); and from A. leucostictus and A. saudades by always lacking spots on the abdomen (vs. spots present).

Description. Morphometrics in Table 1. A large Ancistrus , largest specimen examined 103 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 just anterior to dorsal-fin origin. Caudal peduncle deep, compressed posteriorly. Dorsal profile of head ascending at about a 45 degree angle to above eye, then ascending in shallow convex arc to dorsal-fin origin; from there 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; abdomen slightly concave or convex depending on fullness of intestines.

Head wide, interorbital width less than head depth, 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 (43–105 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, 11–14, 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, usually ending below first preadipose plate; mid-ventral plate series usually one plate longer than mid-dorsal series, ending under 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 vertical column of four square platelets and six to eight triangular 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 straight, 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 length. 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 all fin rays and body plates, largest on posterior margins of plates. All fin spines with small odontodes, more developed in pectoral-fin spine of males.

Meristics (N=13). mid-ventral plates 17–19, x= ̃17; median plates 22–23, x= ̃ 22; mid-dorsal plates 16–19, x =17; plates bordering dorsal-fin base six to seven, x= ̃six; plates between dorsal and adipose fins six to seven, x= ̃ six; preadipose plates one to two, x= ̃one. Fin-ray formulae invariable: dorsal II,7; pectoral I,6; pelvic i,5; anal i,4; caudal i,14,i. Caudal procurrent spines: dorsal: five; ventral: two to five, x= ̃four.

Sexual dimorphism. Snout tentacles of nuptial males long, largest over twice 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 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. From Eigenmann’s (1920:8) original description: “Dorsal, caudal, ventrals and pectorals, each with four or five conspicuous, wavy bars; faint darker spots about the size of the eye in front of the dorsal, ventral surface uniform. In the female, the smaller paratype, the number of bands is smaller and they are less well marked”. In general, tan in alcohol, with lighter whitish abdomen. Fins dark with large light, irregular, and sometimes horizontally elongate spots, that are centered on fin rays, especially noticeable on caudal fin with some spots combining across rows to make wavy lines as noted by Eigenmann. Spines of the dorsal, adipose, caudal, pelvic and pectoral fins with four to six alternating dark and light sections, mirrored on the branched rays, with dark and lighter areas also extending onto membranes. Dorsum and sides of body often faintly marked with traces of dark saddles and plates often two-toned with dark and light brown sections, forming mottled appearance ( Fig. 8 ).

Life colors. Based on photographs from Mr. Shane Linder on PlanetCatfish.com of specimens said to be from Tuy River drainage. Base color black and gray on dorsum, and all fins. Body mostly gray with rows of darker gray to black spots forming horizontal rows to upper sides and dorsum. Fins two-toned, gray and black. Dorsal fin edged in gray, with two to three rows of alternating black and gray spots, not really aligning to form lines; adipose spine gray with black spot; caudal fin with dark background and light gray spots, some aligning to form vertical rows and some combining across rows. Top of head and most barbels black. Ventrum of head and body light gray.

Distribution. Known only from the Río Tuy that drains into the Caribbean Sea of Venezuela ( Fig. 7 ).

Comments. Ancistrus brevifilis is very similar to A. triradiatus , but is generally brighter in color and has more intense spotting on the caudal fin than A. triradiatus from Venezuelan Andean streams.

Figures

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

FIGURE 8. Ancistrus brevifilis in dorsal, lateral, and ventral views, MCNG 14304, 61.2 mm SL. Scale = 1 cm. Photos by J.W. Armbruster.