Pseudancistrus reus, Armbruster, Jonathan W. & Taphorn, Donald C., 2008

Armbruster, Jonathan W. & Taphorn, Donald C., 2008, A new species of Pseudancistrus from the Río Caroní, Venezuela (Siluriformes: Loricariidae), Zootaxa 1731, pp. 33-41 : 34-38

Pseudancistrus reus , new species

( Fig. 1 , Table 1 )

Holotype: MCNG 18447, 72.2 mm SL, Venezuela, Estado Bolivar, Río Caroní in a small side channel very close to the confluence of the Río Claro, 07°54'30"N, 063°02'50"W, D.C. Taphorn, O. León M., L. Balbás, R. Smith, J. García T. and A. Barbarino, 6 March 1988.

Paratype: AUM 47152, 1, 76.5 mm SL, same locality data as holotype.

Diagnosis: Pseudancistrus reus can be separated from all other described Pseudancistrus by the presence of bars on the body (vs. spots, mottling, or entirely dark coloration), and from all examined Pseudancistrus except P. genisetiger and P. papariae by having an incomplete mid-dorsal plate row with 18 plates (vs. a complete mid-dorsal row with 21–25 plates). In the one specimen of P. genisetiger examined and the holotype of P. papariae , the mid-dorsal row has 14 plates, then a break around the adipose fin and then two more plates at the posterior end of the caudal peduncle (vs. 18 continuous plates in P. re u s). The other specimen of P. papariae (AUM 20768) examined had a complete mid-dorsal row (the plate rows were not examined on the paratypes).

Description: Morphometrics presented in Table 1 . Meristics based on two individuals. Largest specimen 76.5 mm SL. Body very dorsoventrally flattened and fairly narrow. Head and nape gently convex to maximum depth at insertion of dorsal fin, then very gradually decreasing to dorsal procurrent caudal-fin spines, then angled dorsally ~45° to caudal fin. Ventral surface flat to ventral procurrent caudal fin rays, then angled ventrally ~30° to caudal fin. Eyes set fairly close together, almost completely dorsally oriented. In dorsal profile, head broadly triangular, body widest at pectoral-fin insertions, then narrowing slightly to dorsal-fin origin, then expanding to about middle of dorsal fin before tapering to end of caudal peduncle.

Anterior margin of snout with small to medium-sized hypertrophied odontodes; tentacules of snout odontodes not longer than odontodes, unbranched. Evertible cheek plates not strongly evertible (to ~30° from head), with relatively short hypertrophied odontodes that reach maximally to posterior edge of pectoral-fin spine. Head contours smooth with slightly raised supraorbital crest from anterolateral corner of nares to posterior edge of pterotic.

Mouth relatively small with premaxillary and dentary tooth cups forming gentle arcs. Premaxillary teeth 62–77; dentary teeth 68. Teeth viliform and bicuspid with very short cusps (medial cusp longer than lateral cusp). Lateral edge of oral disk not extending beyond lateral margins of head. Maxillary barbels short, not reaching base of evertible cheek plates. Ventral surface of lips papillose. Papillae increasing in size distally. Dentary papillae absent. Buccal papilla absent in one individual and barely present in other. Buccal valve fairly unusual, with median, ridge-like, thickened region, and very thin, transluscent lateral wings (usually in loricariids lateral wings are fairly thick and only slightly thinner than median ridge).

Dorsal fin II,7; dorsal-fin spinelet short and V -shaped; dorsal-fin lock functional. Dorsal fin short, reaching preadipose plate when adpressed. First dorsal-fin ray longer than dorsal-fin spine. Pectoral fin I,6; pectoral spine short (just slightly longer than pelvic spine) extending to middle of pelvic fin when adpressed. Pectoralfin spine fairly weak with odontodes that increase in size and density distally; tentacules of pectoral-fin spine not longer than odontodes, unbranched. Distal odontodes slightly elongated. Anterior pectoral-fin rays longer than pectoral-fin spine, decreasing to about half of length of spine posteriorly. Pelvic fin I,5; pelvic-fin spine weak, reaching middle of base of anal fin when adpressed; anterior pelvic-fin rays longer than pelvic-fin spine with posterior margin of fin curving out beyond posterior tip of spine. Anal fin I,5; anterior anal-fin rays slightly longer than unbranched anal-fin ray, posterior anal-fin rays slightly shorter than unbranched anal-fin ray. First anal-fin pterygiophore not exposed to form a plate-like structure. Adipose-fin spine straight with adipose membrane extending beyond posterior extent of spine. Caudal fin I,14,I; at least upper caudal-fin spines longer than caudal-fin rays (lower spines broken on both specimens). Dorsal procurrent caudal-fin rays four or five, ventral procurrent caudal-fin rays three. Posterior caudal-fin margin slightly concave. Rays of all fins supporting small odontodes.

Median plate series with 20–22 plates. Ventral plates forming gentle arc on caudal peduncle and not forming strong rounded keel. Plates in mid-dorsal row weakly arched submedially forming low ridge from cleithrum to posterior insertion of pelvic fin. Four rows of plates on caudal peduncle (mid-dorsal plate series ending at level of adipose fin). Abdomen naked.

Color: Alcohol preserved specimens mostly brown on head and sides, lighter tan spots on nose and top of head, as well as below and behind eye. On dorsum of body of paratype, three lighter tan saddles, first from middle of dorsal fin base to end of dorsal fin base, next begins just behind the dorsal fin base and extends posterior to about one plate before adipose insertion, last begins just anterior to adipose insertion and continues to caudal base. No saddles in smaller specimen (holotype), vertical bars extend up from sides to unite at midline. Sides brown with darker brown oblique narrow vertical bars; six bars in paratype, stronger posteriorly; nine bars in holotype that begin under middle of dorsal-fin base. Undersurfaces lighter, creamy white on unplated breast and abdomen, tan on plated caudal peduncle. Oral disk with inner papillated surfaces pale tan but brown on outer anterior margin. All fin spines and rays with alternating wide dark and narrow light bands (pattern most evident in caudal and dorsal fin, least evident in pectorals); fin membranes hyaline or dusky with melanophores. Small but distinct black spot present at base of anteriormost dorsal-fin membrane in both specimens.

Range: Known only from the type locality in the Río Caroní, Bolivar, Venezuela (Fig. 5). The type locality is now part of the Caruachi Reservoir. Therefore, a status survey of the species should be performed to determine the extent of its range.

Water conditions: The following water conditions were recorded at the time of capture: water tea-colored, low conductivity (12 Μmho/cm), visibility ~ 2m, moderate current, pH 6.6, temperature 28°C.

Etymology: From the Latin reus , meaning one who is accused or arraigned like a defendant, prisoner, criminal, or culprit; in reference to the barred pattern that looks like the stripes of the stereotypical prisoner’s uniform. Treated as a noun in apposition.

Figures

FIGURE 1. Dorsal, lateral and ventral views of holotype of Pseudancistrus reus, MCNG 18447, 72.2 mm SL. Photos by N. K. Lujan.

Tables

TABLE 1. Selected morphometrics of Pseudancistrus reus (n = 2). Landmarks represent the two landmarks the measurement is between (see Armbruster 2003). Measurements are ratios of SL (predorsal l. to pelvic-dorsal l.) or head l. (headeye l. to premaxillary tooth cup l.).

Landmarks	Measurement	Average	Holotype	Paratype
1–20	SL	74.3	72.2	76.5
1–10	Predorsal L.	44.1	43.2	45.0
1–7	Head L.	33.9	33.2	34.6
7–10	Head-dorsal L.	10.0	9.8	10.2
8–9	Cleithral W.	33.0	32.2	33.8
1–12	Head-pectoral L.	30.0	28.8	31.2
12–13	Thorax L.	23.1	23.1	23.2
12–29	Pectoral-spine L.	25.5	25.0	26.0
13–14	Abdominal L.	24.5	24.7	24.3
13–30	Pelvic-spine L.	23.8	23.6	24.0
14–15	Postanal L.	28.1	29.5	26.7
14–31	Anal-fin spine L.	11.1	10.7	11.5
10–12	Dorsal-pectoral D.	26.0	26.3	25.6
10–11	Dorsal spine L.	26.3	25.1	27.4
10–13	Dorsal-pelvic D.	22.0	21.4	22.6
10–16	Dorsal-fin base L.	29.2	30.6	27.8
16–17	Dorsal-adipose D.	15.3	14.6	16.0
17–18	Adipose-spine L.	5.6	6.1	5.2
17–19	Adipose-up. caudal D.	11.9	12.3	11.4
15–19	Caudal peduncle Dp.	10.9	10.6	11.1
15–17	Adipose-low. caudal D.	18.4	18.9	18.0
14–17	Adipose-anal D.	19.4	18.3	20.5
14–16	Dorsal-anal D.	13.1	12.8	13.4
13–16	Pelvic-dorsal D.	27.2	25.9	28.5
5–7	Head-eye L.	30.2	31.6	28.7
4–5	Orbit Dia.	19.3	19.5	19.1
1–4	Snout L.	65.8	65.9	65.8
2–3	Internares W.	8.5	9.5	7.5
5–6	Interorbital W.	52.2	56.7	47.8
7–12	Head Dp.	62.4	63.7	61.2
1–24	Mouth L.	60.5	61.1	59.9
21–22	Mouth W.	63.1	69.2	57.0
22–23	Barbel L.	7.6	5.6	9.6
25–26	Dentary tooth cup L.	18.3	18.3	18.3
27–28	Premaxillary tooth cup L.	17.4	19.0	15.7