Isorineloricaria acuarius, Ray, C. Keith & Armbruster, Jonathan W., 2016

Ray, C. Keith & Armbruster, Jonathan W., 2016, The genera Isorineloricaria and Aphanotorulus (Siluriformes: Loricariidae) with description of a new species, Zootaxa 4072 (5), pp. 501-539 : 527-530

Isorineloricaria acuarius new species

( Fig. 15 )

Holotype. INHS 35685, 269.1mm SL, Venezuela: Rio Portuguesa, 3 km northeast of El Barriero, Portuguesa. 09˚03’08”N, 069˚29’18”W. 1 January 1995. Collected by J.W. Armbruster, P.A. Ceas, M.H. Sabaj, C.A. Laird, S.M. Phelps, M.L. Manrique, F.T. Burbrink.

Paratypes. Venezuela: ANSP 134482, Rio Orituco, tributary of Rio Guarico, 15 km SSE of Calabozo on Cazorla Road; Orinoco drainage, Edo. Guarico, 25 November 1966, col. by N.R.Foster, J.Ramsey; ANSP 134519, Rio Orituco, tributary of Rio Guarico, 15 km SSE of Calabozo on Cazorla Road, Edo. Guarico, 26 November 1966, col. by N.R.Forster; ANSP 165834, Rio Orituco: ca. 15 km SE of Calabozo, Guarico, 2 November 1989, col. by S.Schaefer, et al.; ANSP 166888, Rio Orinoco Basin: Caicara; L. Bartolico, Bolivar, 12 January 1988, col. by M. Rodriguez; FMNH 105992, Rio Suripa ca. 0.5 hrs by boat above confluence with Rio Caparo, Barinas, 07º40’00”N 070º28’00”W, 9 January 1991, col. by B. Chernoff, A. Machado, R. Royero, F. Gil; FMNH 105993, Playa Los Chicos in the Rio Suripa ca. 2.5 hrs. above Hato Mercedes, Barinas, 12 January 1991, col. by B. Chernoff, A. Machado, R. Royero, F. Gil; INHS 34432 (1), Rio Tucupido at Santuario de la Coromoto, Portuguesa, Venezuela, 08°54'46"N, 69°46'16"W, col. by L. M. Page et al., 31 December 1994; INHS 35685 (1), Rio Portuguesa, 3 km northeast of El Barriero, Portuguesa Venezuela, 09˚03’08”N, 069˚29’18”W, col. by J.W. Armbruster, P.A. Ceas, M.H. Sabaj, C.A. Laird, S.M. Phelps, M.L. Manrique, F.T. Burbrink, 1 January 1995; MCNG 34719 (3), Río Arauca, playa al oeste del hato Doña Barbara, 7°25’00”N 69°25’00”W, col. by D. Jepsen, D. Rodríguez, 4 July 1997; UF 80345, Rio Guanare on Las Garcitas, near Laguna Chiriguare, 8°33'20"N 68°40'0"W, col. by D.C.. Taphorn, C.R. Gilbert, L. Nico, 3 April 1984; UF 80390 (3), Rio Apure in Apurito, near chalana site., Apure, 7º56’0”N 68º28’50”W, col. by D.C. Taphorn, C.R. Gilbert, L. Nico, 6 April 1984; USNM 348458, Rio Orituco where crossed by road from Calabozo, Guarico, 8.867, -67.300, 27 January 1983, col. by A. Machado-Allison et al.

Diagnosis. Isorineloricaria acuarius can be diagnosed from from I. spinosissima by having a larger caudal fin depth to head length ratio (see diagnosis of I. spinosissima ); from I. tenuicauda by having a larger caudal peduncle width to pectoral spine length ratio (59.6– 65.2% vs. 31.5– 56.2%), which separates 95% of individuals; and from I. spinosissima and I. villarsi by having a flattened compound pterotic (vs. sharp ridges present in I. villarsi ). Isorineloricaria acuarius can be further diagnosed from Aphanotorulus ammophilus and A. unicolor by having a single, large buccal papillae (vs. multiple buccal papillae present in A. ammophilus and A. unicolor ); from A. emarginatus by having a larger orbit diameter to interorbital width ratio (40.6–63.7% vs. 32.4–40.5%), which separates 96% of individuals; from A. horridus by having a supraoccipital crest with posterior edge perpendicular to head (vs. A. horridus with posterior edge gently sloping into nape)

Description. Morphometric data given in Table 5 . Head deep with elevated supraoccipital crest; crest ending abruptly with posterior edge perpendicular to head. Rounded ridge forming on outer edge of each nare, rising dorsally over orbit, abruptly ending postorbitally. Large flap covering posterior opening of nare. Interorbital surface flat. Nape flat.

Dorsal-fin spine not longer than first dorsal-fin ray. Pectoral-fin spine reaches past insertion of pelvic fin. Pelvic-fin spine just reaches insertion of anal fin. Adipose-fin membrane extending to end of third adipose base plate (one plate separates adipose-fin membrane and first dorsal procurrent caudal-fin spine).

Lateral line plates 27–30 (mode= 30; n= 23); dorsal-fin base plates seven to eight (mode= eight; n= 23); folded dorsal plates 11–13 (mode= 13; n= 23); plates between dorsal and adipose fins seven to 10 (mode= nine; n= 23); adipose fin plates two to four (mode= three; n= 23); anal fin base plates two to three (mode= two; n= 23); plates from anal fin insertion to last plate on caudal peduncle 16–19 (mode= 19; n= 23); plates in folded pectoral fin five to eight (mode= six; n= 22); number of teeth on dentary 20–35 (mode= 24; n= 23); number of teeth on premaxilla 17–41 (mode= 24; n= 23).

Sexual dimorphism. Breeding males with hypertrophied odontodes on pectoral-fin spine, which increase in density and length distally along spine. Paired-fin spines swell distally. Hypertrophied odontodes on caudal fin with largest spines occurring on caudal-fin spines and along the caudal-fin rays. Slightly hypertrophied odontodes present on distal end of adipose-fin spine. Hypertrophied odontodes covering posteromedial edge of most plates along body. Longest plate odontodes occur on mid-dorsal, median, and mid-ventral plate rows. Slightly hypertrophied odontodes also present on opercle, edge of snout, and cleithrum.

Color in alcohol. Body base color light brown or tan with large, dark, longitudinally oblong brown spots. Spots larger than orbit diameter. Spots rarely circular on body. Spots cover entire body except abdomen; faint spots occur across ventral aspect of pectoral girdle in some specimens. Spots on paired fins combining to form bands, some separate spots distally. Dorsal-fin spine with dark spots anteriorly; interradial membrane of dorsal fin with two rows of spots. Caudal fin with spots that appear to form bands on upper lobe, and randomly distributed spots on lower lobe; lower lobe of caudal fin with dark brown background color in most specimens. Large spots sometimes visible on lower lobe of caudal fin when dark background absent or faded.

Spot patterning less concentrated in juveniles (more background color showing). Spotting pattern on fins becomes denser as fish ages. In juveniles one row of spots on interradial membranes of dorsal fin, bifurcating distally in larger specimens, eventually becoming two rows in adults.

Ecology. The holotype was collected in the Rio Portuguesa on a sandy run with moderate flow. The holotype is a nuptial male with breeding odontodes, suggesting that January is within the time of spawning as was suggested for A. ammophilus ( Armbruster and Page, 1996) .

Distribution. This species has so far only been found in the Apure River and middle Orinoco rivers and their tributaries in Venezuela. Only one specimen was from the main stem Orinoco River, just downstream of the mouth of the Apure (Fig. 10).

Comments. The one specimen of Isorineloricaria acuarius collected in the Orinoco River was also collected with a specimen of Aphanotorulus emarginatus . This is the only known instance of the two being collected together. The waters where the two rivers connect may act as an extension of available habitat for each species, because the two are not known to occur downstream of the connection in either river. Isorineloricaria acuarius appears to be restricted to white waters and A. emarginatus to clear and blackwater rivers, or rivers intermediate between black- and whitewater.

Etymology. The name acuarius is latin for needle maker. This is in reference to the numerous hypertrophied odontodes found on breeding males, which can make study of these fishes difficult. Treated as a noun in apposition.

Figures

FIGURE 15. Lateral, dorsal, and ventral views of Isorineloricaria acuarius, INHS 35685 (holotype), 269.1 mm SL. Scale = 1 cm.

Tables

TABLE 5. Selected morphometrics of Isorineloricaria acuarius and I. spinosissima.

	Isorineloricaria acuarius	Isorineloricaria spinosissima
Measurement	N Average SD Range	N Average SD Range
Standard Length (SL, mm)	23 53.2–208.4	11 39.4–416.0
% SL
Predorsal Length	23 39.1 3.2 33.4–33.5	11 33.5 4.4 25.1–38.3
Head Length (HL)	23 32.9 3.9 20.9–27.9	11 27.9 4.4 19.9–33.7
Cleithral Width	22 26.1 1.4 23.2–22.3	11 22.3 3.3 16.3–25.6
Dorsal spine Length	21 29.4 4.6 18.4–27.3	11 27.3 3.8 19.9–31.3
Folded dorsal-fin Length	23 36.8 2.0 32.8–33.9	11 33.9 2.9 28.5–37.6
Dorsal-fin base Length	23 24.1 1.0 21.7–22.6	11 22.6 1.8 20.3–27.0
Dorsal- adipose Length	23 21.5 1.9 19.0–22.1	11 22.1 2.9 16.6–26.3
Thorax Length	23 23.0 1.5 20.4–21.4	11 21.4 1.8 18.4–23.6
Pectoral spine Length	23 28.6 2.0 24.6–22.2	11 22.2 4.6 15.1–28.5
Abdominal Length	23 19.1 1.0 16.9–18.3	11 18.3 1.2 16.7–20.4
Pelvic spine Length	23 22.7 2.1 17.4–20.2	11 20.2 2.6 14.9–23.8
Postanal Length	23 38.9 2.8 35.3–42.7	11 42.7 4.0 37.0–51.0
Caudal peduncle Depth	23 8.1 0.6 6.7–5.2	11 5.2 1.1 3.7–6.6
Caudal peduncle Width	23 15.7 1.4 12.1–11.5	11 11.5 1.7 8.3–13.5
Adipose-fin spine Length	23 7.8 1.2 5.5–6.9	11 6.9 1.6 4.3–9.8
Anal-fin Length	23 13.2 2.2 9.6–13.7	11 13.7 1.2 11.8–15.4
Anal-fin base Length	23 4.0 0.5 2.6–4.1	11 4.1 1.0 2.2–5.9
Adipose- upper caudal Length	23 20.9 1.2 18.5–26.0	11 26.0 2.3 22.8–29.5
Adipose- lower caudal Length	23 26.7 1.4 22.7–28.7	11 28.7 2.3 26.1–33.4
%HL
Head Depth	23 59.0 9.1 52.9–55.3	11 55.3 2.8 49.4–57.9
Snout Length	23 61.1 8.6 55.2–59.6	11 59.6 3.6 52.9–64.7
Orbit Diameter	23 20.9 5.6 14.0–18.5	11 18.5 3.9 14.7–27.4
Interorbital Width	23 44.7 7.2 39.2–37.7	11 37.7 1.6 33.5–39.5
Snout opercle Distance	23 72.7 10.9 67.7–71.9	11 71.9 4.7 67.1–83.9
Head Width	23 81.3 11.2 72.7–80.2	11 80.2 3.7 76.2–86.3
Head eye Length	23 38.5 6.8 32.9–34.9	11 34.9 3.7 28.7–42.7
Eye nare Length	23 13.1 2.2 9.6–11.9	11 11.9 1.9 9.0–14.5
Internares Width	23 17.4 3.5 13.5–15.2	11 15.2 1.2 13.4–18.1
Snout nares Length	23 40.1 6.3 33.7–39.9	11 39.9 2.7 35.0–44.3
Snout pectoral Length	23 75.1 11.6 68.6–76.5	11 76.5 4.0 72.3–83.9
Pectoral orbit Distance	23 25.5 5.0 20.1–27.9	11 27.9 4.0 22.7–36.7
Mouth Width	23 42.7 6.1 37.5–41.4	11 41.4 3.0 37.5–45.6
Mouth Length	23 45.7 7.4 40.2–44.2	11 44.2 4.4 37.4–51.9
Dentary Length	23 14.4 2.9 11.1–12.8	11 12.8 1.3 11.0–15.7