Nemuroglanis furcatus, Ribeiro, Frank Raynner V., Pedroza, Wellington S. & Rapp, Lúcia H., 2011

Ribeiro, Frank Raynner V., Pedroza, Wellington S. & Rapp, Lúcia H., 2011, A new species of Nemuroglanis (Siluriformes: Heptapteridae) from the rio Guariba, rio Madeira basin, Brazil, Zootaxa 2799, pp. 41-48 : 42-45

Nemuroglanis furcatus , new species

Fig. 1 , 3 ; Table 1

Holotype. INPA 33757, 46.7 mm SL, Brazil, Amazonas State, Apuí municipality, rio Aripuanã, rio Guariba, unnamed stream, right bank of rio Guariba, 0 8°46’31’’S 60°31’27.7’’W, 13 Nov 2009, W. Pedroza, W. Ohara, F. Ribeiro and T. Teixeira.

Paratypes. All collected by W. Pedroza, W. Ohara, F. Ribeiro and T. Teixeira. Brazil: Amazonas State: Apuí municipality: ANSP 190675, 10, 21.3-30.1 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. INPA 33758, 3, 29.7–38.6 mm SL (1 c&s, 38.6 mm SL), collected with the holotype. INPA 33759, 15, 17.7–33.1 mm SL (3 c&s, 26.1–28.8 mm SL), rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. INPA 33760, 25, 19.5–31.5 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. INPA 33761, 5, 17.0– 26.7 mm SL, rio Aripuanã, rio Guariba, igarapé Santa Isabel, 0839’10.6’’S 60°25’58.3’’W, 0 4 Nov 2009. INPA 33762, 3, 23.1–29.7 mm SL, rio Aripuanã, rio Guariba, igarapé Bom Jesus, 0 8°40’15.9’’S 60°24’29.8’’W, 0 3 Nov 2009. MCP 45779, 8, 21.5–29.7 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. MPEG 19265, 7, 23.1–25.2 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. MZUSP 107304, 10, 21.9–31.7 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009. UNT 10032, 5, 23.5–29.5 mm SL, rio Aripuanã, rio Guariba, igarapé das Araras, 0 8°46’10.1’’S 60°26’39.9’’W, 0 5 Nov 2009.

Diagnosis. Nemuroglanis furcatus is distinguished from all congeners by the possession of a long lateral line, reaching middle portion of the adipose-fin base (vs. lateral line extending slightly beyond dorsal-fin base origin); narrow posterior cranial fontanel in adult specimens, 16 to 27% of its length (vs. greater than 40% of its length); and pointed contour of the anterior border of the pectoral bridge (vs. rounded contour). The new species differs further from N. lanceolatus and N. pauciradiatus by possessing a forked caudal fin (vs. lanceolate); the ventral caudalfin lobe with six branched rays (vs. three or four rays); the dorsal caudal plate supporting eight rays (vs. six rays); and seven pairs of pleural ribs (vs. five or six). In addition, it is distinguished from N. mariai by having fewer analfin rays (12–14, mode = 13, vs. 13–15) and vertebrae (41 vs. 42–44); and by possessing more branched pectoral-fin rays (seven, rarely six vs. six, rarely seven).

Description. Morphometric data in Table 1. Body cylindrical anteriorly, becoming laterally compressed from pelvic fin towards caudal region; relatively elongated. Dorsal profile of body slightly convex from snout tip to dorsal-fin origin; straight to gently sloping from dorsal-fin insertion to adipose-fin origin. Dorsal and ventral profiles of caudal peduncle slightly concave. Preventral profile of body slightly convex or straight. Anal-fin base straight. Head depressed, covered by thin skin; anterior margin broadly rounded in dorsal view; ventral profile anterior to isthmus straight.

Anterior fontanelle elongate, open from mesethmoid to epiphyseal bridge; its width 47–57% of its length. Posterior fontanelle elongated, located in front of supraoccipital spine, open from posterior margin of articulation between frontal bones to median portions of supraoccipital; its width 16 to 27% of its length. Eye small; round, laterodorsally placed; orbital rim covered by skin. Anterior nostril with fleshy tubular rim. Posterior nostrils closer to orbital margin than to anterior nostrils, with thin, fleshy, rim elevated anteriorly. Mouth subterminal, not very wide; margin curved in ventral view when mouth is closed and not exposing premaxillary tooth rows.

Premaxillary tooth-patch short, rectangular and transversely elongate; rounded laterally, without posteriorly projecting angle; teeth small and villiform (5 or 6 rows; mode = 5). Dentary tooth-patch posteriorly projected, longer than premaxillary tooth-patch (4 or 5). Palate without teeth.

Barbels thin, flattened in cross section. One maxillary- and two mental barbels. Maxillary barbel longest, reaching to dorsal-fin base origin; inserted slightly posterior to vertical through tip of anterior nostrils. Mental barbels inserted at vertical through corner of mouth. Outer mental barbel reaching beyond pectoral-fin base. Inner mental barbel extending to pectoral-fin base.

Branchiostegal membrane free from isthmus, supported by 4 or 5 (mode = 5) branchiostegal rays. Gill rakers short; 6–9 (mode = 7; n = 17) on first branchial arch; 1–3 on epibranchial (mode = 2), 4–7 on ceratobranchial (mode = 5). Lateral line incomplete, reaching vertical through middle of adipose-fin base; continuous portion not reaching vertical through dorsal-fin origin, followed by isolated patches reaching vertical through middle of adipose-fin base. Lateral line pores 18–33 (mode = 22; n = 18).

Dorsal fin I,6 (n=18), margin rounded, entire dorsal-fin base anterior to middle of standard length; unbranched dorsal-fin ray smaller than first branched rays, stiffened proximally and segmented distally. Dorsal fin, when adpressed, not reaching origin of adipose-fin base. Adipose fin long, low, confluent with procurrent caudal-fin rays and with posterior margin round and free. Adipose-fin origin slightly posterior to vertical through anal-fin origin.

Caudal fin deeply forked, with dorsal-fin lobe greatly enlarged and longer than ventral lobe; principal caudalfin rays; i,6–7 (mode = 7; n = 18) on dorsal lobe and i,6–7 on ventral lobe (mode = 6; n = 18). Procurrent caudal-fin rays become progressively longer posteriorly; dorsal procurrent rays 11–12 (mode = 11; n = 4); ventral procurrent rays 8 (n = 2) or 10 (n = 2).

Pectoral fin I,6–7 (mode = 7; n = 18); basal half of unbranched ray stiffened, distal half segmented, not pungent. Pectoral-fin margin rounded; not reaching base of pelvic fin. Pelvic fin with i,5 rays (n = 18), margin rounded, not reaching anal-fin origin. Origin of pelvic fin vertically aligned with insertion of second or third dorsal-fin ray. Anal fin iv–vi,6–8 (mode = v,7; n = 18), margin rounded; anal-fin base slightly longer than dorsal-fin base and not confluent posteriorly with caudal fin.

Anterior border of pectoral girdle pointed; anterior tips of both cleithrum and coracoid directed anteriorly. Cleithrum tip pointed. Conspicuous sutural articulation between coracoids; cleithrae articulation just abutted.

Postweberian vertebrae 36. Pleural ribs 6 (n = 2) or 7 (n = 2), becoming progressively smaller posteriorly.

Color in alcohol. Body light brownish to yellowish with scattered chromatophores. Dark pigmented stripe on lateral line extending posteriorly to adipose-fin or caudal-fin base. Ventral region light to yellowish. Head surface blackish. Eye dark. Several dark chromatophores on posterior cleithral process, opercle, below orbital region, and sometimes, reaching body flanks; cromatophores more concentrated on lower half of flanks below lateral line. Pectoral and pelvic fins hyaline. Dorsal and anal fins with black chromatophores on interradial membranes. Black chromatophores along interradial membranes of caudal fin, mainly concentrated on median portion of the lobes. Adipose fin with few black chromatophores scattered on basal surface. Maxillary barbel dusky on dorsal surface; lighter on ventral surface. Mental barbels pale.

Distribution. Nemuroglanis furcatus is known from streams in the middle and upper portions of the rio Guariba, rio Madeira basin, Brazil ( Fig. 2 ).

Etymology. The species epithet, furcatus , refers to the deeply-forked caudal fin.

Figures

FIGURE 1. Nemuroglanis furcatus, holotype, INPA 33757, 46.7 mm SL, Brazil, Amazonas State, rio Guariba, tributary of the rio Aripuanã, rio Madeira basin.

FIGURE 2. Drainage map of Brazil illustrating the geographic distribution of Nemuroglanis furcatus. FLOREST = State Forest; RESEX = Extractive Reserve; PAREST = State Park.

FIGURE 3. Lateral view of caudal skeleton and associated rays of Nemuroglanis furcatus, INPA 33758, 38.6 mm SL, paratype. Abbreviations: EP, epural; HU 1 + HU 2, plate formed by hypurals 1 and 2; HU 3 + HU 4, plate formed by hypurals 3 and 4; HU 5, hypural 5; PH, parhypural; PU 1 + U 1, centrum formed by preural crentrum 1 and ural centrum 1; UR, uroneural. Scale bar = 1 mm.