Leporinus amazonicus, Santos, Geraldo Mendes Dos & Zuanon, Jansen, 2008

Santos, Geraldo Mendes Dos & Zuanon, Jansen, 2008, Leporinus amazonicus, a new anostomid species from the Amazon lowlands, Brazil (Osteichthyes: Characiformes), Zootaxa 1815, pp. 35-42 : 36-40

Leporinus amazonicus , new species

( Figs. 1–4 ; Table 1 )

Holotype. INPA 22861 (218.0 mm SL), Brasil, Amazonas: Lago Catalão (03º10’08’’S, 59º55’01’’W), Rio Amazonas at the confluence of rios Negro and Solimões; gill net; 0 4 Aug 2004, A. Negrão.

Paratypes. All specimens collected at the same locality as the holotype. INPA 22125 (1, 185.0 mm SL), 10 Sept 2003, V. S. Dias; INPA 22860 (1, 218.0 mm SL), 29 May 2003, J. Zuanon; INPA 22863 (1, 97.0 mm SL), Oct 1999, V. S. Dias; INPA 24734 (1, 250.0 mm SL), 16 July 2005, J. Zuanon; INPA 22864 (1, 135.0 mm SL), 0 9 Apr 2003, S. Amadio & J. Zuanon; INPA 26059 (1, 206.0 mm SL), May 2006, C. Sotero & J. Monteiro; INPA 26060 (1, 180.0 mm SL), 10 Apr 2006, A. Silva Filho & F. Andrade; INPA 26061 (1, 160.0 mm SL), April 2005, V. S. Dias; INPA 26062 (1, 138.0 mm SL), 11 May 2005, A. Silva Filho & V. S. Dias; INPA 26063 (1, 250.0 mm SL), 11 May 2005, A. Silva Filho & V. S. Dias; MZUSP 95170 (ex-INPA 22862), (1, 205.0 mm SL), 0 5 July 2004, C. Sotero da Silva.

Diagnosis. Leporinus amazonicus n. sp. belongs to the friderici -group, as defined by Géry (1977) and Garavello (1979). It differs from most of congeners (except L. fasciatus , L. affinis and L. y-ophorus ) by the high lateral line scale count (45–47 versus 43 or fewer), and from these species by the color pattern (brownish-grey with one small and elongated dark blotch on the flanks in L. amazonicus vs. yellow ground color with several single or divided vertical dark bars on the side in the others). Leporinus amazonicus is morphologically similar to the slender bodied species L. cylindriformis Borodin, 1929 and L. brunneus Myers, 1950 , but differs from them by the higher lateral line scale count (45–47 versus 41–43 in L. cylindriformis and 36–42 in L. brunneus ) and by a different color pattern (lateral blotch occupying 2–4 horizontal scales in L. amazonicus versus 5–7 in L. cylindriformis , and absence of well defined blotches on the body sides in L. brunneus ).

Description. Refer to Figs. 1–2 for a general view of the holotype and one of the paratypes (INPA 22863) and to Table 1 for measurements and body proportions. Body medium sized (up to 250.0 mm SL) and elongated, greatest body depth at dorsal-fin origin. Dorsal profile gently curved from snout to dorsal-fin base; slightly slanted posteroventrally at dorsal-fin base, gently slanted to adipose-fin and moderately concave at caudal peduncle. Ventral body profile gently curved from lower jaw tip to pectoral-fin insertion, somewhat convex to almost straight to anal opening, slanted posterodorsally at anal fin base and slightly concave at caudal peduncle. Dorsal and ventral body contour rounded in cross section, somewhat compressed at base of dorsal and anal fins. Prepelvic region a little rounder than other body sections, postpelvic region slightly compressed. Caudal peduncle elongated, almost rectangular, slightly longer than high.

Dorsal fin with ii, 10 rays, almost rectangular, with convex upper margin when fully spread; median dorsal-fin rays larger and approximately with double size of first and last ones. Pectoral fin i, 14–16, with a convex margin. Pelvic fin i, 8–9, wide and with a round edge, its base slightly in advance of mid body and well separated of each other when spread. Anal fin ii, 8–9, its tip not reaching the base of caudal fin when adpressed. Caudal fin deeply forked with similar sized lobes.

Head stout and approximately conical, laterally compressed and covered with thick skin. Eye relatively small, with free orbital rim. Lower edge of orbit below main longitudinal body axis. Gill openings wide, gill rakers short and fleshy, 13–15 on lower half of first branchial arch. Branchiostegal rays 4.

Mouth subterminal. Nasal openings set close together and separated by a thin skin fold. Anterior nares as a short tube with a rounded posterior flap, posterior nares as a round opening with lamellae clearly visible inside. Lower jaw shorter and set inside upper jaw with mouth closed. Lips fleshy and thick, internally covered by numerous papillae. Teeth 4/ 4 in each side of mouth, incisiforms, with borders almost straight, excavated on the lingual side and decreasing in size from symphysis ( Figs. 3 , 4 ).

Scales cycloid. Lateral line (LL) straight, with 45–47 perforated scales. Scales series between dorsal fin origin and LL numbering 5 to 5.5, and 5 from LL to pelvic fin origin. Circumpeduncular scales series 16, and 14–18 irregularly set scales between dorsal and adipose fins.

Color pattern in alcohol. Ground color brownish grey, slightly darker at dorsum. Scale edges darker than centrum, forming an incipient reticulate pattern on body. One slightly elongated dark blotch on body side, occupying 2–4 scales horizontally and 1–2 vertically, situated over the LL scale series and placed at dorsal fin level. Fins yellowish to light grey, with interradial membranes darker (especially on anal and caudal fin). Pelvic yellowish with anterior edge grey. Adipose dark grey at base and free edge, with center yellowish ( Fig. 1 ). Smallest examined specimen (97.0 mm SL) with a series of short and narrow vertical bands along dorsum (up to the LL), more conspicuous between head and dorsal fin origin.

Live color pattern. Dorsum brownish grey, darker on head and anterior portion of body. Ventral portion of body light grey to yellowish. One black, slightly elongated blotch over lateral line scales, at dorsal-fin level. Scales with base and free edge darker than centrum, producing a conspicuous reticulated pattern especially in upper half of trunk. Pectoral fin yellow, dorsal and pelvic fins yellow to bright orange at distal portion. Caudal and anal fins bright orange to red, suffused with dark melanophores at base and along rays. Adipose fin yellowish grey with base and center darker ( Fig. 2 ).

Distribution. All the measured specimens were collected in the central portion of the Rio Amazonas basin near Manaus. Nevertheless, the species may be expected to occur along most of floodplain habitats of the Rio Solimões-Amazonas in the Brazilian states of Amazonas and Pará.

Ecological notes. Leporinus amazonicus was collected in floodplain lakes and backwaters with muddy bottom substrate, in typical várzea habitats. Intensive collecting done monthly in the Lago Catalão near Manaus during seven consecutive years (2001–2007) resulted in only a few specimens of the new taxon, and usually just one collected each time, indicating a low abundance and apparently solitary habits of this species. However, this supposed rarity may be biased by the concentration of our collecting efforts around Manaus, which may represent a marginal distribution of this species.

Etymology. Named after the Rio Amazonas, where all the type series comes from.

Figures

FIGURE 1. Leporinus amazonicus n. sp., lateral view of the holotype (INPA 22861, 218 mm SL).

FIGURE 2. Leporinus amazonicus n. sp., lateral view of a freshly collected specimen (INPA 22863, paratype, 97 mm SL).

FIGURE 3. Inner view of the teeth of Leporinus amazonicus n. sp. (INPA 22860, 218 mm SL, paratype).

FIGURE 4. Lateral view of the teeth of Leporinus amazonicus n. sp. (INPA 22860, 218 mm SL, paratype).

Tables

TABLE 1. Morphometrics of Leporinus amazonicus n. sp. (Characiformes: Anostomidae). Measurements expressed as percentage of SL or head length (*). SD = standard deviation.

	Holotype	Paratypes (n = 11)
		Range	Mean (SD)
Standard length (SL)	218.0	97.0–250.0
head length	25.2	24.4–27.8	25.9 (1.0)
body depth	23.9	23.8–27.0	25.3 (1.2)
body width	15.6	13.1–16.4	14.6 (1.1)
caudal peduncle length	14.4	14.2–16.5	15.3 (0.7)
caudal peduncle depth	9.4	8.6–9.5	9.2 (0.3)
predorsal length	43.1	41.9–46.7	44.4 (1.5)
preventral length	46.8	46.8–50.5	48.9 (1.0)
preanal length	76.6	76.3–82.5	80.2 (2.0)
interdorsal distance	27.1	25.4–28.4	26.9 (0.9)
head depth*	70.9	66.7–75.4	70.8 (3.0)
head width*	52.7	50.0–55.6	53.5 (2.2)
snout length*	36.4	33.3–38.5	35.9 (1.6)
orbit diameter*	20.0	18.5–21.8	20.1 (1.0)
interorbital distance*	41.8	38.2–43.1	40.8 (1.6)