Anostomoides passionis, Santos & Zuanon, 2006

Santos, Geraldo Mendes Dos & Zuanon, Jansen, 2006, Anostomoides passionis, a new fish species from rio Xingu, Brasil (Characiformes: Anostomidae), Zootaxa 1168 (1), pp. 59-68 : 60-66

Anostomoides passionis , new species

( Figs. 1–3 )

Material examined

Holotype. INPA 13182 (262 mm SL), Brasil, State of Pará: rio Xingu, Viracebo do Arroz Cru (03º25’15.7’’S, 51º55’08.3’’W); gill net in rocky outcrops in rapids area; 17 Sept. 1997, J. Zuanon.

Paratypes. All specimens collected in rio Xingu, State of Pará . INPA 13196 (1, 256 mm SL), collected with the holotype ; INPA 14876 (1, 161 mm SL), Ilha Bela Vista (03°24’15’’S, 51°41’53’’W), gill net; 29 Sept. 1996, J. Zuanon ; INPA 4042 (1, 306 mm SL), Arroz Cru (03º25’15. 7’’S, 51º55’08. 3’’W); gill net, 01 Oct 1990, J. Zuanon & L. Py­ Daniel ; INPA 4043 (2, 230 mm and 273 mm SL), Ilha de Babaquara (03º25’44.5’’S, 52º14’24.7’’W); gill net, 05 Oct 1990, J. Zuanon & L. Py­Daniel ; MZUSP 86083 (1, 274 mm SL, ex­INPA 4043, same data as above) ; ZUEC 3386 , (1, 217 mm, ex­INPA 13181, Ilha do Sr. Izaltino Barbosa , (03º16’21.2’’S, 52º04’22.0’’W), gill net, Sept. 1996, J. Zuanon.

Comparative material. Anostomoides laticeps: INPA 20204, 1 ex., rio Araguaia , State of Tocantins , 18 Feb 2000. INPA 10991 , 1 ex., rio Aripuanã , State of Mato Grosso , 01 Aug 1976. INPA 15182 , 1 ex., rio Jamari , State of Rondônia , 05 Apr 1986. INPA 15185 , 1 ex., rio Jamari , State of Rondônia , 18 Jun 1985. INPA 1190 , 1 ex., rio Negro , State of Amazonas, 31 Jul 1979. INPA 1191 , 2 ex., rio Negro , State of Amazonas, 27 Jun 1980. INPA 3210 , 1 ex., rio Pitinga , State of Amazonas, 11 Oct 1989. INPA 17277 , 1 ex., rio Purus , State of Amazonas, 03 Jun 2001. INPA 7106 , 1 ex., rio Tapajós , State of Pará , 27 Oct 1991. INPA 1609 , 3 ex., rio Tocantins , State of Pará , 10 Nov 1981. INPA 20553 , 1 ex., rio Tocantins , State of Pará , 31 Aug 2000. INPA 20554 , 1 ex., rio Tocantins , State of Pará , 5 May 2001. INPA 10091 , 1 ex., rio Uatumã , State of Amazonas, Feb 1985. INPA 15577 , 1 ex., rio Uatumã, State of Amazonas, May 1988; A. atrianalis: MNHN 87798, 1 ex. and MNHN 87799 , 1 ex., río Orinoco, Venezuela , 1887.

Diagnosis Anostomoides passionis n. sp. is distinguished from the other two congeneric species by the lower lateral line scale count (38–39 versus 39–41 in A. atrianalis and 42–44 in A. laticeps ); premaxillary teeth with straight and smooth borders, without cusps (vs. bicuspidate to somewhat tricuspid in the other two species); and by the color pattern (brownish­grey with two round to heart­shaped dark blotches on the side and deep red fins, vs. three transverse dark bands on the side in A. laticeps and absence of dark blotches or bands on the side in A. atrianalis ).

Description

Refer to Figs. 1 and 2 for a general view of the holotype and one of the paratypes, and to Table 1 for measurements and body proportions. Body deep and laterally compressed. Dorsal profile gently sloped from snout to dorsal fin base; slightly slanted posteroventrally at dorsal fin base, slightly convex between end of dorsal fin base and origin of adipose fin, then gently concave to caudal fin base. Ventral body profile gently curved from tip of lower jaw to pectoral fin insertion, slightly convex to almost straight to anal opening, slanted posterodorsally at anal fin base and somewhat concave at caudal peduncle. Caudal peduncle almost rectangular, slightly longer than high. Post pelvic region compressed but without forming keel.

Dorsal fin with upper margin slightly convex when fully spread; median dorsal fin rays approximately two times longer than first and last rays. Dorsal and adipose fins well separated, anterior portion of adipose fin base partially covered with scales. Pectoral fin wide, with convex margin, its tip reaching midway to base of pelvic fin. Pelvic fins wide with round edges, located slightly in advance of mid­body, and well separated from each other when spread. Anal fin with border slanted posterodorsally, its tip surpassing level of hypural joint when adpressed. Caudal fin deeply forked with long and wide lobes with rounded tips. Dorsal fin ii, 10; pectoral fin i, 15–16; pelvic fin i, 8 and anal fin ii, 8–9.

Head stout and approximately conical, laterally compressed and covered with thick skin. Snout conical and relatively long with nasal openings set close together and separated by thin fold of skin. Anterior nare a short tube with posterior flap; posterior nare round with lamellae clearly visible inside. Interorbital distance large (ca. 2.4 times in head length). Eye with free orbital rim, relatively small (contained ca. 5.2 times in head length) and placed low on side of head (orbit’s lower edge located below main longitudinal body axis). Mouth terminal to slightly upturned, with lips fleshy and thick, covered internally with numerous papillae. Lower jaw shorter and set behind anterior margin of upper jaw with mouth closed. Gill rakers short and fleshy, numbering 17–20 on first branchial arch, of which 7–8 are located on epibranchial and 10–12 on hypobranchial.

Teeth incisiform, with borders almost straight, excavated on the inner (lingual) side. Symphyseal teeth larger, wider and showing a slightly convex border, the following ones becoming smaller posteriorly, with truncate border and sometimes with small lateral saliencies forming incipient cusps ( Fig. 3 ). Four teeth in each premaxillary and four in each dentary.

Scales large and cycloid. Lateral line straight with 38–39 perforated scales, the pores ramified and composed of 2–4 divergent, usually independent rami. Six to 6.5 series of scales between the dorsal fin origin and the lateral line and 5.5–6.0 series to the pelvic fin origin. Sixteen series of scales around caudal peduncle; 11–13 irregularly set scales along the space between the dorsal and adipose fins.

Color pattern in alcohol. Background color brownish grey, slightly darker at dorsum. Scales with dark edges and central portion yellowish, forming an incipient reticulate pattern on the body. Two dark blotches on the side, round to heart­shaped, over the lateral line series of scales (one, more conspicuously located at the level of posterior half of dorsal fin, and another at anal fin level); these blotches occupy 2–3 scales horizontally as well as vertically. Caudal fin uniformly yellowish to light grey; anal fin grayish with darker interradial membrane; adipose fin with central portion dark grey, base and free edge yellowish; pelvic fin grey with yellowish edges; dorsal and pectoral fins uniformly light grey.

Live color pattern. Dorsal area olive grey, ventral portion lighter and yellowish. Two black, round to heart­shaped blotches over the lateral line scales, one placed at the level of the anterior portion of dorsal fin, and another at anal fin level. Scales with base and free edge darker than the central area, producing a conspicuous reticulated pattern. Fins red to dark orange, suffused with dark melanophores at the base of dorsal and caudal fins, tip of anal fin and central portion of adipose fin ( Fig. 2 ).

Distribution Presently known only from rio Xingu, State of Pará.

Ecological notes

All specimens of A. passionis collected in rio Xingu were found in areas with moderate to strong current (up to 0.80 m*sec ­1) and bottom substrate composed of sand, pebbles and scattered rocks of various sizes. Partially submerged boulders composed the main landscape at all collecting sites ( Fig. 3 ). On one occasion two specimens were collected side­by­side in a gill net, which suggests that this species may form small groups, at least during the dry season. Local fishermen say that A. passionis may form groups of up to a hundred individuals during the early rainy season, when ripe females are commonly caught.

During snorkeling sessions conducted in the dry season, one of us (JZ) observed a single large specimen of A. passionis swimming among dark recesses among submerged boulders, at a depth up to 2 m. The fish moved slowly among the rocks, foraging in feeding bouts of three to four bites directed to the ceilings of small caves under the boulders or at crevices among rocks. The biting produced a loud rasping sound, clearly audible underwater. Stomach contents of two specimens of A. passionis caught during the low water season were composed mainly of fragments of sponges. On another occasion, one fish was observed in a mixed group of several anostomid species ( Leporinus tigrinus Borodin , L. julii Santos, Jégu & Lima , L. brunneus Myers , L. friderici (Bloch) and Leporellus vittatus (Valenciennes)) . Other anostomid fishes observed occupying the large spaces under and among boulders were Leporinus megalepis Günther , Sartor respectus Myers & Carvalho , Pseudanos sp. , Anostomus ternetzi Fernández­Yépez and Synaptolaemus cingulatus Myers & Fernández­Yépez. Smaller fishes, mainly individuals of the tetragonopterin Astyanax dnophos Lima & Zuanon , pike cichlids ( Crenicichla spp. ) and armored suckermouth catfishes ( Loricariidae ) also shared the rocky shelters in the rapids.

Anostomoides passionis is locally known as “piau do sarão.” Piau is a common popular name for anostomids, and “sarão” is the vernacular name of a plant species of the family Mirtaceae , common in the seasonally flooded margins of small rocky islands in rio Xingu. According to the local fishermen, A. passionis feeds on the fruit of these plants during the early flooding season.

Etymology

From the Latin passio, meaning a feeling, in allusion to the round to heart­shaped dark blotches on the side of the fish, as well as the deep red color of its fins.

Figures

FIGURE 1. Drawing of Anostomoides passionis, holotype, INPA 13182, 262 mm SL. Scale bar = 50 mm.

FIGURE 2. Anostomoides passionis, paratype, ZUEC 3386, 217 mm SL, lateral view of freshly collected specimen.

FIGURE 3. Details of the teeth of Anostomoides passionis (holotype, INPA 13182, 262 mm SL). (a) frontal view and (b) lateral view. Scale bar = 10 mm