Astyanax varzeae, Vinícius Abilhoa & Luiz Fernando Duboc, 2007
Vinícius Abilhoa & Luiz Fernando Duboc, 2007, A new species of the freshwater fish genus Astyanax (Ostariophysi: Characidae) from the rio Iguacu basin, southeastern Brazil., Zootaxa 1587, pp. 43-52: 45-50
treatment provided by
(Figs. 2-4; Table 1)
Astyanax sp. F . Haluch & Abilhoa, 2005: 384 (fig.1), 387 (comparative material).
Holotype. MHNCI 11688, 83.1 mm SL, Brazil, Paraná, Tijucas do Sul, rio Sao Joao , rio da Varzea headwaters, an affluent of rio Negro, upper rio Iguacu basin , approx. 25°55’S 49°10’W, A. Schwarz, March 1999.GoogleMaps
Diagnosis. The combination of shallow body depth (28.7-32.9% vs. more than 35% of SL) and the lower number of branched anal-fin rays (15-20 vs. 20-45) include Astyanax varzeae ZBK in the Astyanax scabripinnis species complex of Bertaco & Lucena (2006). Astyanax varzeae ZBK differs from A. ojiara ZBK and A. paris ZBK by its shallower body depth (28.7-32.9% vs. 34.0-40.0% of SL in A. ojiara ZBK and A. paris ZBK ). Shallow body depth (28.7- 32.9%, mean=30.1) also differs Astyanax varzeae ZBK from A. ita ZBK (34.3-39.8%, mean=37.1), A. rivularis (35.0- 46.0%), A. chico ZBK (37.3-43.0%, mean=40.8), A. tumbayaensis ZBK (39.2-45.3%, mean=42.4), A. hermosus ZBK (33.9- 38.7%, mean=36.3 in females, 36.1 in males), A. endy (36.6-42.2%, mean=39.7 in females, 38.4 in males), A. pampa ZBK (36.9-42.2%, mean=38.7), and A. laticeps (35.3-40.6%, mean=37.9). Astyanax intermedius ZBK can be distinguished from A. varzeae ZBK by its smaller dorsal-fin length (10.7-16.4%, mean=13.4 vs. 19.9-25.9%, mean=23.2). Astyanax varzeae ZBK differs from A. giton ZBK by its larger head length relative to SL (27.1-29.7%, mean=28.6 vs. 21.4-26.3%, mean=23.7), and from A. taeniatus by its shorter snout length compared to head length (16.4-23.3%, mean=20.1 vs. 25.3-32.6%, mean=28.6). Astyanax varzeae ZBK is distinguished from A. jenynsii by its larger orbital diameter relative to head length (30.9-44.5%, mean=37.9 vs. 24.7-27.6%, mean=26.3), and from A. obscurus by the greater interorbital width (29.8-37.7%, mean=34.5 vs. 27.7-28.6%, mean=28.2). The presence of bony hooks on all fins but pectoral-fin rays of males separates A. leonidas ZBK and A. troya ZBK from A. varzeae ZBK , and the presence of bony hooks on pelvic and anal-fin rays of males separates A. totae ZBK , A. cremnobates ZBK and A. brachypterygium ZBK from A. varzeae ZBK . The occurrence of two humeral spots (second one faint) distinguishes A. varzeae ZBK from A. paranae ZBK , A. microschemos ZBK , and A. pelecus ZBK (single humeral spot).
Description. Morphometric data of holotype and paratypes are presented in Table 1. Body moderately elongated, compressed, greatest depth at dorsal fin origin, 3.1 to 3.5 times in SL.
Dorsal profile of head straight. Dorsal body profile between the supraoccipital spine through dorsal-fin origin gently convex, and almost straight from the end of dorsal-fin base to caudal peduncle. Base of dorsal fin straight. Ventral profile of head gently rounded. Body profile from the margin of lower lip to anal-fin origin convex. Anal-fin base straight. Caudal peduncle elongated with dorsal and ventral profiles nearly straight.
Snout profile rounded, shorter than orbital diameter. Postero-ventral edge of third infraorbital distant from preopercle, leaving wide naked border between these bones. Mouth terminal, angled posteroventrally. Maxilla reaching a vertical line through the middle of the orbit, with 1 to 3 (usually 2) tricuspid teeth.
Premaxilla with two tooth rows. Outer row with 3 (2), 4* (21) tricuspid teeth, with central cuspid developed. Inner row with 5 teeth gently expanded distally, slightly compressed at distal tips. Symphysial tooth narrower and deeper, with 4 or 5 cusps. Second, third and fourth teeth with 5 cusps. Fifth tooth smaller, with 4 cusps. In all teeth central cusp slightly larger than remaining ones. Dentary with 7 teeth. First four anterior teeth larger, usually with 5 cusps, followed by 3 very smaller tricuspid teeth (Fig. 4).
Dorsal-fin rays ii, 9. Posterior margin of dorsal-fin straight. Dorsal-fin origin approximately at middle of SL. Pelvic-fin rays i, 7. Pelvic-fin origin located slightly anterior to vertical through dorsal-fin origin. Pectoral-fin rays 11 (3), 12 (14), 13* (13). Anal-fin with iii-iv, 15 (1), 16 (5), 17* (16), 18 (7), 20 (1) rays. Adiposefin located approximately at vertical through insertion of base of last anal-fin rays. Caudal-fin forked, lobes similar in size, slightly rounded, and with 19 principal rays.
Lateral line complete, with 37 (1), 38 (6), 39* (16), 40 (6), 42 (1) perforated scales. Six series of scales between dorsal-fin origin and lateral line. Four or five series of scales between lateral line and pelvic-fin insertion. Circumpeduncular scales 14* (4), 15 (7), 16 (19).
In three cleared and stained specimens procurrent caudal-fin rays 8 or 10 dorsal and ventral. First gill arch with 19 gill rakers (7 epibranchial, 9 ceratobranchial, 1 on cartilage between epibranchial and ceratobranchial, and 2 hypobranchial), vertebrae 36, 37 or 38 (18 precaudal and 18, 19 or 20 caudal). Supraneurals 5.
Color in alcohol. Preserved specimens with dorsal and lateral parts of the body medium brown to pale yellowish. Dark chromatophores concentrated on middorsal surface of head and body. Humeral spot narrow and vertically elongated, two scales wide above lateral line. Body with black, pigmented, midlateral stripe extending from humeral region to the median caudal-fin rays. The anterior portion of the stripe expanded, sometimes forming a faint second humeral spot, more clearly visible in smaller specimens (Fig. 3). Fins with scattered dark chromatophores.
Sexual dimorphism. None of the specimens examined have bony hooks on the fins or any other sexually dimorphic feature.
Etymology. The species name, varzeae, is in reference to the sample locality, rio da Várzea drainage, a tributary of the upper rio Iguaçu basin.
Despite the fact that the Iguaçu River is a large tributary of the Parana River, many fishes that occur in rio Paraná basin are not found in rio Iguaçu basin. In fact, the fish fauna of this hydrographic basin has a unique evolutionary history, and the endemism of its ichthyofauna is probably related with the geographic isolation imposed by the Iguaçu falls (Severi & Cordeiro 1994; Garavello et al. 1997).
Furthermore, recent collecting efforts in the upper rio Iguaçu basin showed that the biogeographic history of the ichthyofauna in that watershed is likely to be more complex than described herein. The fish fauna of the upper rio Iguaçu basin, for example, consists mostly of species that does not occur in the lower portions of the river, and also components endemic to the coastal drainage.
The characterization of the upper reaches of the rio Iguaçu basin as an area of endemism was already proposed by Abilhoa (2004) and Ingenito et al. (2004), who subdivided the upper rio Iguaçu basin in two portions: rio Negro basin and rio Iguaçu headwaters. These authors listed several species with their geographic distribution restricted in each region ( Pareiorhaphis parmula ZBK , Astyanax totae ZBK , Ancistrus ZBK sp., Rineloricaria ZBK sp., Heptapterus stwearti , Trichomycterus naipi ZBK , Cnesterodon carnegiei ZBK , and Jenynsia eigenmanni ). The identification of a new species of Astyanax ZBK endemic to one portion of the upper Iguaçu river basin supports that hypothesis.
Regarding still undescribed Astyanax ZBK species occurring in the rio Iguaçu basin recorded by Sampaio (1988) and Severi & Cordeiro (1994), A. varzeae ZBK can be distinguished by the lower body depth compared to SL (28.7-32.9%, mean=30.1) from Astyanax sp. B (35.2-42.5%, mean=38.5), Astyanax sp. C (35.8-44.9%, mean=39.7), Astyanax sp. D (34.2-39.7%, mean=36.3), and Astyanax sp. E (32.0-46.9%, mean=37.7).
Although the species described here was first identified by Haluch & Abilhoa (2005) as Astyanax sp. F , another endemic morphotype recorded by several authors to the medium and lower portions of the rio Iguaçu basin (Severi & Cordeiro, 1994; Garavello et al., 1997; Baumgartner et al, 2006), the shorter snout length relative to head length differs A. varzeae ZBK from Astyanax sp. F (16.4-23.3%, mean=20.1 vs. 24.6-32.6%, mean=28.2). This morphotype was created by Sampaio (1988) to describe what seems to be a heterogeneous Astyanax ZBK , which exhibit body depth of 28.5 to 39.6% in relation to SL, 2 to 5 maxillary teeth, 1 to 4 teeth in outer row premaxilla, 17 to 22 branched anal-fin rays, and 7 to 9 pelvic-fin rays. Given that Sampaio (1988) did not analyze specimens from rio da Várzea headwaters, and the analysis carried out here clearly distinguish Astyanax varzeae ZBK from Astyanax sp. F , we recognize them as distinct species.
The frequent presence of two humeral spots differs the new species from A. janeiroensis Eigenmann ZBK and Astyanax aff. scabripinnis (from coastal drainage of southeastern Brazil - MHNCI 7824, MHNCI 7844, MHNCI 7858) (humeral spot well-defined, black and round, with a vertically elongated line extended anteroventrally), and from A microschemos ZBK and A. pelecus ZBK . Furthermore, these last two species inhabit drainages very distant from the rio Iguaçu basin. Astyanax varzeae ZBK also differs from the holotype of A. janeiroensis ZBK (MCZ 21057) by the lower body depth (28.7-32.9, mean=30.1 versus 36.9% of SL).
Despite de absence of secondary sexual characteristics (bony hooks) in the specimens examined, the larger orbital diameter also separates A varzeae ZBK from A. brachypterygium ZBK , A. cremnobates ZBK and A. totae ZBK (30.9- 44.5%, mean=37.9 vs. 24.8-34.8%, mean=29.0 in A. brachypterygium ZBK , 28.1-35.4%, mean=32.1 in A. cremnobates ZBK , and 25.4-42.6%, mean=35.7 in A. totae ZBK ; Fig. 5). Although the orbital diameter in A. varzeae ZBK partially overlaps the range of A. brachypterygium ZBK , A. cremnobates ZBK and A. totae ZBK , significant differences using one-way analysis of variance test were found among the species (F=67.91, P=0.001; Fig. 6).
Astyanax varzeae ZBK differs from Eigenmann’s Astyanax scabripinnis subspecies, all recognized as valid species by Bertaco & Malabarba (2001), Lucena & Lucena (2002) and Lima et al. (2003). Astyanax varzeae ZBK differs from the holotype of A. scabripinnis (Jenyns) (BMNH 1917.7.14:15) by the lower number of branched anal-fin rays (15-20 versus 21) and from the syntypes of D. longirostris (Steindachner) (NMW 57633, 2) by the shorter snout length compared to head length (16.4-23.3%, mean=20.1 versus 29.3%). Although it was not possible to analyze the type material of A. paranae ZBK , we examined one lot from the upper rio Tibagi basin (type-region of A. paranae ZBK ): MHNCI 8138 (rio Tibagi, locality of Palmeira), identified by Bertaco & Lucena (2006) as morphologically similar to the A. paranae ZBK holotype. One-way analysis of variance test indicated significant differences (F=11.18, P=0.001; Fig. 7) in snout length compared to head length between A varzeae ZBK (16.4-23.3%, mean=20.1) and A. paranae ZBK (16.0-20.4%, mean=18.1). The occurrence of two humeral spots (second one faint) also distinguishes A. varzeae ZBK from A. paranae ZBK (single humeral spot). Characters distinguishing A. jenynsii , A. laticeps , A. intermedius ZBK , and A. rivularis from A. varzeae ZBK were discussed under diagnosis.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.