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

publication ID

z01587p043

publication LSID

lsid:zoobank.org:pub:B2CDDEA9-F47C-444F-BA47-DB7D7EC8D49A

persistent identifier

http://treatment.plazi.org/id/7A11D37F-F8DE-45C5-B87D-C5ED297E9B76

taxon LSID

lsid:zoobank.org:act:7A11D37F-F8DE-45C5-B87D-C5ED297E9B76

treatment provided by

Thomas

scientific name

Astyanax varzeae
status

new species

Astyanax varzeae  ZBK  , new species

(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 

Paratypes. Collected with the holotype: MCP 40535, 14, 43.9-72.0 mm SLGoogleMaps  ; MHNCI 9146, 1 c&s, 53.1 mm SLGoogleMaps  ; MHNCI 9147, 15, 43.0-81.8 mm SL (including 2 c&s)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.

Distribution. Astyanax varzeae  ZBK  is known only from the rio da Várzea headwaters, an affluent of rio Negro, a tributary of the upper portions of the rio Iguaçu in Paraná State, Brazil.

Ecological notes. Astyanax varzeae  ZBK  was collected in a headwater stream with clear water, light to moderate current water and bottom with stones, sand and moderate amount of vegetal debris.

Discussion

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.