Australoheros ykeregua, Říčan, Oldřich, Piálek, Lubomír, Almirón, Adriana & Casciotta, Jorge, 2011

Říčan, Oldřich, Piálek, Lubomír, Almirón, Adriana & Casciotta, Jorge, 2011, Two new species of Australoheros (Teleostei: Cichlidae), with notes on diversity of the genus and biogeography of the Río de la Plata basin, Zootaxa 2982, pp. 1-26 : 9-15

Australoheros ykeregua sp. nov.

( Figs. 4 , 5 , 6 , 7 ).

“ Cichlasoma “ cf. tembe (arroyo Fortaleza)— Casciotta e t al. 2003: 68, 70 “ Cichlasoma “ cf. tembe — Stawikowski and Werner 2004: 455

Australoheros sp. Forquilha—Říčan and Kullander 2006: 6

Australoheros forquilha (non-type material from ZSM)— Říčan and Kullander 2008: 16 N Min-Max Mean ± SD N Min-Max Mean ± SD

Head length 10 31.5 – 34.6 33.2 ± 1.2 49 33.2 – 39.1 36.2 ± 1.2 Snout length 10 7.6 – 12.6 10.5 ± 1.6 49 8.8. – 18.4 14.9 ± 2.3 Body depth 10 40.9 – 46.6 43.9 ± 1.9 49 41.7 – 47.8 44.9 ± 1.5 Orbital diameter 10 9.3 – 12.6 11.3 ± 0.8 49 8.1 – 13.8 10.5 ± 1.4 Head width 10 15.6 – 18.0 16.5 ± 0.7 49 16.0 – 19.1 17.6 ± 0.6 Interorbital width 10 8.7 – 11.5 10.1 ± 0.9 49 8.7 – 14.3 10.9 ± 1.6 Preorbital distance 10 6.4 – 10.8 9.1 ± 1.4 49 6.4 – 12.3 9.3 ± 1.3 Caudal peduncle depth 10 16.6 – 18.3 17.4 ± 0.5 49 15.6 – 18.8 17.2 ± 0.7 Caudal peduncle length 10 8.9 – 11.1 10.2 ± 0.7 49 8.4 – 13.9 10.9 ± 1.3 Pectoral fin length 10 25.6 – 29.5 26.9 ± 1.2 49 25.9 – 32.5 29.4 ± 1.6 Ventral fin length 10 22.1 – 29.6 26.1 ± 2.2 49 23.3 – 34.7 29.6 ± 2.0 continued.

A. angiru A. kaaygua

N Min-Max Mean ± SD N Min-Max Mean ± SD Holotype. MACN-ict 9467, 102.0 mm SL, Argentina, río Uruguay basin, arroyo Paraiso (or Canal Muerto), 27°14'15.1" S, 54°02'38.5" W, col: Říčan et al., December 2007.

Paratypes. 30 specimens, 39.5–136.8 mm SL, all from Argentina, Misiones province, río Uruguay basin. MACN-ict 9468, 4 ex., 39.5–108.7 mm SL, same data as holotype. MACN-ict 9469, 3 ex., 101.1–136.8 mm SL, arroyo Fortaleza, 26°45'56.6" S, 54°10'57.4" W, col: Říčan et al., December 2007. AI 270, 3 ex. (C&S), 57.0–64.0 mm SL, arroyo Fortaleza, 26°45'56.6" S, 54°10'57.4" W, col: Casciotta et al., April 2000. MACN-ict 9470, 3 ex., 90.5–112.0 mm SL, arroyo Guerrero, 27°45'57.4" S, 55°09'33.7" W, col: Říčan et al., December 2007. MACN-ict 9471, 4 ex., 86.5–102.1 mm SL, arroyo Shangai or arroyo Pindaiti, 27°28'13.8" S, 54°41'24.5" W, col: Říčan et al., December 2007. MACN-ict 9472, 13 ex., 47.0– 86.3 mm SL, arroyo Tamandua, 27°05'56.5" S, 54°45'48.9" W, col: Říčan et al., December 2007.

Additional non-type material. ZSM 23060b, 6 ex., río Soberbio, El Soberbio, col: J. Foerster, 1966. ZSM 23482b, 13 ex., río Soberbio, El Soberbio, col: J. Foerster, 1966. ZSM 23482c, 2 ex. (C&S), río Soberbio, El Soberbio, col: J. Foerster, 1966.

Diagnosis. Australoheros ykeregua is distinguished from all Australoheros species except A. forquilha (with which it was previously associated) in having a series of opalescent pale blue dots along the postero-lateral border of the suborbital series (dark markings in preserved specimens), in having checkerboard-spotted dorsal, anal and caudal fins (red spots in live animals and dark grey in preserved specimens), a red to orange branchiostegal membrane, mouth and lower head area and base of pectoral fin, by having comparativelly thick lips (shared also with A. tembe ), the lower jaw shorter than the upper, by having 25–26 E0 scales (vs. less than 25), by having the longest dorsal fin scale cover (shared also with A. tembe ), and by the narrowest head (head width less than 50% vs. more than 50% of HL), shortest interorbital (10.9% of SL) and longest preorbital (9.3% of SL) distances.

Australoheros ykeregua is distinguished from A. forquilha by not having opalescent pale blue dots on each body scale, by not having them widely distributed on the head, but limited to a single line below the suborbital series, and in having a red coloration limited to the head region and the base of the pectoral fin (vs. red coloration on the whole belly to the end of the anal fin). Further distinguished by lower counts of caudal vertebrae (13–14 vs. 14–15), less caudal peduncle vertebrae (modally 2 vs. modally 3), lower total dorsal fin counts (25–26 vs. 26–27) and 25 vs. 26 E0 scales.

Australoheros ykeregua is distinguished from the only other similar species, Australoheros tembe , by the above listed unique characters and by coloration (shared only with A. forquilha ) and additionally by a shorter caudal peduncle (including 2 vs. 3 vertebrae) and more dorsal fin rays (10–11 vs. 9).

For distinguishing characters from all other Australoheros species see the Notes section.

Description. Based on specimens over 60 mm SL. Meristic data are summarized in Table 2, morphometric data are summarized in Table 3.

Body rather slender (44.9% SL), head with a rounded profile, mouth subterminal with comparativelly thick lips, short interorbital (10.9% SL) and long preorbital (9.3% SL) distances. Lacrimal bone deeper than wide. A rather long caudal peduncle containing modally two vertebrae, 14 caudal vertebrae. Caudal peduncle considerably deeper than long (mean length 63% of depth).

Scales on chest smaller than half the size of the biggest scales in the E0 row above the pectoral fin. About 8 scale rows between the opercular flap and the anterior insertion of the pelvic fin in the holotype. Scales in E0 row 24(1), 25(32*), 26(13). Upper lateral line scales 14(1), 15(1), 16(5), 17(15), 18(19*), 19(5). Lower lateral line scales 7(1), 8(4), 9(26*), 10(10), 11(5). Scales between upper lateral line and dorsal-fin scale cover 3 posteriorly, 4 plus two small parallel scales anteriorly, forming a sheath of smaller scales arranged in pairs per scale row, along the insertion of the dorsal fin. Cheek scale rows 4(2), 5(16*), 6(1). Dorsal fin with interradial scales appearing from 13th(1), 14th(6), 15th(8), 16th(4*) spine membrane, in single rows. One (5), two (10*) or three (4) last interradial membranes without scales. Anal fin with one basal scale row; interradial scales in single rows, from the 4th(1), 5th(8), 6th(10*) spine membrane lacking on one (17*) or two (2) last interradial membranes. Caudal fin densely scaled, scales ctenoid; interradial scales in one or two rows; posterior margin of scaly area concave, extending to between one-third and middle of caudal fin.

Soft dorsal fin pointed, extending to the middle or almost to the end of the caudal fin. D. XV,10(3), XV,11(3), XVI,9(2), XVI,10(16), XVI,11(22*), XVII,9(1), XVII,10(2). Soft anal fin pointed, of about the same length as dorsal fin. A. V,8(3), V,9(1), VI,7(14), VI,8(29*), VI,9(3). Anal fin pterygiophores 11(15), 12(7). Pelvic fin base slightly posterior of pectoral fin base; first branched ray longest. Pelvic fin not reaching (2), reaching (10) or surpassing (7*) anal fin origin. Pectoral fin shorter than pelvic fin, with a rounded tip. P. 13(14), 14(18), 15(15*). Caudal fin with rounded corners.

Oral jaw teeth caniniform, slightly curved. Outer row teeth increasing in size symphysiad, upper-jaw anterior teeth more robust, lower-jaw anterior teeth subequal.

Lower pharyngeal tooth plate in a dissected specimen about one quarter wider than long (length 59–62% of width). Dentigerous area wider than long. 7–9 teeth along midline, 22–26 teeth along posterior margin. Posterior teeth tend to be progressively more compressed, except for medial teeth. Larger teeth medially and posteriorly, gradually smaller anteriad and laterad. Posterior teeth with forwards curved posterior cusp and subapical anterior shelf. Large laterally compressed teeth with a second cusp projecting anteriorly from shelf.

Gill rakers externally on first gill arch: 1-2 epibranchial, 1 in angle, 7(3), 8(13), 9(4) ceratobranchial.

Vertebrae 13+13=26(3), 13+14=27(19), 14+13=27(3). Caudal peduncle contains 1(1), 1.5(5), 2(11), 2.5(6), 3(1) vertebrae.

Color pattern in alcohol. Six or seven vertical flank bars, a midlateral blotch in the fourth flank bar (sensu Říčan et al. 2005), a caudal fin spot, and the caudal peduncle bar make up the principal markings. Base of caudal spot at level of the lower lateral line. Lateral band 1, 1/2 or 2 scales deep posteriorly from the posterodorsal edge of opercular to the midlateral blotch (not clearly visible in the holotype). Lateral band extending behind the midlateral blotch, widening towards the end of dorsal-fin base level in five adult specimens and in eight juveniles (arroyo Tamandua, MACN-ict 9472).

Vertical bars are relatively wide, indistinct in their ventral parts. The fourth bar, bearing the midlateral blotch is centered above the anteriormost portion of the anal fin. Many thin parallel stripes on flanks, more evident on lower half of body.

Dorsal fin with a dark pigmentation from interradial membranes from 8th or 9th spine to 3rd to 4th branched ray. This pigmentation extended to the tip of the dorsal filament. Same dark pigmentation on basal third of the remaining branched rays. Soft dorsal and anal fins, and caudal fin with dark spots in a checker-board pattern on interradial membranes (missing in some specimens).

One (MACN-ict 9468, MACN-ict 9472), two (in the holotype MACN-ict 9467 and in MACN-ict 9468, MACN-ict 9472) or three (MACN-ict 9472) small and inconspicuous dark blotches below the orbit along the postero-lateral border of the suborbital series.

Life coloration. The most distinct color markings include the diagnostic 1) red/orange branchiostegal membrane, base of pectoral fin, mouth and lower head area, 2) the single interrupted line of blue dots along the suborbital series (dark blotches in preserved specimens), and 3) the checkerboard pattern of red dots on unpaired fins ( Fig. 7 ). This character combination is unique among Australoheros . The most similar species, A. forquilha , is easily distinguished in that the blue dots are not limited to a single line below the orbit. Instead, they cover the whole head and are present in all body scales and are also present on all fins except the pectorals (see Fig. 7 and also “ Cichlasoma “ cf. tembe in Stawikowski & Werner 2004, p. 455).

Distribution. Australoheros ykeregua is so far known only from Argentinean territory in the tributaries of the río Uruguay below the Salto Moconá, province of Misiones.

Etymology. The Guaraní word ykeregua means neighbor (vecino in Spanish). The etymology is based on the fact that A. ykeregua and A. forquilha have been preliminarily treated as conspecific ( Říčan & Kullander 2008). New data have however demonstrated that they are two sister group species living in the same river drainage (río Uruguay), though not sympatrically.

Notes. Říčan and Kullander (2006, 2008) treated part of the ZSM non-type material from Argentina as conspecific with A. forquilha . New fresh material collected in 2007 has revealed that the Argentinean and Brazilian material do not represent the same species. The ZSM lots 23060 and 23482 have been divided since they contained two different species and lots ZSM 23060b, 23482b and 23482c hold A. ykeregua .

We hypothesize that the barrier between the two species, A. forquilha and A. ykeregua , is formed by the Salto Moconá on the río Uruguay just below the confluence with the río Pepirí Guazú (which forms the international bor- der between Argentina and Brazil). The two species are closely related, but important differences in morphology and DNA demonstrate that there is no gene flow between them and they are thus evolutionarily independent units.

Additional diagnostic characters that separate Australoheros ykeregua from all other species except A. forquilha and A. tembe are as follows. From A. facetus , by having more caudal vertebrae (14 vs. 13), more caudal peduncle vertebrae (2 vs. 0–1), more E0 scales (25–26 vs. 24), and by a longer snouth (14.9 vs. 9.4 % SL) and a longer preorbital distance (9.3 vs. 5.7 % SL).

Australoheros ykeregua is additionally distinguished from A. kaaygua by having more caudal vertebrae (14 vs. 13), more C1 gill rakers (8 vs. 6), more caudal peduncle vertebrae (2 vs. 0–1), more E1 scales (18 vs. 16) and by a slightly longer snouth (14.9 vs. 10.9 % SL). It is additionally distinguished from A. minuano by lacking a pinkish body coloration of live specimens, by having more caudal vertebrae (14 vs. 13), more pectoral fin rays (14 vs. 12), more C1 gill rakers (8 vs. 6), more caudal peduncle vertebrae (2 vs. 0–1), more E0 scales (25–26 vs. 24), and by a longer snouth (14.9 vs. 10.6 % SL) and a longer preorbital distance (9.3 vs. 6.0 % SL).

Australoheros ykeregua is distinguished from A. guarani by also having more caudal vertebrae (14 vs. 13), more pectoral fin rays (14 vs. 13), more C1 gill rakers (8 vs. 7), more E0 scales (25–26 vs. 24), more caudal peduncle vertebrae (2 vs. 0–1), and by a shorter head (36.2 vs. 32.4 % SL), longer snouth (14.9 vs. 8.5 % SL), and less deep body (44.9 vs. 48.1 % SL). It is additionally distinguished from A. charrua by lacking a pinkish body coloration of live specimens, by less anal fin spines (5–6 vs. 7–8), more C1 gill rakers (8 vs. 6), more caudal peduncle vertebrae (2 vs. 0–1), by a slightly longer head (36.2 vs. 32.4 % SL), slightly longer preorbital distance (9.3 vs. 7.3 % SL) and by a longer snouth (14.9 vs. 8.5 % SL).

Australoheros ykeregua is additionally distinguished from A. scitulus in lacking the dark spot-markings on the head and anterior part of body, less dorsal fin spines (16 vs. 17), more dorsal fin rays (10–11 vs. 9–10), less anal fin spines (5–6 vs. 8–9), more pectoral fin rays (14 vs. 13), by more C1 gill rakers (8 vs. 6), more caudal peduncle vertebrae (2 vs. 0) and less deep body (44.9 vs. 47.7 % SL). It is also distinguished from A. angiru by lacking the yellow background coloration, yellow iris and red dorsal and ventral margins and corners of the caudal fin in live specimens, by having more dorsal fin rays (10–11 vs. 9–10), less anal fin spines (6 vs. 7), more caudal vertebrae (14 vs. 13), more pectoral fin rays (14 vs. 12), more C1 gill rakers (8 vs. 6), more E0 scales (25–26 vs. 24), more caudal peduncle vertebrae (2 vs. 0–1), a longer head (36.2 vs. 33.3 % SL), a longer snouth (14.9 vs. 9.5 % SL), a less deep body (44.9 vs. 49.6 % SL) and a longer preorbital distance (9.3 vs. 7.3 % SL).

Australoheros ykeregua is distinguished from A. acaroides by also having more caudal vertebrae (14 vs. 13), more caudal peduncle vertebrae (2 vs. 0–1), less anal fin spines (6 vs. 7), more E0 scales (25 vs. 23–24), more C1 gill rakers (8 vs. 6), and a smaller interorbital distance (33 vs. 43 % HL). It is additionally distinguished from A. taura by lacking a pink to red body coloration of live specimens, more caudal vertebrae (14 vs. 13), more C1 gill rakers (8 vs. 7), and a deeper body (44.9 vs. 41.4 % SL) and a smaller interorbital distance (33 vs. 41% HL).

Australoheros ykeregua is additionally distinguished from all the Atlantic coast species north of A. acaroides and A. taura ( A. autrani , A. barbosae , A. capixaba , A. ipatinguensis , A. macacuensis , A. macaensis , A. muriae , A. paraibae , A. ribeirae , A. robustus , A. saquarema ) by having more caudal vertebrae (14 vs. 12 or 13), more caudal peduncle vertebrae (2 vs. 0), less anal fin spines (6 vs. 7), a smaller interorbital distance (33 vs. 41% HL), and a shorter pelvic fin (<30 vs.>30 % SL).

Figures

FIGURE 4. Australoheros ykeregua, MACN-ict 9467, 102.0 mm SL, holotype, right side (reversed). This specimen does not show vertical bars after preservation, but see Fig. 7 of the same specimens photographed alive.

FIGURE 5. Australoheros ykeregua, MACN-ict 9470, 90.5 mm SL. This specimens shows the dark color of the dorsal fin and the midlateral blotch and vertical bars.

FIGURE 6. Australoheros ykeregua, MACN-ict 9472, 66.2 mm SL. This specimen shows a continuous lateral band extending beyond the midlateral spot and the checker-board spot pattern of unpaired fins (also evident in the holotype and the majority of specimens).

FIGURE 7. Color plate. Horizontaly from upper left to lower right. Australoheros forquilha, rio Forquilha, rio Uruguai drainage, Rio Grande do Sul, Brazil (not preserved). Australoheros ykeregua (MACN-ict 9467, holotype), río Uruguay drainage, arroyo Paraiso (or Canal Muerto), Misiones province, Argentina. Australoheros kaaygua (MACN-ict 9473), río Iguazú drainage, small stream 7 km SW from Andresito, Misiones province, Argentina. Australoheros angiru, male in neutral colors, rio Chopim, rio Iguaçu drainage, Paraná, Brazil (not preserved). A. angiru, male and female in breeding colors guarding fry, same locality (not preserved). All A. angiru photographs courtesy of Wolfgang Staeck.