Comprehensive Description

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Pterolebias phasianus Costa, 1988 ZBK

(Figs. 9-10)

Pterolebias phasianus Costa, 1988a ZBK : 658 ( type locality: lagoon at Caceres , Cuaiaba River [correctly Paraguay River] floodplains , Mato Grosso , Brazil ).

Material examined. All from Paraguay River basin. Brazil : Mato Grosso : MZUSP 38109 , holotype , male, 31.4 mm SL; MZUSP 38110 , 1 paratype , female, 29.2 mm SL (c&s); MZUSP 38111 , 1 paratype , female, 25.7 mm SL; lagoon in Caceres , Paraguay River floodplains , Mato Grosso ; P. D. Cardoso-Filho , March 1987 . UFRJ 3649 , 39; UFRJ 3673 , 4 (c&s); Paraguay River floodplains, Caceres ; W. J. E. M. Costa, M. I. Landim, R. D'Arrigo & C. L. Moreira , 30 April 1996 . UFRJ 318 , 7; UFRJ 273 , 1 (c&s); Cuiaba River basin , Mato Grosso ; J. D. Soares , March 1990 . UFRJ 4899 , 8; UFRJ 4903 , 2; swamp near Porto Cercado, Cuaiba River floodplains ; W. J. E. M. Costa, F. Autran, A. C. Bacellar & A. Barbosa , 9 June 1999 . UFRJ 5182 , 2; same locality and collectors as UFRJ 4899 , 11 June 1999 . UFRJ 4914 , 1; beach on Cuiaba River, RPPN SESC-Pantanal ; idem , 10 June 1999 . UFRJ 4885 , 9; temporary pool at Posto SaoLuis , SaoLourenco River drainage, RPPN SESC-Pantanal ; idem , 12 June 1999 . Mato Grosso do Sul : MZUSP 38112 , 1; MZUSP 38113 , 1; Ladário ; E. K. Bastos , 10 March 1985 . MZUSP 49027 , 4; Passo do Lontra, Corumba ; O. Froehlich & E. A. Gonçalves , 23 May 1990 . UFRJ 3674 , 9; UFRJ 3675 , 3 (c&s); floodplains of Miranda River, Miranda ; W. J. E. M. Costa, M. I. Landim, R. D'Arrigo & C. L. Moreira , 21 April 1996 .

Diagnosis: Readily distinguished from P. longipinnis ZBK by having slender body (body depth 19.5-23.0 % SL vs. 25.0-28.8 % SL in males, 19.4-23.1 % SL vs. 25.3-27.0 % SL in females; caudal peduncle depth 11.8-14.8 % SL vs. 15.8-17.8 % SL in males, 11.9-13.7 % SL vs. 14.9-16.8 % SL in females), a single row of scales on the anal-fin base in males (vs. three to seven rows), no scales on the dorsal-fin base in males (vs. one or two rows of scales), pelvic-fin bases separated (vs. medially united), fewer neuromasts in the infraorbital series (1-2 + 16-17 + 1, vs. 2-3 + 19-21 + 1), preopercular series (2 + 9-10, vs. 2 + 11-14), and mandibular series (5 + 2, vs. 6-7 + 2-4), flank blue with dark brown stripes (vs. light brown with oblique rows of green dots), and presence of a subdistal zigzag bluish white line on anal fin in males (vs. absence). Pterolebias phasianus ZBK usually has fewer dorsal and anal fin rays than P. longipinnis ZBK (7-9 and 15-17, respectively, vs. 9-11 and 17-22).

Description. Morphometric data appear in Table 2. Males larger than females, largest male 41.8 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile slightly convex from lower jaw to end of anal-fin base, nearly straight on caudal peduncle. Body slender, subcylindrical anteriorly, slightly deeper than wide, to compressed posteriorly. Greatest body depth at level of pelvic-fin base. Jaws short, snout slightly pointed.

FIGURE 9. Pterolebias phasianus ZBK , UFRJ 5182, male, 35.8 mm SL; Brazil: Mato Grosso: Porto Cercado: rio Paraguay basin.

FIGURE 10. Pterolebias phasianus ZBK , UFRJ 5182, female, 32.0 mm SL; Brazil: Mato Grosso: Porto Cercado. Photo by W. J. E. M. Costa.

Tip of dorsal fin pointed with short filamentous rays in males, rounded to slightly pointed in females. Anal fin approximately rectangular, longer than deep; tip pointed with filamentous rays, long, reaching vertical through middle of caudal fin in males, rounded and short in females. Caudal fin elliptical, long; filamentous rays on posterior edge of male caudal fin. Pectoral fin elliptical, posterior margin reaching vertical just posterior to pelvic-fin base. Pelvic fin long, its tip reaching between middle of anal-fin base and caudal-fin base in males, and between urogenital papilla and base of 2nd anal-fin ray in females. Dorsal-fin origin on vertical between base of 11th and 12th anal-fin ray, and between neural spines of 20th and 22nd vertebrae. Anal-fin origin between pleural ribs of 14th and 16th vertebrae. Dorsal-fin rays 7-9; anal-fin rays 15-17; caudal-fin rays 24-25; pectoral-fin rays 14-15; pelvic-fin rays 8.

Scales large, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Body squamation slightly extending on caudal-fin base, with 3-5 transverse rows of scales on caudal-fin base; row of scales along anal fin in males; no scales on dorsal fin.

Frontal squamation E-patterned; E-scales not overlapping medially; scales arranged in circular pattern around central A-scale without exposed margins. Longitudinal series of scales 31-33, transverse series of scales 8, scale rows around caudal peduncle 16. Contact organs absent. Supraorbital neuromasts 3 + 3.

Cephalic neuromasts: supraorbital 3 + 3, parietal 1-2, anterior rostral 1, posterior rostral 1, infraorbital 1 + 16-17 + 1, preorbital 2-3, otic 1, postotic 2, supratemporal 1, median opercular 1, ventral opercular 2, preopercular 2 + 9-10, mandibular 5 + 2, lateral mandibular 3. One neuromast on each scale of lateral series.

Coloration: Males: Side of body iridescent blue with three reddish brown stripes along flank, more dorsal area lighter, often short brown stripe or row of spots between pelvic-fin base and posterior portion of anal-fin base; few small brown spots on anterior portion of flank between stripes; usually horizontal row with one to five bright orange rounded spots on humeral region, sometimes surrounded by black pigmentation. Dorsum pale brown, venter white. Opercular region golden with two or three dark brown to black oblique stripes, sometimes fragmented forming irregular blotches. Snout and jaws dark brown. Iris brown, with dark brown to black bar. Dorsal fin green with transverse rows of dark brownish red spots. Anal fin light blue on basal portion, yellow on median portion and black on distal portion; transverse row of reddish brown spots, sometimes coalesced forming stripe, between light blue and yellow zones; zigzag bluish white line on black distal zone. Caudal fin greenish blue with reddish brown spots; dorsal and ventral portions greenish yellow, edges brownish orange; sometimes narrow ventral black stripe. Pectoral fin hyaline with dark gray bars. Pelvic fin yellow with brown dots; filament yellow to light orange.

Females: Side of body pale blue with dark brown stripes arranged in pattern similar to male pattern. Head color pattern as in males, but colors fainter. Unpaired fins hyaline with dark brown spots, sometimes spots coalesced forming stripe on median portion of anal fin; anal-fin base pale blue. Paired fins hyaline.

Distribution: Middle Paraguay River basin, in Brazil and Bolivia (Fig. 8).

Habitat notes: Temporary lagoons in the Pantanal. Often sympatric with P. longipinnis ZBK , in which cases P. phasianus ZBK is usually found in shaded areas and P. longipinnis ZBK is found in sunny areas.


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