Comprehensive DescriptionRead full entry
Holotype . UFRJ 5929 , male, 38.6 mm SL; Brazil : Estado do Amazonas : Sao Gabriel da Cachoeira, pools near igarape Palestina, Airport road, upper rio Negro drainage, rio Amazonas basin ( 0°9’19.2”S66°59’58.9”W ; altitude 110 m ); W. J. E. M. Costa, S. Lima and L. Silva , 30 August 2003 .
Paratypes . UFRJ 5930 , 2 males, 33.5-39.9 mm SL, 4 females, 29.0-32.6 mm SL, and 5 juveniles, 13.8-21.8 mm SL; UFRJ 5931 , 3 females, 24.8-34.7 mm SL (c&s); MCP 34859 , 2 juvenile females, 19.1-21.5 mm SL; all collected with holotype.
Diagnosis: Similar to R. altivelis ZBK , R. atratus ZBK , R. ornatus ZBK , R. rectocaudatus ZBK , R. romeri ZBK , R. tecminae ZBK , and R. uakti ZBK , and distinguished from all other congeners by possessing a frontal squamation pattern consisting of one scale with all margins exposed just posterior to snout (vs. scale with all margins exposed near the center of median portion of frontal region) and an oblique infraorbital dark gray bar through chin (vs. never a similar color pattern). Similar to R. tecminae ZBK and R. rectocaudatus ZBK and distinguished from all other species of the genus by the caudal fin truncate in males (vs. rounded or subtruncate). Distinguished from R. tecminae ZBK and R. rectocaudatus ZBK by having more scales on the longitudinal series (48-49, vs. 38-43), flank with oblique rows of bright green dots in females (vs. bright green dots absent), caudal fin with dark red line on the dorsal and ventral margins in males (vs. dark marginal line absent). Differs from R. tecminae ZBK by having short pelvic fins, their tips reaching the anterior portion of the anal-fin base in males (vs. reaching the middle of anal-fin base). Differs from R. rectocaudatus ZBK by having flank with narrow red stripes in males (vs. horizontal rows of orange spots) and hyaline caudal fin in females (vs. pale yellow with bright yellow stripe on dorsal and ventral margins).
Description: Morphometric data given in Table 2. Male larger than female, largest male 39.9 mm SL. Dorsal profile slightly convex from snout to end of dorsal-fin base, approximately straight on caudal peduncle. Ventral profile convex on head, almost straight from anterior portion of venter 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.
Tip of dorsal and anal fins pointed in male, rounded in female. Caudal fin truncate in male, rounded in female. Pectoral fin rounded, posterior margin on vertical anterior to pelvic-fin base. Tip of pelvic fin reaching between base of 1st and 3rd anal-fin ray in male, and urogenital opening in female. Pelvic-fin bases in close proximity. Dorsal-fin origin on vertical between base of 11th and 13th anal-fin ray, and between neural spines of 21st and 23rd vertebra. Anal-fin origin between pleural ribs of 15th and 17th vertebra. Dorsal-fin rays 8; anal-fin rays 14-15; caudal-fin rays 28-30; pectoral-fin rays 13; pelvic-fin rays 6.
Scales small, cycloid. Body and head entirely scaled, except anterior ventral surface of head. Few scales on caudal-fin base; no scales on dorsal and anal fins. Frontal squamation S-patterned; E-scales not overlapping medially; scales arranged in transverse pattern, each scale with posterior margin exposed. Longitudinal series of scales 48-49; transverse series of scales 9; scale rows around caudal peduncle 18. Ctenii-like contact organ on each scale of ventral portion of male flank. Supraorbital neuromasts 3 + 3. Preopercular canal absent.
Interhyal vestigial, not ossified. Six branchiostegal rays. Second pharyngobranchial teeth absent. Gill-rakers of first branchial arch 1 + 8. Three or four vomerine teeth. Dermosphenotic absent. Ventral process of posttemporal absent. Total vertebrae 36-37.
Coloration: Male: Side of body pale purple anteriorly to pale green posteriorly, with eight narrow red stripes. Dorsum light yellowish brown, venter light. Opercular region greenish golden with red spots. Infraorbital region and ventral surface of head light gray; transverse gray bar on chin. Iris light green. Dorsal fin bluish hyaline with gray dots, distal portion pale greenish yellow, sometimes with narrow red line on margin. Anal fin light blue with gray dots, distal portion pale greenish yellow, sometimes with narrow red line on margin. Caudal fin light blue with gray dots, marginal region greenish yellow; narrow red line on dorsal and ventral margins; oval gray spot on subdorsal portion of caudal-fin base. Pelvic fin pale yellow. Pectoral fin hyaline.
Female: Side of body light brownish with light pink stripe on lateral midline and oblique rows of light green dots. Dorsum light brown, venter white. Opercular region pale golden. Infraorbital region and ventral surface of head white; transverse gray bar on chin. Iris light yellow. Dorsal fin hyaline. Anal fin light orangish yellow. Caudal fin pinkish hyaline; oval black spot on dorsal portion of caudal-fin base. Pectoral fin hyaline. Pelvic fin greenish yellow.
Distribution: Known only from the type locality, floodplains of igarapé Palestina, upper rio Negro drainage, rio Amazonas basin, northern Brazil.
Habitat notes: All specimens of the type series were collected in small shallow temporary pools within the forest, about 0.5-2.0 m of diameter, and about -15 cm deep (Fig. 6). The water was turbid and the bottom was litter. No other fish was found in these pools, which were almost contiguous to a lagoon, where no specimen of the new species was found.
Etymology: The name amana-pira-miri (amana = rain, pira = fish, miri = small) was recorded by Wallace as the Indian native name for a smaller species similar to R. amanapira ZBK , collected by him in the upper rio Negro region, tentatively now identified as R. tecminae ZBK . This note was recently published (Wallace, 2002) in a book consisting of fish drawings and respective notes made during Wallace’s journey to Amazon (1850-1852). According to the notes, the fish is found in small pools in the litter within the forest after rain (exactly the same conditions in which R. amanapira ZBK was collected), and consequently the Indians believed that it failed with the rain from the sky. Wallace (2002) mentions another Indian name for the species, owiyeye, which was also mentioned by a Tucano Indian at the moment of the collection of the type series of R. amanapira ZBK .
Monophyly of the R. atratus species group ZBK (i. e., R. atratus ZBK , R. ornatus ZBK , R. rectocaudatus ZBK , R. romeri ZBK , R. uakti ZBK , R. tecminae ZBK , and R. amanapira ZBK ) is tentatively supported by two apomorphic features: frontal squamation consisting of one scale with all margins exposed just posterior to snout (Huber, 1992; Costa, 2003c) and an oblique infraorbital dark gray bar through chin (Costa, 2003c). In all other species of Rivulus ZBK and in other rivulids, all the scales of the anterior portion of the frontal region have the posterior margin overlapped by the anterior margin of the scale posterior to them, the scales with all margins free are uniquely placed near the center of the frontal region; and, there is never an infraorbital oblique bar ventrally extending to cross the chin.
Among species of the R. atratus group ZBK , Rivulus uakti ZBK , R. romeri ZBK , R. tecminae ZBK , and R. amanapira ZBK share two apomorphic conditions: preopercular canal and dermosphenotic absent. Rivulus rectocaudatus ZBK , not examined in the present study, probably is a member of this group, since it shares some derived conditions with Rivulus uakti ZBK , R. tecminae ZBK , and R. amanapira ZBK (presence of caudal spot in males; see below), and with R. tecminae ZBK and R. amanapira ZBK (caudal fin truncate in males). The preopercular canal is present in all other species of Rivulus ZBK , except in species of the R. punctatus group ZBK (Costa, 1995a, 1998) that includes R. apiamici Costa ZBK , R. decoratus Costa ZBK , R. modestus Costa ZBK , R. paracatuensis Costa ZBK , R. pictus Costa ZBK , R. pinima Costa ZBK , R. punctatus Boulenger ZBK , R. violaceus Costa ZBK , and R. zygonectes Myers ZBK ; the dermosphenotic is present in all other species of Rivulus ZBK . Absence of dermosphenotic both in the R. punctatus species group ZBK , and in an assemblage within the R. atratus group ZBK is possibly homoplastic, since the R. punctatus species group ZBK is closely related to species with a preopercular canal (Costa, 1995a, 1998), none of them possessing the diagnostic derived features of the R. atratus species group ZBK .
A group comprised of R. uakti ZBK , R. tecminae ZBK , R. rectocaudatus ZBK and R. amanapira ZBK , is supported by the presence of a pale spot on the caudal-fin base of males. In other species, a spot on the caudal-fin base is present only in juveniles and adult females. However, two derived features occurring in these four species have an incongruent distribution. Whereas, a truncate caudal fin in males is uniquely shared by R. amanapira ZBK , R. rectocaudatus ZBK , and R. tecminae ZBK , a long pelvic fin is uniquely shared by R. uakti ZBK and R. tecminae ZBK . Rivulus altivelis ZBK , not examined in the present study, shares with R. uakti ZBK and R. tecminae ZBK the possession of long pelvic fins, but has a different frontal squamation pattern (Huber, 1992), making doubtful its phylogenetic relationships without examination of osteological features.