Hypoptopoma muzuspi, Aquino, Adriana E., 2010

Aquino, Adriana E., 2010, Systematics Of The Genus Hypoptopoma Günther, 1868 (Siluriformes, Loricariidae), Bulletin of the American Museum of Natural History 2010 (336), pp. 1-110 : 48-51

Hypoptopoma muzuspi , new species Figure 28 , table 7

HOLOTYPE: MZUSP 52135 (³, 36.3 mm SL) Brazil: Tocantins State, Araguaçu, rio Agua Fria, fazenda Praia Alta 2, estrada Araguaçu / Barreira do Piqui , 27 km ao norte

TABLE 7 Morphometric and Meristic Data for Hypoptopoma muzuspi Holotype: MZUSP 52135 . Paratypes: MZUSP 95186 ; AMNH 243578 .

de Araguaçu; collected by Lima et al., 6 July 1997 .

PARATYPES (collected with holotype): MZUSP 95186 (24 ♀, 2 cs, 19.0–31.0 mm SL). AMNH 243578 (5 ♀, 1 cs, 28.0–32.0 mm SL).

DIAGNOSIS: Hypoptopoma muzuspi is distinguished from all congeners by having the bifid neural spines of vertebra 10–12 expand- ed distally (vs. bifid neural spines progressively pointed distally). It can be further distinguished from all congeners, except H. brevirostratum , by the preopercle constricted medially (vs. preopercle without constriction) and canal in preopercle present, semicircular, and located posterior to the preopercle constriction. Hypoptopoma muzuspi can be readily distinguished from H. brevirostratum by its more elongated body and head (body depth 13.8–16.7 (14.7) vs. 15.5–19.2 (17.6); cleithral width 19.1–23.5 (22.2), vs. 23.7–27.0 (25.7); caudal-peduncle depth 5.2–6.7 (5.8) vs. 6.4–9.1 (7.7)), and caudal-fin pigmentation comprised of 7–10 bars of brown melanophores on unbranched and branched rays (vs. 3–6 dark blotches along unbranched rays, weakly extended over branched rays).

DESCRIPTION: Morphometric and meristic data presented in table 7. Body moderately elongate; greatest depth at dorsal-fin origin, trunk most shallow at origin of caudal-fin procurrent rays. Dorsal profile of head and body, from tip of snout to dorsal-fin origin, smoothly convex; straight posterior to dorsal-fin origin, smoothly tapering to caudal fin base. Head moderately depressed; lateral process of lateral ethmoid bone not visible dorsally. Snout rounded in dorsal view; smoothly concave anterior to naris. Posterior surface of bony pit of nasal organ sharply inclined. Trunk cross section between pectoral- and pelvic-fin origins horizontally ovoid, posterior to dorsal fin slightly rectangular, at level of two posteriormost trunk lateral plates slightly compressed.

Eyes moderately large, positioned slightly closer to posterior tip of compound pterotic than to tip of snout. Ventral margin of orbit located close to ventral surface of head. Dorsal interorbital distance shorter than ventral interorbital distance.

Total plates in lateral medial series 22–23 (23). Dorsal series plates 19–20 (19); middorsal series plates 3; midventral series plates 13– 14 (13), with four plates anterior to first plate of ventral series; ventral series 19. Second plate of midventral series contacting a single plate of medial lateral series.

Abdomen covered by paired series of lateral sickle-shaped plates, with unequal number of plates between left and right sides, 4–8; medial series of 4–5 (5) roughly squared plates; anterior azygous plate absent; medial series occasionally absent, in which case paired series make contact along midline in fully developed individuals; abdominal shield fully developed in specimens greater ca. 30 mm SL. Single anal plate present. Thoracic plates absent. Canal in the preopercle present, semicircular; anteriormost pore located between ventral canal-bearing plate and fourth infraorbital; lateral margin of fourth infraorbital with notch for semicircular canal better defined than on posterolateral margin of canal-bearing plate.

Small odontodes evenly distributed on head. Odontodes on anterior rostral plate not arranged in well-defined series; no odontode-free discontinuity between ventral and dorsal odontode series; odontodes dorsal to tip of snout slightly larger than those on head. Odontodes on lamina of trunk plates arranged in longitudinal rows; progressive smoothing of plates with increased specimen size not observed; marginal odontodes on posterior border of trunk plates in specimens greater than 34 mm SL.

Total vertebrae 27. Premaxillary teeth 15– 21 (18), dentary teeth 13–18 (15). Maxillary barbels short, not reaching ventral canalbearing plate in adults.

Dorsal-fin origin located slightly posterior of vertical through pelvic-fin origin. Depressed dorsal fin reaching to vertical through posterior third of anal-fin length. Pectoral fin reaching to vertical through midpoint of pelvic-fin length. Pectoral fin reaching second half of pelvic-fin spine. Pectoral spine serrae extended along posteri- or margin of spine shaft, except for short basal segment; serrae oriented oblique to spine shaft. Pelvic fin short, longest branched rays slightly longer than spine; when depressed reaching to plate anterior to anal-fin spine. Caudal-fin posterior margin forked, upper and lower lobes not elongate. Adipose fin absent.

COLOR IN ALCOHOL: Ground color tan and pale ochre. Light to dark brown melanophores, clustered on trunk resulting in mottled appearance. Melanophores more densely concentrated on compound pterotic, supraoccipital, frontals, lateral rostral plates, at base of pectoral and anal fins, on anterior surface of lip, lateral half of branchiostegal membrane, and mesial portion of naris softtissue flap. Melanophores along dorsal midline between dorsal-fin base and caudal fin concentrated in irregular clusters, often defining darker outline on posterior margin of plates of dorsal series. Midlateral stripe situated along medial, midventral, and ventral series of plates, becomming progressively more pigmented between medial and ventral series. Ventral surface of body mostly unpigmented except for scattered melanophores on posterior portion of trunk, anterolateral to cleithral processes, on ventral canal-bearing plates and lateral portions of lateral abdominal plate series. Paired and unpaired fins with relatively numerous narrow, dark brown bars. Caudal-fin with 7–10 bands of brown melanophores on unbranched and branched rays. Series of lanceolate plates at caudal-fin base slightly darkened with black melanophores. Variably shaped dark brown to black spot over lower lobe of caudal-fin. Posteriormost plates of both dorsal and ventral series of lateral plates less pigmented, whitish.

SEXUAL DIMORPHISM: Male urogenital papilla covered by flaplike anus. Males with patch of more tightly arranged small odontodes from fourth to sixth plates of ventral series, lateral to urogenital papilla. Female anus tubular, without separate urogenital papilla. In females, size and arrangement of odontodes on plates lateral to anus similar to those on adjacent plates, without distinct patch of differentially arranged odontodes.

ETYMOLOGY: The specific epithet muzuspi is given in recognition of the Museu de Zoologia, Universidade de São Paulo, Brazil (MZUSP), as one of the leading institutional collections for ichthyology in South America. The name is treated as a noun in apposition to the generic name.

DISTRIBUTION: Rio Tocantins basin; known only from Rio Agua Fria, in the drainage of Rio Araguaia (main tributary of Rio Tocantins) (fig. 27) .

Hypoptopoma spectabile ( Eigenmann, 1914)

Figures

Fig. 28. Hypoptopoma muzuspi, holotype, MZUSP 52135, 36.3 mm SL male, in dorsal, lateral, and ventral views.