Hypoptopoma elongatum, 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 : 67-70

Hypoptopoma elongatum , new species Figure 35 , table 12

HOLOTYPE: INPA 7240 (♀, 95.4 mm SL) Brazil: Pará, Rio Tapajos , Itaituba; collected by L. Rapp Py-Daniel and J. Zuanon, 18 October 1991.

PARATYPES: INPA 29657 (32 ♀ + 26 ³, 2 cs, 62.7–102.7 mm SL) (collected with holotype).

OTHER MATERIAL EXAMINED: BRAZIL, Pará: CAS 6748 (1 ♀, 93.2 mm SL) Santarem market ; INPA 5405 (6 ♀, 93.0– 96.2 mm SL) Rio Trombetas , Cach. Porteira a jusante da cachoeira ; INPA 5406 (1 ♀,

TABLE 12 Morphometric and Meristic Data for Hypoptopoma elongatum Holotype: INPA 7240. Paratype: INPA 29657. Nontype: MZUSP 38187.

101.4 mm SL) Rio Trombetas , Lago Tapagem ; INPA 5570 (3 ♀, 88.4–104.2 mm SL) Rio Trombetas , R. Cumina, Lago Salgado ; INPA 7130 (1 ♀ + 2 ³, 90.6–94.1 mm SL) Rio Cupari , afluente do Rio Tapajos (próximo a boca) ; INPA 7131 (3 ♀ + 1 ³, 88.8–94.3 mm SL) Rio Cupari , afluente do Rio Tapajos (próximo a boca) ; INPA 7213 (2 ♀, 88.2– 9.2 mm SL) Rio Cupari , afluente do Rio Tapajos ; MZUSP 34193 (8 ♀ + 3 ³, 87.9–97.0 mm SL) Rio Tapajos , beira do rio, entre Itaituba e São Luis ; MZUSP 36187 (2 ♀ + 2 ³, 79.9–89.5 mm SL) Rio Tapajos , ihla confrontando Monte Cristo ; MZUSP 36220 (1 ♀, 77.0 mm SL) Rio Tapajos , Igarape Jacare, margen dereita do Rio Tapajos, perto de Boim .

DIAGNOSIS: Hypoptopoma elongatum is distinguished from all congeners by having a nonpigmented band on the head positioned parallel to the ventral margin of the rostral and lateral snout plates, with the margin between pigmented and nonpigmented plates very well defined (fig. 35C) (vs. absence of a distinct pigmented band). Hypoptopoma elongatum can be further distinguished from congeners, except for H. inexspectatum , by having the ventral surface of the anterior rostral plate as wide as the ventral surface of the first lateral rostral plates (vs. ventral surface gradually widening from anterior rostral to lateral rostral plates). Hypoptopoma elongatum is readily distinguished from H. inexspectatum by having a greater number of plates along the trunk medial series (23 vs. 20–21 (21)), by having the snout appearing pointed in dorsal view due to a slight concavity between rostral plate and first infraorbital (fig. 35A) (vs. snout typically spatulate), and by having, if present, a distinct series of odontodes along dorsal and ventral rostral margin of snout restricted to the anterior rostral plate (vs. series of odontodes along dorsal and ventral rostral margin of snout extended laterally to include second and third infraorbitals).

DESCRIPTION: Morphometric and meristic data presented in table 12. Body robust; greatest body depth at dorsal-fin origin. Dorsal profile of head and body straight from snout tip to dorsal-fin origin, slightly elevated at posterior tip of supraoccipital; straight from dorsal-fin origin to anteriormost procurrent caudal-fin ray. Ventral profile of head and body straight to slightly concave from snout tip to anteriormost procurrent caudal-fin ray. Head moderately depressed, almost as wide as cleithral width; lateral process of lateral ethmoid bone visible dorsally. Anterior snout margin acute; slightly concave anterior to naris. Posterior surface of bony pit of nasal organ sharply inclined. Trunk cross section slightly triangular between pectoral- and pelvic-fin origins, ovoid to progressively round posterior to dorsal fin, caudal peduncle posterior to adipose-fin base progressively compressed.

Eyes relatively large, positioned closer to posterior tip of compound pterotic than to tip of snout. Ventral margin of orbit located on ventral side of head. Dorsal interorbital distance greater than ventral interorbital distance.

Total plates in medial series typically 23. Dorsal series plates 20; middorsal series plates 4; midventral series plates 12–13 (13), three plates anterior to first ventral series plate; ventral series plates 20. Second plate of midventral series contacting two plates of medial series.

Abdomen covered by paired series of lateral sickle-shaped plates, with unequal number of plates between left and right series, 4–7 each; anterior azygous plate usually present. Single anal plate. Thoracic plates present, 2–6. Preopercular canal in preopercle present, semicircular; anteriormost pore located between ventral canal-bearing plate and fourth infraorbital; framed by notch at posterolateral margin of canal-bearing plate and ventral margin of fourth infraorbital.

Small odontodes evenly distributed on head; odontodes on rostral margin not arranged in well-defined series, without odontode-free discontinuity. Odontodes on ventral surface of rostral plate variably enlarged. Lamina of trunk plates with odontodes arranged in longitudinal rows, becoming progressively smoother ontogenetically; marginal odontodes present in mature adults. Anterior margin of pectoral-fin spine and ventral surface of pelvic-fin spine with enlarged odontodes.

Total vertebrae 27. Premaxillary teeth 16– 23 (21); dentary teeth 14–22 (18). Maxillary barbels short, only reaching to anterior margin of ventral canal-bearing plate.

Dorsal-fin origin located slightly posterior to vertical through pelvic-fin origin. Depressed dorsal fin reaching to or surpassing vertical through posterior half of anal-fin base. Depressed pectoral fin reaching to anus. Pectoral spine serrae typically along middle three-fifths of spine length, involving less of spine shaft with growth; individual serrae oriented oblique to spine shaft. Pelvic fin short, unbranched and first branched rays of equal length. Depressed pelvic fin reaching to anus, not reaching analfin origin. Caudal-fin margin markedly forked; upper and lower lobes equal. Adipose fin variably present; when present, small and membranous.

COLOR IN ALCOHOL: Ground color tan and pale ochre. Light to dark brown melanophores clustered on trunk and at base of plates, yielding mottled appearance. Melanophores slightly more concentrated on narrow area along compound pterotic, between cleithral process and opercle, and at base of both dorsal and pectoral fins. Well-defined nonpigmented band parallel to ventral surface of snout plates, including two plates lateral to barbel; margin between pigmented and nonpigmented plates distinct. Deep-lying melanophores arranged in series of blotches posterior to dorsal-fin base; butterfly-shaped blotch anterior to dorsal-fin origin, centered at anteriormost predorsal plate, anterior arms lateral to supraoccipital. Trunk lateral stripe involving medial plate series. Ventral surface of body mostly unpigmented except for scattered melanophores on posterior portion of trunk and anterior surface of lip. Paired and unpaired fins with few dark brown bands. Dorsal fin typically with faint bar at base followed by one dark bar roughly orthogonal to rays and closer to tip than to base of fin, with one or two additional faint bars intervening. Caudal-fin rays with melanophores arranged in parallel V-shaped pigmented bands, typically fainter on medial branched rays; anterior band located at base of branched rays, typically lighter than posterior band; posterior band located near posteror fin margin; unbranched rays and tip of median caudal-fin branched rays light. Lanceolate plates at base of caudal fin light brown, variably connected with basal faint vertical band.

SEXUAL DIMORPHISM: Male urogenital papilla well developed, pointed, joined at base to anterior flaplike anus. Patch of tightly arranged small odontodes on second, third, and fourth plates of ventral series, lateral to urogenital papilla. Males with softtissue flap along posterior margin of pelvic spine and along basal one-third to two-thirds of spine. Female anus tubular, without separate urogenital papilla. In females, size and arrangement of odontodes on plates lateral to anus similar to adjacent plates, without distinct patch of differentially arranged odontodes.

DISTRIBUTION: Lower Rio Tapajos and lower Rio Trombetas (fig. 32).

ETYMOLOGY: The specific epithet elongatum (Lt. elongatus, meaning ‘‘prolonged’’) is a reference to the elongated general shape of the body, particularly marked at the tip of snout, caudal peduncle, and caudal fin.

Figures

Fig. 35. Hypoptopoma elongatum, holotype, INPA 7240, 95.4 mm SL, female, in dorsal, lateral, and ventral views.