Hypoptopoma psilogaster Fowler, 1915

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 : 32-37

Hypoptopoma psilogaster Fowler, 1915 Figure 22 , table 4

Hypoptopoma psilogaster Fowler, 1915: 235 , fig. 9 (original description; Peruvian Amazon).— Fowler, 1915: 237 (assigned to subgenus Hypoptopoma ).— Fowler, 1939: 286 ( Peru: occurrence in Rio Ucayali basin, Nauta).— Fowler, 1945: 100 (list of freshwater fishes of Peru).— Fowler, 1954: 126, fig. 729 (list of freshwater fishes of Peru).— Boeseman, 1974: 264–265 (list of nominal species of Hypoptopoma ).— Isbrücker, 1980: 88 (list of loricariid species).— Böhlke, 1984:124 (catalog of type specimens at ANSP).— Ortega and Vari, 1986: 17 (list of fishes of Peru; Carachama).— Eschmeyer and Ferraris, 1998: 1390 (catalog of fishes).— Isbrücker, 2002: 28 (list of loricariid species).— Schaefer, 2003: 323 (list of hypoptopomatine species).— Ferraris, 2007: 250 (list of catfish species).

HOLOTYPE: ANSP 21922 (juvenile, 51.0 mm SL) Peruvian Amazon; collected by J. Orton, 1873.

OTHER MATERIAL EXAMINED: PERU, Loreto: ANSP 21921 (1 ♀, 45.6 mm SL) Peruvian Amazon ; ANSP 138868 (5 ♀, 33.4– 66.5 mm SL) Río Nanay, vicinity of Iquitos, well above Morona Coché (coché 9 m. above Río Amazonas ) ; ANSP 138869 (2; 35.5– 39.0 mm SL) Río Nanay, vicinity of Iquitos just above Coché Morona (above 9 m. Río Amazonas ) ; ANSP 138871 (1 ³ + 3 juveniles, 1 cs, 33.4–66.5 mm SL) Río Nanay, vicinity of Iquitos, Morona Coché outlet (about 9 m. above Río Amazonas ) ; ANSP 178335 (2 ♀, 32.6–41.0 mm SL) Río Itaya at bridge on Iquitos-Nauta highway, approx. 25 miles SSW of Iquitos ; CAS 134254 (1 ♀, 32.8 mm SL) Río Ampiyacu ; CAS 134255 (1 ♀, 38.1 mm SL) Río Ampiyacu ; INHS 39826 (6 ♀, 44.0– 70.1 mm SL) Río Nanay, Miz Playa, about 1 hr by canoe upstream from Santa Clara ; INHS 44076 (9 ♀ + 2 ³, 38.9– 53.9 mm SL) Río Nanay, Pampa Chica, 4.5 km W center of Iquitos ; INHS 44125 (2 ♀, 42.8–48.5 mm SL) Río Napo and Quebrada, Mazán , 33.3 km NE Iquitos ; MUSM 7655 (1 ♀ + 1 ³, 49.7–50.8 mm SL) Río Nanay, Maynas, Iquitos ; NRM 18000 (1 ♀, 35.6 mm SL) Río Nanay dr., Caño Puñuisiqui ; NRM 47511 (5 ♀, 28.9–35.8 mm SL) Río Nanay dr., small tahuampa cocha on left bank, second left bend above Mishana ; SIUC 23560 (83 ♀ + 14 ³, 5 cs, 28.8–55.9 mm SL) Maynas, Río Nanay at Santa Clara , NW of Iquitos ; SIUC 28015 (3 ♀ + 1 ³, 32.8– 48.7 mm SL) Río Nanay at Santa Clara ; SIUC 28180 (2 ♀, 35.0– 40.2 mm SL) Río Nanay, Pamachica Beach in Iquitos ; SIUC 28997 (3 ♀, 29.9–44.0 mm SL) Río Nanay, Miz Playa ; SIUC 29489 (1 ♀, 46.5 mm SL) Miz Playa just upstream from Santa Clara, 13.9 km from Iquitos ; SIUC 29645 (4 ♀ + 2 ³, 38.4–56.3 mm SL) Maynas, Río Nanay, Pampachica Beach 4.5 km from Iquitos center ; SIUC 67367 (2 ♀, 44.6–51.9 mm SL) Maynas, Río Itaya and Quebrada Mazana , 11 km from Iquitos center ; SU 60557 (1 ♀, 41.3 mm SL) Rio Yaguas Yacu ; USNM 284882 (2 ♀, 47.3– 47.3 mm SL) Río Nanay at Nanay beach, W of Iquitos ; USNM 284876 (1 juvenile, 47.2 mm SL) Río Nanay approx- imately 20 km upstream of mouth ; USNM 284883 (2 ♀, 30.7– 30.7 mm SL) Río Nanay approximately 20 km upstream of mouth .

DIAGNOSIS: Hypoptopoma psilogaster is distinguished from all congeners by the presence of an elongated dark spot along the middle caudal-fin branched rays, not involving the lanceolate plates at the base of the fin; the spot is typically extended over

TABLE 3 Sheared Principal Component Loadings from the Morphometric Analysis of Head and Trunk of Hypoptopoma guianense , H. psilogaster and H. thoracatum

equal number of upper- and lower-lobe branched rays and along more than twothirds of the ray length (figs. 17B, 23).

DESCRIPTION: Morphometric and meristic data presented in table 4. Body elongate, moderately depressed, greatest body depth at dorsal-fin origin, trunk most shallow at caudal peduncle anterior to caudal fin. Dorsal profile of head and body straight from tip of snout to dorsal-fin origin; straight from dorsal-fin origin to anteriormost procurrent caudal-fin ray. Head moderately depressed and narrow; lateral process of lateral ethmoid not visible dorsally. Snout rounded in dorsal view; dorsally smoothly round, slightly concave to flat anterior to naris. Body cross section between pectoral- and pelvic-fin origin horizontally ovoid, vertically ovoid posterior to dorsal fin, progressively compressed posterior to adipose fin.

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 24–26 (24); when total plates 25 or 26, posterior- most plate very small, with canal not reaching to posterior border of plate. Dorsal series 20–22 (21); middorsal series 3–4 (4); midventral series 13–14 (13), with 4–5 (4) plates anterior of first plate of ventral series; ventral series 20–22 (21). 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 series, 6–10 each; medial series of 6–10 (8) roughly squared plates; anterior azygous plate absent; medial series occasionally absent, in which case paired series make contact along midline in fully developed individuals. Single anal plate present. Thoracic plates absent. Preopercular canal absent. Posterolateral margin of canal-bearing plate and lateral margin of fourth infraorbital smooth; pore between canal-bearing ventral plate and fourth infraorbital absent.

Small odontodes evenly distributed on head. Odontodes ventral and dorsal to tip of snout not arranged in aligned series. No odontode-free discontinuity between ventral and dorsal odontodes; odontodes dorsal to tip of snout slightly larger than those on head. Lamina of trunk plates bearing longitudinal rows of odontodes, plates becoming progressively smoother ontogenetically; distinct column of marginal odontodes on posterior plate border in mature adults.

Total vertebrae 28. Premaxillary teeth 19– 26 (22), dentary teeth 16–24 (19). Maxillary barbels short; almost reaching to or slightly surpassing anterior margin of ventral canalbearing plate in adults.

Dorsal-fin origin located at vertical through pelvic-fin origin. Depressed dorsal fin reaching to vertical through midpoint of anal-fin base. Pectoral fin reaching to vertical through posterior half of pelvic-fin length. Extension of serrae along pectoral spine margin, except for short basal segment; serrae of oblique type; teeth of serrae progressively smaller toward distal end of spine. Pelvic fin short, two longest branched rays slightly longer than spine. Depressed fin reaching to plate anterior to anal-fin spine. Caudal-fin margin forked; upper and lower lobes equal and elongate. Adipose fin present.

COLOR IN ALCOHOL: Ground color tan and pale ochre. Melanophores dark brown, clustered on trunk and head resulting in mottled appearance. Melanophores slightly more concentrated dorsally on head, narrow area among compound pterotic, cleithral process and opercle, and at base of dorsal fin. Deeplying melanophores slightly more concentrat- ed along midline posterior to dorsal-fin base. Midlateral stripe situated mostly along medial series of trunk plates. Ventral surface of body mostly unpigmented, except for scattered melanophores on soft tissue along base of pectoral-fin branched rays and anterior surface of lip. Paired and dorsal fins with dark brown bands. Black melanophores slightly more concentrated over lanceolate plates. Caudal-fin bars variable defined. Presence of elongated dark spot along middle caudal-fin branched rays; spot typically extending over equal number of upper- and lower-lobe branched rays and along more than two-thirds of ray length; spot not distinctly connected to lanceolate plates at base of fin (fig. 17B). Tip of upper and lower lobes pigmented with dark melanophores.

SEXUAL DIMORPHISM: Male urogenital papilla short and conical, covered by anterior flaplike anus. Males with patch of tightly arranged small odontodes, variably covering first to fourth plates of ventral series, lateral to urogenital papilla. Males with poorly developed soft-tissue flap along posterior margin of pelvic spine. Female anus tubular,

TABLE 4 Morphometric and Meristic Data for Hypoptopoma psilogaster Holotype: ANSP 21922 . Nontypes: ANSP 138868 ; INHS 39826 , 44076 , 44125 ; SIUC 23560 , 29645 .

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. Female pelvic spine without flap of soft tissue on posterior surface.

DISTRIBUTION: Ríos Ampiyacu, Itaya, Nanay, Napo, and Yaguas in Western Amazon (fig. 19).

TAXONOMIC REMARKS: Fowler (1915) established the new species Hypoptopoma psilogaster on the basis of a single specimen. He compared his new species only with H. thoracatum , from which he distinguished the new species by the presence of two rows of abdominal plates separated by an unplated surface (vs. complete cover of the abdominal region with three rows of plates). Our examination of specimens of various size from across an extensive range of the Peruvian Amazon allowed us to confirm that the specimen examined by Fowler possesses the typical arrangement of abdominal plates observed in immature developmental stages in all speces of Hypoptopoma . Adults of H. psilogaster have the abdominal region completely covered by three rows of plates, similar to the condition observed in H. thoracatum . Nevertheless, we provide new evidence supporting the valid taxonomic status of H. psilogaster on the basis of the caudal-fin pigmentation, in addition to a combination of morphometric and meristic characteristics. A multivariate analysis of the overall morphometric variation among H. guianense , H. psilogaster , and H. thoracatum is included in the Taxonomic Remarks section of the systematic account of H. guianense .

Figures

Fig. 22. Hypoptopoma psilogaster, holotype, ANSP 21922, 51.0 mm SL, juvenile, in dorsal, lateral, and ventral views.