Physopyxis lyra Cope, 1871

Sousa, Leandro M. & Rapp Py-Daniel, Lúcia H., 2005, Description of two new species of Physopyxis and redescription of P. lyra (Siluriformes: Doradidae), Neotropical Ichthyology 3 (4), pp. 625-636 : 628-630

Physopyxis lyra Cope

Figs. 3-4

Physopyxis lyra Cope, 1871: 112 ; described in detail and illustrated in Cope, 1872: 273 pl. 5 fig. 1a-c, type locality: rio Ampyiacu, Peru (stated in Cope, 1872: 275 as rio Ambyiacu (sic), Equador).

Material examined (N = 1662). ANSP 8282 (holotype, 35.0 mm TL), río Ampyiacu, Peru. Other specimens: Brazil: Amazonas : AUM 44217 (10, not measured), igarapé Juá Grande, lago Amanã, rio Japurá , rio Solimões basin . INPA 77 (1, 21.83 mm SL), rio Aripuanã, rio Madeira basin . INPA 15470 (21 of 354, 13.37-23.05 mm SL), igarapé Caititu, rio Uatumã, Balbina . INPA 20321 (4 c&s, not measured), rio Tefé, rio Solimões basin . INPA 21922 (1, 14.81 mm SL), rio Padauari, rio Negro basin . INPA 21926 (34 of 949, 15.25-30.63 mm SL), igarapé Juá Grande, lago Amanã, rio Japurá , rio Solimões basin . MPEG 9718 (15, not measured), same data as INPA 21926 . MZUSP 88066 (15, not measured), same data as INPA 21926. Mato Grosso : INPA 25029 (5, 19.1-20.91 mm SL), rio Guaporé . MZUSP 37670 (1, 21.26 mm SL), rio Guaporé , ferry boat harbour. Rondônia : INPA 11318 (1, not measured), rio Guaporé, Costa Marques county . INPA 21920 (3, 16.37-23.94 mm SL), rio Cautário, rio Guaporé basin . INPA 21921 (6, 18.53-24.66 mm SL), rio Jatobá, rio Guaporé basin . INPA 21923 (1, 18.81 mm SL), rio Novo , Pacaás Novos (10º56’24”S, 65º56’24”W) . INPA 21924 (1, 20.03 mm SL), rio Novo , Pacaás Novos (11º13’11”S, 65º14’02”W) . INPA 21925 (9, 18.63-27.67 mm SL), rio Cautário, rio Guaporé basin . INPA 21927 (14, 12.62-26.28 mm SL), rio Cautário, rio Guaporé basin. Peru: Loreto : ANSP 116359 (1 c&s, not measured), río Nanay, vicinity Iquitos . ANSP 149338 (9, 18.17-26.62 mm SL), río Nanay . ANSP 167610 (13, not measured), río Nanay (03º53’S, 73º27’W) . ANSP 167615 (53, 16.14-30.34 mm SL) (2 c&s, not measured), río Nanay (03º45’S, 73º17’W) . ANSP 167619 (15, 14.34-29.84 mm SL), río Nanay (03º45’S, 73º17’W) . ANSP 174930 (1, 25.78 mm SL), río Ucayali, río Nanay (05º00’S, 73º38’W) . ANSP 178442 (12, 20.04-29.00 mm SL), río Nanay (03º45’09”S, 73º17’00”W) . ANSP 179872 (151, not measured), río Nanay (03º46’45”S, 73º22’06”W) . ANSP 179873 (17, not measured), río Nanay, Pampa Chica village (03º45’09”S, 73º17’00”W) . MZUSP 26783 (1, 23.26 mm SL), Jenaro Herrera .

Diagnosis. Physopyxis lyra differs from the other species of the genus by possessing a single row of spines on the lateral plates and a strong scapular girdle with long, broad coracoid processes having distal tips enlarged and divergent.

Description. Morphometric data summarized in Table 1. Largest specimen examined measures 30.63 mm SL (39.07 mm TL) representing largest known specimen. Body short and deep with greatest body depth at origin of dorsal fin (body depth 27-35.6% of SL). Head and scapular girdle strongly ossified, exposed. Top of head and nuchal plates roof shaped, with bony ornamentation organized in shallow grooves concentrated along nuchal shield crest and borders. Single fontanel oval shaped. Eye anterior, orbital diameter approximately same size as fontanel. Anterior nostril tubular and placed near bor- der of snout. Posterior nostril nearer to orbit than to snout. Snout short, its length twice orbital diameter. Lacrimal bone well developed, dorsal and ventral margins serrated with conspicuous spines. Mouth terminal. Barbels simple, long, covered with papillae along inferior surfaces. Maxillary barbel reaching to or surpassing tip of postcleithral process. Outer mental barbel reaching point of insertion of pectoral spine. Inner mental barbel shorter, approximately two thirds of length of outer mental barbel.

Scapular girdle extremely well developed anteriorly and ventrally, forming deep groove along its anterior contour. Cleithrum laterally expanded and visible from above, sculptured with shallow grooves up to postcleithral process. Postcleithral process relatively short, its tip reaching to or slightly surpassing vertical through origin of dorsal spine. Coracoid processes very long and broad (larger than postcleithral process), with expanded distal tip. Ventral surface of coracoid process ornamented with well-defined longitudinal pattern of parallel grooves and ridges along its entire length. At posterior tip of coracoid, grooves and ridges curve outwards following expansion of process.

Dorsal and pectoral spines strongly ossified. Dorsal spine pentagonal in cross-section with longitudinal groove along each lateral side, serrate along basal portion of anterior margin, posterior margin smooth. Pectoral spine well developed, depressed and curved, its tip usually reaching anal-fin origin. Two or three grooves on both upper and lower surfaces of pectoral spine. Strong hook-like teeth present along anterior and posterior margins of pectoral spine; basal most teeth (i.e., first five) along anterior margin directed toward base of spine, more distal teeth directed toward spine tip; all teeth along posterior margin directed toward pectoral-spine base.

Vast majority of observed specimens with 26 lateral plates, each with single posteriorly directed spine. Number of lateral plates 23-27, with few juvenile specimens (less than 16.37 mm SL) from Guaporé drainage lacking plates entirely (see Table 1). Portion of lateral plate above spine and lateral line (dorsal wing) deeper than portion below (ventral wing). Lateral plates meeting dorsally in large specimens.

Dorsal-fin rays I,5. Dorsal-fin origin situated at anterior third of body. Pectoral-fin rays I,4. Pectoral fin located at vertical through branchial opening. Pelvic-fin rays 7. Pelvic fin inserted at vertical through coracoid process tip, approximately at middle of body; tip of pelvic fin slightly surpassing anal-fin origin. Anal fin moderately long, with 16 rays in total (branched and unbranched). Adipose fin small, membranous. Caudal fin truncate to slightly emarginate, with 8,4 rays.

Color in alcohol. Body ground color tan with brown blotches and spots. Head usually more pigmented than body. Three or four dark brown irregular saddles on dorsum extending onto sides as full or partial bars: anteriormost at base of dorsal fin and usually reaching to lateral line; second from adipose fin to anal fin; third at beginning of caudal peduncle, and fourth at base of caudal fin rays. Last two bars may be joined into one that covers entire caudal peduncle. Barbels tan with brown transverse bands along its entire length. All fins similar in appearance, with dark transverse bands across rays and membranes separated by unpigmented interspaces. Dorsal and pectoral spines with unpigmented tips. Spines and rays with brown transverse bands. Ventral surface variably pigmented, light or dark, with chromatophores regularly spaced over abdomen and scapular bridge. Coloration in fresh specimens similar to above, but more conspicuous.

Distribution. Known from the rio Ampyiacu (and lowland portions of other tributaries to the upper Amazon in northeastern Peru) to the rio Uatumã, a left bank tributary to the Amazon in easternAmazonas State, Brazil. No reliable records exist for the rio Negro basin (one specimen recorded from upper rio Negro may be incorrectly labeled) ( Fig. 6 ).

Manicoré (05º38’52”S, 61º02’36”W). INPA 24530 (8, not measured), igarapé without name, rio Atininga, rio Madeira basin, Manicoré (05º36’14”S, 61º00’55”W). MPEG 9719 (5, not measured), same data as INPA 21918. MZUSP 88067 (5, not measured), same data as INPA 21918. Pará: INPA 25030 (25, not measured), unnamed stream, Caxiuanã National Forest, Melgaço county (01º45’58”S, 51º30’34”W). MPEG 6151 (2, 13.62-17.17 mm SL), rio Puraquequara, Caxiuanã National Forest . MPEG 7189 (60, not measured), same data as INPA 25030. MPEG 7190 (7, not measured), igarapé Curuá, Caxiuanã National Forest . MZUSP 12419 (2, 12.14-12.70 mm SL), lago Jacaré, rio Trombetas basin. MZUSP 15553 (1, 15.71 mm SL), lago Jacaré, rio Trombetas basin. MZUSP 21960 (8, 9.11-11.27 mm SL), rio Tapajós, island in front of Monte Cristo. Roraima: ANSP 180961 (9, not measured), INPA 20192 (1, 12.1mm SL), INPA 20195 (1, 13.53 mm SL), and INPA 20196 (20 of 64, 10.35-

Habitat. Physopyxis lyra is usually found in places with accumulated organic debris, like dense meshes of roots of floating macrophytes that are abundant in rivers with turbid water. Specimens also can be found among submersed leaf litter and among root mats of riparian plants, like Symmeria paniculata (Polygonaceae) . Aquarium observations indicate that P. lyra is predominantly nocturnal, and spends most of day time sheltered among submersed root mats or buried in sand.

Figures

Fig. 3. Physopyxis lyra Cope, 1871, holotype. ANSP 8282 (35.0 mm TL), río Ampyiacu, Peru. Photo by Mark Sabaj.

Fig. 6. Geographic distribution of Physopyxis lyra (circle), Physopyxis ananas (triangle), and Physopyxis cristata (squares). Open symbols are type localities. Record of P. lyra in rio Negro questionable.