Phenacorhamdia suia, Silva & Ochoa & Castro, 2022

Silva, Gabriel S. C., Ochoa, Luz E. & Castro, Íthalo S., 2022, New species of Phenacorhamdia (Siluriformes: Heptapteridae) from the Xingu River basin, Neotropical Ichthyology (e 210143) 20 (2), pp. 1-12 : 3-10

Phenacorhamdia suia , new species urn:lsid:zoobank.org:act:74342E2A-673C-405D-9CEA-46CC289C4C7E

( Figs. 1−3 ; Tab. 1)

Phenacorhamdia n. sp. 2. Xingu. —Silva et al., 2021: fig. 1 [phylogenetic relationships of Heptapteridae ].

Holotype. MNRJ 24850 , 81.8 mm SL, Brazil, Mato Grosso State, São Félix do Araguaia, Xingu River basin, Comandante Fontoura River basin, Santa Luzia stream, 11°19’30”S 52°17’06”W, 16 Jan 2002, P. Buckup, A. Aranda, F. Silva & C. Figueiredo.

Paratypes. All from Brazil, Xingu River basin. Mato Grosso State: LBP 15885, 1, 32.9 mm SL, Canarana , Tanguro River , Culuene River , 13º25’30.9”S 52º16’47.0”W, 1 Aug 2012, C. Oliveira, M. I. Taylor, G. J. Costa-Silva & J. H. M Martinez. LBP 15886, 6, 57.1−79.9 mm SL (2 c&s, 44.9−51.3 mm SL), Canarana , Tanguro River , Culuene River , 13º25’30.9”S 52º16’47.0”W, 1 Aug 2012, C. Oliveira, M. I. Taylor, G. J. Costa-Silva & J. H. M Martinez. LBP 15910, 1, 32.6 mm SL, Canarana , Coronél Vanick River , 13º31’34.1”S 52º43’52.5”W, 2 Aug 2012, C. Oliveira, M. I. Taylor, G. J. Costa-Silva & J. H. M Martinez. LBP 16013, 1, 37.1 mm SL, unnamed stream affluent of Culuene River , 13º27’26.9”S 53º09’36.6”W, 3 Aug 2012, Oliveira, M. I. Taylor & G. J. Costa-Silva. LBP 16014, 1, 47.8 mm SL, Gaúcha do Norte , Culuene River , 13º27’26.9”S 53º09’36.6”W, 3 Aug 2012, Oliveira, M. I. Taylor & G. J. Costa-Silva. LBP 16017, 1, 47.6 mm SL, Gaúcha do Norte , affluent of Culuene River , 13º26’32.8”S 53º08’45.1”W, 3 Aug 2012, Oliveira, M. I. Taylor & G. J. Costa-Silva. MZUSP 86862 , 15 , 23.2−44.9 mm SL, Ribeirão Cascalheira, Suiazinho River , 12º57’10.0”S 51º51’08.0”W, 16 Out 2004, O. T. Oyakawa, J. L. Birindelli & C. Oliveira. MZUSP 86875.0, 2, 24.5−26.4 mm SL, Canarana, Capim stream, 13º30’46.0”S 52º23’36”W, 17 Out 2004, C. Moreira, M. I. Landim, J. C. Nolasco & A. Datovo. MZUSP 86846 , 1 , 30.0 mm SL, Ribeirão Cascalheira, Turvo River , 13º13’28.0”S 51º55’50.0”W, 16 Out 2004, Axe team. Pará State: LBP 16703, 2, 31.4−35.7 mm SL, Vitória do Xingu , Fonte Boa stream, 02º58’12.3”S 52º05’11”W, C. Oliveira, R. Britzke & L. M. Souza .

Diagnosis. Phenacorhamdia suia differs from all congeners by having an atypical mottled colored body ( Figs. 1−2 ) (vs. uniformly counter-shaded, without mottled pattern; with a longitudinal dark brown stripe along the dorsal half of the body in P. unifasciata ), and by having all fins with interradial membranes pigmented and mottled (vs. fins with interradial membranes hyaline). Additionally, P. suia differs from all congeners, except P. taphorni by having multicuspid teeth (vs. conical teeth) ( Fig. 3 ). The new species differs from some of its congeners by maxillary barbel reaching pectoral-fin origin (vs. maxillary barbel reaching the end of adpressed pectoral fin in P. anisura , P. boliviana , P. nigrolineata , and P. tenebrosa ; reaching half the length of pectoral fin in P. tenuis ; surpassing pectoral fin in P. provenzanoi and P. taphorni ; reaching pelvic-fin origin in P. macarenensis ); lacking a short extension of the first pectoral-fin ray (vs. present in P. anisura , P. macarenensis , P. nigrolineata , P. provenzanoi , and P. taphorni ), by caudal fin deeply forked with extremely elogated and pointed lobes (vs. moderately pointed in P. hoehnei ; rounded in P. somnians ); and by having 43−45 total vertebrae (vs. 39 in P. taphorni ; 41 in P. hoehnei ; 41−42 in P. tenebrosa ; 46− 47 P. unifasciata; 47−48 in P. provenzanoi ; 53−55 in P. tenuis ).

Description. Morphometric data are summarized in Tab. 1. Small-sized Heptapteridae (largest specimen 81.8 mm SL). In dorsal view, body elongated progressively more compressed from dorsal-fin base to caudal peduncle. Greatest body width at cleithral region, progressively narrowing anteriorly towards snout tip and posteriorly towards caudal fin. In lateral view, body depressed and convex profile from the end of head to dorsal-fin origin; slightly convex from dorsal-fin origin to adipose-fin origin; straight from adipose-fin origin to caudal peduncle. In lateral view, ventral profile convex and descending from snout tip to opercular region; slightly convex from opercular region to pelvic-fin origin; straight from that point to anal-fin origin; slightly concave from that point to lower procurrent caudal-fin ray origin. Head depressed, dorsally covered by skin with small papillae. Snout short and rounded in dorsal view. Dorsal profile of head convex (in large specimens) or straight (in small specimens) from snout tip to the occipital region. Subcutaneous eyes, dorsally positioned, just anterior of the midpoint of head. Mouth gape slightly superior (prognathous). Premaxillary and dentary teeth arranged in a rectangular patch of several irregular rows. Distal portion of teeth flattened and multicuspid. Maxillary barbel reaching the base of first pectoral-fin ray, when adpressed. Outer mental barbel longer than inner barbel. Inner and outer mental barbels aligned. Outer mental barbels reaching posterior margin of branchiostegal membrane. Anterior and posterior nares tubular. Gill membranes free, supported by seven (2) branchiostegals and joined to isthmus only at anterior point. Five (2) gill rakers along the anterior border of the first ceratobranchial.

Laterosensory canal of the head with simple tubes ending in single pores. Supraorbital sensory canal usually with five branches and pores: s1, s2, s3, and s8. Supraorbital pore 1 medially adjacent to anterior nares. Supraorbital s2 and infraorbital i2 fused (forming complex s2+i2) at midway between anterior and posterior nares, s3 inside posterior nares, at the notch of the cutaneous membrane. s4, s5, and s6 pores absent. The s8 at the posterior surface of the frontal. Infraorbital laterosensory canal with six branches pores: i1, i2, i3, i4, i5, and i6, with i2 fused to s2. Infraorbital pore i1 adjacent to anterior nares, between nares and maxillary barbel; i2+s2 neared to anterior nares. Pore i3 laterally positioned at midway between anterior and posterior nares; i4 at vertical through anterior orbit; i5 posterior to eye. Pore i6 located posterior to pore i5, vertical through pm9. Preoperculo mandibular canal with 12 lateral-line branches and pores: pm 1 in the medial portion of dentary; pm2, pm3, and pm4 aligned anteriorly to inner and outer mental barbel; pm5 dorsal to outer mental barbel base; pm6 just posterior to pm5; pm7 and pm8 at vertical through anterior and posterior orbit respectively. Four pores in the preopercle region: pm9, pm10, pm11+po1, and po2 ( Fig. 4 ).

Precaudal vertebrae 15*(3), caudal vertebrae 27*(1) or 30(2), totaling 43*(1) or 45(2) vertebrae. First hemal spine on vertebra 16*(1) or 17(2). Hemal spine of vertebrae 26*(1) or 27(2) to 31(2) or 32*(1) bifid ( Fig. 5 ). Eight(2) or nine*(1) ribs ( Fig. 6 ).

Pectoral fin with one unbranched and seven branched rays (30). Pelvic-fin origin at vertical through dorsal-fin origin and with i,5(30) rays. First pelvic-fin ray shortest, second and third branched rays longest. Dorsal fin with i,6(30) rays. Dorsal fin unbranched ray slightly convex. First basal radial inserted in the 13º vertebra, and last basal radial anterior to the neural spine of vertebra 18. Adipose fin long (15.3−22.5% SL). Anal fin with v,8*(7) or v,9(23) rays. Anal fin supported by 10 basal and 8 distal radials. Caudal skeleton composed of a plate formed by parhypural + hypurals 1 and 2 in the lower lobe, upper lobe plate formed by hypurals 3 and 4 fused, hypural 5 free, and a pleurostyle. Caudal fin forked with i,7*(3)+7,i*(1) or 8,i(2) principal rays. Caudal-fin lobes long, the ventral longer (27.6−35.6% SL) than dorsal lobe (25.8−32.1% SL). Twelve (2) to thirteen (2) procurrent rays in dorsal and ventral lobes.

Color in alcohol. Overall pigmentation mottled (with light brown background and irregular dark brown blotches formed by minutes and concentrated melanophores that overlap each other) ( Figs. 1−2 ), becoming ventrally mostly unpigmented. Interradial membranes of all fins pigmented as the body.

Geographical distribution. Phenacorhamdia suia is known from nine localities from the upper and lower Xingu River basins ( Fig. 7 ). The type-locality is Santa Luzia stream, Comandante Fontoura River basin. Other sites are Culuene, Coronel Vanick, Suiazinho, Turvo Rivers, Capim and Fonte Boa streams, and two unnamed streams.

Etymology. The specific name “ suia ” refers to the Suias indigenous people who, since the 90’s, have stood out in the fight to protect the Suiá-Missu River environment and for recovery of their traditional lands outside the limits of Xingu park. A noun in apposition.

Conservation status. Phenacorhamdia suia is a widely distributed species in the Xingu basin, known from nine localities; moreover, the areas where the specimens were collected are relatively well preserved. Because there is no imminent threat to the species, P. suia is recommended to be categorized as Least Concern (LC), according to the International Union for Conservation Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2019).

Figures

FIGURE 1 | Phenacorhamdia suia, MNRJ 24850, holotype, 81.8 mm SL, Brazil, Mato Grosso State, São Félix do Araguaia, upper Xingu River basin. Photographed by Dario Faustino-Fuster.

FIGURE 2 | Phenacorhamdia suia, paratypes, LBP 15886: A. 79.9 mm SL; B. 65.7 mm SL; C. 56.0 mm SL. Photographed by Lais Reia.

FIGURE 3 | Left dentary of Phenacorhamdia suia, paratype, LBP 15886, 51.3 mm SL (c&s). A. Dorsal view of medial portion of dentary teeth (scale bar = 0.1 mm) and B. Dorsal view of entirely dentary teeth (scale bar = 0.5 mm).

FIGURE 4 | Lateral, dorsal and ventral view of head of Phenacorhamdia suia, LBP 15886, 79.9 mm SL, paratype, showing the cephalic laterosensory pores. Infraorbital pores (i1–i6); Preoperculomandibular pores (pm1–pm11); Postotic pores (po1–po2); Supraorbital pores (s1–s3, and s8).

FIGURE 5 | Lateral view of bifid hemal spines of vertebrae 27 to 31, located dorsally to anal-fin pterygiophores. Phenacorhamdia suia, paratype, LBP 15886 (1 c&s), 51.3 mm SL.

FIGURE 6 | Radiograph images of the holotype of Phenacorhamdia suia, MNRJ 24850, 81.8 mm SL. Lateral (top) and ventral (bottom) views.

FIGURE 7 | Geographic distribution of Phenacorhamdia suia in Brazilian Shield. Black star = holotype. Red circles = paratypes localities.