Phenacogaster lucenae, Souza & Mattox & Vita & Ochoa & Melo & Oliveira, 2023

Souza, Camila S., Mattox, George M. T., Vita, George, Ochoa, Luz E., Melo, Bruno F. & Oliveira, Claudio, 2023, Molecular species delimitation and description of a new species of Phenacogaster (Teleostei, Characidae) from the southern Amazon basin, ZooKeys 1164, pp. 1-21 : 1

Phenacogaster lucenae sp. nov.

Fig. 2

Phenacogaster sp. Xingu: Souza et al. 2022: 9, figs 3, 5 [molecular phylogeny; cited in figures also as Phenacogaster sp. Xingu].

Type material.

Holotype. MZUSP 126754, 26.7 mm SL, Brazil, Pará, Novo Progresso, Amazon basin, Rio Xingu, stream affluent of Rio Curuá, 08°29'59"S, 54°58'06.1"W, 08 Aug 2015, F.C.P Dagosta, M.M.F. Marinho, P. Camelier, V. Giovannetti.

Paratypes: All from Brazil, Amazon basin, Rio Xingu. LBP 15807, 2, 21.5-28.1 mm SL, Mato Grosso, Querência, Rio Feio, 12°33'20.5"S, 52°16'16.1"W, 31 Jul 2012, C. Oliveira, M. Taylor, G.J.C. Silva, J.H.M. Martinez. LBP 15835, 2, (tissue: 64949) 19.3-26.9 mm SL, Mato Grosso, Querência, Rio Suiá-Missu, Rio Feio, 12°31'55.7"S, 52°20'29.8"W, 31 Jul 2012, C. Oliveira, M. Taylor, G.J.C. Silva, J.H.M. Martinez. LBP 16061, 9, 22.9-35.4 mm SL, Mato Grosso, Primavera do Leste, Rio Culuene, Córrego Xavante, 14°38'24"S, 53°55'38"W, 05 Aug 2012, C. Oliveira, M. Taylor, G.J.C. Silva, J.H.M. Martinez. LBP 25217, 1, (tissue: 94032) 30.5 mm SL, Pará, Altamira, Rio Treze de Maio, 08°39'06.9"S, 55°02'09.1"W, 24 Sep 2017, A.C. Dias, C.S. Souza, C. Souto, N. Flausino Jr, R. Devidé. LBP 30738, 1, 38.0 mm SL, Mato Grosso, Primavera do Leste, Rio Culuene, Córrego Xavante, 14°38'24"S, 53°55'38"W, 23 Aug 2021, C.S. Souza, L. Reia, G.S.C. Silva, E.V. Ywamoto. LBP 32224, 1, 30.3 mm SL, Pará, Altamira, Castelo dos Sonhos, Rio Iriri, waterfall in Rio Curuá, 08°19'07"S, 55°05'22"W, 23 Aug 2022, T. Faria, G.S.C. Silva. MZUSP 97621, 49, 21.6-33.6 mm SL (7 c&s, 22.0-32.5 mm SL), Pará, Altamira, Amazon basin, Rio Curuá-Iriri, 08°15'17"S, 55°06'40"W, 27 Oct 2007, J.L.O. Birindelli, L.M. Souza, A.L. Netto-Ferreira, M.H. Sabaj, N.K. Lujan. MZUSP 120058, 28, 20.4-34.9 mm SL (5 c&s, 22.7-29.9 mm SL), collected with holotype.

Non-type specimens.

LBP 32258, 1, 28.3 mm SL, Mato Grosso, Sinop, Rio Tapajós, Rio Teles Pires, Arroio São José, Tujá, 11°36'04.47"S, 55°25'37.79"W, 25 Aug 2022, T. Faria, G.S.C. Silva. LBP 32321, 14, 19.0-25.7 mm SL (4 c&s, 18.8-22.7 mm SL), Mato Grosso, Guarantã do Norte, Rio Tapajós, Rio Teles Pires, igarapé of Rio Braço Norte, 09°56'54"S, 55°01'50"W, 24 Aug 2022, T. Faria, G.S.C. Silva. LBP 32332, 1, 22.6 mm SL, Mato Grosso, Sinop, Rio Tapajós, Rio Teles Pires, Arroio São José, Tujá, 11°36'04.47"S, 55°25'37.79"W, 27 Aug 2022, T. Faria, G.S.C. Silva. MZUSP 97708, 8, 27.3-32.4 mm SL, Mato Grosso, Santo Antonio do Leste, Araguaia basin, Rio das Mortes, Rio Suspiro, 14°52'30.0"S, 54°05'0.0"W, 18 Jan 2002, N.A. Menezes, O.T. Oyakawa, G.M. Guazzelli, R. Quevedo. MZUSP 118678, 8, 26.9-29.6, Mato Grosso, Santo Antonio do Leste, Araguaia basin, Rio das Mortes, Rio Suspiro, 14°52'30.92"S, 54°05'1.47"W, 17 Nov 2014, F.C.P. Dagosta, W.M. Ohara, V. Giovannetti.

Diagnosis.

Phenacogaster lucenae is distinguished from all congeners except P. tegata (Eigenmann, 1911), P. carteri (Norman, 1934), P. napoatilis Lucena & Malabarba, 2010, and P. capitulata Lucena & Malabarba, 2010 by having an incomplete lateral line (vs. complete lateral line). It differs from P. tegata by the presence of a round or slightly longitudinal oval humeral blotch near the pseudotympanum and distant from the vertical through dorsal-fin origin (vs. humeral blotch longitudinally elongated distant from pseudotympanum, closer to vertical through dorsal-fin origin). The new species differs from P. carteri by having a humeral blotch in males and females (vs. absence of humeral blotch in both sexes) and from P. napoatilis and P. capitulata by having a humeral blotch in both sexes (vs. absence of humeral blotch in males). In addition to the incomplete lateral line (vs. complete), P. lucenae differs from P. retropinna Lucena & Malabarba, 2010 by the anal-fin origin at vertical through base of first or second dorsal-fin branched ray (vs. anal-fin origin located posteriorly to that point), and from P. ojitata Lucena & Malabarba, 2010 by the round caudal peduncle blotch slightly reaching over the middle caudal-fin rays (vs. a diamond-shaped caudal peduncle blotch and further extending over the middle caudal-fin rays).

Description.

Morphometric data summarized in Table 2 . Body compressed. Dorsal profile convex from anterior tip of upper jaw to origin of dorsal fin with a slight concavity in occipital region; slightly straight from dorsal-fin base to origin of adipose fin and slightly concave from that point to base of dorsal procurrent caudal-fin rays. Ventral profile of body convex from tip of lower jaw to anal-fin origin, straight along anal-fin base, straight to slightly concave from that point to ventral procurrent caudal-fin rays. Preventral area flattened with two longitudinal series of elongate scales overlapping; scales different in shape from remaining body scales and forming zigzag pattern in ventral view. Pseudotympanum triangular extending from region of rib of fifth vertebra to anterior border of rib of sixth vertebra.

Mouth terminal, lower jaw slightly shorter than upper jaw; posterior tip of maxilla reaching vertical at midpoint of second infraorbital. Premaxillary teeth in two rows. Outer row with 6(4), 7(3), 8(4), 9(4), or 10(1) total teeth, divided in medial and lateral sections by gap; medial section with 2(6), 3(9) or 4(1) tricuspid teeth; lateral section with 3(1), 4(4), 5(5), or 6(6) conical teeth. Inner row with 8(1), 9(2), 10(6), 11(4), or 12(3) teeth, 3(2), 4(6), or 5(8) tricuspid teeth followed by 4(3), 5(1), 6(7), 7(3), or 8(2) conical teeth. Maxilla with 20(1), 21(2), 22(1), 23(1), 24(1), 25(1), 26(2), 27(5), or 29(1) conical teeth. Dentary with single row of 14(1), 15(1), 16(1), 17(3), 18(5), 19 (3), 20(1), or 21(1) teeth, with 4(2), 5(1), 6(7), 7(5), or 8(1) tricuspid teeth followed by 10(3), 11(5), 12(5), 13(1), or 14(2) conical teeth (Fig. 3 ).

Dorsal-fin rays ii,8(7) or 9*(17). Anal-fin rays iii-v,29(2), 30(8), 31(3), 32*(4), 33(6), or 34(1). Pectoral fin rays i,11*(13) or i,12(12). Pelvic-fin rays i,7*(28); its tip reaching beyond anal-fin origin. Lateral line incomplete. Longitudinal line of scales 32(2), 33(2), 34*(19), or 36(4). Pored scales 8(6), 9*(9), 10(3), 11(5), 12(4), 13(1), 14 (3), or 16(1); some specimens with 2(3) or 3(3) perforated scales anterior to last vertical series of scales. Scale series between lateral line and dorsal-fin origin 5(3), 6*(22), or 7(5). Scale series between lateral line and anal-fin origin 4(12), 5*(14), or 6(4). Gill rakers on upper limb of first gill arch 3(10) or 4(6); gill rakers on lower limb 7(10) or 8(6). Total vertebrae 33(1), 35(9), 36(1), or 37(1): precaudal 14(1), 15(11), or 16(1), caudal 19(1), 20(9), or 21(3). Supraneurals 3(1), 4(13), or 5(2).

Color in alcohol.

Overall ground coloration pale yellow (Fig. 2A ). Dorsolateral region of body with melanophores along margins of scales. Ventrolateral region less pigmented. Thin lines of melanophores accompanying myosepta along flanks, more evident in the hypaxial musculature. Females and males with rounded or slightly longitudinally oval humeral blotch immediately posterior to pseudotympanum, covering roughly three to five scale rows vertically and two to five scales longitudinally. Caudal peduncle with circular patch of melanophores covering whole caudal peduncle depth and reaching base of caudal-fin middle rays. Thin line of melanophores extending along horizontal septum between humeral and caudal peduncle blotches. Anal, pelvic, pectoral, and dorsal fins scattered by small melanophores. Adipose fin hyaline (Fig. 2 ).

Color in life.

Overall ground coloration yellowish to golden on slightly translucent background (Fig. 2B, C ). Dorsolateral body region with melanophores along margins of scales. Ventrolateral area less pigmented. Humeral blotch rounded or oval with anterior portion black and posterior edge iridescent yellow to orange. Round black blotch on middle portion of caudal peduncle extending vertically over entire caudal peduncle depth and extending posteriorly to proximal portion of caudal-fin middle rays. Some specimens with bright golden or white patches on posterior portion of caudal peduncle blotch, covering base of caudal-fin rays in upper and lower lobes. Thin line of melanophores between humeral and caudal peduncle blotches. Abdominal cavity, opercular series and portion of infraorbitals covered with guanine. All fins orange to yellowish coloration, with anterior halves of caudal-fin lobes more intensely colored. Posterior tip of caudal and dorsal fins scattered by small dark chromatophores (Fig. 2B, C ).

Sexual dimorphism.

Our samples consist of two adult males (MZUSP 97621, 30.4-34.4 mm SL) with hooks on pelvic- and anal-fin rays (Fig. 4 ). Four to six lateralmost branched pelvic-fin rays with five to nine curved hooks on medial edge of rays, one hook per segment towards the tips and more hooks per segment toward the base of the rays. Hooks more developed and frequent on medial regions of branched rays (Fig. 4A ). Anal-fin rays with four to nine curved hooks on the posterior edges of the last unbranched and the first to eleventh branched fin rays. Fin hooks more developed and abundant on anterior branched rays. In most cases, one pair of small hooks per segment, but occasionally two pairs per segment. Hooks in some cases incipient in the form of bumps. A few rays with additional single hook on the anterior edge of distal portion (Fig. 4B ).

Distribution and habitat.

Phenacogaster lucenae is known from tributaries of the Rio Curuá-Iriri, Rio Culuene, and Rio Suiá-Miçu (upper Xingu basin), tributaries of Rio das Mortes (upper Araguaia basin), and Rio Teles Pires (upper Tapajós basin), Amazon basin, Pará and Mato Grosso states, Brazil (Fig. 5 ). The new species was found in association with marginal vegetation (Fig. 6 ).

Etymology.

Phenacogaster lucenae is named in honor of Dr. Zilda Margarete Seixas de Lucena, an eminent ichthyologist who has significantly contributed to our knowledge of Phenacogaster taxonomy. A noun in genitive case.

Conservation status.

Phenacogaster lucenae is found in the upper Xingu, Araguaia, and Tapajós basins, where specimens were collected during focused expeditions. Although deforestation and hydroelectric plants have affected the region, 18 specimens of P. lucenae have been collected in recent years (2021-2022), demonstrating a likely high resilience to anthropogenic impacts. Therefore, we suggest the categorization Least Concern (LC) according to the International Union for Conservation of Nature criteria (IUCN 2014, Standards and Petitions Subcommittee).

Comparative material examined.

Phenacogaster capitulata : LBP 17802 (6, 27.38-31.97 mm SL), Peru, Pucallpa, Coronel Portillo, Ucayali basin, 08°35'44.2"S, 74°48'04.3"W, 18 Jun 2013, R. Britzke. P. napoatilis : MZUSP 38667 (9, 21.5-35 mm SL), Equador, Napo, Napo basin, Rio Jatuncocha , 2km above Laguna Jatuncocha, 1°3'0.00"S, 75°31'4.0"W, 26 Oct 1981, D. Stewart & M. Ibarra. P. ojitata : MZUSP 30551 (36.3 mm SL), Brazil, Pará, Rio Curua , Serra do Cachimbo , rodovia Santarém- Cuiabá, poço de cachoeira, 09°22'0.0"S, 54°52'0.0"W, 15 Aug 1984, M Goulding. MZUSP 97588 (9, 30.5-48.8 mm SL), Brazil, Pará, Altamira, Xingu basin, Rio Curua , na ponte da BR163, 08°53'54"S, 55°59'20"W, 29 Oct 2007, J. Birindelli, L. Sousa, A. Netto-Ferreira, M. Sabaj, N. Lujan. MZUSP 100922 (22, 28.4-33.5 mm SL; 2 d&c, 31.2- 30.5 mm SL), Brazil, Pará, Rio Curua , Serra do Cachimbo , rodovia Santarém-Cuiabá, poço de cachoeira. P. retropinna : LBP 15676 (105, 21.5-43.3 mm SL), Brazil, Mato Grosso, Ribeirão Cascalheira, Xingu basin, Corrego do Gato , 13°09'13.6"S, 51°55'18.7"W, 30 Jul 2012, C. Oliveira, M. Taylor, G. Silva, J. Henriques . LBP 25926 (2, 33.6-36.4 mm SL), Brazil, Mato Grosso, Paranatinga, Xingu basin, Rio Culuene , 13°50'50.8"S, 53°15'40.2"W, 24 Jan 2018, N.F. Junior, N. Estevão, F.A. Machado. MZUSP 30550 (12, 18.5-30.5 mm SL), Brazil, Mato Grosso, Gaucha do Norte , Rio Xingu , mouth of Rio Culuene and Sete de Setembro , 12°56'0.0"S, 52°49'0.0"W, 23 Jul 1984, M. Goulding, Portugal & Carvalho. MZUSP 81267 (17, 32.9-39.2 mm SL), Brazil, Amazonas, Rio Negro , 00°16'22.0"N, 69°54'3.0"W, 7 Nov 2002, F. Lima et al. MZUSP 99771 (14, 32.0- 40.3 mm SL), Brazil, Mato Grosso, Aripuanã, Madeira basin, Rio Aripuana , Balneário Primavera, a jusante do salto de Dardanelos, 10°09'54"S, 59°26'55"W, 12 Dec 2004, F. Machado, C. Leite, N. Silva, R. Rosa. P. tegata : LBP 7606 (16, 21.7-31.8 mm SL), Brazil, Mato Grosso, Barao de Melgaco , Paraguay basin, Lagoa Marginal rio Cuiaba , 16°11'39.5"S, 55°48'25.1"W, 29 Jan 2021, C. Oliveira, G.A. Lopez, R. Britzke. LBP 7641 (6, 35.8-39.1 mm SL), Brazil, Mato Grosso, Santo Antonio do Leverger , Paraguay basin, 15°46'03.8"S, 55°30'44.5"W, 01 Mar 2009, M. Mehanna, P.A. Campos. MZUSP 35889 (5, 26.9-37.9 mm SL), Brazil, Mato Grosso, Itiquira, Paraguay basin, Rio Piquiri , faz. Santo Antonio do Paraiso , 17°12'0.0"S, 54°9"0.0" W, J.H.B. Medeiros, J.C. Oliveira. MZUSP 96694 (10, 24.8-27.7 mm SL), Brazil, Mato Grosso, Barao do Melgaco , Paraguay basin, Rio Mutum. 16°19'30"S, 55°49'59"W, F.A. Machado et al .

Figures

Figure 2. Phenacogaster lucenae A MZUSP 126754, holotype, 26.7 mm SL, Brazil, Para, Novo Progresso, Xingu basin, stream affluent of Rio Curua B LBP 30738, paratype, 38.1 mm SL, Brazil, Mato Grosso, Primavera do Leste, Xingu basin, Rio Culuene, Corrego Xavante C LBP 25217, paratype, 30.6 mm SL, Brazil, Para, Altamira, Xingu basin, Rio Treze de Maio.

Figure 3. Phenacogaster lucenae, MZUSP 97621, 24.9 mm SL, c & s paratype, lateral view, right side, image flipped. Abbreviations: Aa, anguloarticular; Cm, coronomeckelian; De, dentary; Mx, maxilla; Pmx, premaxilla; Ra, retroarticular. Scale bar: 1 mm.

Figure 4. Phenacogaster lucenae, MZUSP 97621, 30.4 mm SL, c & s paratype, male A pelvic-girdle, ventral view, distal tip of rays damaged B anal-fin rays in lateral view. Scale bars: 2 mm.

Figure 5. Map showing the distribution of Phenacogaster lucenae in the upper Xingu, Tapajos, and Araguaia basins. White star represents the type locality at tributary of Rio Curua, Xingu basin.

Figure 6. Habitats of Phenacogaster lucenae A Rio Treze de Maio, Xingu basin, Altamira, Para, Brazil, 08 ° 39 ' 06.9 " S, 55 ° 02 ' 09.1 " W (LBP 25217) B Corrego Xavante, Rio Culuene, Xingu basin, Mato Grosso, Primavera do Leste, Brazil, 14 ° 38 ' 24 " S, 53 ° 55 ' 38 " W (LBP 30738). Photographs by CS Souza.