Moenkhausia pirahan, Mathubara & Toledo-Piza, 2020

Mathubara, Kleber & Toledo-Piza, Mônica, 2020, Taxonomic study of Moenkhausia cotinho Eigenmann, 1908 and Hemigrammus newboldi (Fernández-Yépez, 1949) with the description of two new species of Moenkhausia (Teleostei: Characiformes: Characidae), Zootaxa 4852 (1), pp. 1-40 : 25-29

Moenkhausia pirahan , new species

( Figs. 13–15 )

urn:lsid:zoobank.org:pub:301C1BCC-51F1-43E0-9774-85DC28741E10

Holotype: MZUSP 125777 (1, 62.5 mm SL), Brasil, Rondônia, Igarapé Traíra, Transamazônica highway, 40 Km from the ferryboat of Humaitá , to Apuí , Humaitá , 7°35’31”S 62°44’45”W, W.M. Ohara, 15 Aug 2015.

Paratypes: MZUSP 125778 (4, 62– 65.8 mm SL) ; ZUEC 17237 (2, 62.4–64.6 mm SL) ; UFRO 15783 (2, 59.1– 60 mm SL), same data as holotype . UFRO 23068 (1, 49.9 mm SL), Igarapé Cachoeira, above Aripuanã, 6°24’45”S 60°21’26”W, Fernandes, Talles, 19 Mar 2013 .

Non-type material: Brazil: Amazonas: rio Madeira basin: UFRO-I 23068 (1-1, 49.4 mm SL), Igarapé Cachoeira, upstream of rio Aripuanã, Novo Aripuanã , 6°24’45”S 60°21’26”W, T. Fernandes ; Pará: rio Tapajós basin, MPEG 28777 (3-3, 39.8–50.2 mm SL), Jacareacanga, rio Tapajós basin, Ambiental Concremat, 20 Aug 2013 ; Pará, rio Trombetas basin: INPA 48615 (4-4, 46.5–53.3 mm SL), Lagoa Sapucuruá , mouth of Igarapé Araticum, Oriximiná, G.M. dos Santos, 21 Jul 2015 ; INPA 50033 (8-8, 30.9–46.8 mm SL), rio Trombetas, igarapé of Tental, left margin, Oriximiná , 1°25’51”S 56°45’52”W, I.M. Soares & A. Akama, 18 Nov 2013 ; INPA 50082 (1-1, 48.4 mm SL), Oriximiná, rio Trombetas, igarapé Terra Preta , right margin, 7°45’45”S 58°49’0”W, I.M. Soares & A. Akama, 19 Nov 2013 ; INPA 34406 (5-5, 37.6–47.6), rio Trombetas, Oriximiná , 1°28’1”S 56°20’5”W, E. Ferreira & J. Zuanon, 25 Nov 2005 ; MPEG 14598 (7-7, 42.5–55.5 mm SL), rio Saracá (Porto Trombetas), Oriximiná, W. Wosiacki, 18 Oct 2007 ; MPEG 15430 (1-1, 45.3 mm SL), Porto Cikel, rio Nhamundá, Faro , 1°42’48”S 57°12’48”W, L.F. Montag, 27 Jan 2008 ; MPEG 23687 (1-1, 38.3 mm SL), Alenquer , 1°34’47”S 55°0’36”W, J, Ready, 20 Jun 2010 ; MPEG 27968 (2-2, 50.3–50.6 mm SL), Vila de São Martins, Jacareacanga , 6°8’13”S 57°40’23”W , T. Begot , 30 Mar 2013 ; MPEG 28055 (1-1, 45.4 mm SL), rio Saracá , 1°48’9”S 56°16’33”W, W. Wosiacki, 20 Oct 2007 .

Diagnosis. Moenkhausia pirahan is distinguished from all congeners, except M. australis , M. cosmops , M. cotinho , M. diktyota , M. forestii , M. lineomaculata , M. oligolepis , M. parecis , M. pyrophthalma , M. sanctaefilomenae , and M. uirapuru by the presence of a reticulate body color pattern resulting from the presence of chromatophores forming a dark rim and delineating the posterior margin of the scales ( Fig. 4B ) and the presence of a dark blotch on the base of the caudal fin (vs absence of both reticulate color pattern( Fig. 4 C–D) and the dark blotch on the caudal-fin base). It is distinguished from all the above-mentioned species by the presence of three interrupted stripes formed by light spots on the central portion of the scales of the three dorsalmost longitudinal series on the body (vs. interrupted stripes absent). It is further distinguished from M. cotinho by having in life, an orange to reddish longitudinal stripe on body just below the ventralmost interrupted dark stripe ( Figs. 13–14 ); (vs. orange to reddish stripe absent).

Description. Morphometric data presented in Table 3. Body compressed, moderately elongate. Largest specimen examined 66.5 mm SL; greatest body depth slightly anterior to dorsal-fin origin. Dorsal profile of head convex from snout tip to vertical through posterior nostril; slightly convex from that point to tip of supraoccipital spine. Dorsal profile of body convex along predorsal region; straight and posteriorly inclined along dorsal-fin base; posteriorly inclined to moderately convex to adipose fin; concave from along dorsal margin of caudal peduncle. Ventral profile of head and body convex from anterior tip of dentary to anal-fin origin; posterodorsally inclined from latter point to base of last anal-fin ray; concave along ventral margin of caudal peduncle. Mouth terminal, jaws equal. Posterior portion of maxilla extending beyond vertical through middle of orbit. Premaxillary teeth in two rows; outer row with 3(2), 4*(20) tricuspid teeth inner row 5*(22) tri- to pentacupid teeth. Dentary with 5 (22) large pentacuspid teeth followed by a series of 10(1) or 11(2) diminutive tricuspid teeth ( Fig. 16 ). Central median cusp of all teeth longer than lateral cusps ( Fig. 16 ). Branchiostegal rays 4(3). First gill arch with 2(3) rakers on hypobranchial, 9(2) rakers on ceratobranchial, 1(2) on intermediate cartilage, and 7(2) rakers on epibranchial.

Supraneurals 4(1) or 5(2), obliquely oriented. First supraneural anterior to neural spine of 5 th vertebra, fourth supraneural between neural spines of 7 th and 8 th (1) or 8 th and 9 th (2) vertebra. Origin of dorsal fin at approximately half of SL; first pterygiophore of dorsal fin anterior to neural spine of 9 th vertebra. Dorsal-fin rays ii, 9 (43); supernumerary dorsal-fin rays 1(2). Origin of anal fin near half of SL, first pterygiophore of anal fin anterior to haemal spine of 16 th (1) or 17 th (22) vertebra. Anal fin falcate; anal-fin rays iv, 15(1), 16(12), 17*(16), 18(11), 19(2), or 21(1). Pectoral fin i, 12(2), 13(16), 14*(18), 15(6), or 16(1), longest pectoral-fin ray not extending beyond the base of distal pelvic fin ray. Pelvic-fin origin anterior to vertical through dorsal-fin origin. Pelvic-fin rays i, 7*(43), longest ray of pelvic fin reaching urogenital opening. Caudal fin forked, principal caudal-fin rays on dorsal lobe i, 9(3), and on ventral lobe i, 8(1), 9(2); dorsal procurrent caudal-fin rays 9(3), ventral procurrent caudal-in rays 8(3). Adipose fin anterior to vertical through base of posteriormost anal-fin ray.

Scales cycloid, with five (3) radii moderately diverging posteriorly from focus to posterior field of scale; conspicuous circulii present dorsally and ventrally of radial field and continuous anteriorly on embedded portion of scale ( Fig. 7C ). Axillary scale on pectoral and pelvic fins. Proximal one third of caudal fin lobes covered by small scales. Lateral line complete; lateral-line tube present on caudal fin posterior to last perforated scale. Pored lateral-line scales 29(1), 30(10), 31*(24), 32(4), or 33(2). Predorsal scales 9(7), 10*(32), or 11(1). Longitudinal scale rows between dorsal-fin origin and lateral line 5*(42), longitudinal scale rows between lateral line and pelvic-fin origin 3*(41). Middorsal scales between base of posteriormost dorsal-fin ray and adipose-fin 8(10), 9(29), 10(1). Circumpeduncular scales 12(2), 13(14), 14*(14), or 15(5). Total vertebrae 25(3): precaudal vertebrae 12(3), caudal vertebrae 13(3).

Color in alcohol. Overall ground coloration of head and body yellowish. Dorsal portion of head darker than ventral. Tips of upper and lower jaws dark. Infraorbitals with scattered dark pigmentation. Predorsal and preadipose scales dark, forming a longitudinal line along the dorsal midline of body. Posterior margin of scales delineated by chromatophores forming a dark rim resulting in a reticulate pattern on body, more evident on region dorsal of lateral line ( Fig. 4B ). Scales of longitudinal rows on body dorsal to lateral line with dark spots on posterior edge; spot on scales sometimes extending to anterior portion of adjacent scale. Central area of scales of three dorsalmost longitudinal series with lighter spots forming three interrupted stripes. Humeral blotch vertically elongate, with dorsal portion covering horizontally approximately three scales and distinctly darker than ventral portion. Humeral blotch extending vertically on scales of four longitudinal rows. A longitudinal stripe extending from humeral blotch to caudal peduncle; stripe silver on specimens that retain guanine on body, dark on other specimens. A large blotch on base of caudal fin not reaching tips of median caudal-fin rays. Blotch almost rounded with scattered chromatophores on dorsalmost and ventralmost principal caudal-fin rays. Middle portion of caudal-fin rays whitish and tips hyaline. Dorsal, anal, adipose, pectoral and pelvic fins mostly hyaline with few scattered chromatophores ( Fig. 15 ).

Color in life. Based on photographs of specimens just after collection. Dorsal portion of head and body olivaceous, ventral portion silvery. Dark pigmentation pattern of coloration in life similar to that described for preserved specimens except that reticulate pattern is less marked than in preserved specimens. An orange to reddish longitudinal stripe on body just below ventralmost interrupted dark stripe. Dorsal region of eyes reddish. A silvery longitudinal stripe extending from humeral spot to caudal peduncle. Middle portion of caudal fin rays, anterior rays of anal fin, dorsal, adipose, pelvic and pectoral fin rays yellow to orange ( Figs. 13–14 ).

Distribution. Moenkhausia pirahan occurs in the basins of rio Madeira, rio Trombetas and rio Tapajós, in four of the regions proposed by Dagosta & de Pinna (2017) for the Amazon and neighboring regions (7. Teles Pires, 14. Middle-Lower Madeira, 15. Madeira Shield Tributaries, 26. Trombetas ( Fig. 17 ).

Etymology: The specific epithet, pirahan , is in honor to the Pirahã tribe that live close to type locality of this species, in the county of Humaitá, Amazonas state, Brazil.

Figures

FIGURE 4. Detail of body at region ventral of dorsal fin of A) Moenkhausia cotinho, MNRJ 34892, 38.8 mm SL. B) M. pirahan, MZUSP 122063, 45.6 mm SL; C) M. rondoni, UFRO 3800, 40.1 mm SL and D) Hemigrammus newboldi, INHS 60312, 37.9 mm SL. Note the line of chromatophores forming a dark rim and delineating the posterior margin of the scales in A and B (reticulate pattern). 1: dark spot on posterior edge of scale, sometimes extending to anterior portion of adjacent scale; 2: light spot on central portion of scale.

FIGURE 7. Scales from region between dorsal-fin origin and lateral line of: A) Moenkhausia cotinho; B) M. rondoni; C) M. pirahan; D) Hemigrammus newboldi. Left side, lateral view. Scale bar = 1 mm.

FIGURE 13. Moenkhausia pirahan, shortly after collection, UFRO 15783, Brazil, Amazonas, Humaitá, Igarapé Traíra. (Photo: Bruno Barros)

FIGURE 14. Moenkhausia pirahan, unpreserved specimen kept in aquarium, collected with MPEG 28777, Brazil, Pará, Jacareacanga, rio Tapajós (Photo: Fernando Dagosta)

FIGURE 15. Moenkhausia pirahan, holotype, MZUSP 125777, 62.5 mm SL, Brazil, Amazonas, Humaitá, Igarapé Traíra.

FIGURE 16. Premaxilla, maxilla and dentary of Moenkhausia pirahan, UFRO 15783, 59.1 mm SL. Right side, medial view. Scale bar = 1 mm.

FIGURE 17. Map of central and northern South America showing geographic distribution and type locality (red star) of Moenkhausia pirahan.