Thayeria tapajonica, Moreira & Lima, 2017

Moreira, Cristiano R. & Lima, Flávio C. T., 2017, Thayeria tapajonica (Characiformes: Characidae), a new species from rio Tapajós basin, Brazil, Zootaxa 4344 (1), pp. 137-146 : 138-143

Thayeria tapajonica new species

( Figs. 1–3 )

Thayeria sp. 2: Hoffman & Hoffman, 2010: 12–13 ( Brazil, rio Tapajós basin; picture of a freshly collected specimen). Thayeria sp. "Tapajós": Ohara et al., in press: 224–225 ( Brazil, lower rio Teles Pires; photograph, short description).

Holotype: MZUSP 122872 , 31.0 mm SL, Brazil, Pará, Jacareacanga, rio Cristalino (tributary of rio São Benedito ), pousada Thaimaçu , 9°4'46''S, 56°31'51''W; A.K. Zeinad, 27 Sept–2 Oct 2008 .

Paratypes: Brazil, Pará: ZUEC 8914, 4, 18.4–27.8 mm SL ; MCP 51299, 3, 24.2–24.8 mm SL, Santarém, igarapé Capixauã / Vista Alegre (trib. rio Tapajós ), Vista Alegre village , 2°37'23''S, 55°10'58''W; F.C.T. Lima, J.S. Ready, E. Cerdeira et al., 14–15 Nov 2013 . ZUEC 11784, 4, 19.1–26.2 mm SL; MCP 51300, 2, 19.1–23.3 mm SL, Santarém, Lago Camará, rio Tapajós , Muratuba village , 2°56'4''S, 55°12'34''W; W.G.R. Crampton, J.A. Oliveira, F.C.T. Lima, B.B. Calegari & E. Cerdeira, 17 Nov 2015 . ZUEC 11653, 3, 23.2–27.4 mm SL; UF 239078, 2, 24.9– 25.3 mm SL, Belterra, igarapé Bararuá (trib. rio Tapajós ), Piquiatuba village , 2°58'59''S, 55°5'38''W; W.G.R. Crampton, J.A. Oliveira, F.C.T. Lima, B.B. Calegari & E. Cerdeira, 14 Nov 2015 . ZUEC 11684, 3, 17.6–23.9 mm SL, Belterra, igarapé Jandá (trib. rio Tapajós ), Piquiatuba village , 3°0'48''S, 55°6'21''W; W.G.R. Crampton, J.A. Oliveira, F.C.T. Lima, B.B. Calegari & E. Cerdeira, 14–15 Nov 2015 . ZUEC 11728 , 1 , 24.7 mm SL, Belterra, igarapé Dominguinho (trib. rio Tapajós ), Piquiatuba village , 3°0'48''S, 55°6'21''W; W.G.R. Crampton, J.A. Oliveira, F.C.T. Lima, B.B. Calegari & E. Cerdeira, 15–16 Nov 2015 . MZUSP 18244, 2, 15.1–23.9 mm SL, Aveiro, igarapé Açu , c. 3°36'S, 55°19'W; EPA, 30 Oct 1970 . INPA 7265, 9, 20.5–34.8 mm SL, Aveiro, rio Tapajós, flooded area near the mouth of Rio Cupari , 3°43'S, 55°24'W; L.H. Rapp Py-Daniel & J. Zuanon, 27 Oct 1991 . NRM 14588, 7, 17.5–24.9 mm SL, Aveiro, mouth of rio Cupari, left bank of rio Tapajós , 3°43'S, 55°24''W; S.O. Kullander, 25 Sep 1980 . MZUSP 22056 , 3 , 20.6 –24.0 mm SL, Lago da Santa Clara, Monte Cristo, rio Tapajós , c. 4°4'30''S, 55°38'40''W; EPA, 6 Dec 1970 . MCP 15292, 2, 24.1–27.7 mm SL, Itaituba, rio Tapajós, dead branch at bairro Piracuna , c. 4°14'S, 55°58'W; C.A.S. Lucena, 11 Dec 1991 . MNRJ 35215 , 70 , 4 C&S, 15.2–30.2 mm SL, Itaituba, igarapé Bom Jardim (trib. rio Tapajós ), at city perimeter, 4°16'36''S, 56°0'17''W; M. Britto, J. Birindelli, C. Chamon, J. Maldonado & F. Carvalho, 28 Sept 2008 . MNRJ 35216, 2, 19.81–21.3 mm SL, Itaituba, igarapé Capitua (trib. rio Tapajós ), Transamazônica road, 4°18'20''S, 56°5'55''W; P.A.Buckup, C. Zawadski, L..Fries, F. Carvalho & F. Jerep, 28 Sept 2008 . MPEG 22500 , 1 , 28.6 mm SL, Itaituba, rio Tapajós, Vila de Miritituba , 4°16'42.6''S, 55°56'43.5''W; C. Ramos, 7 Sept 2010 . MPEG 27980, 2, 24.9–27.5 mm SL, Itaituba, rio Tapajós at road to Vila de Buburé , 4°22'34''S, 56°14'10''W; T. Begot, 25 March 2013 . MZUSP 25406, 11, 21.6–26.9 mm SL, Itaituba, mouth of igarapé Pimental (trib. rio Tapajós ), Pimental, Amazônia National Park, c. 4°34'S, 56°16'W; J.C. Oliveira, 15 Jul 1979 . MZUSP 23705, 9, 22.3–30.4 mm SL, Itaituba, rio Tapajós, Barreirinha , near São Luís , c. 4°6'S, 55°41'W; EPA, 23 Nov 1970 . MZUSP 92696 , 11 , 1 C&S, 20.4–27.5 mm SL, Itaituba, Pimental, stream trib. rio Tapajós, road Pimental-Itaituba , 4°33'48''S, 56°15'40''W; L.M. Sousa & J.L.O. Birindelli, 10 Nov 2006 . MPEG 26556, 7, 19.3–28.9 mm SL, Jacareacanga, rio Tapajós, South of Vila de Buburé , 4°44'10''S, 56°37'19''W; N. Benone, 7 Jan 2013 . MPEG 26557 , 17 , 24.0– 30.6 mm SL, Jacareacanga, igarapé Jutaí (trib. rio Tapajós ), Vila de Jatobá , 5°3'50''S, 56°51'47''W; N. Benone, 10 Jan 2013 . MPEG 27845, 11, 9.8–21.7 mm SL Jacareacanga, Rio Crepori (trib. rio Tapajós ), Vila de Mamãe Anã , 5°46'48''S, 57°17'24''W; T. Begot, 27 March 2013 . MPEG 27823, 18, 8.7–19.9 mm SL; MPEG 27801, 9, 11.9–20.3 mm SL, Jacareacanga, Vila de Mamãe Anã , 5°45'S, 57°16'W; T. Begot, 27–28 March 2013 . MZUSP 100062 , 5 , 22.0– 32.8 mm SL, same data as holotype . CPUFMT 2862 , 2 , 24.0– 28.2 mm SL, Jacareacanga, mouth of rio São Benedito, 9°6'8''S, 57°2'19''W; A.C. Ribeiro & S. Silva, 10 Sept 2015. Mato Grosso: INPA 48406, 2, 23.1–26.2 mm SL, Paranaíta , trib. rio Teles Pires , 8°21'54''S, 57°40'36''W; W.M. Ohara, 27 Jul 2014 . ZUEC 14194, 4, 1 C&S, 21.8–24.6 mm SL, LIRP 14151, 3, 22.5–24.8 mm SL; Alta Floresta, rio Ximari (trib. rio Teles Pires ), 9°1'59''S, 57°6'13''W; D.M.F. Nunes, F.T. Normando et al., 26 Jul 2015.

Not types: Brazil, Pará: MZUSP 50094 , 1 , 19.9 mm SL, rio Tapajós, lake at Ilha Tapaiúna , c. 2°54'S, 55°5'W; EPA, 28 Oct 1970 . INPA 41332 , 1 , 17.6 mm SL, Aveiro, Igarapé Suqui (trib. rio Tapajós), vila de Cametá , 3°18’29’’S, 55°18’59’’W; R.P. Ota et al., 23 Aug 2013 . MZUSP 31984 , 1 , 27.2 mm SL, Itaituba, rio Tapajós , Pederneiras, below Itaituba; M. Goulding, 24 Oct 1983 . MPEG 28786, 2, 18.5–19.6 mm SL, Jacareacanga, rio Tapajós, Penedo , 5°32'S, 57°6'W; Concremat staff, 25 Aug 2013 . MPEG 27801 , 9 , 10.0–20.0 mm SL, Jacareacanga, rio Tapajós, vila de Mamãe Anã , 5°44’S, 57°22’W; T. Begot, 28 March 2013 . INPA 45794 , 1 , 26.7 mm SL, Jacareacanga, rio São Benedito , 9°6’13’’S, 57°1’53’’W; S. Arrolho et al., 25 June 2013 . ZUEC 14738 , 1 , 23.5 mm SL, Jacareacanga, rio São Benedito , c. 9°6’S, 57°2’W; C.M.C. Leite et al., 4 Feb 2008 .

Diagnosis. Thayeria tapajonica can be distinguished from all congeners, except from T. boehlkei , by the midlateral stripe extending anteriorly to immediately behind head (vs. midlateral stripe restricted to caudal peduncle merging with an oblique stripe running antedorsally in T. obliqua , and T. ifati ). It is distinguished from T. boehlkei by presenting a single scale between lateral-line perforated scales and midlateral stripe (vs. half scale; Fig. 2 ), and by anterior terminus of midlateral stripe dorsal to upper portion of opercle (vs. anterior terminus of midlateral stripe originating on upper portion of opercle and dorsal to it). Additionally, in Thayeria tapajonica the midlateral stripe is typically considerably thinner, especially at its anterior portion, where it is less than one scale wide (vs. thicker midlateral stripe, one and half scales wide, thickening only slightly along body in T. boehlkei ; see “Remarks”, below).

Description. Morphometric data for the holotype and paratypes presented in Table 1. Body compressed. Greatest body depth situated at vertical through dorsal-fin origin. Dorsal profile of head convex from upper lip to vertical through posterior nostril, straight from that point to posterior tip of supraoccipital spine. Dorsal profile of body slightly convex from supraoccipital spine tip to origin of dorsal fin. Dorsal-fin base straight, posteroventraly slanted, approximately straight from posterior terminus of dorsal fin to adipose-fin insertion and slightly concave between adipose-fin insertion and origin of anteriormost dorsal procurrent caudal-fin ray. Ventral profile of head from chin to isthmus approximately straight to slightly convex. Ventral profile of body convex from tip of lower jaw to origin of anal fin. Anal-fin base approximately straight, posterodorsally slanted. Ventral profile of caudal peduncle slightly concave.

Jaws equal, mouth terminal. Posterior terminus of maxilla surpassing vertical through anterior margin of eye. Maxilla approximately at 45 degree angle relative to longitudinal axis of body. Nostrils close to each other, anterior opening roundish, posterior opening oval to crescent-shaped. Premaxillary teeth in two rows. Outer teeth row with 3(11), 4(38), or 5(5) tricuspid teeth. Inner row with 5(48) or 6(4) tri- to pentacuspid teeth, symphyseal tooth of inner series narrower than adjacent teeth. Maxilla with 1(3), or 2(3) tri- to pentacuspid teeth. Dentary with anteriormost four (55) larger pentacuspid teeth, and posterior 5–10 teeth small, cylindrical, uni- to tricuspid. Central cusp of all teeth more developed than remaining lateral cusps.

Scales cycloid. Four to nine strongly marked radii, circuli well marked anteriorly and laterally, absent posteriorly. Lateral line slightly deflected downward and incompletely pored, with 7(6), 8*(10), 9(15), 10(9), or 11(1) perforated scales. Longitudinal scales series including lateral-line scales 27(12), 28*(17), 29(7), or 30(1). Longitudinal scale rows between dorsal-fin origin and lateral line 5(49). Longitudinal scale rows between lateral line and pelvic-fin origin 3*(48), or 4(1). Scales in median series between tip of supraoccipital spine and dorsal-fin origin 8(1), 9*(16), 10(17), or 11(5). Circumpeduncular scales 10(1), 11(1), or 12*(36). Caudal fin with scales basally, extending posteriorly to proximal third of ventral portion of ventral lobe.

Dorsal-fin rays ii, 9(55). Dorsal-fin origin slightly anterior from middle of standard length. First dorsal-fin pterygiophore main body located behind neural spine of 9th (6) vertebrae, with small bony expansion over 9th neural spine. Adipose fin present, except for one specimen. Anteriormost anal-fin pterygiophore inserting posterior to haemal spine of 15th(1) or 16th(5) vertebrae. Anal-fin rays iv(6), 12(4), 13(23), 14(24), or 15*(8). Last unbranched and first three anteriormost branched rays distinctly longer than remaining rays, approximately three times longer than shorter branched fin ray, subsequent rays abruptly decreasing in size. Distal margin of anal fin strongly concave, with elongate anterior lobe. Pectoral-fin rays i, 10(6), 11(24), 12*(24), or 13(5). Pelvic-fin rays i, 7*(59). Tip of pelvic-fin reaching anterior anal-fin rays. Caudal fin forked, lower lobe slight longer than upper lobe. Nine (4), or 10(2) dorsal procurrent caudal-fin rays, and 7(1), or 8(5) ventral procurrent caudal-fin rays. Vertebrae 30(4) or 31(2). Supraneurals 4(4), or 5(2), rod-like. Branchiostegal rays 4(6). First gill arch with 2(4), 3(2) hypobranchial, 9(1), 10(5) ceratobranchial, 1(6) on cartilage between ceratobranchial and epibranchial, and 5(1) or 6(5) epibranchial gill-rakers.

Color in alcohol. Overall ground coloration of head and body light beige ( Fig. 1 ). Dorsal portion of head dark. Snout, anterior portion of dentary and maxilla with concentration of dark chromatophores. Infraorbitals and preopercle with few scattered dark chromatophores, concentrated on dorsal half of opercle. Dorsal dark line of deep chromatophores running from supraoccipital to dorsal procurrent rays. Dorsalmost two scale rows with pigmentation concentrated on anterior portion of scale and line of chromatophores at posterior border of scale, forming inverted c-shaped patches of pigmentation, with few chromatophores close to posterior margin of scales. Immediately ventral to this area, dark chromatophores almost absent, imparting homogeneous clear area running above longitudinal dark stripe. Wide, oblique longitudinal stripe extending from immediately after rear of neurocranium to caudal peduncle, extending into caudal-fin lower lobe. Longitudinal stripe approximately one to one and a half scale wide, thinner anteriorly, becoming gradually broader posteriorly. Lateral surface of abdominal region, immediately below longitudinal dark stripe, with scattered dark chromatophores, gradually becoming almost devoid of pigmentation ventrally. Moderate concentration of dark chromatophores concentrated immediately above anal-fin. Dorsal, pectoral and pelvic fins hyaline, with few small dark chromatophores outlining fin rays. Anal fin with dark chromatophores concentrated on fin lobe. Caudal fin with sparse dark chromatophores outlining fin rays on dorsal lobe, concentrated on median portion of lower lobe forming dark stripe continuous with midlateral body stripe, running through the lobe. Outer lower-lobe fin rays ventral to dark stripe with scattered dark chromatophores. Adipose fin hyaline. Midlateral stripe ontogenetic variable ( Fig. 3 ). In specimens below 15 mm SL, midlateral stripe thicker and darker, occupying almost all caudal peduncle, one and half scale wide anteriorly, in contrast to the half scale wide of adults. Consequently, there is only one and half scale between midlateral stripe and dorsal-fin origin, contrasting with two and half scales in adults. While in adults the general aspect of the midlateral stripe is straight, in juveniles it is inclined ( Fig. 3 ).

Color in life. Based on photographs taken on the field of specimen from lots MZUSP 92696 and ZUEC 11684. Dorsal area light olivaceous, with iridescent scales. Guanine concentrated on most of iris, and sides of head, and ventrolateral half of body, imparting a whitish to silvery pigmentation. Iris yellowish, more evident on anterodorsal half. Pectoral fin hyaline to yellowish, pelvic fin hyaline. Dorsal and adipose fin with yellowish pigmentation. Anal fin with yellow pigmentation concentrated on anal-fin lobe. Base of caudal fin yellowish, with pigmentation ventral to caudal band extending to ¾ of ventral most rays.

Ecological notes. Specimens of Thayeria tapajonica were collected by the second author (FCTL) at the lower rio Tapajós, upstream of Santarém (see list of paratypes) in variously-sized clearwater tributaries within the seasonally flooded igapó forest, typically close to submerged logs or aquatic plants. The examination of gut contents of two cleared and stained specimens (MZUSP 92696; ZUEC 14194) was composed by insect remains, from which several ant heads could be identified.

Distribution. Thayeria tapajonica is only known from the rio Tapajós basin (see Fig. 4 ). The species seems to be almost restricted to the area after the meeting of the rio Juruena and rio Teles Pires, i.e., at the rio Tapajós itself, although the species is also recorded for the lower rio Teles Pires basin, where its distribution potentially overlaps with Thayeria boehlkei (Ohara et al., in press; see Remarks, below).

Etymology. The specific name of the species, tapajonica , is an allusion to the fact that the species is essentially restricted to the rio Tapajós mainstream. An adjective.

Remarks. Thayeria tapajonica is most similar to T. boehlkei , both possessing a midlateral stripe extending anteriorly to immediately behind the head, while T. ifati and T. obliqua have a short midlateral stripe present only on caudal peduncle, confluent with an oblique stripe running anterodorsally. The new species can be recognized from T. boehlkei based solely on the thickness and position of the midlateral stripe. In T. tapajonica , the midlateral stripe is overall thinner than in T. boehlkei , not wider than the height of one and half scale even on the caudal peduncle, while in T. boehlkei , it can be the height of two scales (one entire scale with half scale dorsally and half scale ventrally). Anteriorly, the midlateral stripe of T. tapajonica is much thinner than of T. boehlkei , not wider than half scale height, while in the latter it is at least the height of one and half scale ( Fig. 2 ). This causes the midlateral stripe to appear dislodged dorsally compared to T. boehlkei , since it is restricted to the horizontal line through the dorsal margin of the opercle. In contrast, since the midlateral stripe of T. boehlkei is wider, it extends further ventrally, to the level of the dorsal tip of the opercle. Also, as a consequence of the thinner midlateral stripe of T. tapajonica , an entire scale row separates anteriorly the lateral-line scales series from the ventral margin of the midlateral stripe, while in T. boehlkei there is just half scale separating them ( Fig. 2 ).

Thayeria boehlkei is broadly distributed in the rio Tocantins /Araguaia basin, rio Xingu, and rio Tapajós basins ( Lima & Ribeiro, 2011; Moreira & Lima, work in progress). In contrast, T. tapajonica occurs only in the rio Tapajós basin, where its distribution overlap marginally with T. boehlkei in the lower rio Teles Pires. Despite of this overlap, we have not found any indication that they might be sympatric. The more downstream locality known for Thayeria boehlkei at the rio Teles Pires (INPA 45567) is located slightly more 50 km upstream (in a straight line) from the most upstream locality known for T. tapajonica (ZUEC 14194, LIRP 14151).

Figures

FIGURE 1. Thayeria tapajonica, new species: a, MZUSP 122872, holotype, 31.0 mm SL, Brazil, Pará, Jacareacanga, rio Cristalino (tributary of rio São Benedito); b, MNRJ 35215, paratype, 26.5 mm SL, Brazil, Pará, Itaituba, Igarapé Bom Jardim (tributary of rio Tapajós); c, ZUEC 8914, paratype, 24.8 mm SL, Brazil, Pará, Santarém, Igarapé Capixauã (tributary of rio Tapajós).

FIGURE 2. Lateral view of left side of the posterior portion of head and anterior portion of body of: a, Thayeria tapajonica, MNRJ 35215; b, Thayeria boehlkei, MNRJ 25103. O: opercle. L. L.: Lateral line scales. Posterior border of some scales marked in red. Scale bar: 1 mm.

FIGURE 3. Ontogenetic variation on colour pattern of Thayeria tapajonica, MPEG 27823. From top to bottom: 9.7 mm SL, 11.5 mm SL, 12.8 mm SL, and 15.2 mm SL. Scale bar: 1 mm.

FIGURE 4. Map of central and eastern Amazon basin in Brazil, showing distribution of Thayeria tapajonica. Star indicates type-locality.