Curculionichthys tukana, Roxo & Dias & Silva & Oliveira, 2017
Roxo, Fábio F., Dias, Angelica C., Silva, Gabriel S. C. & Oliveira, Claudio, 2017, Two new species of Curculionichthys (Siluriformes: Loricariidae) from the rio Amazonas basin, Brazil, Zootaxa 4341 (2): -
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Curculionichthys tukana , new species
Fig. 1 View FIGURE 1 , Table 1
Holotype. MZUSP 123010, 23.4 mm SL, Brazil, state of Maranhão, municipality of Estreito, ribeirão Bofe, rio Tocantins basin, 06°53’55” S, 46°57’00” W, 22 March 2005, A. Akama & E. Baena.
Paratypes. All from Brazil, rio Tocantins basin. LBP 22288 View Materials , 1, 22.4 mm SL, 1 c&s, 27.8 mm SL, collected with holotype . MZUSP 87452, 2, 20.2–22.6 mm SL, collected with holotype . MZUSP 87545, 24, 17.2–20.7 mm SL, small unnamed tributary of rio Caraíbas, municipality of Feira Nova do Maranhão , state of Maranhão, 07°02’45” S, 46°36’09” W, 25 March 2005, A. Akama & E.G. Baena GoogleMaps . MZUSP 87553, 7, 18.5–27.6 mm SL, 1 c&s, 21.3 mm SL, córrego Bom Jardim, tributary of rio Caraíbas, municipality of Feira Nova do Maranhão , state of Maranhão, 07°04’05” S, 46°35’50” W, 25 March 2005, A. Akama & E.G. Baena GoogleMaps . MZUSP 105178, 6, 19.4–21.4 mm SL, rio Parauapebas, municipality of Canaã dos Carajás , state of Pará, 06°24’41” S, 50°11’45” W, 18 January 2010, M.V. Loeb & H.R. Varella GoogleMaps . MZUSP 106572, 3, 14.7–20.7 mm SL, rio Parauapebas, municipality of Canaã dos Carajás , state of Pará, 06°24’46” S, 50°01’36” W, 21 June 2010, M. Loeb & H.R. Varella GoogleMaps . MZUSP 106584, 14, 14.8–20.8 mm SL, rio Sossego, municipality of Canaã dos Carajás , state of Pará, 06°24’24” S, 50°02’44” W, 19 June 2010, M.V. Loeb & H.R. Varella GoogleMaps . NUP 19280 View Materials , 2, 23.7 –24.0 mm SL, córrego Bom Jardim, tributary of rio Caraíbas, municipality of Feira Nova do Maranhão , state of Maranhão, 07°04’05” S, 46°35’50” W, 25 March 2005, A. Akama & E.G. Baena. GoogleMaps
Non-types. MZUSP 114384 View Materials , 1 View Materials , 20.5 View Materials mm SL, rio Montes Claros, municipality of Cavalcante , state of Goiás, 13°51’25” S, 47°36’01” W, 29 November 2011, A.M. Zanata, P.C.A. Cardoso, F.A.G. Melo & O.T. Oyakawa. GoogleMaps
Diagnosis. Curculionichthys tukana differs from all congeners, except C. karipuna and C. oliveirai by having one abdominal median plate series, Fig. 2A View FIGURE 2 (vs. three or more abdominal medial plates series); from C. karipuna by the absence of an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portion of the first unbranched anal-fin ray (vs. presence of such pigmentation pattern); from C. oliveirai , and also from C. insperatus , C. paresi and C. sagarana , by having seven to eight plates in abdominal lateral plates series, Fig. 2A View FIGURE 2 (vs. four to six plates in abdominal lateral plates series); from C. itaim , C. luteofrenatus and C. piracanjuba by having papillae aligned in series that extends from the distal portion of lower lip to dentary (vs. all papillae randomly distributed throughout lower lip, see figure 4 of Silva et al.  for illustration of both character states). The new species can be further diagnosed from C. insperatus and C. oliveirai by the absence of large conspicuous odontodes forming rows on head and trunk (vs. presence of large, conspicuous odontodes forming rows on the head); from C. oliveirai and C. coxipone by having the anterior profile of the head pointed (vs. anterior profile of head rounded); from C. paresi by having 12–18 premaxillary teeth (vs. 6–10) and 10–16 dentary teeth (vs. 4–7); from C. sabaji by the absence of dark-brown spots scattered over the body (vs. the presence of darkbrown spots); from C. paresi by the lack of contrasting dark spots at the anterodorsal region of body (vs. the presence of such pigmentation pattern). Curculionichthys tukana can additionally be distinguished from C. piracanjuba by presence of odontodes forming aligned rows, more evident in the dorsal portion of head and in the lateral portion of caudal peduncle (vs. odontodes not forming rows on the supraoccipital, on the compound pterotic, and on the lateral plates series).
Description. Morphometric and meristic data are given in Table 1. Small sized loricariid (18–24 mm SL). Head and snout slightly rounded, snout tip pointed anteriorly (48–56% HL). Area around tip of snout completely covered by odontodes. Snout elongate (48–57% HL); anterior region slightly depressed. Nostril small, almost reaching same diameter of eyes. Dorsal profile of head ascending approximately 45° to parieto-supraoccipital; slightly concavity between nostrils. Eyes relatively small (12–17% HL), dorsolaterally positioned, just posterior of midpoint of head. Superior margin of orbits not elevated. Presence of inconspicuous odontodes on suboperculum. Mouth moderate in size; oral disk ellipsoid with papillae randomly distributed. Lips without odontodes; lower lip larger than upper lip, almost reaching cleithrum; its border fringed; lower lip inner surface covered with small papillae, similar in size. Maxillary barbel short, slender and not adnate to lower lip. Teeth slender with two symmetrical cusps; central cusp larger than lateral cusps. Premaxillary teeth 10–18 (mode 12). Dentary teeth 12–18 (mode 12).
Lower surface of head naked. Head lacking ridges. Supraoccipital process not elevated and without conspicuous tuft of odontodes in specimens of all sizes. Predorsal region without ridges. In dorsal view, body elongated and slightly depressed on caudal peduncle. Greatest body width at cleithral region (23–26% SL), progressively narrowing towards snout tip and caudal-fin insertion. Dorsal profile of head and trunk covered by dermal plates, except on area around dorsal-fin insertion. In lateral view, body depressed. Body convex from snout tip to posterior margin of parieto-supraoccipital; slight concave from that point to dorsal-fin origin; slightly concave and descending from dorsal-fin origin to first upper procurrent caudal-fin ray origin, elevating posteriorly to insertion of caudal fin. Greatest body depth at unbranched dorsal-fin ray insertion (16–19% SL). Cleithrum and coracoid exposed in ventral view, covered by odontodes. Arrector fossa partially enclosed by ventral lamina of coracoid.
Ventral profile straight and descending from snout tip to opercular region; convex from opercular region to anal-fin origin; slightly concave from that point to lower procurrent caudal-fin ray origin. Lateral surface of body entirely covered by plates; mid-dorsal plate series poorly developed (six plates), reaching middle of dorsal-fin base; median plate series uninterrupted in median portion of body and perforated by lateral line 24–26 plates (mode 25); mid-ventral series of lateral plates developed and almost reaching middle of caudal peduncle (13 plates). Body plates covered with minute, uniformly sized and evenly distributed odontodes.
Ventral portion of body totally covered by plates, except on ventral part of head and around pectoral- and pelvic-fin insertions, and urogenital opening. Abdomen entirely covered by bony plates. Lateral plates series larger and forming regular series of seven to eight elongate plates on each side; median plate series smaller, arranged in single series from distal portion of cleithrum to anal plate series on anterior portion of urogenital opening; anal plates series formed by four to five large plates ( Fig. 2A View FIGURE 2 ).
Dorsal-fin rays ii,7; its origin slightly anterior through pelvic-fin origin. Dorsal-fin unbranched ray slightly convex. Tip of adpressed dorsal-fin rays surpassing anal fin unbranched ray insertion. Dorsal-fin spinelet small and V -shaped, Fig. 2B View FIGURE 2 ; lock mechanism functional. Pectoral-fin rays i,6; its tip almost reaching pelvic-fin insertion when adpressed. Pectoral-fin axillary slit present above pectoral-fin insertion. Pelvic-fin rays i,5; its distal margin straight to slightly convex; tip of adpressed pelvic fin reaching anal-fin origin in males, but not in females. Absent of adipose fin. Anal-fin rays i,5; distal margin slightly convex. Caudal-fin rays i, 7–i,7; slightly emarginated; unbranched rays of same size. Rays of all fins covered with pointed odontodes. Least body depth at caudal peduncle. Caudal peduncle ellipsoid in cross section, rounded dorsally and ventrally.
Neurocranium presented in Fig. 2C, D View FIGURE 2 . In dorsal view ( Fig. 2C View FIGURE 2 ), parieto-supraoccipital (soc) octagonal, bordered by compound pterotic (cpt) and sphenotic (sp) laterally and by frontal (f) anteriorly. Snout composed by two rostral square-shaped plates (r); two prenasals square-shape, and two rectangular-shape plates (pn) between nares, and two nasal bones (n) slightly chevron-shape, forming superior margin of orbit, bordered by infra-orbital (io2) and posteriorly by frontals (f). Upper region of neurocranium composed by three large bones: compound pterotic (cpt), parieto-supraoccipital (soc) and by frontal (f), largest bones of head; and one small bone: sphenotic (sp), bordering anteriorly by frontal (f), posteriorly by compound pterotic (cpt) and laterally by parietosupraoccipital (soc).
In lateral view ( Fig. 2D View FIGURE 2 ), posterior rostrum plates large, pr1 triangular-shaped, pr2 small, rectangular-shaped, pr3 larger, pentagon-shaped and pr4 triangular-shaped. Infraorbital plate series incomplete (io1-io4), io1 and io2 largest; io3 and io4 smallest, forming inferior orbital margin of eyes. Opercular series complete, preopercle (pop) and supraopercular (spop) reduced, rectangular-shaped, covered by laterosensory canal; opercle (op) rounded; two subocular cheek plates, cp1 largest, triangular-shaped; cp2, smaller; bordering by cp1, preopercle (pop) and opercle (op), forming posterior lateral margin of head.
Color in Alcohol. In dorsal view, light brown background; trunk with two longitudinal light bars from predorsal region to caudal peduncle. Three inconspicuous light dark bars along dorsal portion of body: one at end of dorsal-fin base; second at middle of caudal peduncle; third at lower procurrent caudal-fin ray origin. Unpigmented portion of lateral cleithral region and latero-anterior portion of head. Two hyaline parallel strips on snout, from rostral plate to nares. Pectoral fins hyaline, without chromatophores, except in region of its insertions. In lateral view, light brown head and hyaline trunk. Dark bar inconspicuous in median region of body flowing lateral line. Few chromatophores irregularly distributed on cleithral region. Dorsal-fin hyaline, without chromatophores. Caudal-fin hyaline, except by a dark spot at anterior to middle region of rays and two small bars of chromatophores on posterior portion of caudal-fin rays. Body hyaline in ventral view; chromatophores irregularly distributed on anal-fin base and caudal peduncle.
Sexual dimorphism. Males with a urogenital papilla in ventral view, positioned anteriorly to anal opening; a dermal flap along dorsal margin of unbranched pelvic-fin ray; a tip of pelvic-fin rays extending beyond anal-fin origin. All features are absent in females. Males and females have a membrane covering almost entire urogenital opening, a feature more developed in females.
Distribution. Curculionichthys tukana is known from five small rivers of the rio Tocantins basin ( Fig. 3 View FIGURE 3 ): ribeirão Bofe, córrego Bom Jardim, rio Parauapebas, rio Sossego and a small unnamed tributary of rio Caraíbas.
Etymology. The specific name, tukana , is from the Tupi-Guarani language, and it is related to the name of the rio Tocantins, where this new species is distributed. Tocantins came from Tupi-Guarani language and means “Tucano beak” with the junction of the two words tukana (Tucano) and tim (beak). A noun in apposition.
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