Corumbataia acanthodela, Thimotheo & Benine & Oliveira & Silva, 2020

Thimotheo, Mateus Giovanni Rocha, Benine, Ricardo Cardoso, Oliveira, Claudio & Silva, Gabriel de Souza da Costa e, 2020, New species of the Corumbataia cuestae group (Siluriformes: Loricariidae) from the Rio Tocantins basin, with comments on its phylogenetic relationships, Neotropical Ichthyology (Neotrop. Ichthyol.) 18 (4), pp. 1-16 : 7-12

Corumbataia acanthodela , new species

urn:lsid:zoobank.org:act:6690E445-1BCA-46AA-A212-A63D32E235E1

( Fig. 2 , Tab. 3 )

Corumbataia tocantinensis Bristki, 1997:237 (original description; in part, paratypes MZUSP 51224 , 51225 , 50158 ; UFRJ 3000, 3001, 2999; Rio Maranhão, Rio Tocantins). — Carvalho , 2008:554 (diagnosis, fig. 2A, MCN 13462).

Holotype. MZUSP 125794 , 27.9 mm SL, male, Goiás, Niquelândia, Rio do Peixe , Rio Maranhão , Rio Tocantins basin, 14°30’39.3”S 48°41’10.0”W, 23 Nov 2012, B. F. Melo, J. H. Martinez, G. S. C. Silva & R. Devidé.

Paratypes. All from Brazil, Goiás: LBP 17153 , 10, 28.9– 16.8 mm SL, 2 c&s, 26.1–26.4 mm SL, collected with holotype. LBP 19095 , 10, 27.3– 16.1 mm SL, 2 c&s, 29.4– 26.5 mm SL (tissues 77006–10), Goiás, Niquelândia, Rio Maranhão , Rio Tocantins basin, 14°38’16.9’’S 48°45’59.1” W, 5 Aug 2014, B. F. Melo, C. Oliveira, G. S. C. Silva & M. Taylor. LBP 25634 , 1, 28.4 mm SL, Goiás, Mara Rosa, Rio Vaivém , Rio Maranhão , Rio Tocantins basin, 14º03’45.10”S 49º05’34.25”W, 25 Nov 2017, R. Devidé, B. F. Melo, C. Araya, G. S. C. Silva. NUP 22694 , 3, 17.1–24.9 mm SL, Goiás, Niquelândia, Rio Maranhão , Rio Tocantins basin, 14°38’16.9’’S 48°45’59.1”W, 5 Aug 2014, B. F. Melo, C. Oliveira, G. S. C. Silva & M. Taylor .

Diagnosis. The new species differs from all congeners, except for the members of Corumbataia cuestae group by having a conspicuous pair of tufts with enlarged odontodes on the tip of the supraoccipital (vs. absence of crest of enlarged odontodes in C. anosteos , C. canoeiro , and C. veadeiros ); by the absence of an adipose fin or single series of platelets at adipose fin position (vs. presence of an adipose fin in C. canoeiro , or single series of platelets in C. anosteos and C. veadeiros ); by anastomosis of the infraorbital and otic sensory canals over the pterotic-supracleithrum ( Fig. 3A ) (vs. anastomosis of infraorbital and otic sensory canals over the sphenotic in C. anosteos , C. canoeiro , and C. veadeiros ) ( Fig. 3B ). Additionally, the new species differs from all species of Corumbataia cuestae group by having a small naked area on snout tip (vs. large naked area on snout tip, Fig. 4 ). Moreover, Corumbataia acanthodela differs from C. cuestae , C. liliai , C. lucianoi , and C. britskii by having abdominal platelets reaching the mid-ventral lateral plates (vs. abdominal platelets far from reaching mid-ventral lateral plates); from C. cuestae , C. liliai , and C. tocantinensis by having two rounded and more anteriorly positioned hyaline areas on the caudal-fin ( Fig. 2 ) (vs. absence of two smaller rounded hyaline areas, see fig. 3 in Silva et al., 2018). It differs from C. tocantinensis by having the anterior profile of the head rounded in dorsal view (vs. elliptical) and from C. lucianoi and C. liliai by the presence of plates on dorsal portion of snout (vs. presence of a broad naked area without plates or odontodes on dorsal portion of snout). It differs from C. britskii , C. lucianoi , and C. liliai by the presence of 28–29 vertebrae (vs. 27) and from C. britskii by having lower lip far from reaching pectoral girdle line (vs. reaching pectoral girdle transversal line).

Description. Morphometric and meristic data are summarized in Tab. 3 . Small-sized loricariid (maximum 27.3 mm SL). Snout rounded in dorsal view. Dorsal profile of head ascending convexly approximately 45° to parieto-supraoccipital. Eyes relatively small (15.3–21.8% of HL), dorsolaterally positioned, just posterior to midpoint of head. Iris operculum present and poorly developed. Mouth moderate in size; oral disk ellipsoid with papillae randomly distributed. Lower lip larger than upper lip, not reaching cleithrum; its border fringed; lower lip inner surface covered with small papillae, similar in size. Maxillary barbel adnate to lower lip. Teeth slender with two cusps; central cusp larger than lateral cusp. Premaxillary teeth 29–42 (mode 37). Dentary teeth 22–37 (mode 32).

Lower surface of head naked. Head lacking ridges. Parieto-supraoccipital process elevated and with conspicuous pair of tufts of hypertrophied odontodes in specimens of all examined sizes. Predorsal region without ridges. Body elongate and compressed at caudal peduncle. Greatest body width at cleithral region, progressively narrowing anteriorly towards snout tip and posteriorly towards caudal-fin. Head and trunk covered by dermal plates, except for naked area around dorsal-fin insertion. Body dorsoventrally compressed. Dorsal profile convex from snout tip to posterior margin of parieto-supraoccipital and slightly concave from that point to dorsal-fin origin. Dorsal profile slightly concave and descending from dorsal-fin origin to first upper procurrent caudal-fin ray, rising posteriorly to insertion of caudal fin. Greatest body depth at unbranched dorsal-fin ray insertion. Cleithrum and coracoid exposed in ventral view, covered by odontodes. Arrector fossae completely enclosed by ventral lamina of coracoid.

Ventral profile straight and descending from snout tip to opercular region, slightly convex from opercular region to anal-fin origin and slightly concave from that point to lower procurrent caudal-fin ray origin. Lateral surface of body entirely covered by plates; dorsal series with 23–24 plates. Mid-dorsal plate series truncated with 18– 19 plates not reaching end of caudal peduncle. Lateral plate series with 22–23 plates. Lateral line incomplete, with gaps in line of pores along mid-length of body. Mid-ventral series of lateral plates well-developed, reaching middle of caudal peduncle (17– 19 plates). Ventral plates series with 20–21 plates. Body plates covered with minute odontodes.

Dorsal fin ii,7; its origin slightly posterior to vertical with pelvic-fin origin. Unbranched rays of dorsal fin slightly convex. Tip of adpressed dorsal-fin rays surpassing anal-fin origin. Dorsal-fin spinelet small and rounded (4 c&s). Pectoral-fin rays i,6; tip of adpressed pectoral fin surpassing pelvic-fin origin. Pectoral-fin axillary slit small. Pelvic-fin rays i,5. Distal margin of pelvic fin straight to slightly convex; tip of adpressed pelvic-fin ray reaching anal-fin origin in mature males, but not in females. Adipose fin absent. 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. Lowest body depth at caudal peduncle. Caudal peduncle ellipsoid in cross section, rounded dorsally and ventrally. Hypurals elements fused in a unique hypural plate. Total vertebrae 28 or 29 (4 c&s).

Color in alcohol. Background color of dorsal region of head and trunk brown. Four dark brown saddles along dorsal portion of body: first at dorsal-fin origin, second at end of dorsal-fin base, third at middle of caudal peduncle, and fourth reaching anteriormost caudal procurrent ray. Unpigmented portion of snout appears as two parallel hyaline stripes from rostral plate to nares. Mid-lateral dark brown stripe extending from tip of snout to caudal peduncle. Ventral portion of body almost entirely yellowish, except for dark, randomly-distributed chromatophores and for a concentration of chromatophores at anal-fin origin. Dorsal, pectoral, and pelvic fins with dark, irregularly distributed chromatophores. Caudal-fin brown, with two smaller rounded hyaline areas anteriorly, and two large rounded hyaline areas posteriorly ( Fig.1 ).

Sexual dimorphism. Adult males possess a papilla located posterior to the urogenital opening; an unbranched pelvic-fin ray that supports dermal flap along its dorsal surface; and a wider head (84.5–88.6% vs. 80.6–85.3 of HL in female) with hypertrophied odontodes on its lateral margin ( Fig. 5 ).

Geographical distribution. Corumbataia acanthodela is known from Rio dos Patos, Rio do Peixe , and Rio Vaivém, all tributaries of the Rio Maranhão, in the headwaters of the Rio Tocantins basin, Goiás, Central Brazil ( Fig. 6 ). The new species was found in clear water of fast-flowing stream with rocks and marginal vegetation.

Etymology. The specific epithet acanthodela is from Greek akantha meaning thorn, and delos meaning conspicuous, in reference to the hypertrophied odontodes in the head of mature males. An adjective.

Conservation status. Corumbataia acanthodela is known from three localities in the Rio Maranhão basin. The areas where the specimens were collected are mountainous and relatively well preserved, which do not qualify it for threatened status. Therefore, C. acanthodela is here recommended to be categorized as Least Concern ( LC) under the categories and criteria of the International Union for Conservation Nature ( IUCN Standards and Petitions Subcommittee, 2019).

Figures

FIGURE 1 | A. Maximum likelihood – ML (LogL = -3132.01) tree of Corumbataia species using TN93+G+I nucleotide substitution model and based on the analysis of partial sequence of cytochrome oxidase C subunit I (COI). Numbers at nodes are bootstrap values based on 1000 pseudoreplicates. Values below 50% are not shown. B. Majority rule consensus tree obtained in Bayesian analysis using GTR+I. Numbers below branches are posterior probabilities obtained from 10000 trees.

FIGURE 2 | Corumbataia acanthodela, holotype, MZUSP 125794, male 27.9 mm SL, from Rio Maranhão, Rio Tocantins basin, Niquelândia, Goiás, Brazil.

FIGURE 3 | Infraorbital series of Corumbataia acanthodela, LBP 19095, paratype (A), and C. anosteos, LBP 17125 (B). io1-io5 (Infraorbitals); sp (sphenotic); cpt (pterotic-supracleithrum). Scale bars = 1 mm.

FIGURE 4 | Frontal view of snout tip showing a naked area without odontodes. A. Corumbataia acanthodela, LBP 19095, paratype; B. Corumbataia cuestae, LBP 1309. Scale bars = 1 mm.

FIGURE 5 | Hypertrophied odontodes on the lateral margins of head in Corumbataia acanthodela, paratypes, male (left), NUP 22694 and female (right), LBP 19095. Scale bars = 1 mm.

FIGURE 6 | Distribution of Corumbataia species. Yellow circles: C. acanthodela, Rio Maranhão; Green circle: C. anosteos, Rio Piçarras; Blue circle: C. britskii, Rio Sucuriu; White circle: C. canoeiro, Rio Paranã; Orange circles: C. cuestae, Rio Tietê; Purple circle: C. liliai, Rio Correntes; Brown circles: C. lucianoi, Rio Correntes; Red circle: C. tocantinensis, Rio Vermelho; Pink circle: C. veadeiros, Rio Paranã.