Tatia akroa, Souza & Sarmento-Soares & Canto & Ribeiro, 2020

Souza, Jordson de Souza e, Sarmento-Soares, Luisa M., Canto, André L. Colares & Ribeiro, Frank Raynner V., 2020, Description of a new species of Tatia from rio Tocantins drainage, central Brazil, with notes on Tatia simplex Mees, 1974 (Siluriformes, Auchenipteridae), Neotropical Ichthyology (Neotrop. Ichthyol.) 18 (1), No. e 190111, pp. 1-18 : 4-12

Tatia akroa , new species

urn:lsid:zoobank.org:act:4ECA9898-25FD-417D-90F8-4C757A37C2A0

( Fig. 1 , Tab. 1 )

Holotype. UFOPA-I 671 , 38.4 mm SL, Brazil, Tocantins State, rio Tocantins basin, rio Perdida , 9°11ʼ23.44ʼʼS 47°15ʼ59.14ʼʼW, 30 May 2013, L. Brito.

Paratypes. MZUSP 82349 , 14 , 2 CS, 27.3–35.4 mm SL, rio Palma, near village of Taipas, on road Dianópolis-Conceição do Tocantins, Dianópolis , 23 Nov 2002, C . R. Moreira, J. C. Nolasco . UFOPA-I 670 , 1 , CS, 34.26 mm SL, collected with the holotype .

Diagnosis: Tatia akroa differs from its congeners, except T. britskii , by the absence of adipose fin (vs. present). Differs from T. britskii by the caudal peduncle length (24.1– 30.5% SL, mean 25.3 vs. 20.0–22.7%, mean 20.9); caudal peduncle depth (10.9–16.8% SL, mean 14.1 vs. 9.4–10.5%, mean 9.8); mesethmoid broad in the new species, smallest width approximately equal to its length, whereas slender in T. britskii (smallest width approximately three times length see Sarmento-Soares, Birindelli, 2014: fig. 2). Further differs from T. simplex by the posterior margin of dorsal-fin spine smooth (vs. with 1 to 3 distal denticulations). Further differs from Tatia aulopygia Kner, 1857 , Tatia brunnea Mees, 1974 , T. caxiuanensis Sarmento-Soares, Martins-Pinheiro, 2008 , Tatia dunni (Fowler, 1945) , Tatia galaxias Mees, 1974 , Tatia gyrina (Eigenmann, Allen, 1942) , Tatia jaracatia Pavanelli, Bifi, 2009 , Tatia intermedia , T. meesi Sarmento-Soares, Martins Pinheiro, 2008 , T. neivai (Ihering, 1930) , and Tatia strigata Soares-Porto, 1995 by the cranial roof with two nuchal plates (vs. cranial roof with three nuchal plates, anterior one smallest, somewhat rounded) and by dotted color pattern on sides of body (vs. color pattern spotted or reticulated on flanks). Additionally distinct from Tatia bockmanni ( Sarmento-Soares, Buckup, 2005) , Tatia concolor Mees, 1974 , Tatia marthae Vari, Ferraris, 2013 , Tatia punctata Mees, 1974 by coracoid process somewhat large, about same length as pectoral-fin base (vs. coracoid process small, comparatively shorter than pectoral fin base). Further differs from Tatia boemia Koch, Reis, 1996 , Tatia caudosignata DoNascimiento, Albornoz-Garzón, García-Melo, 2019 , and T. nigra Sarmento-Soares, Martins-Pinheiro, 2008 , by the number of post-Weberian vertebrae, 30 (vs. between 32 to 36 vertebrae). From Tatia reticulata Mees, 1974 , by posterior margin of dorsal spine with small denticulations, less than half in the width of spine axis (vs. well-formed retrorse denticulations, about same width as spine axis). From Tatia melanoleuca Vari, Calegari, 2014 , Tatia musaica Royero, 1992 , Tatia orca (Sarmento-Soares, Lazzarotto, Rapp Py-Daniel, Leitão, 2017) , by small number of posterior denticulations, 11–15 (vs. large number of posterior denticulations on pectoral-spine, more than 20).

Description. Morphometric data presented in Tab. 1 . Small size, examined adult specimens 38.3–49.3 mm SL. Body short, head slightly depressed anteriorly, progressively more elevated posteriorly. In dorsal view, profile of head longer than broad slightly convex from snout tip to pectoral-fin insertion. In lateral view, dorsal profile of body from dorsal-fin base to caudal fin slightly to distinctly convex. Ventral profile of head and abdomen almost straight. Greatest body width at pectoral-fin origin. Ventral profile of body gently concave between anal-fin base and caudal-fin origin. Greatest body depth at origin of dorsal fin. Trunk from dorsal-fin base to caudal peduncle gradually compressed. Head integument thick, obscuring bones of cranial roof; adipose eyelid weakly developed; eye lateral on anterior portion of head; mouth terminal, upper lip extended posterolaterally, fleshy rictal fold well developed; snout margin rounded in dorsal view; anterior nostril tubular, located on anterior border of snout; posterior nostril somewhat larger, rounded, limited anteriorly by small skin flap; transverse distance between anterior nostrils slightly smaller than distance between posterior ones. Maxillary barbel elongate, reaching approximately vertical through middle of dorsal-fin or beyond; adpressed maxillary barbel fits in groove on the lateral portion of head, immediately above rictal fold and below eye; mental barbels very short, tips not reaching pectoral-fin base; bases of barbels arranged in arc along ventral surface of jaw; inner mental barbel about two-thirds length of outer mental (63.5–67.7% in outer mental). Posterior process of cleithrum moderately large, almost reaching vertical through base of dorsal-fin spine. Coracoid process developed, about same length as pectoral-fin base.

Dorsal fin II,5; originated slightly posterior to vertical through origin of pectoral fin; spinelet rigid, triangular in frontal view, covered by thin layer of skin; dorsal-fin spine straight, strong, pungent, shorter than first branched ray, with filamentous tip; anterior margin of dorsal-fin spine with 9–15 denticulations, posterior margin smooth (n = 6); first branched ray longest, subsequent rays decreasing gradually in length; last dorsal-fin ray approximately half length of first branched ray; distal margin of dorsal fin rounded. Adipose fin absent. Pectoral fin I,5; pectoral spine, rigid, pungent, anterior margin with 15–19 denticulations, posterior margin with 11–15 denticulations (n = 6); pectoral-fin spine denticulations becoming progressively more prominent distally; first branched ray longest, subsequent rays decreasing in length; posterior margin of pectoral fin obliquely truncate. Pelvic fin i,5; origin at or slightly posterior to middle of body; first branched ray longest, subsequent rays decreasing in length; posterior pelvic-fin margin straight or slightly rounded. Anal fin ii-iii,6 (n=4) or ii-iii, 7 (n=13); origin approximately on last third of standard length, posterior to vertical through tips of pelvic-fn rays; last ray unbranched, first and second branched rays longest; distal margin rounded. Caudal fin i,15,i; deeply forked, with approximately rounded lobes; dorsal and ventral caudal-fin lobes equal in length; outer principal rays unbranched, seven branched rays on dorsal lobe and eight branched rays on ventral lobe; 14–17 upper procurrent, 13–15 lower procurrent rays (n = 3).

Rostral border of cranium with mesethmoid longer than broad; premaxilla with synchondral articulation; cranial fontanel narrow and elliptical, enclosed by mesethmoid and frontals ( Fig. 2 ). Nasal ossified as short tubular bone situated between mesethmoid cornua and lateral ethmoid, not sutured to mesethmoid. Lateral ethmoid not participating in dorsal face of cephalic shield. Autopalatine rod-like, oriented almost parallel to longitudinal axis of body; maxilla slightly elongated, about twice the size of autopalatine; vomer arrow-shaped with short rostral-lateral processes. Jaws of equal size; premaxilla and dentary slender, each with two or three rows of robust conical teeth. Anterior nuchal plate absent; middle nuchal plate slightly concave along lateral margins; posterior nuchal plate short, projected laterally, with prominent tip. Epioccipital process very small ( Fig. 2 ).

Hyomandibula broad, projected anteriorly, connected to both quadrate and metapterygoid through cartilage and deeply dentate suture. Metapterygoid as a wide lamina, joined to quadrate via suture ( Fig. 3 ). Quadrate trapezoidal, with broad base, sutured to preopercle, hyomandibula and metapterygoid; long preopercle ventral margins sutured to both quadrate and hyomandibula; suprapreopercle present as long canal bone; preopercular canal exiting on anterior portion of pterotic. Opercle laminate, ornamented, and broadly subtriangular.

Hyoid arch with compact parurohyal with short ventral process; short dorsal hypohyal associated with comparatively large ventral hypohyal; anterior ceratohyal well developed, posterior ceratohyal smaller than others one; branchiostegal ray articulated to hyoid arch; six branchiostegal rays, four slender rays associated with anterior ceratohyal, two flattened rays with posterior ceratohyal ( Fig. 4 ). Branchiostegal membrane broadly united to isthmus.

Branchial arches with urohyal close to basibranchial 2; basibranchial 2 cartilaginous, broadest anteriorly, usually separated by gap from basibranchial 3; basibranchial 3 shorter, forming osseous rod; basibranchial 4 large, flattened and cartilaginous; basibranchial 2 bordered laterally by cartilaginous head of hypobranchial 1; basibranchial 3 between cartilaginous head of hypobranchial 2 and cartilaginous hypobranchial 3; basibranchial 4 bordered laterally by cartilaginous head of ceratobranchial 4 and caudally by cartilaginous head of ceratobranchial 5.

Hypobranchials 1 and 2 subtriangular, mostly osseous, elongate and expanded laterally, with cartilaginous tips; hypobranchial 3 completely cartilaginous, trapezoidal; hypobranchial 4 absent. Five ceratobranchials, mostly ossified, with cartilage on both ends. Ceratobranchials supporting single row of rakers; fifth ceratobranchial expanded postero-medially to support lower pharyngeal toothplate with short conical teeth. Four epibranchials, all largely ossified except for cartilaginous ends, supporting few rakers each, close to articulation with ceratobranchials. Epibranchials 1 and 2 rod-like; epibranchial 3 with posterior uncinate process in articulation to epibranchial 4; epibranchial 4 with laminar extension; reduced accessory cartilage, located on angle between cartilaginous ends of epibranchial 4 and ceratobranchial 4. Pharyngobranchial 1 absent; pharyngobranchial 2 short, cartilaginous, somewhat ellipsoid, placed between anteromedial cartilaginous tips of epibranchials 1 and 2; pharyngobranchial 3 elongate, ossified, with expanded posterior border; pharyngobranchial 4 ossified. Upper pharyngeal tooth plate bearing conical teeth, supported by pharyngobranchial 3 and 4, and also epibranchials 3 and 4.

Infraorbital 1 with ventro-lateral process restricted to anterior border of eye, and followed by four canal-like bones, in incomplete infraorbital series. Lateral line on body straight, inconspicuous, with ossified canal bones only anteriorly, unbranched at caudal fin.

Ribs 8–9 attached to consecutive vertebrae 6–13, becoming progressively smaller posteriorly. Total vertebrae 35 (N= 4), observed in cleared and stained ( CS) and radiographed specimens ( R).

Color in alcohol. Color light brown with dots, formed by chromatophores scattered on the head and mid-dorsal portions of body; sometimes dorsal surface of head and dorsolateral region darker along entire trunk, with more concentrated chromatophores from mid-dorsal region to lateral line. Sides of body with light brown chromatophores, becoming sparse ventrally. Fins almost hyaline; rays mottled with pale brown spots along base. Dorsal fin with a dark spot localized in proximal region. Caudal-fin base with irregular black to brown spots; fin becoming hyaline towards distal margin.

Sexual dimorphism. Observed in one male with partially modified anal fin for insemination ( Figs. 1 , 5 ). Five first proximal radials closely together, not fused, with sutures visible. Last three proximal radials elements arranged as in non-breeding and females (according previous descriptions for congeners). Unbranched and first branched anal-fin rays fused together to form a structure for insemination at anterior portion of the anal fin. Urogenital opening at base of anal fin as simple pore at the distal tip of a tubular structure bound by integument. Deferent duct externally visible as a genital papilla.

Distribution. Tatia akroa is known from the upper portion of the rio Tocantins drainage ( Fig. 6 ).

Ecological notes. One of the specimens examined was dissected and its stomach contained fragments of terrestrial insects including Diptera and Coleoptera.

Conservation status. Tatia akroa is known from the rio Perdida and rio Palma, upper rio Tocantins drainage. Considering its Extent of Occurrence ( EOO) and that no major threats to the species were detected in the area of distribution we suggest that T. akroa should be categorized as least concern ( LC) according to the International Union for Conservation of Nature categories and criteria ( IUCN, 2019).

Etymology. The specific name is a reference to the Akroá indigenous people, inhabitants of lands from eastern Tocantins to southern Piauí until the XIX century ( Apolinário, 2005). The Akroá lived along valleys on Serra Geral do Tocantins, a watershed divide between the right margin of rio Tocantins and rio Parnaíba upper valleys respectively. Their territory included the rio Manuel Alves sub-basin of rio Tocantins, distribution range of the new Tatia species. A noun in apposition.

Figures

FIGURE 1 | Tatia akroa, lateral, dorsal and ventral views. UFOPA-I 671, holotype, male, 38.8 mm SL, rio Perdida, tributary of rio Sono, rio Tocantins basin, Tocantins State, Brazil.

FIGURE 2 | Neurocranium of Tatia akroa, UFOPA-I 670, 34.3 mm SL. Dorsal view. Abbreviations: ep, epioccipital; fo, cranial fontanel; fr, frontal; le, lateral ethmoid; me, mesethmoid; na, nasal; n2, second nuchal plate; n3, third nuchal plate; pe, pterotic; ps, posttemporalsupracleitrum; pt, pterotic; so, supraoccipital; sp, sphenotic. Scale bar = 3 mm.

FIGURE 3 | Left suspensorium, lateral view, of Tatia akroa, UFOPA-I 670, 34.3 mm SL. Abbreviations: hy, hyomandibula; io, interopercle; mt, metapterygoid; op, opercle; po, preopercle; qu, quadrate; sp, suprapreopercle.

FIGURE 4 | Right hyoid arch of Tatia akroa, MZUSP 44071, 26.0 mm SL. Ventral view. Abbreviations: ach, anterior ceratohyal; bra, branchiostegal rays; dhy, dorsal hypohyal; ihy, interhyal; pch, posterior ceratohyal; vhy, ventral hypohyal; uhy, urohyal. Scale bar = 1 mm.

FIGURE 5 | Anal fin of Tatia akroa. UFOPA-I 671, male, 38.8 mm SL, holotype. Abbreviations: br1, branched ray one; br7, branched ray seven; dd, deferent duct; ui, unbranched first ray; uii, unbranched second ray; uiii, unbranched third ray. Scale bar = 1 mm.

FIGURE 6 | Distribution of Tatia akroa (yellow) and T. simplex (orange). Stars represent type localities.