Platydoras brachylecis, Piorski & Garavello & H. & Sabaj Pérez, 2008

Piorski, Nivaldo M., Garavello, Julio C., H., Mariangeles Arce & Sabaj Pérez, Mark H., 2008, Platydoras brachylecis, a new species of thorny catfish (Siluriformes: Doradidae) from northeastern Brazil, Neotropical Ichthyology 6 (3), pp. 481-494 : 485-489

Platydoras brachylecis , new species

Figs. 3 , 4

Doras (Doras) costatus .—Eigenmann & Eigenmann, 1888: 161 [in part, checklist with cited localities from Rio Puty (= Poti),?Rio Preto, San Gonçallo (= São Gonçalo)]

Doras costatus .— Eigenmann & Eigenmann, 1890: 231-234 [in part, same localities cited in Eigenmann & Eigenmann, 1888].

Platydoras costatus .— Fowler, 1941: 139 [in part, three specimens from Forteleza, Ceará].— Fowler, 1951: 509-511 [in part, literature compilation with cited distribution in Ceará and Rio Poti].— Menezes & Menezes, 1948 [gut length and contents in specimens from lagoa de Nazaré, Floriano, Piauí].— Sabaj & Ferraris, 2003: 464 [in part, checklist with cited distribution in Parnaíba].— Soares, 2005: 91 [Mearim basin, photo, diet, habitat, common names, note on undescribed species from rio Pindaré].

Platydoras [sp.].— Piorski, 1999 [comment recognizing undescribed form from northeast Brazil].

Holotype. MZUSP 43593 , 137.7 mm SL, Brazil, Maranhão, lago dos Viana, Pindaré-Mearim river system, 03º13’S, 45º10’W, Apr 1984, B. V. O. Moura.

Paratypes. All Brazil. Ceará : ANSP 81733 , 3, 180-197 mm SL, market at Fortaleza , 1937 , R. von Ihering. Maranhão : LISDEBE 1969, 6, 91.1-112.6 mm SL, lago Açu, Pindaré basin, Codó market, 16 Feb 1994, N. M. Piorski; LISDEBE 1970, 19, 80.5-113.5 mm SL, rio Itapecuru , Itapecuru-Mirim , 03°24’S 44°22’W, 18 May 1996, Márvio and Lucemir ; MCP 22532, 19 , 21.5 - 49.8 mm SL, rio Peritoró, Peritoró Municipality , 04°22’23"S 44°20’07"W, 25 Jul 1998 , R. E. Reis et al .; MNRJ 30919 , 1 , 171.5 mm SL, rio Itapecuru, Coroatá, no date, Departamento Nacional de Obras Contra a Seca ; MZUSP 53240 , 1 , 150.3 mm SL and MZUSP 53241 , 23 , 107.2 - 151 mm SL, same data as LISDEBE 1970 ; MZUSP 53243 , 5 , 71.8 - 96.4 mm SL, same data as LISDEBE 1969 ; MZUSP 62674 , 1 , 123.9 mm SL, rio Itapecuru, Rosário, no date, Departamento Nacional de Obras Contra a Seca ; MZUSP 62675 , 1, 216 mm SL, rio Mearim, no date, Departamento Nacional de Obras Contra a Seca ; MZUSP 100197 , 5 , 126.8 - 173 mm SL, same data as holotype. Piauí : AUM 28560, 2 , 134 - 138.4 mm SL, rio Parnaíba, Barra do Longá , Buriti dos Lopes, 03º10’30"S 41º52’01"W, 26 Aug 1970, J.W. Bezerra et al .; ANSP 187051 , 1, 179 mm SL, Mercado de Teresina, 05°05’S 42°48’W, 19-22 Jun 1966, Expedição do Departamento de Zoologia ; MZUSP 5122 , 8 , 94.7 - 127.3 mm SL, same data as ANSP 187051 ; NMW 46847, 2 , 146.8 - 170 mm SL, rio Parnaíba, Teresina , 1903 .

Diagnosis. Platydoras brachylecis is diagnosed among Platydoras by the following unique combination of characters: pale yellow to white stripe beginning above orbits, continuing midlaterally on body and onto middle rays of caudal fin; skin in axil of each midlateral thorn without concentration of pigment forming small dark spot; midlateral scutes shallow (depth of 10 th scute 8.8-11.9% of SL, n = 15); and midlateral scutes on caudal peduncle distinctly separated by strip of skin from middorsal and midventral caudal-peduncle plates (i.e., modified procurrent caudal-fin rays).

Platydoras costatus lacks the pale yellow to white midlateral stripe and has a small dark spot in the axil of each midlateral thorn. Platydoras armatulus has deeper scutes (depth of 10 th scute 12.0-16.6% of SL, n = 59), and midlateral scutes on caudal peduncle usually contacting, and often interdigitating with, middorsal and midventral caudal-peduncle plates. Platydoras hancockii has deeper scutes (depth of 10 th scute 12.0-17.8% of SL, n = 37), and pale yellow to white midlateral stripe usually punctuated with small dark spots in axils of few to many midlateral thorns.

Description. Morphometric data presented for 15 specimens (111.2-190.0 mm SL) in Table 2. Head moderately depressed, body more evenly rounded anteriorly, gradually becoming slightly compressed beyond dorsal fin origin to caudal peduncle; ventral surface moderately flattened from mouth to vent ( Fig. 3 ). Dorsal profile gradually ascending and very gently rounded, convex to nearly straight, oblique from between anterior nares to middle pitline of supraoccipital, then straight and slightly less oblique from middle pitline to dorsal-fin origin; from dorsal-fin origin to caudal peduncle more gradually descending, very gently rounded, convex to nearly straight, oblique. Ventral profile gently rounded, convex to nearly straight from mouth to anal-fin origin; then rounded, convex, ascending more steeply along anal fin insertion to caudal peduncle. Caudal peduncle moderately long and relatively narrow (minimum depth 7.5-8.4% SL), profile gently concave dorsally and ventrally. Nuchal region subtriangular in cross-section; body depth greatest at dorsal-fin origin (19.3- 26.6% of SL). Body width greatest across cleithral bulges (width 28.1-32.1% of SL), tapering gradually to caudal fin.

Head moderately long (26.4-29.0% SL, 66.4-73.8% predorsal distance); in dorsal view weakly triangular with moderately short, rounded snout. Eyes subcircular, relatively small, without well-developed adipose eyelid (horizontal adipose eyelid diameter 10.3-13.4% predorsal distance), and placed dorsolaterally on head with center slightly less than one-third distance from snout tip to dorsal-fin origin. Bony orbits well separated (interorbital width 20.5-24.5% of predorsal distance); dorsal margin distinctly concave in dorsal view with arch not elevated above dorsal profile of head; enclosed largely by frontal dorsally with anteriormost quarter bordered by lateral ethmoid and posteriormost corner usually formed by anteriormost lateral corner of sphenotic or rarely by posterior lateral corner of frontal. Four infraorbitals (including lacrimal as infraorbital one), well ossified, superficially exposed; second one smallest, excluded from orbit; third one large, horizontal, forming ventral rim of orbit; fourth one narrower, vertical, completing posterior rim of orbit. Anterior and posterior nares well separated (internares distance 9.8- 12.1% of predorsal distance). Anterior naris near anterior margin of snout, opening surrounded by distinct tube of skin. Posterior naris closer to eye than to anterior one, opening surrounded by tube of skin with anterior wall enlarged to form flap. Anterior cranial fontanel with elongate teardrop to wedge shape (tapered anteriorly); rounded posterior rim extending slightly beyond transverse line through centers of orbital concavities; opening enclosed by mesethmoid anteriorly and frontals posteriorly and laterally. Posterior cranial fontanel absent.

Mouth subterminal with moderately fleshy lips weakly expanded posteriorly as rounded flaps at corners of mouth. Lip surfaces rugose, weakly scalloped with low, rounded, closely-space papillae (particularly on lower lip). One pair of simple (non-fimbriate), slender maxillary barbels with tips extending well beyond pectoral-spine insertion, usually to near midlength (before tip) of postcleithral process; weakly compressed anteriorly; surfaces relatively smooth, studded with small papillae. Two pairs of simple, slender mandibular barbels; origin of inner pair slightly more anterior than outer pair, both origins near lower lip; outer pair longer with tips finishing near transverse line through anteriormost origin of pectoral-fin spines; inner pair usually finishing just shy of transverse line through ventralmost extent of gill openings; both pairs of barbels studded with small papillae. Branchiostegal membranes broadly united to isthmus.

Both jaws with many small, conical teeth confined to premaxillae and dentaries. Upper jaw teeth in single rectangular patch relatively continuous across premaxillae; teeth gradually decreasing in size from outermost to innermost rows. Lower jaw teeth in two subrectangular patches; each patch tapered laterally and weakly separated by narrow hiatus at symphysis; teeth relatively uniform in size. Outermost gill arch with 3 upper and 8-10 lower rakers (n = 4); rakers stiffened, moderately spaced and moderately long (length up to about 4 times width).

Nuchal shield well developed, moderately arched in transverse plane; medial furrow generally absent, sometimes evident but shallow from middle pitline of supraoccipital to suture between anterior and middle nuchal plates. Nuchal foramina absent. Anterior nuchal plate moderately wide (length about equal to width), pentagonal with posteriorly directed apex sutured to middle nuchal plate; also sharing transverse anterior suture with supraoccipital and lateral sutures with epioccipitals. Middle nuchal plate broad with shallowly concave lateral margins; anterior lateral tips of anterior wings sharing short, weak suture with posttemporal-supracleithrum (excluding epioccipital from bony margin of shield enclosing tympanal region). Posterior nuchal plate with paired limbs, each L- to widely V-shaped superficially with anterolaterally directed wing contacting third tympanal scute and posteriorly directed wing contacting infranuchal and first postinfranuchal scutes. Dorsal surfaces of nuchal shield and neurocranial bones moderately rugose, ornamented with complex network of low fine ridges and granulations.

Pectoral girdle covered with skin ventrally. Postcleithral process long and narrow, lanceolate with acute tip; dorsal margin rises obliquely from base to moderately defined apex just distal to posterior margin of posttemporal-supracleithrum, then descends gradually, more or less linearly to posterior tip; ventral margin more or less straight, shallowly oblique; both margins largely entire or with minute dentitions. Postcleithral process with surface ornamentation separable into two longitudinal fields from base to posterior tip; dorsal field much wider, dominated by fine granulations and short irregular ridges; ventral field narrow, slightly elevated with more elongate longitudinal ridges and often separated posteriorly from dorsal field by low thin carina that continues to and often ventrally defines posteriormost tip of process.

Tympanal region with three separate ossifications (tympanal scutes); anterior two relatively small, weakly exposed, without well-defined dorsal and ventral wings; third tympanal scute large, well exposed with distinct dorsal and ventral wings spanning distance between posterior nuchal plate and postcleithral process, largely resembling subsequent midlateral scutes except with low medial carina instead of distinct thorn.

Sum of midlateral scutes including infranuchal: 56 (1), 57 (2), 58 (3), 59 (3 including holotype), or 60 (8). Midlateral scutes per left and right sides in 17 specimens: 28 (4), 29 (11), or 30 (19). Each midlateral scute with well-developed dorsal and ventral wings above and below sturdy thorn curved posteriorly (thorn sometimes indistinct on infranuchal scute, replaced by carina). Dorsal and ventral wings further separated by deep V-shaped notch along posterior margin in axil of thorn (location of lateral-line pores). Wings tall, subrectangular, subequal anteriorly (dorsal wing about a third taller) becoming equal near anal-fin origin; surfaces weakly ornamented with low, fine, longitudinal, roughly parallel ridges in vertical column along posterior half of scute; posterior margins nearly entire or with minute dentations imparted by ridges. Infranuchal scute contacts posterior nuchal plate dorsally, and ventrally slips beneath postcleithral process (but does not appear to contact internal surface of process). Scutes weakly overlapping (anterior margin embedded in skin), deepest anteriorly, becoming gradually shallower posteriorly; last scute usually on base of caudal fin beyond hypural flexure. Midlateral scutes on caudal peduncle not contacting middorsal and midventral caudal-peduncle plates (modified procurrent fin rays), distinctly separated from same plates by thin strip of skin.

Dorsal fin II,6 (includes spinelet); pectoral fin I,7 (very rarely I,8); pelvic fin i,6; anal fin iii-iv,8-9; caudal fin i,7/8,i with 10-14 dorsal and ventral procurrent elements (rays and plates). Dorsal fin triangular with relatively short base. Dorsal-fin spine sturdy, gently curved posteriorly over entire length, laterally compressed and relatively smooth sided except for long, fine, nearly parallel striations running the length of the spine from base to tip; anterior margin (except distal-most tip) with 16-29 antrorse serrations; posterior margin (except basal third and distal-most tip) with 5-14 straight to weakly antrorse serrations. Serrations surrounded by thick, porous skin, obscuring their presence; anterior serrations small and crowded basally, becoming gradually larger and more spaced distally; penultimate usually largest; posterior dorsal-spine serrations weaker (thinner), more spaced; largest near midlength. Pectoral fin triangular with folded spine extending more or less to vertical through pelvic-fin origin. Pectoral-fin spines sturdy, gently curved, dorsoventrally compressed, and with surface striations similar to those on dorsal-fin spine; anterior (leading) margin with 26-37 antrorse serrations to tip; posterior (trailing) margin with 18-27 retrorse serrations to tip. Serrations similarly surrounded by thick, extremely porous skin; anterior and posterior serrations similarly developed (smaller and more crowded basally, largest subterminal), except posterior serrations slightly larger, more broadly triangular. Pelvic fins relatively short with broadly rounded distal margin when extended. Anal fin also with broadly rounded distal margin, middle rays longest (length more or less equal to anal-fin base). Caudal fin distinctly forked with moderately pointed lobes; lower lobe slightly broader and more rounded than upper. Upper and lower procurrent caudal-fin rays grading into series of three to five flat, laterally expanded and weakly overlapping plates. Procurrent plates extend to or near bases of adipose and anal fins, thereby framing caudal peduncle dorsally and ventrally. Adipose fin prominent, main portion elongate and tear-drop shaped (tapered anteriorly) with origin vertically aligned to that of the anal fin. Adipose fin continues anteriorly as a low, narrow, fleshy ridge that begins approximately at the midpoint between verticals through last dorsal-fin ray and anal-fin origin.

Gas bladder two part with anterior (main) bladder and much smaller posterior (terminal) bladder ( Fig. 4 ); bladder walls moderately thick and smooth. Main bladder cordiform with internal T-shaped septum that partially isolates single anterior chamber and completely divides paired posterior chambers. Posterior bladder elliptical, without internal septum. Lumen enclosed by terminal bladder apparently continuous with that of only one of the two posterior chambers of main bladder through a narrow opening at point of constriction between two bladders.

Coloration. Ground color of dorsal and lateral surfaces of head and body dusky, dark gray-brown; undersurfaces largely pale white to yellow. Midlateral sides with distinct light stripe along central portions of scutes and thorns (small dark spots in axils of thorns absent); stripe continues anteriorly through tympanal region, becoming less distinct as it converges dorsally with its pair in interorbital region. Thin faint light middorsal stripe usually evident from dorsal to adipose fin and sometimes evident in posterior nuchal region. Barbels dusky gray-brown with mandibular barbels somewhat lighter than maxillary barbels. Dorsal fin with dusky gray-brown spine and dusky spot in distal half of anterior three to four rays and intervening membranes; remaining portions relatively pale with few scattered pigment. Adipose fin largely dusky graybrown, becoming somewhat lighter towards distal margin. Pectoral fin with light to dusky spine; anterior three rays and intervening membranes usually darker, gray-brown; remaining portions relatively pale. Pelvic fins with anterior three to four rays and intervening membranes dusky, becoming lighter, pale posteriorly. Anal fin with large dusky blotch on central rays and membranes, relatively lighter, pale anteriorly and posteriorly. Caudal fin with wide dark gray-brown streaks on central portions of upper and lower lobes (streaks continuous with gray-brown ground color on sides); remaining portions relatively pale.

Distribution. Platydoras brachylecis is known from basins of rio Mearim, rio Pindaré, rio Itapecuru and rio Parnaíba, northeastern Brazil ( Fig. 5 ). Fowler (1941:139) reported three specimens (ANSP 81733) from “Fortaleza, Ceará [State]”, Brazil, collected by Rodolpho von Ihering in 1937. There are no major rivers emptying into the Atlantic Ocean at the coastal city of Fortaleza, and Ihering’s specimens, with bellies slit from pectoral girdle to vent, may have been obtained from a local market. Their precise origin remains uncertain.

Ecological notes. Menezes & Menezes (1948) studied diet and relative gut length among 26 specimens (78-129 mm SL) from lagoa de Nazaré, Floriano municipality, Piauí State, Brazil. Gut contents were dominated by larva and adult insects (found in 17 specimens) with lesser amounts of fishes, shrimp and other crustaceans, plant remains and small stones .

Etymology. The specific name brachylecis is derived from the Greek brachy (short), and lekis (plate or dish), in reference to the relatively shallow midlateral scutes.

Remarks. Species commonly known as “graviola” in the Parnaíba River, “grangiola” in the Itapecuru River, and “corró” in the Mearim river.

Figures

Fig. 3. Holotype of Platydoras brachylecis, MZUSP 43593, 137.7 mm SL, Brazil: Maranhão: lago dos Viana, Pindaré-Mearim river system, 03º13’S 45º10’W, B. V. O. Moura, April 1984. Photos by M.Arce H.

Fig. 4. Ventral (top) and dorsal (bottom) views of gas bladder in Platydoras brachylecis,ANSP 187051, 179 mm SL. Scale bar = 1 cm. Photos by M. Sabaj Pérez.

Fig. 5. Distribution of specimens of Platydoras examined. Type localities denoted with asterisk except for Platydoras armatulus (= Brazil, Paraná, not below 27°30’S) and P. costatus (= likely Suriname).? = locality data questionable. Base map by M. Weitzman.