Microglanis pataxo, Sarmento-Soares & Martins-Pinheiro & Aranda & Chamon, 2006

Sarmento-Soares, Luisa M., Martins-Pinheiro, Ronaldo F., Aranda, Arion T. & Chamon, Carine C., 2006, Microglanis pataxo, a new catfish from southern Bahia coastal rivers, northeastern Brazil (Siluriformes: Pseudopimelodidae), Neotropical Ichthyology 4 (2), pp. 157-166 : 158-164

Microglanis pataxo , new species

Fig. 1

Holotype. MNRJ 28397 (39.0 mm SL), Brazil, Bahia: Itamarajú, Jundiar creek on road BR-101 after joint with road to Jucuruçu , in the neighbourhoods of the city of Itamaraju (17º01’35"S 39º35’57"W), 25 Oct 2004, L.M.Sarmento-Soares, A.T.Aranda, C.C.Chamon & R.F.M.Pinheiro.

Paratypes. Brazil, Bahia: AMNH 236058 (2, 22.1–27.5 mm SL) , UF 148528 (2, 22.2–27.2 mm SL), and MNRJ 28398 (5, 1 c&s, 22.7–38.0 mm SL) all collected with the holotype . MNRJ 28399 (1, 26.3 mm SL); Nova Viçosa, tributary of rio Peruípe on road BR- 418, after 14 km from BR- 101 in direction to Caravelas (17º50’24"S 39º42’01"W), 22 Oct 2004, same collectors as the holotype . MNRJ 28400 (1, 26.2 mm SL); Caravelas; unnamed stream on BR-418, about 27 km from BR- 101 in direction to Caravelas , below the bridge crossing (17º46’34"S 39º36’09"W), 22 Oct 2004, same collectors as the holotype . ANSP 180651 (2, 23.1–23.5 mm SL), and MNRJ 28401 (4, 1 c&s, 23.9–36.4 mm SL), Prado, rio Palmares on road Guarany-Corumbau , in direction to Corumbau after joint with the road to the mouth of rio Cahy (16º57’48"S 39º16’33"W), 24 Oct 2004, same collectors as the holotype . MNRJ 28402 (2, 23.8– 30.8 mm SL), Prado, rio Palmares on road from Guarany to Corumbau , near Palmares (16º56’25"S 39º19’48"W), 24 Oct 2004, same collectors as the holotype . AUM 42221 (2, 23.1– 23.2 mm SL), and MNRJ 28403 (4, 21.9–28.0 mm SL), Mucuri, rio Pau Alto in the village of Ibiranhém (17º50’49"S 40º10’27"W), 31 Oct 2004, same collectors as the holotype .

Diagnosis. Microglanis pataxo can be identified by the color pattern with a dark blotch beneath adipose fin not extending to anal fin and by the high number of anal fin proximal radials, 12, shaped as rod-like thin tubes, the last one bearing a laminar extension. The new species can be also recognized by the following combination of characters: a pectoral fin spine with a bony point and bearing proportionally few serrations on posterior border of pectoral fin spine, eight to ten. Seven pleural ribs and a proportionally short head width (67.8–74.3% in HL).

Microglanis pataxo is distinguished from M. ater by the short body depth, 13.0-17.5% SL (vs. 25.0%). Distinguished from M. cibelae by the short head width, 67.8-74.3% HL (vs. 78.6-81.7%), by the proportionally shorter body depth, 13.0- 17.5% SL (vs. higher 17.2-22.5%), caudal peduncle depth, 8.8- 11.3% SL (vs. 10.3-14.3%) and by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins). Distinguished from M. cottoides by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins); by the shorter head length, 27.0-29.0% SL (vs. 29.3-33.2%), by the low number of serrations on pectoral fin spine, eight to ten (vs. 13 in M. cottoides ) and by the rod-like anal fin proximal radials (vs. bearing laminar projections). Distinguished from M. eurystoma by the shorter body width, 24.4-29.0% SL (vs. 30.3-34.7%), by a shorter predorsal length, 33.0-40.2% SL (vs. 40.4-45.7% respectively) and by the low number of serrations on posterior border of pectoral fin spine, eight to ten (vs. 14). Distinguished from M. garavelloi by the larger head length, 27.0-29.0% SL (vs. 25.0- 26.6%), by the short head width, 67.8-74.3% HL (vs. 87.7- 100.0%), by the higher number of anal fin proximal radials, 12 (vs. 9). Distinguished from M. iheringi by the low number of pleural ribs, 7 (vs. 8) and higher number of anal fin proximal radials, 12 (vs. 11). Distinguished from M. malabarbai by the shorter head length, 27.0-29.0% SL (vs. 29.6-33.5%), by the shorter body width, 24.4-29.0% SL (vs. 29.3-33.1%), by the shorter mouth width, 16.0-18.5% SL (vs. 19.2-22.1%), by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins) and by the caudal fin with scattered dark blotches (vs. almost completely black with narrow white band). Distinguished from M. nigripinnis by the shorter head depth, 27.0- 29.0% SL (vs. 29.0-35.0%), by the short head width, 67.8-74.3% HL (vs. 96.2-100.0%), by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins); by the low number of serrations on pectoral fin spine, eight to ten (vs. 12-15 in M. nigripinnis ), and by the rod-like anal fin proximal radials (vs. bearing laminar projections). Distinguished from M. parahybae by the short head width, 67.8-74.3% HL (vs. 78.4-85.3%), 7 pleural ribs (vs. 6) and by the rod-like anal fin proximal radials (vs. bearing laminar projections). Distinguished from M. pellopterygius by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins). Distinguished from M. poecilus by the rod-like anal fin proximal radials, 12 (vs. bearing laminar projections). Distinguished from M. secundus by the color pattern with a dark blotch beneath adipose fin not extending to anal fin (vs. continuous dark bar between those fins), by the low number of serrations on posterior border of pectoral fin spine, eight to ten (vs. 12) and by the pectoral fin spine with a bony point (vs. pectoral fin spine bifurcated followed by a fleshy tip). Distinguished from M. variegatus by the higher number of pleural ribs, 7 (vs. 5-6), by the higher number of anal fin proximal radials, 12 (vs. 10-11) and by the higher number of vertebrae, 29 (vs. 26). Distinguished from M. zonatus by the higher number of pleural ribs, 7 (vs. 6) and higher number of anal-fin proximal radials, 12 (vs. 8).

Description. Morphometric and meristic data in Table 1. Body moderately short, head and anterior trunk depressed, becoming compressed posteriorly. Head large and dorsoventrally compressed, dorsal profile somewhat quadrangular. Dorsal profile of trunk from dorsal-fin base to caudal peduncle becoming gradually compressed laterally. Lateral profile of head from snout tip to opercular margin slightly convex; becoming straight until dorsal-fin origin. Head and anterior trunk rectangular in cross section, becoming elliptic posteriorly. Ventral profile of head and abdomen almost straight. Ventral profile of body gently curved posterior to anal fin. Caudal peduncle laterally compressed. Eyes very small, latero-superior and covered with skin. Mouth terminal, upper lip extended posterolaterally as fleshy rictal fold. Anterior nostril somewhat tubular, located on anterior border of snout, above lip; posterior nostril larger, rounded. Maxillary barbels short, reaching opercular membrane. Mental barbels four, arranged in arc along ventral surface of jaw. Inner mental barbels half length of outer mental barbels. Maxillary and mental barbels extending to pectoral fin base. Post-cleithral process slender and pointed.

Premaxilla transversely elongate, meeting its counterpart medially. Autopalatine tubular, oriented obliquely to longitudinal axis of body. Maxillary bone small, with large posterior border. Jaws of equal size. Premaxillary tooth patch not forming backwardly projecting angle. Premaxillary and dentary with four to five rows of minute conical teeth.

Dorsal-fin margin rounded, with one spine plus six branched rays. Dorsal-fin spine with anterior surface smooth and two to three small retrorse serrae on distal portion of posterior surface. Pectoral fin with one spine plus five branched rays. Pectoral-fin spine with serrae on both margins: the anterior margin serrae smaller than posterior ones. Anterior pectoral-fin margin with 13-16 serrae: those closer to base of spine retrorse, around middle of spine one or two perpendicular serrae and subsequent ones antrorse. Posterior surface of pectoral-fin spine has 8-10 retrorse serrae ( Fig. 2 ). Pelvic-fin margin rounded, located below posterior edge of dorsal-fin. Pelvic with one unbranched plus five branched rays. Adipose-fin developed, with posterior margin free and angulose, not confluent with caudal-fin, and located above anal-fin origin. Anal-fin margin rounded, with two or three a

b

unbranched rays, plus one anteriormost reduced ray and seven to nine branched rays, not reaching caudal-fin base. Nine branched anal-fin rays rare, found only in one specimen. 12 rod-like, thin anal-fin proximal radials, last one short and laminar ( Fig. 3 ). Twelve distal radials completely cartilaginous. Caudal fin slightly forked, its upper lobe longer than lower, with 13-14 branched rays; principal rays 7+8; upper procurrent 15; lower procurrent nine. Total vertebrae 29. Seven pleural ribs becoming progressively small antero-posteriorlly.

Osteological features. Cranial roof somewhat triangle shaped ( Fig. 4 ). Surface rough, ornamented with small ridges and pits. One single wide cranial fontanel placed between mesethmoid and frontals. Mesethmoid constricted before anterior cranial fontanel, divergent cornua create broad, shallow median cleft; premaxillaries held underneath it through synchondral articulation. Large lateral ethmoids form lateral wings laterally to mesethmoid and frontals. Frontals sutured behind cranial fontanel. Each frontal bone anteriorly narrow and posteriorly expanded, sutured to sphenotic and parietosupraoccipital. Sphenotic bone narrow, forming lateroposterior margin of the skull roof with pterotic and posttemporosupracleithum. Sphenotic and pterotic bearing hyomandibula facet on their ventral surface. Sphenotic synchondrally joined to prootic and pterosphenoid on cranial floor, and sutured to frontal, parieto-supraoccipital and pterotic on cranial roof. Pterotic wider than sphenotic and sutured to it and to parietosupraoccipital, epiotic, and posttemporosupracleithrum on cranial roof. Synchondrally joined to prootic and exoccipital on cranial floor. Parieto-supraoccipital moderately large, sutured dorsally to frontals, sphenotics, pterotics, and epioccipitals. Posteroventrally sutured to exoccipitals. Minute parieto-supraoccipital fontanel represented by single posterior opening. Caudally to fontanel, parieto-supraoccipital crest extended medially. Tubular ossified nasal bone between mesethmoid cornua and lateral ethmoid. Nasal slightly curved, free bone, ligamentously attached to lateral margins of frontals and mesethmoid.

Floor and lateral walls of cranium as for catfishes in general. Vomer ovoid and broad, between cartilaginous wings of lateral ethmoid and in contact with mesethmoid dorsally. Parasphenoid with narrow anterior limb sutured to vomer and with wide lateral projection immediately above foramen for trigeminofascialis nerve. Orbitosphenoid large, sutured to frontals and with broad synchondral joint to lateral ethmoid. Prootic somewhat large making short sutural and synchondral joint with pterosphenoid. Wide foramen for trigeminofascialis nerve between prootic, parasphenoid, and pterosphenoid. Exoccipitals forming lateroposterior corner of cranium, bearing synchondral joints with basioccipital, prootic, and pterotic. Single basioccipital broad and compact, sutured lateroanteriorlly to parasphenoid and synchondrally joined laterally to prootics and exoccipitals. Foramen magnum bordered by basioccipital, exoccipital, and parieto-supraoccipital.

Suspensorium with broad laminar hyomandibula, anteriorly sutured to elongated rectangular metapterygoid. Quadrate thick, articulated to metapterygoid and hyomandibula through cartilage. Preopercle sutured to ventral margins of both quadrate and hyomandibula. No suprapreopercle present. Opercle laminar and broadly triangular ( Fig. 5 ).

Hyoid arch with small ventral hypohyal, well developed anterior ceratohyal and triangular posterior ceratohyal. Ten branchiostegal rays articulated with hyoid arch: six with anterior ceratohyal, two with interceratohyal cartilage between bones, and two with posterior ceratohyal. Posteriormost brachiostegal rays, on posterior ceratohyal, largest, expanded and curved ( Fig. 6 ).

Urohyal with expanded, narrowly paired lateral processes and short pointed posterior processes. Basibranchial 1 absent; basibranchial 2 plus 3 forming cartilaginous rod with anterior tip reaching dorsal surface of ceratohyal and posterior, osseous, tip nearly in contact with basibranchial 4. Basibrachials 2 plus 3 rod bordered laterally by cartilaginous head of hypobranchials 2 and 3. Basibranchial 4 bordered anteriorly by cartilaginous hypobranchials 3, laterally by cartilaginous head of ceratobranchials 4 and posteriorly by cartilaginous head of ceratobranchials 5. Hypobranchials 1 and 2 osseous, elongate, trapezoid, contoured with cartilage along its lateral and posterior borders. Hypobranchial 3 completely cartilaginous and approximately trapezoidal. Hypobranchial 4 absent. Five ceratobranchials present, mostly ossified, with cartilage on their extremities. First ceratobranchial giving support to single row of four finely-shaped elongated rakers. Second ceratobranchial also with single row of rakers. Third, fourth and fifth ceratobranchials with two rows of short rakers. Fifth ceratobranchial expanded posteromedially to support lower pharyngeal toothplate dorsally, with finely-shaped conical teeth arranged in four or five rows. Five epibranchials, first four largely ossified; except for its cartilaginous extremities. Epibranchials 1 and 2 rod-like, with short rakers arranged in one row. Epibranchial 3 with elongate posterior uncinate process. Epibranchial 4 broad, somewhat convex posteriorlly. Epibranchial 5 completely cartilaginous, placed between posterior cartilaginous tips of epibranchial 4 and ceratobranchial 4. Pharyngobranchial 1 absent. Pharyngobranchial 2 short, completely cartilaginous, placed between anterior cartilaginous tips of epibranchials 1 and 2 and subsequent pharyngobranchial. Pharyngobranchial 3 elongate, ossified, with well developed posterior border. Pharyngobranchial 4 ossified, giving support to upper pharyngeal tooth plate, with robust conical teeth arranged in four to five rows ( Fig. 7 ). mandibular symphysis and last one next to preopercular canal opening. Lateral line on body interrupted, with seven pores anterior to origin of dorsal fin; no isolated pores posteriorly.

Antorbital slim, with pronounced anterior process. Infraorbitals thin and tubular, almost reduced to their canalicular portions. Three canal bones: anterior and middle about same size; posteriormost one longest. Infraorbital laterosensory canal branch bearing four to five paired pores: first, anterior, infraorbital pore close to antorbital and last, posterior, infraorbital pore close to sphenotic opening for laterosensory canal. Supraorbital laterosensory canal branch with seven or eight paired pores; first one close to anterior nasal opening; last one close to supracleithrum border. Preopercle-mandibular laterosensory canal branch with eight to nine paired pores, anteriormost four associated with lower lip. First pore near Color in alcohol. Head almost completely dark dorsally, with lighter areas below eyes and around cephalic lateral line pores. Conspicuous, transverse, light band just behind head, crossing pectoral-fin base, as typically for Microglanis species. First dark blotch shaped as large “x”, around dorsal-fin base in dorsal view; and second one between dorsal and adipose fins. Adipose fin with characteristic dark band on its anterior or middle portion. Ventral region of head with dark melanophores, concentrated around mental barbels, and becoming sparse towards belly. Dorsal-fin base and spine dark, its distal portion crossed by large dark bar. Caudal peduncle with dark patch of coloration beginning in its central portion becoming larger towards its margins, triangle shaped, and ending in transverse dark bar onto caudal-fin base. Caudal fin with scattered dark melanophores and narrow dark bar along contour of each lobe, near its tip.

Live coloration. Ground color light brown with irregular dark areas on head, dorsal fin and between dorsal and adipose fins. Caudal-fin base with conspicuous dark bar. Ventral surface of body lighter, with melanophores distributed on belly. Most fins hyaline with scattered melanophores over fin rays and membranes; dorsal fin with an irregular dark stripe along its longitudinal axis; adipose fin light brown with small patch of dark pigmentation near to its dorsal margin ( Fig. 8 ).

Distribution. Microglanis pataxo is the first record of the genus in northeastern Brazilian rivers. The new species was found in coastal drainages of southeastern Bahia, in the drainages of rio Peruípe, rio Jucuruçu, and rio Cahy ( Fig. 9 ).

Etymology. The specific name honors the Pataxó native indigenous people, who live in the neighbourhoods of the distribution area of the new Microglanis species.

Ecological notes. The river systems in southern Bahia cross a plain to undulate relief with sediments from Tertiary to Quaternary, responsible for the formation of “tabuleiros”, the regional name in reference to the vast open plain left on landscape. Geologically those coastal “tabuleiros” belongs to the “Formação Barreiras”, dated from the Pliocene, extending from the coast up to 110 km inland from Ilhéus, Bahia, to the mouth of rio Doce, in Espírito Santo ( SRH, 1996). The whole study area was originally covered by the Atlantic Forest, but presently the vegetation around river drainages show different degrees of environmental conservation (MMA, 2000). At the rio Peruípe the vegetation was changed to eucalyptus tree groves, reminiscent of riparian vegetation only on river banks. The upper portion of rio Jucuruçu, called rio do Prado, is one of the heaviest impacted river system, being much deforested and occupied with pastures. The rio Palmares, a tributary of the rio Cahy, passes somewhat closer to the Pataxó indigenous village of Águas Belas, and the catfishes were captured downstream from the Palmares village. The small rio Cahy basin still has patches of original and secondary vegetation and riparian covering along the upper portions of its streams being partially protected in an environmental preservation area, the Parque Nacional do Descobrimento. The new Microglanis species was collected in the middle course of shallow waters, at a depth of 1 to 1.5 m. None of them were captured in the upper portions. Those catfishes were found in moderate flowing sections of the rivers, with sandy or gravel bottom. The environments were moderately vegetated and the water clear or brown ( Fig. 10 ). In the stomach of two examined females (MNRJ 28398, 33.8 mm SL; MNRJ 28401, 23.9 mm SL), it was possible to identify small aquatic insect larvae and pupae. The 33.8 mm individual was a mature female, with large eggs in its gonads.

Figures

Fig. 1. Microglanis pataxo, holotype, MNRJ 28397, 39.0 mm SL, in a. lateral; b. dorsal; and c. ventral views.

Fig. 2. Left pectoral-fin spine of Microglanis pataxo, MNRJ 28398, paratype. Dorsal view. Scale bar, 1 mm.

Fig. 3. Left lateral view of anal fin pterygiophores in M. pataxo (a) and M. parahybae (b). Abbreviations: ar, anal-fin rays; dr, distal radial; lp, laminar process; pr, proximal radials; rr, rudimentary ray; up, uncinate process. Scale bar, 1 mm.

Fig. 4. Cranium ofMicroglanis pataxo,MNRJ 28398, paratype. Dorsal view.Abbreviations: ao, antorbital; ep, epioccipital; fr, frontal; ffr, frontal fontanell; fso, parieto-supraoccipital fontanel; io, anterior, middle and posterior infraorbitals; le, lateral ethmoid; mx, maxilla; na, nasal; pa, autopalatine; pm, premaxilla; pt, pterotic; sc, posttemporosupracleitrum; so, parietosupraoccipital; sp, sphenotic. Scale bar, 1 mm.

Fig. 5. Left suspensorium of Microglanis pataxo, MNRJ28398, paratype. Lateral view.Abbreviations: hy, hyomandibula; io, interopercle; mt, metapterygoid; op, opercle; po, preopercle; qu, quadrate. Scale bar, 1 mm.

Fig. 6. Right hyoid arch of Microglanis pataxo, MNRJ 28398, paratype. Medial view.Abbreviations: ac, anterior ceratohyal; br, branchiostegal rays; ic, interceratohyal cartilage; pc, posterior ceratohyal; vh, ventral hypohyal. Scale bar, 1 mm.

Fig. 7. Branchial skeleton of Microglanis pataxo, MNRJ 28398, paratype. Dorsal view. Abbreviations: bb2-3, basibrachial 2 plus 3; bb4, basibrachial 4; cb1 to cb5, ceratobranchials 1 to 5; dp, dentigerous plate; eb1 to eb4, epibranchials 1 to 4; hb1 to hb4, hypobranchials 1 to 4; pb2 to pb4, pharyngobranchials 2 to 4. Scale bar, 1 mm.

Fig. 8. Microglanis pataxo, live specimen in a field aquarium shortly after collection.

Fig. 9. a. Drainage map of eastern Brazil between rio São Francisco and rio Paraíba do Sul illustrating the distribution of the Microglanis species in the area. Dotted line indicates the study area. Symbols may represent more than one locality. b. Detail of collecting localities of Microglanis pataxo in the study area, between the rio Mucuri and rio Jequitinhonha.

Fig. 10. Jundiar creek, Itamaraju, southern Bahia, type-locality of Microglanis pataxo.