Trichomycterus steindachneri, DoNascimiento & Prada-Pedreros & Guerrero-Kommritz, 2014

DoNascimiento, Carlos, Prada-Pedreros, Saúl & Guerrero-Kommritz, Jürgen, 2014, A new catfish species of the genus Trichomycterus (Siluriformes: Trichomycteridae) from the río Orinoco versant of Páramo de Cruz Verde, Eastern Cordillera of Colombia, Neotropical Ichthyology 12 (4), pp. 717-728 : 718-723

Trichomycterus steindachneri , new species Figs. 1a , 2a , 3a , 4-5

Holotype. MPUJ 4191, 143.5 mm SL, Colombia, Cundinamarca, Ubaque, vereda Pueblo Nuevo, quebrada El Charco , tributary of quebrada Santa Bárbara , río El Palmar system, río Orinoco basin, 04°31’10.3”N 73°58’44.6”W, 2700 m, 19 Aug 2005, S. Prada-Pedreros, C. Rivera & W. Vanegas.

Paratypes. MBUCV-V-35652 (ex MPUJ 2487 ), 2, 86.7- 88.8 mm SL (MBUCV-CT-1047, 1 CS, 86.7 mm SL), MPUJ 2491 , 2 , 74.2-77.1 mm SL, same data as holotype, but collected on 20 Aug 2005. MPUJ 2482 , 9 , 81.1-120.5 mm SL (MBUCV-CT-1053, 3 CS, specimens 2 & 6 completely disarticulated: 105.7-123.9 mm SL, specimen 5 entire: 106.8 mm SL), collected with the holotype .

Diagnosis. Trichomycterus steindachneri is distinguished from most Trichomycterus species (except T. cachiraensis Ardila Rodríguez, 2008 ) by having several broad foramina on cleithrum lamina ( Fig. 1a ) (vs. cleithrum not pierced). The new species is also distinguishable from most congeners except T. cachiraensis and T. brachykechenos Ferrer & Malabarba, 2013 by having a small posterior cranial fontanel ( Fig. 2a ), restricted to the parieto-supraoccipital (vs. a long somewhat rectangular fontanel extending anteriorly between frontal bones and posteriorly into anteromedian region of parietosupraoccipital). Trichomycterus steindachneri differs from T. cachiraensis by having 40 or 41 free vertebrae (vs. 37-39), 14-18 ribs (vs. 12), a single upper hypural plate: 3+4+5 ( Fig. 3a ) (vs. two hypural plates: 3,4+5, Fig. 3b ), and by its coloration pattern (ground color dark brown with a thin mid-lateral dark stripe vs. ground color light brown with three lateral rows of small dark spots). Trichomycterus steindachneri can be distinguished from T. brachykechenos by having four rows of premaxillary and dentary teeth (vs. three), 13-14 opercular odontodes (vs. 8-11), 41-43 interopercular odontodes (vs. 22-30), 6-7 branchiostegal rays (vs. 8), anterior portion of sphenotic anterolaterally directed in dorsal view (vs. directed anteriorly), autopalatine with mesial margin straight (vs. concave), 12-16 teeth on ceratobranchial 5 (vs. 21- 22), 11-14 teeth on upper dentigerous plate (vs. 22-25), infraorbital sensory pores i1 and i3 present (vs. absent), 40 or 41 free vertebrae (vs. 37 or 38), 14-18 ribs (vs. 12), first ray of pectoral fin slightly projected as a short filament ( Figs. 4-5 ) (vs. not prolonged as a filament), 7-8 branched pectoral-fin rays (vs. 5-6), dorsal-fin origin at same level of pelvic-fin insertion (vs. at vertical through last third of pelvic fin), anal-fin origin posterior to dorsal-fin base (vs. at vertical through middle of dorsal-fin base), anal fin with seven basal radials (vs. six), procurrent caudal-fin rays 16-21 dorsally and 14-17 ventrally (vs. 15-16 and 10-13, respectively), and by the color pattern of lateral surface of body consisting in background dark brown with a thin mid-lateral dark stripe (vs. background light yellow with superficial layer of densely mottled dark brown). Trichomycterus steindachneri is further distinguished from T. dorsostriatus ( Eigenmann, 1918) , which also occurs in the río Meta system, by having 40 or 41 free vertebrae (vs. 37), dorsal fin inserted just posterior to neural spine of vertebrae 18 or 19 (vs. vertebra 16), analfin origin behind posterior end of dorsal-fin base, inserted just posterior to hemal spine of vertebrae 22-24 (vs. under posterior portion of dorsal-fin base, just posterior to vertebra 20), a single upper hypural plate (vs. two upper hypural plates), and by the color pattern consisting in a thin mid-lateral dark stripe (vs. a dark band or row of spots from just above the gill-opening to the base of the upper caudal-fin rays). Trichomycterus steindachneri can also be differentiated from the only other species described from western tributaries of the Orinoco in Colombia, T. migrans (río Guaviare system), by its maxillary barbel extending beyond pectoral-fin origin (vs. scarcely reaching this point), anal-fin origin entirely behind dorsal-fin base (vs. at vertical through base of last dorsal-fin ray), and caudal-fin margin slightly rounded (vs. deeply emarginated). Trichomycterus steindachneri can be readily differentiated from remaining congeners described or recorded from Colombia (except T. retropinnis Regan, 1903 ) by its relatively rare pigmentation pattern consisting in background dark brown with a single thin dark stripe along middle of side of body (vs. background light; either plain, with more than one stripe on lateral surface of body, with a single but wide mid-lateral band, or variably spotted or dotted). Trichomycterus steindachneri differs from T. retropinnis by having first pectoral-fin ray slightly projected beyond margin of fin as a short filament of less than 20% length of adjacent branched ray (vs. projecting as a long filament of ca. 40% length of adjacent branched ray), 7-8 branched pectoral-fin rays (vs. 6 branched rays), pelvic fin covering anus (vs. not reaching anus), relative position of the dorsal fin, expressed as dorsal-fin origin at same level of pelvic-fin insertion (vs. dorsal-fin origin behind distal margin of pelvic fin), and anal-fin origin entirely behind of dorsal-fin base (vs. anal-fin origin under anterior third of dorsal-fin base).

Description. Morphometric data presented in Table 1 . Body elongated, depressed in anterior region of trunk and becoming gradually compressed to caudal-fin base. Dorsal and ventral profiles straight and parallel, sloping dorsally and ventrally just posterior to dorsal and anal-fin bases, respectively ( Figs. 4-5 ). Cross-section of body elliptical at pectoral-fin insertion with longest axis along horizontal plane.

Head depressed, nearly as long as wide, parabolic in dorsal view in specimens shorter than 90 mm SL and square in larger specimens. Lateral portion of head of large specimens (90 mm SL or more) swollen by well-developed jaw muscles, resulting in square aspect of head in dorsal view. Eye small, located dorsolateral, approximately on middle of head length. Eye rim not free, skin covering eye continuous with head skin. Mouth subterminal. Lateral fleshy lobe of lower lip scarcely conspicuous as thickening of lateral portion of lip. Premaxilla with four irregular rows of conical teeth. Dentary with four irregular rows of teeth, similar to those of premaxilla. Anterior nostril small, surrounded by low fleshy thin flap, posterolaterally continuous with nasal barbel. Posterior nostril adjacent to anterior nostril; anterior rim thick, not delimited by fleshy elevated margin; posterior rim not delimited by fleshy flap, and continuous with head surface. Barbels dorsoventrally flattened and tapered distally. Nasal barbel originating from posterolateral margin of anterior nostril, and reaching origin of opercular patch of odontodes. Maxillary barbel extending slightly beyond pectoral-fin origin. Rictal barbel extending to anterior third of interopercular patch of odontodes. Interopercular patch with 41-43 odontodes and 21-23 replacement odontodes, arranged in three irregular rows. Posterior interopercular odontodes of medial row largest. Opercle with 13 or 14 odontodes and 6 or 7 replacement odontodes, approximately disposed in five anteroposterior irregular rows. Posterior most opercular odontodes largest. Branchial membrane free from ishtmus, except anteriorly, and supported by 6* or 7 branchiostegal rays. Branchiostegal rays 3 or 4 to lateral most, distally expanded. Branchiostegal ray 4 or 5 with greatest distal expansion.

Anterior margin of mesethmoid cornua straight ( Fig. 2a ). Anterior fontanel small oval opening just anterior to epiphyseal bar, at level of exit of infraorbital canal from neurocranium. Lachrymal-antorbital associated with anterior section of infraorbital canal (sensory pores i1 and i3). Sesamoid supraorbital long straight rod, without lateral processes. Lateral processes of frontal and sphenotic, where infraorbital canal leaves neurocranium, forming conspicuous lateral tube anterolaterally projected. Posterior fontanel short, two times of anterior fontanel length, oval in shape, and placed entirely on parieto-supraoccipital, but continuous with anterior sagittal suture connecting frontal bones medially. Posttemporo-supracleithrum with long and pointed medial process, extending parallel to anterior margin of Weberian capsule, approaching to basi-exoccipital. Vomer arrow-head shaped, with conspicuous lateral processes posterolaterally directed and long posterior process inserted into anterior process of parasphenoid. Posterior process of parasphenoid long and extending over anterior portion of basi-exoccipital, laterally bordered by two anterior membranous processes of basi-exoccipital. Lateral opening of Weberian capsule at tip of lateral tubular projection, around same length of diameter of capsule. Premaxilla rectangular in shape. Maxilla boomerang shaped, shorter than premaxilla. Articular facet of autopalatine for lateral ethmoid on medial margin of bone, just at posteromedial corner. Anteromedial corner of autopalatine in contact with lateral margin of lateral process of vomer. Metapterygoid laminar and triangular in shape. Hyomandibula articulating anteriorly through dorsoanterior membranous outgrowth with metapterygoid. Interopercular plate supporting odontodes, not extended anteriorly to articular facet for preopercle. Basibranchials 2 and 3 and hypobranchial 1 approximately of same length. Anterolateral process of ossified portion of hypobranchial 3 longer than that of hypobranchial 2. Ceratobranchial 3 with broad notch at proximal portion of posterior margin. Ceratobranchial 5 with 12-16 conical teeth, along anterior portion of medial margin, arranged in two irregular rows. Largest teeth posterolaterally placed. Pharyngobranchial 3 with medial process in posterior tip and broad laminar expansion along medial margin. Upper dentigerous plate with conical teeth arranged in two rows. External row restricted to anterior portion, with 2-4 teeth. Internal row complete, along entire medial margin of plate, with 9-10 teeth. Teeth of internal row larger than those of external row.

Supraorbital sensory canal continuous with three pores, and not connected to its counterpart through medial commissure. Sensory pore s1 medially adjacent to anterior nostril. s3 medial to posterior nostril. s6 (epiphyseal) paired, at level of posterior eye rim. Infraorbital sensory canal interrupted in two portions; anterior most portion with sensory pores i1 and i3, laterally adjacent to anterior and posterior nostrils, respectively; posterior most portion connected to supraorbital and otic canals, with sensory pore i10, adjacent to ventroposterior eye rim; i11 posterior to eye at horizontal level of dorsal eye rim. Preopercular canal short with single terminal pore above origin of opercular patch of odontodes. Postotic canal with single pterotic branch and associated pore above opercular patch of odontodes. Lateral line canal very short with two pores above pectoral-fin base. Sensory pore ll1 ventral to main lateral line canal and ll2 terminus of main lateral line canal.

Precaudal free vertebrae 9-13 (10) and caudal vertebrae 27-32 (31), totaling 40 or 41* vertebrae. Ribs 14-18* (one CS specimen with one posterior accessory short rib of similar size of penultimate rib, on left side of last supporting rib vertebra). Penultimate rib shortest, around one third of last rib length. First hemal spine on vertebra 16-19 (18). Anus at vertical through anterior third of dorsal-fin base.

Pectoral fin with i,7-8* rays. First ray longest, slightly projected beyond margin of fin as short filament. Pectoral complex radial completely cartilaginous ( Fig. 1a ). Scapulocoracoid anterior process long and pointed. Cleithrum with broad foramina under scapulocoracoid and adjacent to hypocoracoid portion.

Pelvic fin with i,4 rays, and lateral splint, its length around half of first ray length. First ray shortest and third ray longest. Inner margins of pelvic-fin bases close to each other. Posterior margin of fin covering anus. Basipterygium with two anterior long processes of around same length or medial process slightly longer.

Dorsal fin with 2-4 (3) procurrent rays and ii, 7 principal rays. Shape of fin rectangular in lateral view, posterior margin truncated. Second branched ray longest. Origin of fin at same level of pelvic-fin insertion, at middle of body (including caudal fin). Basal and anterior portions of fin extensively covered by thick integument, anterior most rays (procurrent and unbranched), hardly visible externally. Supporting elements of dorsal fin represented by eight basal radials, inserted between neural spines of vertebrae 18-23, 18-24, or 19-24*, and seven distal radials (last distal radial cartilaginous), associated with second to last basal radials.

Anal fin with 3*-5 procurrent rays and ii, 5* or 6 principal rays. Anal fin similar in size and shape to dorsal fin. Second branched ray longest. Origin of fin entirely behind of dorsalfin base. Base and anterior portion of fin similarly covered by thick integument as in dorsal fin. Basal radials seven (MPUJ 2482 paratype specimen of 105.1 mm SL with six basal radials), inserted between hemal spines of vertebrae 22-26, 23-27, 23-28, or 24-28*. Distal radials six, associated with first to penultimate basal radials. First distal radial entirely cartilaginous.

Caudal-fin margin slightly rounded. Caudal fin with i, 5+6, i principal rays. Dorsal procurrent rays 16-21*, inserted posterior to neural spine of vertebra PU7-PU10*. Ventral procurrent rays 14-17*, inserted posterior to hemal spine of vertebra PU8-PU10*. Caudal skeleton with two similar plates ( Fig. 3a ), ventral plate represented by parhypural fused to hypurals 1+2 and dorsal plate by hypurals 3+4+5. Epural absent. Neural spine of preural centrum 1 complete with conspicuous anterior and posterior processes at base of spine.

Color in alcohol. Ground color uniformly dark brown on lateral and dorsal surfaces of head and body, including barbels, lower lip, ventral surface of head anterior to gular apex and interopercular patch of odontodes. Ventral surface of branchiostegal membrane and small triangular area delimited anteriorly by gular apex, cream. Ventral surface of body from pectoral region to pelvic-fin insertion cream to light brown, becoming darker posteriorly. Trunk with thin and dark, mid-lateral stripe, extending posterior to opercular patch of odontodes to region below dorsal fin, fading posterior to this point. Some chromatophores clustered along ventrolateral row originating above pelvic-fin insertion to anterior portion of anal-fin base. Few chromatophores forming diffuse blotches, along dorsolateral row, anterior to dorsalfin insertion. Both dorsal and ventral surfaces of pectoral and pelvic fins, pigmented as body, except distal margin. First pectoral-fin ray, basal portion of remaining rays, and basal portion of interradial membrane densely pigmented. Distal tip of fin rays light. Anterior two thirds of rays and interradial membrane of pelvic fin darkly pigmented and distal margin light. Basal integument layer of dorsal and anal fins, including basal portion of rays and interradial membrane, pigmented as body, and distal margin hyaline. Basal portion of caudal fin darkly pigmented. Darkest semicircular halo preceding hyaline distal margin of caudal fin.

Distribution and habitat. Trichomycterus steindachneri is known from quebrada El Charco, a tributary of quebrada Santa Bárbara, which drains the east flank of the Eastern Cordillera of Colombian Andes, to empties into río El Palmar of the río Meta drainage, río Orinoco basin ( Fig. 6 ). The collecting site is a typical lotic environment of high altitude (2700 m), about 50 cm wide, with small pools and falls (not higher than 40 cm). Stream banks had dense riparian vegetation, constituted by shrubs and grasses, and dominated by the chusque ( Chusquea scandens ). Other marginal sections were only covered with pasture.

Etymology. The specific epithet steindachneri (adjective genitive masculine singular) is a patronym honoring the prominent Austrian zoologist Franz Steindachner (1834- 1919), in recognition of his dedicated life and significant work in documenting the fish biodiversity, especially that from South America. His profuse morphological descriptions mainly contributed to settle the current standard in ichthyological taxonomic works.

Figures

Fig. 1. Pectoral girdle of: a. Trichomycterus steindachneri (MBUCV-V-35652), paratype, 86.7 mm SL. b. T. cachiraensis (MBUCV-V-35384), paratype, 74.9 mm SL. Ventral view. Abbreviations: cl, cleithrum; pcr, pectoral complex radial; pr, pectoral radial; sco, scapulocoracoid.

Fig. 2. Neurocranium, Weberian complex, and right suspensorium and opercular series of: a. Trichomycterus steindachneri (MBUCV-V-35652), paratype, 86.7 mm SL. b. T. cachiraensis (MBUCV-V-35384), paratype, 74.9 mm SL. Dorsal view. Abbreviations: afo, anterior fontanel; apa, autopalatine; epo, epioccipital; fr, frontal; la, lachrymal-antorbital; le, lateral ethmoid; hy, hyomandibula; i1, infraorbital sensory pore 1; i3, infraorbital sensory pore 3; i10-11, infraorbital sensory pores 10 and 11; me, mesethmoid; mto, metapterygoid; mx, maxilla; op, opercle; pfo, posterior fontanel; pmx, premaxilla; pop, preopercle; pr, preopercular sensory pore; psoc, parieto-supraoccipital; pt, pterotic; ptb, pterotic branch; pttsc, posttemporo-supracleithrum; q, quadrate; s1, supraorbital sensory pore 1; s3, supraorbital sensory pore 3; s6, supraorbital sensory pore 6 (epiphyseal branch); sob, sesamoid supraorbital; sp+pro+pts, sphenotic-prootic-pterosphenoid complex bone; wc, Weberian capsule.

Fig. 3. Caudal skeleton (caudal-fin rays not illustrated) of: a. Trichomycterus steindachneri (MBUCV-V-35652), paratype, 86.7mm SL.b.T.cachiraensis (MBUCV-V-35384),paratype, 74.9 mm SL. Left lateral view. Abbreviations: h1-5, hypurals 1 to 5; ph, parhypural; pu1+u1, compound caudal centrum (preural centrum 1 plus ural centrum 1); un, uroneural.

Fig. 4. Trichomycterus steindachneri, holotype, MPUJ 4191, 143.5 mm SL; Colombia, Cundinamarca, Ubaque, vereda Pueblo Nuevo, quebrada El Charco, tributary of quebrada Santa Bárbara, río El Palmar system, río Orinoco basin, 04°31’10.3”N 73°58’44.6”W, 2700 m. Scale bar = 1 cm.

Fig. 5. Trichomycterus steindachneri, paratype, MBUCV-V-35652, 88.8 mm SL, Colombia, Cundinamarca, Ubaque, Vereda Pueblo Nuevo, quebrada El Charco, tributary of quebrada Santa Bárbara, río El Palmar system, río Orinoco basin. 04°31’10.3”N 73°58’44.6”W, 2700 m. Scale bar = 1 cm.

Fig. 6. Map of Middle Eastern region of Colombia showing the geographic distribution of Trichomycterus steindachneri (circle): Cundinamarca, Ubaque, vereda Pueblo Nuevo, quebrada El Charco, 04°31’10.3”N 73°58’44.6”W, T. dorsostriatus (square): Meta, Villavicencio, 04°09’12”N 73°38’06”W and T. migrans (triangle): Meta, Serranía La Macarena, tributary creek of río Guayabero, 02°28’21”N 73°35’43”W. Inset at lower left corner corresponds to enlargment of distribution region of T. steindachneri.