Trichomycterus balios, Ferrer & Malabarba, 2013

Ferrer, Juliano & Malabarba, Luiz R., 2013, Taxonomic review of the genus Trichomycterus Valenciennes (Siluriformes: Trichomycteridae) from the laguna dos Patos system, Southern Brazil, Neotropical Ichthyology 11 (2), pp. 217-246: 218-231

publication ID

http://doi.org/ 10.1590/S1679-62252013000200001

persistent identifier

http://treatment.plazi.org/id/CA2E0317-9237-8866-EAE3-F52BFB46F984

treatment provided by

Carolina

scientific name

Trichomycterus balios
status

new species

Trichomycterus balios   , new species

Figs. 1 View Fig , 2a View Fig , 3a View Fig , 4a View Fig , 5a View Fig , 6a View Fig , 7 View Fig

Trichomycterus   sp. 2. Becker et al. (2013: Table 1, listed, Taquari-Antas river basin).

Holotype. UFRGS 16229 View Materials , 82.0 mm SL, Brazil, Rio Grande do Sul State, municipality of São Francisco de Paula, rio Santa Cruz, rio Caí basin, 29º21’46”S 50º31’18”W, 11 Sep 2004, G. N. Silva, J. A. Anza, J. Ferrer & L. R. Malabarba. GoogleMaps  

Paratypes. All from Brazil, Rio Grande do Sul State. Rio Caí basin: UFRGS 6831 View Materials , 14 View Materials (2 c&s), 27.3-87.5 mm SL, collected with holotype. UFRGS 16341 View Materials , 3 View Materials (1 c&s), 35.2-67.2 mm SL, municipality of São Francisco de Paula , arroio Cará , 29º14’42”S 50º37’46”W, 12 Sep 2004, G. N. Silva, J. A. Anza, J. Ferrer & L. R. Malabarba. MCN 18927 View Materials , 5, 32.1-56.7 mm SL, municipality of Canela, arroio Saiqui, 29º18’32”S 50º45’41”W, 19 Sep 2006, R. B. Dala-Corte. MCP 46943 View Materials , 5 View Materials (1 c&s), 32.7-81.8 mm SL, municipality of São Francisco de Paula , arroio Lava-Pés, 29º12’49”S 50º44’59”W, 30 Mar 2002, V. A. Bertaco & V. C. Baumbach. Rio Taquari-Antas basin: MCN 14907 View Materials , 1, 78.7 mm SL, municipality of São Francisco de Paula , rio Tomé , 11 Jul 1997, L. F. Guterrez & W. R. Koch. MCN 14879 View Materials , 1, 74.6 mm SL, municipality of Bom Jesus, arroio do Barreiro, 10 Jul 1997, L. F. Guterrez & W. R. Koch. MCP 26920 View Materials , 2 View Materials , 27.6-79.6 mm SL, municipality of São Francisco de Paula , rio Contendas , 29º17’S 50º16’W, 2 May 1998, G. Vinciprova & W. Bruschi. MCP 35064 View Materials , 3 View Materials (1 c&s), 33.0-71.0 mm SL, municipality of Lagoa Vermelha, rio Turvo , 28º24’19”S 51º29’25”W, 22 May 2004, A. M. Liedke, E. H. Pereira, T. P. Carvalho & R. E. Reis. MCP 42790 View Materials , 7 View Materials , 49.0-80.0 mm SL, municipality of Bom Jesus, arroio Bagual, 28º43’32”S 50º43’44”W, 18 Apr 2008, B. B. Calegari, E. H. Pereira & J. F. P. Silva. MCP 42794 View Materials , 2 View Materials , 35.3-80.8 mm SL, municipality of Bom Jesus, arroio Governador, 28º47’42”S 50º42’18”W, 17 Apr 2008, B. B. Calegari, E. H. Pereira & J. F. P. Silva. MCP 46944 View Materials , 1 View Materials , 79.0 mm SL, municipality of São Francisco de Paula , rio Lageado Grande , 29º13’26”S 50º28’14”W, 16 Dec 1998, A. R. Cardoso, F. Melo, P. A. Buckup & R. E. Reis. MCP 46945 View Materials , 7 View Materials (2 c&s), 41.7-79.3 mm SL, municipality of São Francisco de Paula , rio Contendas , 29º16’45”S 50º14’43”W, 3 Feb 2007, C.A. Cramer, E. H. Pereira, T. P. Carvalho & R. E. Reis. MCP 46946 View Materials , 3 View Materials , 63.2-85.8 mm SL, municipality of Bom Jesus, arroio Governador, 28º44’23”S 50º40’42”W, 18 Apr 2008, B. B. Calegari, E. H. Pereira & J. F. P. Silva. MNRJ 18414 View Materials , 6 View Materials , 14.9-72.9 mm SL, municipality of São Francisco de Paula , unnamed stream tributary of rio Tainhas on road RS-453, 29º15’45”S 50º19’55”W, 16 Dec 1998, A. R. Cardoso, F. Melo, P. A. Buckup & R. E. Reis. MPEG 24030 View Materials , 3 View Materials , 48.4-78.1 mm SL, municipality of Cambará do Sul , unnamed stream tributary to rio Tainhas , 29º15’06”S 50º16’39”W, 27 Nov 2004, A. B. Schaan, G. N. Silva, J. A. Anza & V. Lampert. MZUSP 110992 View Materials , 5 View Materials , 55.4-86.5 mm SL, municipality of Vacaria, unnamed stream tributary to rio Quebra-Dentes , 28º38’36”S 50º50’06”W, 10 Nov 2009, C. E. Machado & J. A.Anza. UFRGS 5570 View Materials , 4 View Materials (1 c&s), 44.3-73.1 mm SL, municipality of Cambará do Sul , unnamed stream tributary to rio Camisas , 29º03’54”S 50º09’39”W, 1 Apr 2001, J. A. Anza, J. R. Bastos, L. R. Malabarba & T. O. B. Hasper. UFRGS 5571 View Materials , 1 View Materials , 50.9 mm SL, municipality of Bom Jesus, arroio das Nevilhas, 28º57’12”S 50º29’03"W, 31 Mar 2001, J. A.Anza, J. R. Bastos, L. R. Malabarba & T. O. B. Hasper. UFRGS 13898 View Materials , 4 View Materials , 42.4-92.4 mm SL, municipality of Monte Alegre dos Campos, arroio dos Cães, rio Quebra-Dentes basin, 28º39’26”S 50º49’06”W, 1 Jun 2010, F. G. Becker, G. Rosa & L. de Fries. UFRGS 16230 View Materials , 2 View Materials , 84.4-91.7 mm SL, municipality of São Francisco de Paula , unnamed stream tributary to rio Tainhas , 29º15’47”S 50º19’56”W, 30 Mar 2001, J. A. Anza, J. R. Bastos, L. R. Malabarba & T. O. B. Hasper. UFRGS 16231 View Materials , 11 View Materials (2 c&s), 45.3- 90.3 mm SL, municipality of Vacaria, unnamed stream tributary to rio Quebra-Dentes , 28º33’42”S 50º54’32”W, 10 Nov 2009, C. E. Machado & J. A. Anza. UFRGS 16232 View Materials , 4 View Materials (2 c&s), 46.4-66.3 mm SL, municipality of Vacaria, arroio Maria Inácia, rio Quebra-Dentes basin, 28º27’52”S 51º02’W, 2 Jun 2010, F. G. Becker, G. Rosa & L. de Fries. UFRGS 16233 View Materials , 3 View Materials (1 c&s), 47.1-81.9 mm SL, municipality of São Marcos, unnamed stream near Molin waterfall, tributary to arroio São Marcos, 29º02’35”S 51º01’29”W, F. G. Becker, G. Rosa & L. de Fries. UFRGS 16234 View Materials , 2 View Materials , 40.3-78.3 mm SL, municipality of São Francisco de Paula , rio Buriti , 29º09’40”S 50º32’37”W, 31 Mar 2001, J. A. Anza, J. R. Bastos, L. R. Malabarba & T. O. B. Hasper. UFRGS 16235 View Materials , 3 View Materials , 42.3-73.8 mm SL, municipality of São Francisco de Paula , arroio Ribeirão, 29º13’59”S 50º22’30”W, 29 Nov 2004, A. B. Schaan, G. N. Silva, J. A. Anza & V. Lampert. UFRGS 16236 View Materials , 5 View Materials (1 c&s), 43.8-66.0 mm SL, municipality of Cambará do Sul , unnamed stream tributary to rio Camisas , 29º10’45”S 50º08’13”W, 27 Nov 2004, A. B. Schaan, G. N. Silva, J. A. Anza & V. Lampert GoogleMaps   .

Non-type material. UFRGS 16295 View Materials , 15 View Materials , 36.1-81.6 mm SL, municipality of Cambará do Sul , arroio Perdizes on Parque Nacional Aparados da Serra, rio Mampituba basin, 29º09’25”S 50º03’06”W, 12 May 2012, A. Souza, J. Ferrer, L. Santos, P. Lehmann GoogleMaps   & T. Guimarães   . UFRGS 16299 View Materials , 7 View Materials , 26.4-61.6 mm SL, municipality of Cambará do Sul , arroio Perdizes on Parque Nacional Aparados da Serra, rio Mampituba basin, 29º09’31”S 50º04’49”W, 11 May 2012, J. Ferrer, L. Santos GoogleMaps   & T. Guimarães   .

Diagnosis. Trichomycterus balios   is distinguishable from all congeners except T. davisi (Haseman, 1911)   ; T. diatropoporos   ; T. papilliferus Wosiacki & Garavello, 2004   ; T. payaya Sarmento-Soares, Zanata & Martins-Pinheiro, 2011   ; T. perkos Datovo, Carvalho & Ferrer, 2012   ; T. plumbeus Wosiacki & Garavello, 2004   ; and T. tropeiro   by the modal possession of I+6 pectoral-fin rays (one among 108 specimens with I+7; vs. I+5, I+7, or more pectoral-fin rays) and the first ray of the pectoral fin not prolonged as a filament ( Fig. 1 View Fig ; vs. the first ray of the pectoral fin prolonged as a filament). Trichomycterus balios   is distinguished from T. davisi   , T. diatropoporos   , T. papilliferus   , T. payaya   , T. perkos   , and T. plumbeus   by the color pattern of the dorsal and lateral surfaces of body, which presents circular black blotches variable in size ( Fig. 1 View Fig ; vs. the head and trunk with dark irregularly shaped spots scattered in T. davisi   ; lateral surface of body with dark blotches variable in size and shape progressively larger and coalescent dorsally thus forming extensive black pigmented regions with light yellow gaps in T. diatropoporos   ; dorsal and lateral surfaces of body pale brown to light gray in T. payaya   ; dorsal and lateral surfaces of body gray in T. papilliferus   and T. plumbeus   ; lateral surface of body with three wide dark brown stripes in T. perkos   ). Trichomycterus balios   is distinguished from T. tropeiro   by the presence of the pelvic girdle and pelvic fins ( Fig. 1 View Fig ; vs. absence); and the absence of pores i1 and i3 of the infraorbital sensory canal ( Fig. 2a View Fig ; vs. presence). Additionally, T. balios   is distinguished from the remaining congeners in the laguna dos Patos system by the possession of 36-39 teeth on ceratobranchial 5 ( Fig. 3a View Fig ; vs. 12-13 in T. diatropoporos   and 20-23 in T. poikilos   ); 35-40 teeth on plate connected to pharyngobranchial 4 ( Fig. 3a View Fig ; vs. 18-20 in T. diatropoporos   and 23-25 in T. poikilos   ); by the color pattern of the dorsal and lateral surfaces of body with circular black blotches variable in size [ Fig. 1 View Fig ; vs. the dorsal and lateral surfaces of body mottled dark brown over a light yellow background or with three stripes (dorsosagittal, midlateral, and ventrolateral) with notched borders in T. poikilos   ; the dorsal and lateral surface of body densely mottled dark brown over a light yellow background in T. brachykechenos   ]. Trichomycterus balios   is further distinguishable from T. poikilos   by having the origin of the dorsal fin located at the vertical through the last third of the pelvic fin ( Fig. 1 View Fig ; vs. at the vertical falling between the tip of the pelvic fin and the anterior insertion of anal fin). Trichomycterus balios   is further distinguishable from T. brachykechenos   by having a posterior cranial fontanel extending from the parieto-supraoccipital to the frontals ( Fig. 2a View Fig ; vs. the posterior cranial fontanel restricted to the parieto-supraoccipital); the maxillary barbel length (37.8- 66.6% vs. 68.2-87.7% HL), the number of odontodes of the opercular patch (13-19 vs. 8-11). Trichomycterus balios   is further distinguishable from T. diatropoporos   by the insertion of the first dorsal-fin basal radial anterior to the neural spine of the 19 th- 22 th vertebrae (vs. anterior to the neural spine of the 17 th or 18 th vertebrae).

Description. Morphometric data for holotype and paratypes in Table 1. Body elongate, trunk roughly cylindrical and gradually compressed towards caudal fin. Dorsal profile of trunk convex along anterior half then straight to insertion of dorsal fin. Ventral profile of trunk straight to slightly convex. Dorsal and ventral profile of caudal peduncle straight to slightly concave.

Head depressed, trapezoidal from dorsal view, wider posteriorly. Dorsal profile straight and ventral profile straight to slightly convex. Snout rounded from dorsal view. Eyes readily visible, anteroposteriorly elliptical to rounded, dorsally oriented; orbital rim not free, eyes covered with skin thin and transparent. Each eye located over posterior termination of shallow and small longitudinal crest beginning at posterior nostril and making eyes visible from lateral view.

Nostrils of same size and smaller than eye diameter. Anterior nostril surrounded by fleshy flap of integument posterolaterally continuous with nasal barbel. Posterior nostril surrounded anterolaterally by thin flap of integument. Gill openings not constricted but united with isthmus anteriorly forming a free fold. Mouth subterminal with corners posteriorly oriented. Lower lip with conspicuous fleshy lobes along lateral limits internal to origin of rictal barbels. Lips with small papillae; papillae largest on inner surface of upper lip.

Barbels with large bases and tapering gradually towards tip. Tip of nasal barbel usually reaching to between eye and pore i11 or at most slightly extending beyond pore i11. Origin of nasal barbels on posterolateral portion of integument flap around anterior nostril. Maxillary barbel usually extending between anterior and posterior margins of interopercular patch of odontodes or at most slightly extending beyond to posterior margin but never reaching pectoral-fin insertion. Rictal barbel slightly shorter than maxillary barbel.

Mesethmoid with anterior margin slightly concave, cornua short and thick, width of their bases similar to their length ( Fig. 2a View Fig ).Anterior cranial fontanel restricted to small rounded opening situated between frontals and epiphyseal bar. Posterior cranial fontanel long and narrow, extending from posterior portion of frontals to parieto-supraoccipital. Epiphyseal bar longer than wide (absent in one of 14 specimens). Antorbital short and anteriorly expanded. Tendon-bone supraorbital elongate, approximately three times larger than antorbital, with process along distal margin. Anterior portion of sphenotic laterally directed from dorsal view. Sphenotic, prootic, and pterosphenoid totally fused. Vomer arrow-shaped with long posterior process extending to parasphenoid. Parasphenoid with long pointed process extending to basioccipital.Anterior portion of Weberian complex fused to basioccipital. Weberian capsule with lateral opening smaller than lateral profile of capsule.

Premaxilla rectangular with 75-101 conical, curved and pointed teeth (n = 2). Teeth variable in size and distributed with some irregularity in up to four rows. Maxilla large, boomerang-shaped and shorter than premaxilla. Lower jaw with 89-107 conical, curved and pointed teeth variable in size (n = 2). Outer teeth row slightly flat vertically with blunt tips in largest specimens (greater than 85.4 mm SL). Teeth range from few teeth at base of coronoid process to four discernible rows near dentary symphysis. Autopalatine with anterior margin straight, mesial margin straight to slightly concave, distal margin slightly concave, and large posterior process extending to middle of metapterygoid.

Metapterygoid large and laminar and connecting with quadrate through cartilage. Hyomandibula well-developed. Preopercle long and narrow and in contact with ventral margins of quadrate and hyomandibula. Opercular patch of odontodes rounded with 13-19 conical odontodes (n = 14). Interopercular patch of odontodes elongate with 15-25 conical odontodes (n = 14) more concentrated posteriorly. Odontodes of both opercular and interopercular patches gradually curving medially and increasing in size posteriorly.

Ventral hypohyal trapezoid-shaped ( Fig. 4a View Fig ). Anterior ceratohyal elongate and widening at anterior and posterior limits. Posterior ceratohyal short and triangular. Branchiostegal rays 8-9 (n = 14), usually 9, five on anterior ceratohyal, one on ceratohyal posterior and three articulated on interceratohyal cartilage. Last three branchiostegal rays widest. Dorsal hypohyal and interhyal absent. Urohyal with expanded anterior head, two elongate lateral processes with wide bases and decreasing in width distally with rounded tips and laminar, elongate, narrow posterior process ( Fig. 5a View Fig ).

Basibranchial 1 absent. Basibranchials 2 and 3 connected to each other, of approximately equal lengths and with cartilage at tips ( Fig. 3a View Fig ). Ossified portion of basibranchial 2 distinctly wider than basibranchial 3. Hexagonal basibranchial 4 completely cartilaginous. Hypobranchial 1 of similar size but narrower than basibranchial 2 with cartilage at tips. Hypobranchials 2 and 3 with narrow anterolateral ossified processes; ossified portion more elongate on hypobranchial 3 with large area of cartilage distally; larger in hypobranchial 3. Hypobranchial 4 absent. Five elongate and narrow ceratobranchials with cartilage at tips. Ceratobranchials 2 and 3 with concavity along posterior margins; concavity larger in ceratobranchial 3. Ceratobranchial 5 expanded posteromedially with 36-39 conical, elongate and pointed teeth arranged in 3 rows (n = 1). Five epibranchials, first three elongate and narrow with cartilage at tips. Epibranchials 1 and 2 with triangular process along anterior margins; process slightly larger in epibranchial 1. Epibranchial 3 with robust uncinate process along posterior margin. Epibranchial 4 rectangular. Epibranchial 5 small, narrow, curved and completely cartilaginous. Pharyngobranchials 1 and 2 absent. Pharyngobranchial 3 similar in form but shorter than hypobranchial 1 with cartilage at tips. Pharyngobranchial 4 curved and well ossified connected to plate with 35-40 conical, elongate and pointed teeth arranged in up to 3 rows; teeth increasing in length posteriorly (n = 1).

Sensory canals on head with simple (non-dendritic) tubes ending in single pores ( Fig. 2a View Fig ). Supraorbital sensory canal complete with paired pores s1, s3 and s6. Pore s1 located between anterior nostrils, pore s3 located in same longitudinal row of pore s1 after posterior nostrils and pore s 6 in interorbital space. Infraorbital sensory canal incomplete; pores i1 and i3 absent, pore i10 located behind eye and pore i11 located lateral to posterior margin of eye. Postotic pore po1 located lateral to anterior margin of opercular patch of odontodes. Postotic pore po2 located lateral to middle of length of opercular patch of odontodes. Lateral-line canal very short with 2 pores located above insertion of pectoral fin and just posterior of gill openings.

Pectoral fin with distal margin rounded, I+6* rays (1 of 108 specimens with I+7), first ray short and not prolonged as filament. Pelvic fin with distal margin rounded, reaching at most anterior margin of urogenital papilla, I+4 rays (n = 108). Inner margin of pelvic fins very close basally. Pelvic girdle with two basipterygia united medially by cartilage with two elongate bifid processes (external process and internal process) and medial process short (one of 14 specimens with medial process united to internal process). Pelvic splint thin, comma-shaped and parallel to first pelvic-fin ray. Urogenital papilla nearer tip of pelvic fin than origin of anal fin.

Dorsal fin with distal margin rounded, semicircular when fin expanded with two to four unsegmented rays (n = 14), II+5-8 rays (n = 108), usually II+7*. Dorsal-fin origin located at vertical through the last third of pelvic fin. Dorsal-fin basal radials 8 (n = 14); first inserting anterior to neural spine of 19 th to 22 th vertebrae.

Anal fin slightly smaller than dorsal fin with distal margin rounded, two to four unsegmented rays (n = 14), II+4-6 rays (n = 108), usually II+5*. Anal-fin origin located at vertical through middle of dorsal-fin base. Anal-fin basal radials 6 (n = 14); first inserting anterior to haemal spine of 22 th to 25 th vertebrae.

Caudal fin with distal margin straight and dorsal and ventral lobes rounded at limits. Procurrent caudal-fin rays 14- 17 dorsally (n = 14) and 10-13 ventrally (n = 14). Principal rays I+5+5-7+I (n = 108), usually I+5+6+I*, branched rays splitting two or three times. Lower caudal plate with parhypural and hypurals 1 and 2 co-ossified and fused to compound caudal centrum. Upper caudal plate with a separate uroneural; hypurals 3, 4, and 5 completely fused (n = 3) ( Fig. 6a View Fig ) or with hypural 3 autogenous (n = 8) or partly fused (n = 3) with hypurals 4 and 5 ( Fig. 7 View Fig ).

Vertebrae 38-41 (n = 14); ribs 12-15 (n = 14) with first rib straight and thickest and last rib rudimentary.

Coloration in alcohol. Dorsal and lateral surface of body with circular black blotches variable in size over light yellowish background; dark pigmentation more concentrated dorsally ( Fig. 1 View Fig ). Ventral surface of body light yellow with diffuse small black spots laterally and between pectoral-fin insertions; spots larger and more concentrated between pelvic and anal fins and caudal peduncle. Dorsal surface of head with greater concentration of irregular black rounded blotches variable in size; blotches becoming more scattered on lateral surface, smaller ventrally and restricted to lateral and posterior margins of gill openings. Pectoral, dorsal, anal and caudal fins spotted basally, spotting becoming inconspicuous towards tips and margins lighter. Pelvic fin unpigmented. Barbels with dark pigmentation on both surfaces. Larger specimens (greater than 43.2 mm SL) with pigmentation arranged in two distinct layers; large rounded black spots on inner skin layer and small black spots on outer skin layer ( Fig. 1 View Fig ).

Distribution and ecological notes. Trichomycterus balios   is distributed in the upper portions of the rio das Antas and rio Caí tributaries to the laguna dos Patos system and in the

headwaters of the rio Mampituba ( Fig. 8 View Fig ). The type locality is located at approximately 792 m a.s.l. and the remaining localities of collection between 681 and 941 m a.s.l. The lower portions of the laguna dos Patos system and of the rio Mampituba are widely separated by the rio Tramandaí drainage, were T. balios   is unknow to occur ( Malabarba et al., 2013). The occurrence of the species in the headwaters of these two unconnected and distant drainages (laguna dos Patos system and of the rio Mampituba) is possibly related to headwater capture events.

The localities where the types were collected had clear water with current water and rocky bottoms ( Fig. 9a View Fig ). Trichomycterus balios   was collected with Cnesterodon brevirostratus Rosa & Costa, 1993   ; Pareiorhaphis hystrix (Pereira & Reis, 2002)   ; and Bryconamericus patriciae da Silva, 2004   at the type locality, other species that show some degree of endemism in the region associated with high altitudes ( Rosa & Costa, 1993; Pereira & Reis, 2002, da Silva, 2004). The stomach of 13 c&s specimens contained larvae of Diptera   ( Chironomidae   , Simuliidae   ), Lepidoptera, and Trichoptera; and nymphs of Ephemeroptera and Plecoptera.

Remarks. The type series includes only specimens from laguna dos Patos system. Data of specimens from the rio Mampituba identified as T. balios   are not included in the species description.

Etymology. From the Greek balios   meaning spotted, in reference to the color pattern of the new species formed by circular black blotches. An adjective.

Trichomycterus diatropoporos   , new species Figs. 2b View Fig , 3b View Fig , 4b View Fig , 5b View Fig 6b View Fig , 10 View Fig , 11a View Fig , 12 View Fig

Trichomycterus   sp. 1. Becker et al. (2013: Table 1, listed, Taquari-Antas river basin).

Holotype. MCP 46947 View Materials , 58.8 mm SL, Brazil, Rio Grande do Sul State, municipality of Nova Prata, rio da Prata on Passo do Despraiado, 28º38’04”S 51º36’53”W, 22 May 2004, A. M. Liedke, E. H. Pereira, R. E. Reis & T. P. Carvalho. GoogleMaps  

Paratypes. All from Brazil, Rio Grande do Sul State, rio Taquari- Antas basin. MCP 35050 View Materials , 8 View Materials , 21.6-58.2 mm SL, collected with holotype. MCP 40933 View Materials , 2 View Materials (c&s), 38.8-39.7 mm SL, collected at type locality, 24 Oct 2006, T. P. Carvalho & V. A. Bertaco. MCP 22789 View Materials , 2 View Materials , 39.1-57.1 mm SL, municipality of Lagoa Vermelha , arroio Carazinho , rio Turvo basin, 28º17’36”S 51º24’42”W, 3 Apr 1999, E. H. Pereira, R. E. Reis & V. A. Bertaco. MCP 40940 View Materials , 2 View Materials , 47.9 View Materials -67.0 mm SL, municipality of André da Rocha , arroio Herval, rio da Prata basin, 28º39’32”S 51º37’03”W, 24 Oct 2006, T. P. Carvalho & V. A. Bertaco. MCN 18928 View Materials , 5, 30.7-37.8 mm SL, collected at type locality, 24 Oct 2006, T. P. Carvalho & V. A. Bertaco. UFRGS 16237 View Materials , 1 View Materials (c&s), 57.8 mm SL, collected with holotype. UFRGS 16238 View Materials , 4 View Materials (1c&s), 57.4-68.3 mm SL, collected at type locality, 20 Jan 1999, E. H. Pereira, J. F. P. Silva & R. E. Reis GoogleMaps   .

Non-type material. MCP 22785 View Materials , 1 View Materials , 59.1 mm SL, municipality of Muitos Capões , arroio Espeto, rio Turvo basin, 28º23’26”S 51º03’22”W, 3 Apr 1999. E. H. Pereira GoogleMaps   , R. E. Reis   & V. A. Bertaco   .

Diagnosis. Trichomycterus diatropoporos   is distinguishable from all congeners except T. balios   , T. davisi   , T. papilliferus   , T. payaya   , T. perkos   , T. plumbeus   , and T. tropeiro   by the possession of I+6 pectoral-fin rays (vs. I+5, I+7, or more) and the first ray of the pectoral fin not prolonged as a filament ( Fig. 10 View Fig ; vs. the first ray of the pectoral fin prolonged as a filament). Trichomycterus diatropoporos   is distinguished from T. balios   , T. brachykechenos   , T. davisi   , T. papilliferus   , T. payaya   , T. perkos   , T. plumbeus   , T. poikilos   , and T. tropeiro   by the color pattern of dark blotches variable in size and shape progressively larger and coalescent dorsally thus forming extensive black pigmented regions with light yellow gaps ( Fig. 10 View Fig ; vs. the dorsal and lateral surface of body with circular black blotches variable in size in T. balios   and T. tropeiro   ; the dorsal and lateral surfaces of body densely mottled dark brown over a light yellow background in T. brachykechenos   ; head and trunk with dark brown irregularly shaped spots scattered in T. davisi   ; dorsal and lateral surface of body pale brown to light gray in T. payaya   , dorsal and lateral surface of body gray in T. papilliferus   and T. plumbeus   ; lateral surface of body with three wide dark brown stripes in T. perkos   ; dorsal and lateral surface of body mottled dark brown over a light yellow background and sometimes forming two stripes, midlateral and ventrolateral, with notched borders in T. poikilos   ). Trichomycterus diatropoporos   is further distinguishable from T. poikilos   by having the origin of the dorsal fin located at the vertical through the last third of the pelvic fin ( Fig. 10 View Fig ; vs. at vertical falling between tip of the pelvic fin and the anterior insertion of anal fin) and the origin of the anal fin located at the vertical through the base of the last dorsal-fin ray ( Fig. 10 View Fig ; vs. at the vertical falling between the anterior insertion of the dorsal fin and the middle of its length). Trichomycterus diatropoporos   is further distinguishable from T. brachykechenos   by having the posterior cranial fontanel extending from the parieto-supraoccipital to the frontals ( Fig. 2b View Fig ; vs. the posterior cranial fontanel restricted to the parietosupraoccipital); the maxillary barbel length (38.3-53.9% vs.68.2- 87.7% HL); and the number of odontodes on the opercular patch (13-19 vs. 8-11). Trichomycterus diatropoporos   is further distinguishable from T. balios   by location of the insertion of the first dorsal-fin basal radial anterior to neural spine of 17 th or 18 th vertebrae (vs. anterior to neural spine of 19 th- 22 thvertebrae); and the number of teeth on ceratobranchial 5 and on plate connected to pharyngobranchial 4 ( Fig. 2b View Fig ; 12-13 View Fig View Fig vs. 36-39 and 18-20 vs. 35-40, respectively). Trichomycterus diatropoporos   is further distinguishable from T. tropeiro   by the presence of the pelvic girdle and pelvic fins ( Fig. 10 View Fig ; vs. absence); and the insertion of the first dorsal-fin basal radial anterior to neural spine of 17 th or 18 th vertebrae (vs. anterior to neural spine of 19 th- 20 thvertebrae).

Description. Morphometric data for holotype and paratypes in Table 2. Body elongate, trunk roughly cylindrical and gradually compressed towards caudal fin. Dorsal profile of trunk convex along anterior half then straight to insertion of dorsal fin. Dorsal profile of caudal peduncle straight to slightly convex. Ventral profile of trunk and caudal peduncle nearly straight.

Head depressed, trapezoidal from dorsal view, wider posteriorly. Dorsal profile of head straight and ventral profile straight to slightly convex. Snout rounded from dorsal view. Eyes readily visible, anteroposteriorly elliptical and dorsally oriented, orbital rim not free, eyes covered with skin thin and transparent. Each eye located over posterior termination of small longitudinal ridge beginning at posterior nostril and making eyes fully visible from lateral view.

Nostrils of same size and smaller than diameter of eye. Anterior nostril surrounded by fleshy flap of integument posterolaterally continuous with nasal barbel. Posterior nostril surrounded anterolaterally by thin flap of integument. Gill openings not constricted but united with isthmus anteriorly forming a large free fold. Mouth subterminal, corners posteriorly oriented. Lower lip with conspicuous fleshy lobes along lateral limits internal to origin of rictal barbels. Lips with small papillae; papillae largest on inner surface of upper lip.

Barbels with large bases and tapering gradually towards tip. Tip of nasal barbel usually reaching to between eye and pore i11 or at most slightly extending beyond pore i11. Origin of nasal barbels on posterolateral portion of integument flap around anterior nostril. Maxillary barbel usually extending posteriorly to between anterior margin of interopercular patch of odontodes and middle of patch but never reaching posterior margin of patch. Rictal barbel slightly shorter than maxillary barbel.

Mesethmoid with anterior margin slightly concave, cornua short and thick, width of their bases similar to their length ( Fig. 2b View Fig ). Anterior cranial fontanel restricted to small rounded opening situated between frontals and epiphyseal bar. Posterior cranial fontanel narrow and long extending from posterior portion of frontals to parieto-supraoccipital. Epiphyseal bar longer than wide. Antorbital short and anteriorly expanded. Tendon-bone supraorbital elongate, approximately three times larger than antorbital. Anterior portion of sphenotic anterolaterally directed from dorsal view. Sphenotic, prootic and pterosphenoid totally fused. Vomer arrow-shaped with long posterior process extending to parasphenoid. Parasphenoid with long pointed process extending to basioccipital. Anterior portion of Weberian complex fused to basioccipital. Weberian capsule with lateral opening smaller than lateral profile of capsule.

Premaxilla rectangular with 103 conical, curved and pointed teeth (n = 1). Teeth variable in size and irregularly distributed in up to three rows. Maxilla large, boomerang-shaped and shorter than premaxilla. Lower jaw with 75 conical to slightly vertically flat, curved and pointed teeth of variable size (n = 1). Few teeth at base of coronoid process and up to three discernible rows near dentary symphysis ( Fig. 11a View Fig ). Autopalatine with anterior margin convex, mesial margin concave, distal margin slightly concave and small posterior process extending slightly over metapterygoid.

Metapterygoid large, laminar and connecting with quadrate through cartilage. Hyomandibula well-developed. Preopercle long and narrow and in contact with ventral margins of quadrate and hyomandibula. Opercular patch of odontodes rounded with 13-19 conical odontodes (n = 4). Interopercular patch of odontodes elongate with 20-23 conical odontodes (n = 4) more concentrated posteriorly. Odontodes of both opercular and interopercular patches gradually curving medially and increasing in size posteriorly.

Ventral hypohyal trapezoidal ( Fig. 4b View Fig ). Anterior ceratohyal elongate and widening at anterior and posterior limits. Posterior ceratohyal short and triangular. Nine branchiostegal rays (n = 4); five on anterior ceratohyal, one on posterior ceratohyal and three on interceratohyal cartilage. Last three branchiostegal rays widest. Dorsal hypohyal and interhyal absent. Urohyal with expanded anterior head, two elongate lateral processes with wide bases and decreasing in width distally and bearing rounded tips; and laminar, elongate, narrow posterior process ( Fig. 5b View Fig ).

Basibranchial 1 absent. Basibranchials 2 and 3 of approximately equal lengths connected to each other with cartilage at tips ( Fig. 3b View Fig ). Ossified portion of basibranchial 2 distinctly wider than basibranchial 3. Hexagonal basibranchial 4 completely cartilaginous. Hypobranchial 1 of similar size but narrower than basibranchial 2 with cartilage at tips. Hypobranchials 2 and 3 with reduced portion ossified anterolaterally; ossified portion slightly more elongate on hypobranchial 3; large area of cartilage distally, larger in hypobranchial 3. Hypobranchial 4 absent. Five elongate narrow ceratobranchials with cartilage at tips. Ceratobranchial 3 with concavity along posterior margin. Ceratobranchial 5 expanded posteromedially with 12-13 conical, elongate and pointed teeth arranged in 2 rows (n = 1). Five epibranchials, first three elongate and narrow with cartilage at tips. Epibranchials 1 and 2 with triangular process along anterior margins. Epibranchial 3 with robust uncinate process at posterior margin. Epibranchial 4 rectangular. Epibranchial 5 small, narrow, curved and completely cartilaginous. Pharyngobranchials 1 and 2 absent. Pharyngobranchial 3 similar in form but shorter than hypobranchial 1 with cartilage at tips. Pharyngobranchial 4 curved, well ossified, and connected to plate with 18-20 elongate, conical and pointed teeth arranged in 2 rows; teeth growing in length posteriorly (n = 1).

Sensory canals on head with simple (non-dendritic) tubes ending in single pores ( Fig. 2b View Fig ). Supraorbital sensory canal complete with pores s1, s3 and s6. Pore s1 located between anterior nostrils; pore s3 located in a longitudinal line passing through pore s1, after posterior nostrils, and pore s 6 in interorbital space. Infraorbital sensory canal incomplete; presence of pores i1 and i3 variable (present in 8 specimens, including holotype and absent in 17 specimens); when present located beside nostrils. Pore i10 located behind eye. Pore i11 located laterally to posterior margin of eye. Postotic pore po1 located lateral to anterior margin of opercular patch of odontodes. Postotic pore po2 located lateral to middle of opercular patch of odontodes. Lateral-line very short with 2 pores located above insertion of pectoral fin and just posterior to gill openings.

Pectoral fin with distal margin truncate to slightly rounded, I+6 rays (n = 25), first ray short and not prolonged as filament. Pelvic fin with distal margin rounded reaching at most anterior margin of urogenital papilla, I+4* rays (1 of 25 specimens with I+3). Inner margin of pelvic fins very close basally and sometimes in contact. Pelvic girdle with two basipterygia united medially by cartilage with two elongate bifid processes (external process and internal process) and medial process short ( Fig. 12 View Fig ). Pelvic splint thin, comma-shaped, and parallel to first pelvic-fin ray. Urogenital papilla nearer tip of pelvic fin than anal-fin origin.

Dorsal fin with distal margin rounded, semicircular when fin expanded with two unsegmented rays (n = 4), II+6-8 rays (n = 25), usually II+7*. Dorsal-fin origin located at vertical through last third of pelvic fin. Dorsal-fin basal radials 8 (n = 4); first inserting anterior to neural spine of 17 th or 18 th vertebrae.

Anal fin slightly smaller than dorsal fin with distal margin rounded, two or three unsegmented rays (n = 4), II+5 (n = 25). Anal-fin origin located at vertical through base of last dorsalfin ray. Anal-fin basal radials 6 (n = 4); first inserting anterior to haemal spine of 21 th or 22 th vertebrae.

Caudal fin with distal margin straight and dorsal and ventral lobes rounded at limits. Procurrent caudal-fin rays 15- 16 dorsally (n = 4) and 10-12 ventrally (n = 4). Principal rays I+5+6+I (n = 18), branched rays splitting two or three times. Lower caudal plate with parhypural and hypurals 1 and 2 coossified and fused to compound caudal centrum ( Fig. 6b View Fig ). Upper caudal plate with uroneural and hypural 3 autogenous, hypurals 4 and 5 fused.

Vertebrae 36-38 (n = 4); ribs 12-13 (n = 4) with first rib straight and thickest and last rib rudimentary.

Coloration in alcohol. Lateral surface of body covered with dark blotches variable in size and shape over light yellow background ( Fig. 10 View Fig ). Blotches progressively larger and coalescent dorsally thus forming extensive black pigmented regions with light yellow gaps.Ventral surface of body yellow on trunk with irregular black blotches between pelvic and anal fins and on caudal peduncle. Dorsal and lateral surface of head black with small lighter areas; ventral surface yellow. Pectoral, dorsal, anal and caudal fins spotted with irregular black marks and lighter along margins. Pelvic fin unpigmented. Barbels with dark pigmentation dorsally and yellow ventrally. Larger specimens (greater than 57.4 mm SL) with pigmentation arranged in two distinct layers; dark blotches variable in size and shape on inner skin layer and small black spots on outer skin layer more evident in caudal peduncle. Distribution and ecological notes. Trichomycterus diatropoporos   is apparently endemic to the rio da Prata and rio Turvo basins, tributaries of rio das Antas, in the laguna dos Patos system ( Fig. 8 View Fig ). At the type locality the rio da Prata is a rapid flowing, wide and shallow, with an average depth of 0.5 m, with clear water, rocky bottom and large amounts of submerged vegetation (Carvalho & Reis, 2011) ( Fig. 9b View Fig ). It is upstream of a waterfall known as Cascata da Usina at approximately 660 m a.s.l. At this site T. diatropoporos   occurs sympatrically with Hisonotus prata Carvalho & Reis, 2011   , another endemic species to the rio da Prata. The other two localities of the paratypes are located at approximately 642 m and 825 m a.s.l. The stomach of three c&s specimens contained larvae of Diptera   ( Chironomidae   , Simuliidae   ) and nymphs of Ephemeroptera.

Remarks. The presence of the infraorbital sensory canal is variable among the specimens of T. diatropoporos   , even in specimens from same lot and of the same size (e. g., MCP 40933 View Materials ). Although characters related to the reduction of the sensory canal have been used in defining species and even genera in the Trichomycterinae   (seeArratia, 1998), there are no additional detectable differences in morphometrics, meristics data and coloration pattern among specimens bearing or lacking pores i1 and i3 of infraorbital sensory canal to justify the recognition of two different species. Apparently, this variation in the presence of pores i1 and i3 of infraorbital sensory canal is unique among species of Trichomycterus   . One specimen ( MCP 22785 View Materials ) also from rio da Prata basin with counts, morphometrics, and color pattern similar to T. diatropoporos   lacks pelvic fins and was not included in type-series. The specimen definitely is not T. tropeiro   , the species from laguna dos Patos system that consistently lacks pelvic fins, but rather appears to be an anomalous individual of T. diatropoporos   . Among other trichomycterines, intraspecific variation in the presence/absence of pelvic fins is also known in Ituglanis parahybae ( Eigenmann, 1918)   (Costa & Bockmann, 1993).

Etymology. From the Greek diatropos meaning variable, and poros meaning pore, in reference to the variation in the presence of pores i1 and i3 of infraorbital sensory canal of the new species. A noun in apposition.

R

Departamento de Geologia, Universidad de Chile

MCP

Pontificia Universidade Catolica do Rio Grande do Sul

V

Royal British Columbia Museum - Herbarium

T

Tavera, Department of Geology and Geophysics