Ituglanis inusitatus, Ferrer & Donin, 2017

Ferrer, Juliano & Donin, Laura M., 2017, A new species of Ituglanis (Siluriformes: Trichomycteridae) from the rio Uruguai basin, southern Brazil, Neotropical Ichthyology 15 (3), No. e 170057, pp. 1-10 : 2-7

Ituglanis inusitatus , new species

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( Figs. 1-4, Table 1)

Ituglanis sp. 2 : Bertaco et al. (2016): p. 421 (table 1; list of species from the Rio Grande do Sul State).

Holotype. UFRGS 21829 , 62.2 mm SL, Brazil, Rio Grande do Sul, Município de Alegrete, arroio São João tributary of rio Ibicuí , rio Uruguai basin, 29°46’52”S 55°24’56”W, ca. 92 m, 28 Oct 2013, C. Hartmann, T. Guimarães, R. Dala- Corte, M. Dalmolin & L. Poldgaiski.

Paratypes. All from Brazil, Rio Grande do Sul, rio Uruguay basin: MCN 19975, 1, 54.9 mm SL, collected with holotype. UFRGS 19310 , 1 (tec), 70.6 mm SL, Município de Alegrete, unnamed stream tributary of arroio São João , rio Ibicuí basin, 29°46’16”S 55°24’00”W, 28 Oct 2013, C. Hartmann, T. Guimarães, R. Dala-Corte, M. Dalmolin & L. Poldgaiski. UFRGS 19311 , 4 (3 tec), 56.6- 64.9 mm SL, collected with holotype. UFRGS 20201 , 8 (6 tec, 1 c&s), 43.3-70.2 mm SL, boundary between Município de Itaquí and Município de Maçambará, unnamed stream tributary of rio Butuí at road RS-472, 29°00’06”S 56°10’38”W, 15 May 2015, J. Chuctaya, K. Bonato, L. R. Malabarba, M. C. Malabarba & R. Angrizani. UFRGS 21242 , 1 , 32.8 mm SL, Município de São Francisco de Assis , rio Ibicuí at Jacaquá beach, 29°41’24” S 55°11’40”W, 22 Mar 2007, B. Klotzel, L. E. Lanés & M. Volcán .

Paragenetype COI. GenBank accession numbers MF975518 (voucher tec 5502A): UFRGS 20201, MF975519 (voucher tec 5502B): UFRGS 20201, MF975520 (voucher tec 4966): UFRGS 19311.

Neotropical Ichthyology, 15(3): e170057, 2017 J. Ferrer & L. M. Donin

Diagnosis. Ituglanis inusitatus is distinguished from most congeners by the presence of two to three pairs of ribs (vs. 4-10). The following species exhibit one to three pairs of ribs: I. amazonicus (Steindachner) , I. apteryx Datovo , I. eichhorniarum (Miranda Ribeiro), I. gracilior (Eigenmann) , I. herberti (Miranda Ribeiro), I. ina Wosiacki, Dutra & Mendonça , I. macunaima Datovo & Landim , I. metae (Eigenmann) , I. nebulosus de Pinna & Keith , I. parkoi (Miranda Ribeiro); and I. compactus Castro & Wosiacki. Ituglanis inusitatus is distinguished from these species by the color pattern composed of an outer layer with scattered round black blotches equivalent in size to the eye circumference over a reddish brown background on the lateral surface of the body ( Fig. 1; vs. color pattern uniform, i.e. lacking a conspicuous outer layer in I. compactus , I. herberti , I. ina and I. parkoi ; color pattern composed of an outer layer with reticulated brown blotches over a pale yellow or whitish background on the lateral surface of the body in I. amazonicus , I. eichhorniarum , I. guayaberensis (Dahl) , I. gracilior , I. macunaima and I. metae ; color pattern composed of an outer layer with longitudinal stripes over a pale yellow background on the lateral surface of the body in I. apteryx ; or color pattern composed of an outer layer with blotches larger than twice the eye diameter in I. nebulosus ). Additionally, the presence of i+6 pectoral-fin rays distinguishes Ituglanis inusitatus from I. amazonicus (i+5), I. macunaima (i+3-5), I. metae (i+5) and I. nebulosus (i+5). Ituglanis inusitatus is further distinguished from I. apteryx by the presence of pelvic fins (vs. absence). Ituglanis inusitatus is further distinguished from I. compactus by the absence of the antorbital segment of infraorbital laterosensory canal (vs. presence). Ituglanis inusitatus is further distinguished from I. gracilior by the maxillary barbel not extending beyond the pectoral-fin insertion (vs. maxillary barbel reaching tip of pectoral fin). Ituglanis inusitatus is further distinguished from I. ina by the absence of neuromasts extending along the midlateral line of the body (vs. presence). Ituglanis inusitatus is distinguished from its sympatric congener in the rio Uruguay basin, I. australis , by the presence of the nasal canal of laterosensory system (vs. absence) and by the number of pectoral-fin rays (i+6 vs. i+4-5).

Description. Morphometric data in Tab. 1. Body elongate, trunk roughly cylindrical, gradually compressed towards caudal fin. Dorsal profile of body straight up to dorsal-fin insertion and slightly concave from this point to caudal-fin insertion. Ventral profile slightly convex up to pelvic-fin insertion and straight to slightly concave from this point to caudal-fin insertion.

Head depressed, trapezoidal from dorsal view, wider posteriorly. Dorsal profile straight and ventral profile straight to slightly convex. Snout straight to slightly round from dorsal view. Eyes dorsally oriented but also visible from lateral view; located on anterior half of head, near to posterior nostrils; orbital rim not free, eyes covered by thin and transparent skin. Nostrils 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 united with isthmus anteriorly forming free fold. Mouth subterminal and slightly convex from ventral view. Lower lip with lateral fleshy fold in corners continuous with rictal barbel. Lips with small papillae.

Barbels with large bases and tapering gradually towards tips. Nasal barbel emerging from posterolateral edge of anterior nostril and reaching posterior limit of skull. Maxillary barbel always extending beyond interopercle, usually reaching pectoral-fin insertion. Rictal barbel sligthly smaller than maxillary barbel.

Mesethmoid large at middle portion with anterior margin slightly concave and cornuas tapering at ends ( Fig. 3). Anterior cranial fontanel absent; posterior cranial fontanel small and round located in posterior portion of parieto-supraoccipital. Antorbital short and extending into autopalatine. Tendonbone supraorbital elongate, approximately three times larger than antorbital, anterior third over the posterior portion of autopalatine ( Fig. 3). Sphenotic with anterior margin pointed surpassing adjacent tip of frontal. Sphenotic, prootic, and pterosphenoid totally fused. Vomer arrow-shaped with long posterior process over parasphenoid. Parasphenoid with pointed posterior process extending over basioccipital. Weberian capsule with small lateral opening and with anterior margin fused to basioccipital.

Premaxilla rectangular with 21 pointed teeth variable in size distributed in two well-defined rows and curved inward. Maxilla boomerang-shaped, shorter than premaxilla ( Fig. 3). Lower jaw with 24-27 pointed teeth variable in size distributed in two or three irregular rows and curved inward. Autopalatine with anterior margin straight; medial margin with deep concavity and lateral margin concave ( Fig. 2); posterior process of autopalatine extending over metapterygoid.

Metapterygoid large and laminar, connected with quadrate through cartilage ( Fig. 4). Quadrate L-shaped with two small process in anterior margin. Hyomandibula well-developed with deep notch in dorsal margin. Preopercle long, narrow, in contact with ventral margins of quadrate and hyomandibula. Opercle elongate with small process directed upward and 17-19 pointed odontodes inserted in posterior margin. Interopercle elongate with dorsal process near anterior margin and 18-20 pointed odontodes along inferior margin extending from dorsal process up to posterior margin. Odontodes of opercle and interopercle curved at tips and gradually increasing in size posteriorly.

Ventral hypohyal trapezoid-shaped. Anterior ceratohyal elongated and with small concavity at middle length. Proximal and distal ceratohyals of approximately same depth. Posterior ceratohyal short with distal portion rounded. Eight branchiostegal rays: two or three in contact with anterior ceratohyal, four or five in contact with posterior ceratohyal and one laterally free of contact. Last four branchiostegal rays widest distally. Urohyal with expanded anterior head bearing two lateral elongated processes with wider base and pointed tips and smaller posterior process pointed, elongated and laminar; posterior process smaller than lateral processes.

Basibranchials 2 and 3 connected to each other by cartilage, basibranchial 2 slightly wider than basibranchial 3 ( Fig. 2). Ossified portion of basibranchial 2 distinctly wider than basibranchial 3. Basibranchial 4 hexagonal and entirely cartilaginous. Hypobranchial 1 elongated with cartilage at tips and with small process at lateral portion of anterior margin. Hypobranchial 2 and 3 with narrow anterolateral ossified processes with large area of cartilage distally. Hypobranchial 2 more elongated than hypobranchial 3. Five elongate ceratobranchials with cartilage at tips. Ceratobranchial 3 with distinct concavity in posterior margin. Ceratobranchial 5 with approximately 12 teeth. Four epibranchials; first three elongate and narrow with cartilage at tips. Epibranchial 1 with elongate process in anterior margin; epibranchial 2 with small process in anterior margin. Epibranchial 3 with distinct curved process in posterior margin. Epibranchial 4 rectangular. Pharyngobranchial 3 narrow and curved at middle length with cartilage at tips, Pharyngobranchial 4 ossified and connected to curved plate with approximately 16 teeth arranged in up to two rows; teeth increasing in length posteriorly.

Vertebrae 42; abdominal vertebrae 5. Ribs 2 to 3 pairs, first rib thickest. Most anterior free vertebrae with parapophyses directed laterally. First complete haemal arch on sixth free vertebrae and first complete haemal spine on 15 th free vertebrae.

Pectoral fin with distal margin rounded; one unbranched ray prolonged as short filament and six branched rays (16*). Pelvic fin with distal margin rounded, reaching anterior margin of urogenital papilla; one unbranched ray and four branched rays (16*). Dorsal fin with distal margin rounded, semicircular when fin expanded and with three unsegmented rays, one (8*) or two (8) unbranched rays and six (1) or seven (15*) branched rays. Origin of dorsal fin located at vertical through tip of pelvic fin. Dorsal fin with eight pterygiophores; first inserted anteriorly to neural spine of 26 th vertebrae. Anal fin with distal margin slightly rounded and with three unsegmented rays (1), one (15*) or two (1) unbranched rays and five (2) or six (14*) branched rays. Origin of anal fin located slightly posterior to vertical through dorsal-fin origin. Anal fin with six pterygiophores; first inserted anterior to haemal spine of 28 th vertebrae.

Caudal fin with distal margin rounded. Procurrent caudal-fin rays 15 dorsally and 13 ventrally. Upper plate with one unbranched ray and 5 branched rays. Lower caudal plate with one unbranched ray and 6 branched rays (16*). Lower caudal plate with parhypural and hypurals 1 and 2 co-ossified and fused to compound caudal centrum. Upper caudal plate with separate uroneural; hypural 3 autogenous; hypurals 4 and 5 fused.

Laterosensory canals with simple (non-dendritic) tubes ending in single pores. Nasal and frontal canals of supraorbital line fused to each other, with three pores (“s1”, “s3” and “s6”) present in all types (16*); three of them with extra pore on left side near to “s3” (1) or near to “s6” (2). Posterior segment of frontal, sphenotic and otic canals fused to each other. Antorbital segment of infraorbital line absent (16*). Sphenotic canal present (16*) with two pores (“i10” and “i11”); one of them with pore “i10” absent on left side and one of them with extra pore near to “i11” on left side. Otic, postotic and scapular canals present (16*) with preoperculo-mandibular and pterotic branches short and with one associated pore each. Trunk canal short with two pores (16*).

Coloration in alcohol. Dorsal and lateral surfaces of body with scattered black round blotches (equivalent in size to eye circumference) over reddish brown background ( Fig. 1). Blotches more conspicuous in dorsolateral surface. Ventral surface of body white with few brown spots along pelvic fin insertion to caudal peduncle. Dorsal and lateral surfaces of head with black blotches over reddish brown background; larger black blotch in region of parietosupraoccipital bone. Maxillary and nasal barbels with reddish brown blotches over light-yellow background; blotches more concentrated near base. Rictal barbel light yellow. Anal, dorsal, pelvic and pectoral fins with scattered round black blotches over light brackground. Caudal fin with black blotches forming vertical stripes over light brackground; distal stripe larger.

Geographical distribution. Ituglanis inusitatus is so far known only from four localities of the rio Ibicuí and rio Butuí basins, tributaries of the left bank of the rio Uruguai ( Fig. 5), State of Rio Grande do Sul, southern Brazil. These localities are included in the Pampa grasslands, the southernmost Brazilian biome according to IBGE (2004). Ituglanis australis and Ituglanis sp. 3 are the two congeners found in the rio Uruguai basin. Despite this fact, the three species have never been collected sintopically: I. australis is distributed over a larger area in the rio Uruguai basin and occurs in the south tributaries of the laguna dos Patos system, restricted to the Pampa biome; and Ituglanis sp. 3 is so far known from only a few localities in the rio Uruguai basin ( Fig. 5), all inside the Atlantic forest biome. Ecological notes. The arroio São João ( Fig. 6; type locality) and its unnamed tributary are surrounded by preserved riparian vegetation. The bottom is mostly sandy (granulation of 0.6-2.0 mm) with few fallen leaves and branches. Water velocitywasmoderateattypelocalityanditsphysicochemical parameters between 2.40 and 4.00 pm were as follows: temperature (20.4°C), dissolved oxygen (6.85 mg /L), pH (5.76) and specific conductive (22.7 µS/cm). According to R. Dala-Corte, PhD (oral communication, November 2016), all three specimens collected at type locality were not visible on sand bottom until the use of the electroshock. The following species were collected with Ituglanis inusitatus at the type locality, not necessarily in the same microhabitat: Bryconamericus iheringii (Boulenger) , Bunocephalus doriae Boulenger , Crenicichla lepidota Heckel , Eigenmannia trilineata López & Castello , Hisonotus charrua Almirón, Azpelicueta, Casciotta & Litz , Phalloceros caudimaculatus (Hensel) , Pseudohemiodon laticeps (Regan) , Rineloricaria stellata Ghazzi and Scleronema operculatum Eigenmann.

Etymology. From Latin inusitatus (unusual, rare) in reference to the recent discovery of the new species (see discussion). Treated as an adjective.

Conservation status. Ituglanis inusitatus is known from only four localities corresponding to an Extent of Occurrence (EOO) of approximately 1,400 km 2. Although the species seems to be rare and known only from habitats with preserved riparian vegetation, no specific treats were detected and the species can be classified as LC according to IUCN criteria (IUCN, 2016).