Ituglanis compactus, Castro, Íthalo Da Silva & Wosiacki, Wolmar Benjamin, 2017

Castro, Íthalo Da Silva & Wosiacki, Wolmar Benjamin, 2017, Ituglanis compactus, a new species of catfish (Siluriformes: Trichomycteridae) from the rio Jari drainage, lower Amazon, Brazil, Zootaxa 4244 (2), pp. 207-218 : 208-213

Ituglanis compactus , new species

( Figs. 1 and 2 , Table 1 )

Holotype. INPA –ICT 0 53200, 25.6 mm SL, Brazil, Amapá, Laranjal do Jari municipality, rio Iratapuru, left tributary of the rio Jari ; June 1987; M. Jégu & J. Zuanon.

Paratypes. INPA 13006, 35 + 1c&s (12.5–25.8 mm SL); MPEG 34486, 4 + 4 c&s, (18.6–25.6 mm SL); MZUSP 121276, 5 , (16.8–21.6 mm SL), same data as holotype.

Diagnosis. Ituglanis compactus is distinguished from all other congeners, except I. amazonicus ( Steindachner 1882) , I. apteryx Datovo 2014 , I. eichhorniarum ( Miranda Ribeiro 1912) , I. gracilior ( Eigenmann 1912) , I. ina Wosiacki, Dutra & Mendonça 2012 , I. macunaima Datovo & Landim 2005 , I. nebulosus de Pinna & Keith 2003 , and I. parkoi ( Miranda Ribeiro 1944) , by the number of ribs reduced to two pairs (vs. four in I. cahyensis Sarmento-Soares, Martins-Pinheiro, Aranda & Chamon 2006 ; five in I. epikarstikus Bichuette & Trajano 2004 ; five or six in I. agreste Lima, Neves & Campos-Paiva 2013 , I. australis Datovo & de Pinna 2014 , and I. boitata Ferrer, Donin & Malabarba 2015 ; six in I. mambai Bichuette & Trajano 2008 , I. paraguassuensis Campos-Paiva & Costa 2007 , I. parahybae ( Eigenmann 1918) , and I. proops ( Miranda Ribeiro 1908) ; six or seven in I. bambui Bichuette & Trajano 2004 and I. ramiroi Bichuette & Trajano 2004 ; 6–8 in I. passensis Fernández & Bichuette 2002 ; and six to eight in I. boticario Rizzato & Bichuette 2014 ). Moreover, I. compactus differs in the smaller number of vertebrae, 36 or 37 (vs. 38 or 39 in I. eichhorniarum ; 38–40 in I. ina ; 41–43 in I. amazonicus , I. gracilior ; 42 in I. metae ( Eigenmann 1917) ; 42 or 43 in I. herberti ; 43 in I. parkoi ; and 43–45 in I. apteryx ). Ituglanis compactus also differs from I. guayaberensis ( Dahl 1960) , and I. parkoi in the rounded caudal fin (vs. truncate). Ituglanis compactus is distinguished from I. nebulosus in the reduced number of interopercular odontodes, 12–15 (vs. 17); and seven or eight branchiostegal rays (vs. six). Ituglanis compactus is distinguished from I. nebulosus and I. amazonicus by the presence of an elongated fontanel in the parieto-supraoccipital (vs. fontanel reduced to a small orifice). Ituglanis compactus differs from I. macunaima by the presence of a fontanel in the parieto-supraoccipital (vs. absent); by the presence of cephalic pores s1, i1 and i3 (vs. absent) and by the number of rays in the pectoral fins i,5 (vs. i,4). Ituglanis compactus also differs from I. amazonicus by the head length, 18.9–25.0 (vs. 14.5–17.9). Ituglanis compactus is distinguished from I. goya Datovo, Aquino & Langeani 2016 by the presence of the anterior cranial fontanel (vs. absence). Ituglanis compactus is distinguished from I. laticeps ( Kner 1863) by caudal peduncle length 7.8–8.5 in standard length [vs. 5.5; Eigenmann (1918)].

Description. Species of small size, largest specimen, 25.8 mm SL. Morphometric data in Table 1 . Body elongate and laterally compressed in posterior direction. Dorsal profile of body slightly convex, ventral profile of body straight ( Fig. 1 ).

Head longer than wide, slightly depressed, trapezoidal in dorsal view, wider at posterior margin of opercle. Anterior margin of snout slightly elongated. Eyes rounded located dorsally on anterior half of head; without free margin, orbits covered by fine and translucent membrane. Anterior nostril encircled by membrane forming small tube from which nasal barbel extends. Posterior nostril located nearer margin of orbit than anterior nostril, occluded anteriorly by fold of integument shaped like a half-shell.

Mouth subterminal, margins slightly curved ventrally in frontal view; lower lip with fold of integument continuous with base of rictal barbel. Maxillary barbel depressed and elongated, inserted at corner of mouth; distal extremity passing insertion of pectoral fin when distended. Rictal barbel under maxillary barbel; extremity not reaching posterior portion of insertion of pectoral fin. Nasal barbel located laterally from anterior nostril; distal extremity reaching posterior portion of opercular patch of odontodes. Branchial membrane thick, attached to isthmus at anterior portion.

Pectoral fin inserted just posterior to interopercular patch of odontodes ( Fig. 2 ); pectoral-fin rays i,5(33*) or i,6(17); first ray not branched, more robust than the others, distinctly longer, up to 17.8% of SL, prolonged as filament; remaining rays with one branch, getting gradually smaller, making margin oblique. Pelvic-fin rays, i,4; distal edge of pelvic fin when depressed not passing origin of anal-fin. Anal and urogenital openings at posterior half of length of pelvic fin. Dorsal fin semicircular, distal margin rounded, origin on posterior half of body; dorsal rays, ii,6(7) or ii,7(43*); branched rays single branching; two or three supernumerary rays anterior to origin. Analfin origin on line passing over base of first branched ray of dorsal fin; length base similar to dorsal-fin base, distal margin rounded; anal-fin rays, ii,5.

Caudal peduncle short and compressed. Caudal fin slightly rounded; principal caudal-fin rays, i,5/5,ii(4), i,5/ 6,i(45*) or i,6/6,i(1). Procurrent caudal-fin rays beginning at anterior half-length of caudal peduncle; 10–14 dorsally and 9–11 ventrally.

Osteology. Anterior margin of mesethmoid straight, wide axis. Conspicuous concavity in anterior margin of autopalatine; posterior process moderately long and wide at base. Premaxilla rectangular, two regular rows of 13– 16 conical teeth. Triangular mandible, two irregular rows of 15–18 conical teeth. Sphenotic in anterior direction. Sphenotic, prootic, and pterosphenotic fused with anterior projection and opening of infraorbital sensory canal. Fontanels restricted to a small opening; anterior elongated between frontals, posterior at parieto-supraoccipital. Weberian apparatus with small lateral openings and tiny pores along its entire surface ( Fig. 3 ).

Opercular patch of odontodes small and rounded, arranged dorsolaterally in posterior region of head, reaching base of pectoral fin; 8–10 long, straight odontodes. Interopercular patch of odontodes elongated, curved in posterior region, arranged ventrolaterally on head, slightly anterior of opercular patch; 12–15 long, straight odontodes ( Fig. 4 ).

Urohyal with two long, lateral, laminar processes, wide from base to medial portion, narrowing gradually towards distal extremity. Branchiostegal rays seven or eight, seventh notably expanded in its posterior extremity. First basibranchial absent, second and third basibranchials ossified with cartilaginous extremities; fourth basibranchial elongated and cartilaginous. First hypobranchial ossified, elongated and slightly twisted; second hypobranchial elongated, slightly trapezoidal, mostly cartilaginous, anterolateral process ossified; third hypobranchial depressed, mostly cartilaginous, anterolateral process ossified too. First, second, third, and fourth ceratobranchials ossified, cartilaginous extremities; fifth ceratobranchial curved, small teeth present on anterior half. First epibranchial with long anterior process; second epibranchial with two small alternating processes; third with rounded posterior process; fourth flattened, slightly rectangular; fifth reduced, cartilaginous when present. First and second pharyngobranchials absent; third and fourth slightly twisted, fourth attached to dental plate. Pharyngeal dental plate with conical teeth arranged ventromedially in two rows.

Cleithrum approximately rectangular or triangular in ventral view. Scapulocoracoid in lateral region of cleithrum, approximately rectangular in ventral view.

Two pairs of ribs. First hemal canal complete on third vertebrae after Weberian apparatus. First hemal spine complete between vertebrae 14 and 16. Total number of vertebrae 36 or 37. Two vertebrae between first pterygiophore of dorsal fin and first pterygiophore of anal fin. Eight dorsal pterygiophores located between neural spines of vertebrae 23 and 27. Six anal pterygiophores between hemal spines of vertebrae 24 and 27.

Caudal skeleton composed of the parhypural fused to hypurals 1 and 2, hypural plates fused, probably 3 and 4, and hypural 5 free. Uroneural, central preural 1 and neural arch of central preural 1 fused. Neural and hemal spines of the preural centrum 2 ( Fig. 5 a).

Pores present on cephalic laterosensory canals. Supraorbital pores s1, s3, and s6 supraorbital; s1 between and immediately behind anterior nostril; s3 between and just behind posterior nostril; s6 posterior to interorbital region. Pores i1 and i3 of infraorbital canal located anteriorly, near base of nasal barbel; i10 and i11 located posteroventrally to interorbital region. Pores po1 and po2 of postotic canal, po1 anterodorsal to opercular patch of odontodes and po2 posterolateral to opercular patch of odontodes. Lateral line short, with two pores, ll1 and ll2, posteriorly to opercle and posterodorsal to pectoral-fin base.

Coloration in alcohol. Specimens contain no chromatophores on body, pale yellow to light orange coloration in dorsolateral region, gradually becoming lighter in ventral and caudal regions, probably due the long date and exposure to light.

Notes on conservation. Ituglanis compactus was found only along the rio Iratapuru. It occurs outside the boundaries of two protected areas in Amapá State, the rio Cajari Extractive Reserve ( RESEX), a federal conservation area for sustainable use with an area of 481,650 hectares, and the Uitapuru Sustainable Development Reserve ( RDS) with an area of 806,180 hectares. The main threat to the conservation of Ituglanis compactus is the hydroelectric dam of Santo Antônio do Jari, located between the municipalities of Almeirim in Pará and Laranjal do Jari in Amapá, because it abruptly alters the natural characteristics of the regional aquatic ecosystem and can affect the survival of this and other species.

Distribution. Ituglanis compactus is known only from the type locality on the rio Iratapuru, a left-bank tributary of the rio Jari, Amapá State, Brazil ( Fig. 6 ).

Etymology. From the Latin, compactus ; in reference to the small body size and internal and external characters maintained compared to the larger size congeners.

Figures

FIGURE 1. Ituglanis compactus, INPA 13006, holotype, 25.6 mm SL, lateral view of left side; Brazil, Amapá, Laranjal do Jari, rio Iratapuru, tributary of the rio Jari.

FIGURE 2. Ituglanis compactus, INPA 13006, holotype; lateral view of left side of head. Scale bar = 2 mm.

FIGURE 3. Dorsal view of skull and Weberian apparatus of Ituglanis compactus, paratype, INPA 13006, 22.4 mm SL. AOR, antorbital; APA, autopalatine; EPO, epioccipital; FRO, frontal; i 1 – 11, infraorbital sensory pores 1 to 11; laf, ramus lateralis acessorius facialis foramen; LET, lateral ethmoid; MAX, maxila; MET, mesethmoid; PMX, premaxila; po 1 – 2, postotic sensory pores 1 to 2; PSC, “ posttemporosupracleithrum ”; PSO, parieto-supraoccipital; PTE, pterotic; SOR, supraorbital tendon-bone; s 1 – 6, supraorbital sensory pores 1 to 6; SPH + POT + PSF, sphenotic + prootic + pterosphenoid; WEB, Weberian apparatus. Left laterosensory canals and pores do not view. Scale bar = 1 mm.

FIGURE 4. Left view of the suspensorial and opercular series of Ituglanis compactus, paratype, INPA 13006, 22.4 mm SL. HYO, hyomandibula; IOP, interopercle; MPT, metapterygoid; OPE, opercle; POP, preopercle; QUA, quadrate. Scale bar = 0.5 mm.

FIGURE 5. Left side view of the caudal skeleton. a) Ituglanis compactus, INPA 13006, 22.4 mm SL; b) Ituglanis gracilior, MCP 36241, 42.4 mm SL; c) Ituglanis macunaima, MZUSP 103799, 46.3 mm SL; d) Ituglanis proops, MZUSP 60255, 55.6 mm SL. NPU 1, neural arch of the preural centrum 1; PU 1 + U 1, compound centrum formed from preural 1 and ural centrum 1; PU 2, preural centrum 2; HE, hemal spine; NE, neural spine; NSPU 1, neural spine of the preural centrum 1; H 3, hypural 3; H 4 + H 5, hypurals 4 and 5 fused; H 3 + H 4 + H 5, hypurals 3, 4 and 5 fused; PH + H 1 + H 2, parhypural and hypurals 1 and 2 fused; UN, uroneural. Scale bar = 1 mm.

FIGURE 6. Geographic distribution of Ituglanis compactus, indicating type locality (yellow circle) in the rio Iratapuru, a tributary of the rio Jari, Amapá, Brazil.

Tables

TABLE 1. Morphometric data of Ituglanis compactus (holotype and 49 paratypes). SD: Standard deviation.

Standard length (mm)	Holotype 25.6	Range (Min.–Max.) 12.5–25.8	Mean –	SD –
Percents of Standard Length Total length Body depth	119.8 16.1	114.4–125.9 11.7–17.0	120.1 14.3	2.2 1.3
Caudal peduncle depth Caudal peduncle length Predorsal length	11.6 14.9 74.5	8.9–12.5 11.1–19.7 70.0–80.5	10.7 15.4 75.2	0.7 1.6 2.3
Preanal length Prepelvic length Dorsal-fin base length	75.4 62.5 9.4	71.7–80.3 59.8–74.3 7.2–13.2	76.0 67.0 10.2	1.7 2.5 1.2
Anal-fin base length First pectoral-fin length Head length	8.9 9.8 18.9	7.3–10.6 9.8–22.5 18.9–25.0	8.9 16.1 20.8	0.7 2.4 1.0
Percents of Head Length Head depth Head width	86.4 41.0	74.4–101.7 34.3–58.2	84.8 48.0	5.5 5.1
Interorbital width Snout length Eye diameter	24.2 26.4 10.1	21.4–31.5 19.8–33.5 6.9–12.9	25.9 27.3 9.9	2.3 2.5 1.0
Width of mouth Nasal barbel length Maxilar barbel length	49.6 50.0 81.8	36.3–54.2 33.5–63.6 34.9–97.6	46.1 51.1 77.5	4.1 6.6 13.6
Rictal barbel length	55.8	22.8–80.3	56.2	12.7