Corydoras ortegai, Britto & Lima & Hidalgo, 2007

Britto, Marcelo R., Lima, Flávio C. T. & Hidalgo, Max H., 2007, Corydoras ortegai, a new species of corydoradine catfish from the lower río Putumayo in Peru (Ostariophysi: Siluriformes: Callichthyidae), Neotropical Ichthyology 5 (3), pp. 293-300 : 294-297

Corydoras ortegai , new species

Figs. 1-3

Holotype. MUSM 28000 , 32.7 mm SL, Peru, Departamento Loreto, Provincia Maynas, río Putumayo basin, Quebrada Coronel Díaz , tributary to río Yaguas , 2º51’13”S, 71º27’02”W (UTM 19M 0231999/9683442), altitude 92 m, 5 Aug 2003; M. Hidalgo & R. Oliveira.

Paratypes. 102 specimens. All from Peru, Departamento Loreto, Provincia Maynas , río Putumayo basin: MNRJ 29404 , 8 , 3 cs, 18.9-28.9 mm SL (5, 25.0- 28.9 mm SL); MUSM 26961 , 23 , 12.5- 25.8 mm SL (12, 21.8-25.8 mm SL); MUSM 27154 , 27 , 17.0- 28.2 mm SL (5, 25.0- 28.2 mm SL); MZUSP 91411 , 8 , 18.4-28.3 mm SL (1, 28.3 mm SL), collected with the holotype. FMNH 117263 , 8 , 16.6-18.3 mm SL; MUSM 27155 , 28 , 18.4-31.2 mm SL (4, 25.9- 31.2 mm SL), río Yaguas , 2º51’41”S, 71º24’38”W (UTM 19M0231996/9683445), altitude 99 m, 7 Aug 2003; M. Hidalgo & R. Oliveira .

Diagnosis. Corydoras ortegai is distinguished from all other species of Corydoras , except C. panda , C. reynoldsi , C. weitzmani , and C. tukano , by having a transverse, dark bar (“mask”) across the orbit, and ground color of body uniform with large, dark rounded blotch midlaterally on trunk below adipose fin. The new species is distinguished from C. reynoldsi , C. weitzmani , and C. tukano by the absence of a midlateral trunk blotch at the dorsal-fin level, and the rounded shape of the trunk blotch at adipose-fin level. Corydoras ortegai differs from C. panda by its greater number of lateral body plates (24 dorsolateral/ 21-22 ventrolateral vs. 22-23/20), dark brown dorsal-fin blotch absent (vs. present), several scattered chromatophores surrounding yellowish white area on midregion of cleithrum (vs. chromatophores absent or nearly absent on cleithrum), caudal fin with narrow series of dark brown blotches restricted to rays (vs. caudal fin hyaline), a slenderer body (depth of body 28.3-35.1% SL vs. 40.0% SL), and a narrower intercleithral area (maximum cleithral width 10.7-15.5% SL vs. 18% SL).

Another feature helpful to distinguish the new species from its congeners is the unique condition of its inner mental barbels, which are distinctly separated only at their distal tips (vs. barbels distinctly separated along their entire lengths). Although an exclusive character-state among corydoradine catfishes, this condition is variable among Corydoras ortegai specimens.

Description. Morphometric data presented in Table 1. Head compressed, roughly triangular with rounded apex in dorsal view; dorsal profile slightly convex, nearly straight, rising moderately from nares to tip of parieto-supraoccipital process ( Fig. 3 ). Snout profile rounded from upper lip to horizontal through anterior nares. Dorsal profile of body slightly convex from tip of parieto-supraoccipital process to last dorsalfin ray, then slightly concave to adipose-fin spine and descending straight downwards from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to anal-fin origin, mainly in pectoral- and pelvic-girdle region. Profile markedly straight, ascending obliquely from first analfin ray to caudal-fin base. Body roughly triangular in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye round, located dorso-laterally on head; orbit delimited dorsally by frontal and sphenotic, ventrally by infraorbitals.Anterior and posterior nares proximal, only separated by flap of skin. Anterior naris tubular; its free tip with minute, roughly lanceolate, fleshy flap. Posterior naris close to anterodorsal margin of orbit, separated from it by distance slightly smaller than naris diameter. Mouth small, subterminal, width nearly equal to bony orbit diameter. Maxillary barbel elongate, usually reaching anteroventral limit of gill opening ( Fig. 3 ). Outer mental barbel slightly shorter than maxillary barbel. Inner mental barbels short, fleshy and depressed; proximal for much of their lengths, separated only at distal tips in most examined specimens. Small rounded papillae covering entire surface of all barbels, upper and lower lips, and isthmus. Gill membranes united to isthmus. Four branchiostegal rays covered by thin layer of skin; lateralmost two rays united at their distal tips by branchiostegal cartilage. Teeth on upper pharyngeal tooth plate 46 (1), or 50 (1), and on fifth ceratobranchial 31 (1), or 38 (1). Tooth plate rounded.

Nasal, frontal, sphenotic, compound pterotic, and parietosupraoccipital visible externally, all covered by thin layer of skin and bearing minute scattered odontodes. Frontal fontanel elongate, ellipsoid, covered by thin layer of skin; posterior tip extending into parieto-supraoccipital. Nasal slender, slightly curved laterally, mesial border contacting frontal. Frontal roughly rectangular; anterior expansion in contact with nasal bone, posterior portion contacting sphenotic and parieto-supraoccipital. Sphenotic trapezoid in shape, contacting parieto-supraoccipital dorsally, compound pterotic posteriorly, second infraorbital ventrally. Compound pterotic roughly pipe-shaped, with slender posterior expansion contacting first dorsal body plate and first lateral-line ossicle. Contact region between compound pterotic and first dorsal body plate covered by area of thick skin. Ventral margin of compound pterotic contacting opercle and cleithrum. Parietosupraoccipital quadrangular with posterior process notched at its tip, sutured with nuchal plate.

Two infraorbital bones, externally visible, covered by thin layer of skin. First infraorbital with slender anterior expansion. Opercle exposed, compact in shape, with free border angular. Preopercle externally visible, slender and covered by thin layer of skin.

Trunk lateral-line with two laterosensory canals, reduced to small ossicles. Two specimens (MUSM 26961, 22.3-24.6 mm SL) with one perforated dorsolateral body plate. Lateralline canal entering neurocranium through compound pterotic, splitting into two branches, pterotic and preoperculomandibular, each with single pore, before entering sphenotic. Sensory canal continuing through compound pterotic, entering sphenotic as temporal canal, which splits into two branches: infraorbital canal, and supraorbital canal entering through frontal bone. Supraorbital canal with two branches: epiphyseal, opening in frontal bone, and anterior, running through nasal bone. Nasal canal with single opening at each end. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two pores. Preoperculomandibular branch giving rise to preoperculomandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively.

Body plates with minute odontodes restricted to posterior margins. Nuchal plate exposed. Cleithrum and mesial process of scapulocoracoid exposed. Minute odontodes scattered over area between scapulocoracoids. Body plates not touching counterparts in specimens up to 24.0 mm SL, leaving narrow naked groove on medial dorsal and ventral surfaces; gap more conspicuous between dorsal body plates. Dorsolateral body plates 24* (n=27), one specimen (MUSM 27155, 26.9 mm SL) with 23 plates; ventrolateral body plates 21* (25), or 22 (3); dorsolateral body plates along dorsal-fin base 6 (3), 7* (10), or 8 (15); dorsolateral body plates from adipose fin to caudal-fin base 8* (27), one specimen (MUSM 27155, 26.9 mm SL) with seven plates; preadipose platelets 3* (17), or 4 (11). Precaudal vertebrae 8, caudal vertebrae 14, in all cleared-and-stained specimens; five pairs of ribs, first pair conspicuously larger than others.

Dorsal fin roughly triangular; its origin just posterior to second or third dorsolateral body plate. Dorsal spine shorter than first branched ray.Anterior margin of dorsal spine smooth; posterior margin with minute serrations. Dorsal-fin rays II,8* (27); II, 9 in one specimen (MUSM 26961, 27.0 mm SL). Adipose fin roughly triangular; its origin separated from base of last dorsal-fin ray by 6-8 dorsolateral body plates. Anal fin roughly triangular; its origin located posterior to 12th or 14th ventrolateral body plates, at vertical through posterior margin of last preadipose platelet. Anal-fin rays ii, 5 in all specimens. Pectoral fin triangular; its origin located just posterior to gill opening. Ossified portion of pectoral spine shorter than first branched ray. Distal tip of spine with minute segmented unossified portion. Pectoral spine flattened with smooth anterior margin and small serrations along entire posterior margin, less conspicuous distally; serrations more developed than in dorsal fin spine. Pectoral-fin rays I,8* (23), or I,7 (5). Pelvic fin ellipsoid; its origin just below first ventrolateral body plate, at vertical through intermembrane between second and third branched dorsal-fin rays. Pelvic-fin rays i, 5 in all specimens. Caudal fin bilobed, weakly forked; lower lobe slightly longer. Principal caudal-fin rays i,6/6,i; upper and lower procurrent caudal-fin rays 4 and 5, respectively. Total number of caudal-fin rays 23. All fins with minute odontodes scattered over all rays.

Color in alcohol. Ground color of head yellowish light brown. Wide, slightly oblique dark brown vertical blotch (“mask”) from top of head across anterior and posterior margins of eye to ventral anterior corner of opercle. Scattered chromatophores over snout and outer mental barbel; remaining barbels yellowish light brown. Scattered chromatophores on posterior process of parieto-supraoccipital; more concentrated on its midline. Surfaces of opercle and preopercle with several, relatively large, scattered chromatophores; chromatophores more concentrated on contact region between both bones.

Ground color of trunk uniform light brown. Large, yellowish white area on midregion of cleithrum, surrounded by several scattered chromatophores concentrated posteriorly. All body plates anterior to adipose and anal fins with irregular, short, narrow patches of scattered chromatophores; patches more concentrated just above and below junction of dorsal- and ventral-body plates, forming two faint, broken longitudinal stripes that fade posteriorly ( Figs. 1 , 2 ). Large, roughly rounded, dark brown blotch midlaterally below adipose fin; blotch fading dorsally and ventrally towards adipose- and anal-fin bases, respectively ( Figs. 1 , 2 ). Region of body plates junction between both blotches without chromatophores. Body plates at caudal peduncle with few chromatophores, some concentrated on dorsolateral plate just posterior to adipose fin. Several chromatophores scattered over preadipose platelets, extending to adipose spine.

Dorsal and pectoral fins hyaline, with few chromatophores concentrated on spines. Adipose-fin membrane hyaline, with few scattered chromatophores. Anal fin hyaline, with few chromatophores concentrated on first ray. Pelvic fin hyaline. Caudal fin with small, dark brown blotches restricted to rays and arranged into three or four, roughly vertical, narrow bands.

Sexual dimorphism. No sexually dimorphic characters found. Corydoradine catfishes often have dimorphic genital papillae (see, e.g. Britto, 2003), but specimens of C. ortegai display no modifications.

Distribution. Corydoras ortegai is only known from tributaries of the Río Yaguas, a tributary of the lower Río Putumayo, in Departamento Loreto, Peru, very close to the border with Colombia and Brazil ( Fig. 4 ).

Habitat and ecological notes. Corydoras ortegai was mostly found inhabiting lotic habitats in the Río Yaguas basin, a whitewater tributary of Río Putumayo. The Río Yaguas has a muddy-brown color, with soft bottom of clay and sand where

C. ortegai was relatively abundant. No individuals were captured in the small black or clearwater forest streams, nor lagoons that were also present in the area. The only congener found living syntopically with C. ortegai at the type locality was C. pastazensis . The region where C. ortegai was discovered has a high diversity of fishes (207 species recorded), and it is being proposed as a new protected area in Peru (Hidalgo & Olivera, 2004).

Etymology. After Hernán Ortega Torres, curator of the fish collection of the Museo de Historia Natural, Universidad Nacional Mayor de San Marcos, in recognition of his deep interest in the freshwater fish fauna of Peru and his contributions to our knowledge of its diversity.

Figures

Fig. 1. Corydoras ortegai, MUSM 28000, holotype, 32.7 mm SL: Peru, Depto. Loreto, Quebrada Coronel Díaz, tributary of río Yaguas.

Fig. 2. Corydoras ortegai, MUSM 28000, holotype, 32.7 mm SL: Peru, Depto. Loreto, Quebrada Coronel Díaz, tributary of río Yaguas. Caudal fin reconstructed after MUSM 27154, 27.7 mm SL.

Fig. 3. Dorsal (left) and ventral (right) views of head and pectoral fins of Corydoras ortegai, MUSM 28000, holotype, 32.7 mm SL: Peru, Depto. Loreto, Quebrada Coronel Díaz, tributary of río Yaguas.

Fig. 4. Northern South America, showing the distribution of Corydoras ortegai (dot), C. panda (diamond), C. reynoldsi (square), C. tukano (triangles), and C. weitzmani (cross). Distribution of C. weitzmani is depicted with its center at Puerto Maldonado, capital of the Departamento Madre de Dios in Peru, since precise localities for the species are not known (see text). Segmented line: Purus structural arch.