Corydoras pavanelliae, Tencatt & Ohara, 2016

Tencatt, Luiz Fernando Caserta & Ohara, Willian Massaharu, 2016, Two new species of Corydoras Lacépède, 1803 (Siluriformes: Callichthyidae) from the rio Madeira basin, Brazil, Neotropical Ichthyology (Neotrop. Ichthyol.) 14 (1), No. e 150063, pp. 1-16 : 8-11

Corydoras pavanelliae , new species

urn:lsid:zoobank.org:act:3DDD5672-0B60-49C4-8720-E7DA1013CDE3

( Figs. 2c,d , 3b,d , 6 , Table 1)

Holotype. MNRJ 43317 , 45.1 mm SL, Brazil, Mato Grosso State, Colniza Municipality, Guariba District, tributary to the rio Guariba , rio Aripuanã drainage, rio Madeira basin, 09°06’47.4”S 60°25’14.1”W, 15 Jul 2013, W. M. Ohara, D. B. Hungria & B. Barros.

Paratypes. INPA 48033 , 5 , 22.5-23.2 mm SL ; MCP 48748, 5 , 19.0- 23.5 mm SL ; MZUSP 117335 , 10 , 21.8-25.4 mm SL ; NUP 17314, 17 , 20.8-30.7 mm SL ; NUP 17315, 3 c&s, 24.7- 26.8 mm SL ; ZUFMS-PIS 4064 , 8 , 20.0- 22.9 mm SL; same data as the holotype .

Diagnosis. Corydoras pavanelliae can be distinguished from its congeners, with exception of species from lineages ‘4’, ‘5’, ‘6’, ‘7’ and ‘9’ sensu Alexandrou et al. (2011) by the presence of a short mesethmoid, with anterior portion smaller than 50% of the bone length (vs. long, equal or larger than 50% of the bone length). Corydoras pavanelliae can be distinguished from species of lineages ‘4’, ‘5’ and ‘7’ sensu Alexandrou et al. (2011) by the absence of contact between infraorbital 2 and compound pterotic ( Figs. 2c,d ) (vs. presence (see Tencatt & Pavanelli (2015: 291, fig. 3))). Corydoras pavanelliae can be distinguished from lineages ‘6’ and ‘9’ sensu Alexandrou et al. (2011), withtheexception of C. axelrodi , C. evelynae , C. loxozonus , C. parallelus Burgess, 1993 , C. schwartzi and C. surinamensis , by the presence of two or three longitudinal black stripes on flanks (vs. a longitudinal black stripe along midline of flank in C. acrensis , C. baderi , C. boesemani , C. bondi Gosline, 1940 , C. coppenamensis Nijssen, 1970 , C. habrosus , C. julii Steindachner, 1906 , C. nattereri , C. sipaliwini , C. trilineatus Cope, 1872 ; a longitudinal series of large black blotches along midline of flank in C. diphyes Axenrot & Kullander, 2003 , C. ehrhardti Steindachner, 1910 , C. flaveolus Ihering, 1911 , C. longipinnis Knaack, 2007 , C. paleatus ( Jenyns, 1842) , C. reynoldsi Myers & Weitzman, 1960 and C. tukano Britto & Lima, 2003; flanks densely covered by small rounded black spots, which can be diffuse or absent in some specimens, in C. albolineatus Knaack, 2004 and C. potaroensis Myers, 1927 ; a single oblique black stripe from dorsal-fin base region descending to base of caudal peduncle in C. melini Lönnberg & Rendahl, 1930 ; four to six longitudinal rows of black spots on flanks, which may be coalescent and form stripes in some specimens of C. sterbai Knaack, 1962 ; presence of a single arched black stripe on dorsal portion of flank in C. urucu ; absence of stripes on flanks in remaining species). Corydoras pavanelliae can be distinguished from C. axelrodi , C. evelynae , C. loxozonus , C. parallelus , C. schwartzi and C. surinamensis by the absence of an oblique or vertical black blotch across the eye (vs. presence); from C. axelrodi , C. evelynae , C. loxozonus , C. parallelus and C. surinamensis by presenting anterior portion of dorsal fin with sparse black chromatophores, not forming any conspicuous pattern (vs. entirely or almost entirely conspicuously blackened); from C. evelynae and C. schwartzi by having ventral surface of trunk naked or covered by sparse platelets (vs. densely covered by coalescent platelets).

Description. Morphometric data presented in Table 1. Head compressed with convex dorsal profile; triangular in dorsal view. Snout short and slightly pointed. Head profile convex from tip of snout to anterior nares; ascending nearly straight from this point to tip of posterior process of parieto-supraoccipital; region just anterior to nares slightly concave in some specimens. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile nearly straight to adipose-fin spine; concave from this point to caudal-fin base. Ventral profile of body slightly convex from isthmus to pelvic girdle. Profile nearly straight from pelvic girdle to base of first anal-fin ray; abruptly concave from this point to caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye rounded, located dorso-laterally on head; orbit delimited dorsally by lateral ethmoid, frontal and sphenotic, ventrally by infraorbitals. Anterior and posterior nares close to each other, only separated by flap of skin. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from it by distance equal to naris diameter. Mouth small, subterminal, width nearly equal to bony orbit diameter. Maxillary barbel moderate in size, not reaching anteroventral limit of gill opening. Outer mental barbel slightly larger than maxillary barbel. Inner mental barbel fleshy, base slightly separated to its counterpart; insertion of barbel in middle of lower lip. Small rounded papillae covering entire surface of all barbels, upper and lower lips, and isthmus.

Mesethmoid short; anterior tip moderately developed, smaller than 50% of bone length (see Britto, 2003: 123, character 1, state 1; fig. 1B); posterior portion relatively wide and entirely covered by thick layer of skin. Nasal slender, curved laterally, with inner margin laminar; mesial border contacting only frontal. Frontal elongated, narrow, with width slightly smaller than half of entire length; anterior projection short, size smaller than nasal length. Frontal fontanel large, oval; posterior tip extension slightly entering anterior margin of parieto-supraoccipital. Parietosupraoccipital wide, posterior process long and contacting nuchal plate; region of contact between posterior process and nuchal plate covered by thick layer of skin.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion poorly developed; moderately developed in larger specimens (see Britto, 2003: 128, fig. 5B); anterior portion with well-developed expansion ( Fig. 2c ); infraorbital 2 small, slender; with posterior laminar expansion very reduced; posteroventral margin contacting posterodorsal ridge of hyomandibula, dorsal tip contacting only sphenotic ( Fig. 2d ). Posterodorsal ridge of hyomandibula close to its articulation with opercle oblong; slender, exposed and bearing small odontodes; dorsal ridge of hyomandibula between compound pterotic and opercle covered by thick layer of skin. Interopercle entirely covered by thick layer of skin, somewhat triangular, anterior projection well-developed. Preopercle slender, elongated, minute odontodes sparse on external surface. Opercle elongated dorso-ventrally, width smaller than half of its length; free margin smoothly convex, without serrations and covered by small odontodes. Anteroventral portion of cleithrum and posterolateral portion of scapulocoracoid exposed; minute odontodes sparse on exposed areas. Vertebral count 21 (3); ribs 6 (3), first pair conspicuously large; complex vertebra compact in shape. Neural and haemal spines with pointed distal tips.

Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossified portion well developed, about twice size of cartilaginous portion. Five ceratobranchials with expansions increasing posteriorly; ceratobranchial 1 with small process on anterior margin of mesial portion; ceratobranchial 3 notched on postero-lateral margin; ceratobranchial 5 toothed on postero-dorsal surface, 33 to 39 (3) teeth aligned in one row. Four epibranchials with similar size; epibranchial 2 slightly larger than others, with small pointed process on laminar expansion of posterior margin; epibranchial 3 with curved mesially uncinate process on laminar expansion of posterior margin. Two wide pharyngobranchials (3 and 4), pharyngobranchial 3 with small triangular laminar expansion on posterior margin. Upper tooth plate oval; 41 to 43 (3) teeth aligned in two rows on postero-ventral surface.

Lateral-line canal entering neurocranium through compound pterotic, splitting into two branches before entering sphenotic: pterotic branch with a single pore; preoperculomandibular branch conspicuously reduced, with a single pore opening close to postotic main canal. Sensory canal continuing through compound pterotic, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch entering frontal through supraorbital canal, both with a single pore. Supraorbital canal not branched, running through nasal bone. Epiphyseal pore opening at supraorbital main canal. Nasal canal with three openings, first on posterior edge, second on posterolateral portion and third on anterior edge. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two pores. Preoperculomandibular branch giving rise to preoperculo-mandibular canal, which runs through entire preopercle with three openings, leading to pores 3, 4, and 5, respectively.

Dorsal fin triangular, located just posterior to second dorsolateral body plate. Dorsal-fin rays II,8, posterior margin of dorsal-fin spine with nine to 12 reduced serrations directed towards tip of spine; serrations absent proximally ( Fig. 3b ). Nuchal plate moderately developed; exposed, with minute odontodes; spinelet short; spine relatively large, adpressed distal tip surpassing last dorsal-fin branched ray origin; anterior margin with small odontodes. Pectoral fin triangular, its origin just posterior to gill opening. Pectoral-fin rays I,8 (17), I,9* (3); posterior margin of pectoral-fin spine with 17 to 22 small serrations along its entire length; serrations directed towards pectoral-fin spine tip ( Fig. 3d ). Pelvic fin oblong, located just below first ventrolateral body plate, and at vertical through first branched dorsal-fin ray. Pelvic-fin rays i,5. Adipose fin roughly triangular, separated from base of last dorsal-fin ray by generally six dorsolateral body plates. Anal fin triangular, located just posterior to 12 th ventrolateral body plates, and at vertical through anterior margin of adipose-fin spine. Anal-fin rays ii,6. Caudal-fin rays i,12,i, generally four dorsal and ventral procurrent rays; bilobed; dorsal lobe generally slightly larger than ventral lobe.

Three laterosensory canals on trunk; first ossicle tubular, second ossicle laminar, third canal encased in third dorsolateral body plate. Body plates with minute odontodes scattered over exposed area, a conspicuous line of odontodes confined on posterior margins; dorsolateral body plates 22 (4), 23* (14), 24 (2); ventrolateral body plates 20* (12), 21 (8); dorsolateral body plates along dorsal-fin base 6* (18), 7 (2); dorsolateral body plates between adipose and caudal fins 6 (7), 7* (12), 8 (1); preadipose platelets 2 (1), 3* (18), 4 (1); small platelets covering base of caudal-fin rays; small platelets disposed dorsally and ventrally between junctions of lateral plates on posterior portion of caudal peduncle. Anterior margin of orbit, above lateral ethmoid, covered with small platelets bearing odontodes. Ventral surface of trunk covered by sparse platelets; naked in some specimens.

Color in alcohol. Overall color of body in Fig. 6 . Ground color of body light yellow, with top of head and snout dark brown; parieto-supraoccipital entirely dark brown. Maxillary barbel and proximal region of outer mental barbel covered by black chromatophores. Anterior portion of body with irregular black blotches. Posterior margin of first and second dorsolateral body plates blackened. Dorsal portion of body irregularly black pigmented, forming diffuse slender longitudinal black stripe, more conspicuous from dorsal-fin base to adipose-fin origin. Body with two or three conspicuous longitudinal black stripes. Medial portion of dorsal half of dorsolateral body plates with black blotches anteriorly to adipose fin; blotches aligned forming short and narrow longitudinal stripe below dorsal-fin base in some specimens. Midventral half of dorsolateral body plates blackened, forming broad longitudinal stripe along flank. Dorsal half of medial portion of ventrolateral body plates blackened, forming slender longitudinal black stripe along flank; stripe absent or diffuse posteriorly to analfin last branched ray region. Dorsal fin covered by sparse brown chromatophores, more concentrated on its base; upper half of first and second dorsal-fin rays, including membranes, with more concentrated black chromatophores; dorsal-fin spine brownish. Pectoral-fin rays with sparse black chromatophores; pectoral-fin spine brownish. Pelvic fin hyaline. Adipose fin with posterior margin brownish or blackened; adipose-fin spine dorsal half blackened. Caudal fin with scattered brownish chromatophores; black spots arranged in one to four transversal black bars; bars diffuse or absent in some specimens; caudal-fin base blackened; region just posterior to caudal fin base hyaline and with light yellow pigmentation.

Sexual dimorphism. Except for the presence of lanceolate genital papilla in males, which occurs in all Corydoradinae (see Nijssen & Isbrücker, 1980; Britto, 2003), no other sexually dimorphic feature was observed.

Distribution. The new species is known from its typelocality, a tributary to the rio Aripuanã, Mato Grosso State ( Fig. 5 ).

Ecological notes. The only known specimens of Corydoras pavanelliae were collected among C. brittoi specimens. For notes on its ecology, see Ecological notes of C. brittoi .

Etymology. Corydoras pavanelliae is named in honor of Carla Simone Pavanelli, advisor of the first author and dear friend, forherextensivecontributionstotheknowledgeofthe ecology and taxonomy of the Neotropical fishes. A genitive.

Conservation status. The known specimens of Corydoras pavanelliae are relatively numerous and were collected among C. brittoi specimens. For this reason, we also suggest that C. pavanelliae would be classified as Least Concern (LC) according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014).

Figures

Fig. 2. Lateral view of the head of c&s specimens of Corydoras brittoi, NUP 17313, 34.1 mm SL, showing the poorlydeveloped ventral expansion of the infraorbital 1 (a) and infraorbital 2 in contact with compound pterotic (b), and of Corydoras pavanelliae, NUP 17315, 25.4 mm SL, showing the poorly-developed ventral expansion of the infraorbital 1 (c) and infraorbital 2 not in contact with compound pterotic (d). The dotted lines in (b) and (d) represent the suture between sphenotic and compound pterotic bones. Abbreviations: io1: infraorbital 1, io2: infraorbital 2, sph: sphenotic, cpt: compound pterotic. Scale bar = 1.0 mm.

Fig. 3. Dorsal- and pectoral-fin spines of (a, c) Corydoras brittoi, NUP 17313, 34.1 mm SL, showing serrations directed towards the origins of the spines on posterior margins of the (a) dorsal-fin spine (8.6 mm long) and of the (c) right pectoral-fin spine (8.9 mm long), and of (b, d) Corydoras pavanelliae, NUP 17315, 26.8 mm SL, showing serrations directed towards the tips of the spines on posterior margins of the (b) dorsal-fin spine (7.9 mm long) and of the (d) right spine (7.6 mm long).

Fig. 6. Corydoras pavanelliae, holotype, MNRJ 43317, 45.1 mm SL, Brazil, Mato Grosso State, Colniza Municipality, Guariba District, tributary to the rio Guariba, rio Aripuanã drainage, rio Madeira basin, 09°06’47.4”S 60°25’14.1”W. Dorsal (top), lateral (middle) and ventral (bottom) views. Photo by Celso Ikedo.

Fig. 5. Map showing the type-locality (red circle) of Corydoras brittoi and Corydoras pavanelliae, a tributary to the rio Guariba, Mato Grosso. The blue triangle represents the Igarapé Pica-Pau, also a tributary to the rio Guariba, and the yellow triangle represents the rio Aripuanã, both representing additional records of C. brittoi.