Corydoras hephaestus, Ohara, Willian Massaharu, Tencatt, Luiz F. C. & Britto, Marcelo R., 2016

Ohara, Willian Massaharu, Tencatt, Luiz F. C. & Britto, Marcelo R., 2016, Wrapped in flames: Corydoras hephaestus, a new remarkably colored species from the Rio Madeira basin (Teleostei: Callichthyidae), Zootaxa 4170 (3), pp. 539-552 : 540-548

Corydoras hephaestus , new species

( Figs. 1 , 5 , 6 )

Holotype. MZUSP 119087, 22.6 mm SL. Brazil, Rondônia, Vilhena, Rio Madeira basin, upper Rio Machado , tributary of Igarapé Piracolina , near the road BR-364, 12°48’56”S 60°06’37”W; W. M. Ohara, F. C. P. Dagosta & V. Giovannetti, 12 Nov 2014.

Paratypes. All from Brazil, Rondônia State, Vilhena . MZUSP 117059, 3, 24.2–29.4 mm SL, same as holotype. MZUSP 118570, 6 (1 CS, 25,4 mm SL), 25.4–33.2 mm SL, W. M. Ohara, D. B. Hungria & B. S. Barros, 14 Sep 2013 . MZUSP 118571, 1 , 18.9 mm SL, same locality as holotype, I. D. Costa 19 Jul 2013 . MNRJ 13459, 7 (1 CS, 24.7 mm SL), 12.8–34.0 mm SL, Igarapé Piracolina , tributary of Rio Comemoração , G. W. Nunan & W. D. Bandeira, 18 Jul 1986 . INPA 53091, 2, 25.1–26.8 mm SL; MNRJ 46763, 1 , 25.9 mm SL; NUP 18142, 1, 27.8 mm SL, same locality as holotype, W. M. Ohara & P. L. Cunha, 3 Sep 2014 . MCP 36270, 1 , 12.3 mm SL, Rondônia, Vilhena, Igarapé Piracolina , about 6 km to Vilhena on BR-364, 12°43’32”S 60°11’34”W; R. E. Reis, P. A. Buckup, A. R. Cardoso & E. H. L. Pereira, 17 Jul 2004 .

Diagnosis. Corydoras hephaestus can be distinguished from all its congeners, with exception of C. difluviatilis Britto & Castro, 2002 , C. flaveolus Ihering, 1911 , C. gladysae , C. gracilis , C. hastatus Eigenmann & Eigenmann, 1888 , C. latus , C. micracanthus , C. nanus , C. petracinii , C. pygmaeus Knaack, 1966 , and C. undulatus Regan, 1912 , by the absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate (vs. bones in contact). The new species can be distinguished from C. gladysae , C. gracilis , C. hastatus , C. latus , C. micracanthus , C. nanus , C. petracinii , C. pygmaeus and C. undulatus by having a ventral laminar expansion of infraorbital 1 conspicuously well-developed (vs. poorly to moderately developed); from C. difluviatilis and C. flaveolus by having a posterior margin of the pectoral-fin spine with serrations along almost its entire length, only absent on distal portion (vs. serrations, when present, restricted to the proximal portion of the spine).

Description. Morphometric data presented in Table 1 . Head compressed with convex dorsal profile; triangular in dorsal view. Snout moderately developed and pointed. Head profile slightly convex from tip of snout to anterior nares; ascending slightly convex or nearly straight from this point to posterior tip of parieto-supraoccipital process; slightly convex from that point to dorsal-fin origin; region between eye and posterior tip of parieto-supraoccipital slightly concave in specimens with more than 27.0 mm SL. Profile slightly convex along dorsal-fin base. Dorsal body profile posterior to dorsal fin slightly concave to adipose-fin spine; concave from that point to caudal-fin base. Ventral profile of body slightly convex from isthmus to pelvic-fin origin; nearly straight from that point to anal-fin origin; concave to caudal-fin base. Body roughly elliptical in cross section at pectoral girdle, gradually becoming more compressed toward caudal fin.

Eye rounded, located dorsolaterally 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 skin flap. Anterior naris tubular. Posterior naris close to anterodorsal margin of orbit, separated from it by distance equal to naris diameter. Mouth small, subterminal, width slightly larger than bony orbit diameter. Maxillary barbel moderate in size, generally not reaching anteroventral limit of gill opening; surpassing it in two specimens. Outer mental barbel slightly larger than maxillary barbel. Inner mental barbel fleshy, with base close to its counterpart. Lower lip moderately developed, forming small rounded fleshy flap. Small rounded papillae covering entire surface of all barbels, upper and lower lips, and isthmus. Area between junction of opercle and compound pterotic and region of lateral ethmoid with small platelets; ventral surface of trunk with scarce small platelets.

Mesethmoid short; anterior tip relatively poorly developed, slightly smaller than half bone length, covered by thick layer of skin; posterior portion wide and externally visible, covered by thin layer of skin. Nasal slender, curved laterally, inner margin with moderately-developed laminar expansion; outer margin with reduced laminar expansion; mesial border contacting only frontal. Nasal and mesethmoid bones not in contact. Frontal elongated, relatively thick, with width slightly larger than half of entire length; anterior projection short, size smaller than nasal length. Frontal fontanel elongate and narrow; posterior tip surpassing anterior margin of parietosupraoccipital. Parieto-supraoccipital wide, posterior process moderately developed, not contacting nuchal plate ( Fig. 2 ).

Two laminar infraorbitals externally visible, covered by thin layer of skin with minute odontodes. Infraorbital 1 very large, ventral laminar expansion conspicuously well developed, significantly covering lateral portion of snout; anterior portion with well-developed laminar expansion, almost reaching to anterior margin of nasal capsule. Infraorbital 2 small, thickened, with posterior laminar expansion well developed; posteroventral margin contacting posterodorsal ridge of hyomandibula, dorsal tip contacting sphenotic and compound pterotic ( Fig. 3 ). Posterodorsal ridge of hyomandibula close to its articulation with opercle oblong, externally visible, covered by thin layer of skin, relatively slender. Dorsal ridge of hyomandibula between compound pterotic and opercle covered by posterodorsal laminar expansion of infraorbital 2; exposed areas bearing small odontodes. Interopercle almost entirely exposed, somewhat triangular, anterior projection moderately developed. Preopercle approximately at 45° angle relative to longitudinal body axis. Preopercle relatively thick, elongated, minute odontodes sparse on external surface. Opercle compact in shape, width larger than half of its length; free margin convex; posterodorsal region with smoothly concave area in some specimens. Opercle surface 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(2), precaudal and caudal vertebrae 8(2) and 13(2), respectively; ribs 6(2), first pair conspicuously large; complex vertebra slender in shape.

Gill membranes united to isthmus. 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 posterolateral margin; ceratobranchial 5 toothed on posterodorsal surface, 32(1) or 34(1) 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 triangular uncinate process on laminar expansion of posterior margin. Two wide pharyngobranchials (3 and 4), pharyngobranchial 3 with triangular laminar expansion on posterior margin. Upper tooth plate oval; 29(1) or 33(1) teeth aligned in two rows on posteroventral surface.

Lateral-line canal entering neurocranium through compound pterotic, branching twice before entering sphenotic: pterotic branch with single pore; preoperculomandibular branch conspicuously reduced, with 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 single pore. Supraorbital canal branched, running through nasal bone. Epiphyseal branch of supraorbital canal reduced, pore opening close to supraorbital main canal. Nasal canal with three openings, first on posterior edge, second on posterolateral portion, fused with first pore, and third on anterior edge. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two pores. Preoperculo-mandibular 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; posterior margin slightly rounded; located just posterior to third dorsolateral body plate, when adpressed tip not reaching to preadipose platelets in specimens longer than 25.1 mm SL. Dorsal-fin rays II,7*(17). Dorsal-fin spine short, approximately half-length of first branched ray, when adpressed tip reaching to middle portion of dorsal-fin base; anterior margin with small odontodes; posterior margin smooth and with medial sulcus. Nuchal plate moderately developed, not reaching to posterior process of parieto-supraoccipital, and almost entirely exposed. Dorsal spinelet short, almost entirely exposed; exposed areas with small odontodes. Pectoral fin triangular, its origin just posterior to gill opening. Pectoral-fin rays I,7(2), I,8*(14), or I,9(1). Tip of adpressed pectoral fin reaching to fourth ventrolateral plate. Pectoral-fin spine reaching to second ventrolateral plate when adpressed. Posterior margin of pectoral spine with 9 to 14 poorly-developed serrations along its entire length; absent on distal portion of spine in some specimens. Pectoral-spine serrations generally simple and directed distally; some serrations perpendicularly directed; presence of bifid serrations in some specimens ( Fig. 4 ). Small, sharp odontodes on dorsal surface of pectoral spine just adjacent to fin membrane in males. Pelvic fin ellipsoid, located just below second ventrolateral body plate, and at vertical through first or second branched dorsal-fin ray. Pelvic-fin rays i,5*(17). Adipose fin roughly triangular, separated from base of last dorsal-fin ray by 8*(12) dorsolateral body plates. Anal fin somewhat triangular, located just posterior to 12th*(10) or 13th(2) ventrolateral body plates, and at vertical through region of preadipose platelets. Anal-fin rays i,4(1) or ii,6*(16). Caudal-fin rays i,12,i*(16), generally four dorsal and ventral procurrent rays. Caudal fin bilobed, dorsal and ventral lobes with similar size.

Two (5) or three (2)* laterosensory canals on trunk; first ossicle tubular, second ossicle laminar, third lateralline canal, when present, encased in third dorsolateral body plate. Body plates with minute odontodes scattered over exposed area, conspicuous line of odontodes confined on posterior margins. Dorsolateral body plates 23*(17); ventrolateral body plates 20(11) or 21(6)*; dorsolateral body plates along dorsal-fin base 6(9) or 7*(8); dorsolateral body plates between adipose- and caudal-fin 7(3), 8*(10), or 9(5); preadipose platelets 3(4), 4*(9), 5(2), or 6(1). Small platelets covering base of caudal-fin rays, and disposed dorsally and ventrally between junctions of lateral plates on posterior portion of caudal peduncle.

Juveniles description. Based on two paratypes of 12.8 mm SL (MNRJ 13459) and 12.3 mm SL (MCP 36270) in postflexion stage ( Fig. 5 ). Body elongate. Barbels with well-developed papillae; tip not reaching anteroventral limit of gill opening. Dorso- and ventrolateral plates absent. All fins completely formed, except adipose fin. Skin membrane from base of last dorsal-fin ray to caudal-fin base, with adipose-fin spine contained within it. Pectoralfin spine formed. Dorsal-fin spine (partially damaged) possibly formed. All rays segmented. Ground color of body yellowish white. Proximal area of dorsal fin, dorsal surface of caudal peduncle and caudal-fin base reddish-brown. Body with few small dark, sparsely distributed chromatophores. All fins and barbels without dark chromatophores.

Color in alcohol. Overall color of body in Fig. 1 . Head entirely covered by black chromatophores, including ventral surface; chromatophores less concentrated on lateral and ventral portions of head. Region of parietosupraoccipital process reddish brown. Barbels covered by black chromatophores, more concentrated on their distal portions. Body almost entirely covered by black chromatophores, including ventral surface. Dorsolateral-body plates just posterior to dorsal-fin base with reddish brown dorsal portion, increasing in size towards caudal peduncle; remaining areas of dorsolateral plates densely covered by black chromatophores. Ventrolateral body plates on caudal peduncle reddish brown; remaining areas of ventrolateral plates with less concentrated black chromatophores. Ventral surface of trunk covered by sparse, black chromatophores. Pectoral-, pelvic- and anal-fin rays covered by black chromatophores; anal-fin base with reddish brown chromatophores, becoming sparse distally. Dorsal fin with reddish-brown chromatophores more concentrated on ventral portion, becoming sparse distally. Caudal-fin rays with reddish-brown chromatophores more concentrated ventrally, becoming sparse distally.

Color in life. Observations based on field photographs of five live specimens and on field observations by WMO. Overall body coloration black and red ( Fig. 6 ). Greenish metallic hue on opercle and cleithrum. Intense red coloration close to dorsal- and caudal-fin base, adipose fin and on dorsal portion of caudal peduncle; less intense on posterior region of dorsal and caudal fins, anal-fin base, predorsal area, and on dorsolateral portion of head. Pectoral and pelvic fins hyaline. Anal fin hyaline or red. Black on remaining parts of body, except on ventral portions of head and abdomen.

Sexual dimorphism. Male specimens of C. hephaestus can exhibit a lanceolate genital papilla, feature also common to all Corydoradinae (see Nijssen & Isbrücker, 1980; Britto, 2003). In addition, males present small, sharp odontodes on dorsal surface of pectoral spine just adjacent to fin membrane. This feature is observed in some Scleromystax Günther, 1864 species (Britto et al. in press).

Distribution. The new species is only known from its type locality, Igarapé Piracolina , a tributary of the upper Rio Machado, Rio Madeira basin, about 9 km south of Vilhena, near the border of Rondônia and Mato Grosso States, Brazil ( Fig. 7 ).

Ecological notes. The type locality of Corydoras hephaestus is located 585 m above sea level on the Chapada dos Parecis . It is a small terra-firme igarapé (= highland creek) with little preserved riparian vegetation and surrounded by large plantation fields (mostly soy and corn), near Vilhena, Mato Grosso. It is a clear water stream 1.5‒2.5 m wide and 0.3‒0.8 m deep, with swift currents, and a bottom composed of sand and dead leaves ( Fig. 8 ). The new species are not abundant, and specimens were collected one by one. Shoalling behavior was not observed. Syntopic species included Ancistrus verecundus Fisch-Muller, Cardoso, da Silva & Bertaco, 2005 , Bryconops piracolina Wingert & Malabarba, 2011 , Cetopsorhamdia sp. 3 (cf. Bockmann & Slobodian, 2013: 25), Hyphessobrycon lucenorum Ohara & Lima, 2015 , Hyphessobrycon aff. melonostichos Carvalho & Bertaco, 2006, Moenkhausia parecis Ohara & Marinho, 2016 and Pyrrhulina sp. The analysis of stomach contents of one paratype (MZUSP 118570) revealed the presence of sand, algae and nematodes.

Etymology. The specific epithet hephaestus is from the Greek, Ἥφαιστος (or Hēphaistos), the Greek god of fire, metalworking, forges, and blacksmiths. Alluding to the red color of the body and fins. A noun in apposition.

Figures

FIGURE 1. Corydoras hephaestus, new species, holotype, MZUSP 119087, 22.6 mm SL, Brazil, Rondônia, Vilhena, upper Rio Machado. Lateral (a), dorsal (b), and ventral (c) views.

FIGURE 2. Dorsal view of head of a cleared-and-stained specimen of Corydoras hephaestus, MZUSP 118570, 25.4 mm SL, showing absence of contact between the posterior process of the parieto-supraoccipital and the nuchal plate.

FIGURE 3. Lateral view of the head of a cleared-and-stained specimen of Corydoras hephaestus, MZUSP 118570, 25.4 mm SL. Abbreviations: io 1: infraorbital 1, io 2: infraorbital 2, sph: sphenotic, cpt: compound pterotic.

FIGURE 4. Ventral view of left pectoral-fin spine of Corydoras hephaestus, MZUSP 118570, 25.4 mm SL, showing the small conical serrations on inner margin of the right spine.

FIGURE 5. Juvenile of Corydoras hephaestus in lateral view, MCP 36270, 12.3 mm SL.

FIGURE 6. Color in life of Corydoras hephaestus, paratype, MZUSP 117059, immediately after capture.

FIGURE 7. Type locality (red square) of Corydoras hephaestus, a tributary of the Igarapé Piracolina, upper Rio Machado drainage, Rio Madeira basin, Brazil.

FIGURE 8. Tributary of the Igarapé Piracolina, upper Rio Machado, Rio Madeira basin, Vilhena, Rondônia, Brazil, type locality of Corydoras hephaestus.

Tables

TABLE 1. Morphometric data for holotype and paratypes of Corydoras hephaestus. Values for the holotype (included in range, N = 17), range and mean ± SD (standard deviation).

Characters	Holotype Range	Median±SD
Standard length	22.7 18.9–33.41	27.1
Percents of standard length
Depth of body	37.7 34.9–41.5	37.0±1.5
Predorsal distance	53.8 48.4–54.7	50.6±1.9
Prepelvic distance	52.1 47.1–52.4	48.9±1.6
Preanal distance	81.8 78.4–83.3	81.2±1.4
Preadipose distance	87.9 84.9–91.6	86.9±1.7
Length of dorsal spine	12.8 9.7–15.8	12.5±1.7
Length of pectoral spine	20.3 16.5–22.2	19.3±1.8
Length of adipose-fin spine	8.9 5.9–9.3	7.4±1.1
Depth of caudal peduncle	17.1 14.1–18.3	16.4±1.1
Dorsal to adipose distance	19.1 19.1–25.6	22.6±2.2
Length of dorsal-fin base	22.7 17.9–22.7	20.9±1.2
Maximum cleithral width	11.7 8.2–12.1	10.5±1.3
Head length	44.6 38.9–44.7	41.7±1.8
Length of maxillary barbel	19.6 16.1–22.4	19.1±1.9
Percents of head length
Head depth	87.2 79.0–91.1	85.1±3.0
Least interorbital distance	40.0 36.5–43.1	40.1±1.6
Horizontal orbit diameter	18.3 14.9–20.1	17.5±1.5
Snout length	37.1 37.1–41.7	39.6±1.6
Least internarial distance	21.5 18.8–29.2	25.0±2.8