Corydoras froehlichi, Tencatt & Britto & Pavanelli, 2016

Tencatt, Luiz Fernando Caserta, Britto, Marcelo Ribeiro de & Pavanelli, Carla Simone, 2016, Revisionary study of the armored catfish Corydoras paleatus (Jenyns, 1842) (Siluriformes: Callichthyidae) over 180 years after its discovery by Darwin, with description of a new species, Neotropical Ichthyology (e 150089) 14 (1), pp. 1-20 : 11-15

Corydoras froehlichi , new species urn:lsid:zoobank.org:act:5C878AD9-653C-4556-8EAC-9D56455E5F93

( Figs. 3b , 4b , 8 , 9 ; Table 1)

Holotype. MCP 48433 , 51.5 mm SL, Brazil, Rio Grande do Sul, Esmeralda, rio Pelotas , 27°47’51”S 51°10’17”W, 11 Dec 1988, E. H. L. Pereira, L. Bergmann, P. Azevedo & R. E. Reis.

Paratypes. All from Brazil, upper rio Uruguai basin. Rio Grande do Sul : MCP 19354 , 6 , 26.9-36.5 mm SL, rio Uruguai, Barracão , 27°36’22”S 51°27’40”W, 13 Nov 1996, E. Pereira, J. Silva & R. Reis . MCP 19368 , 5 , 41.4-44.5 mm SL, rio Pelotas , Esmeralda, 27°47’51”S 51°10’42”W, 12 Nov 1996, J. Pezzi & E. Pereira . MCP 12945 , 18 , 39.7- 45.6 mm SL, 2 c&s, 38.3-43.1 mm SL ; MNRJ 44488 , 4 , 43.0- 45.6 mm SL ; MZUSP 118698 , 4 , 43.3-47.9 mm SL ; NUP 17733 , 4 , 47.0- 48.8 mm SL; collected with holotype. Santa Catarina : MCP 12362 , 8 , 33.6-44.6 mm SL, rio Canoas , Tupitinga, 27°35’11”S 51°24’09”W, 9 Sep 1988, A. Ramires, A. Bergmann, P. Azevedo & E. Pereira . MCP 12782 , 3 , 42.6 -44.0 mm SL, rio Canoas , Tupitinga, 27°35’11”S 51°24’09”W, 10 Nov 1988, C. Lucena, E. Pereira, P. Azevedo & A. Ramires . MCP 13388 , 9 , 36.7- 46.2 mm SL, 1 c&s, 40.2 mm SL, rio do Peixe , Concórdia, 27°27’55.11”S 51°53’8.55”W, 16 Feb 1989, R. Reis, E. Pereira, L. Bergmann & P. Azevedo .

Diagnosis. Corydoras froehlichi can be distinguished from its congeners, with exception of C. aurofrenatus , C. carlae , C. cochui , C. difluviatilis , C. diphyes , C. ehrhardti , C. ellisae Gosline, 1940 , C. flaveolus , C. garbei , C. gladysae , C. gryphus , C. habrosus , C. lacrimostigmata , C. longipinnis , C. lymnades , C. micracanthus , C. microcephalus , C. orcesi , C. paleatus , C. petracinii , C. reynoldsi , C. septentrionalis Gosline, 1940 , C. steindachneri , C. tukano and C. weitzmani by having a longitudinal series of relatively large black blotches, with size similar or larger than the size of orbit, on midline of flank (vs. midline of flank with a longitudinal series of small black blotches, with size conspicuously smaller than the size of orbit, in C. agassizii , C. ambiacus Cope, 1872 , C. araguaiaensis Sands, 1990 , C. breei , C. copei , C. cruziensis , C. haraldschultzi , C. incolicana Burgess, 1993 , C. isbrueckeri , C. lamberti , C. noelkempffi , C. ornatus , C. orphnopterus , C. paucerna , C. punctatus , C. robineae Burgess, 1983 , C. robustus , C. spectabilis , C. sterbai Knaack, 1962 and C. xinguensis ; midline of flank lacking a distinct longitudinal series of blotches in the remaining species). The new species can be distinguished from C. aurofrenatus , C. carlae , C. cochui , C. diphyes , C. ehrhardti , C. ellisae , C. flaveolus , C. garbei , C. gladysae , C. gryphus , C. lacrimostigmata , C. longipinnis , C. lymnades , C. micracanthus , C. microcephalus , C. orcesi , C. paleatus , C. petracinii , C. reynoldsi , C. septentrionalis , C. steindachneri , C. tukano and C. weitzmani by the presence of striated black spots from the snout tip to nuchal plate region, forming a somewhat marbled pattern (vs. spots, when present, conspicuously rounded or irregular, not forming a marbled pattern); from C. difluviatilis by the presence of contact between the tip of the process of the parieto-supraoccipital and nuchal plate (vs. absence); from C. habrosus by the presence of conspicuously thick transversal black bars on caudal-fin lobes (vs. conspicuously slender). Additionally, C. froehlichi can be distinguished from its most similar congeners, C. carlae , C. ehrhardti , C. longipinnis and C. paleatus , by the absence of small plates on the ventral surface of the trunk (vs. presence); and by having markedly rounded snout (vs. relatively pointed snout).

Description. Morphometric data presented in Table 1. Head compressed with slightly convex dorsal profile; triangular in dorsal view. Snout roughly rounded. Head profile convex from snout to tip of posterior process of parieto-supraoccipital. Profile slightly convex along dorsal-fin base. Postdorsal-fin body profile concave to adipose-fin spine; markedly concave from this point to caudal-fin base. Ventral profile of body nearly straight from isthmus to pectoral girdle; slightly convex from this point until pelvic girdle. Profile nearly straight from pelvic girdle to base of first anal-fin ray; slightly concave until 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 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 diameter of naris. Mouth small, subterminal, width nearly equal to bony orbit diameter. Maxillary barbel short, not reaching anteroventral limit of gill opening. Outer mental barbel slightly longer than maxillary barbel. Inner mental barbel fleshy, base slightly separated from 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), with small lateral cornua; posterior portion widened, partially exposed and possessing minute odontodes. Nasal slender, curved laterally; inner margin laminar, outer margin laminar in some specimens; mesial border contacting mesethmoid and frontal. Frontal elongated, narrow, width less than half entire length; anterior projection short, size smaller than nasal length. Frontal fontanel large, oval; posterior tip extension slightly entering anterior margin of parieto-supraoccipital. Parieto-supraoccipital wide, posterior process long and contacting nuchal plate; region of contact between posterior process and nuchal plate covered by thick layer skin.

Two laminar infraorbitals with minute odontodes; infraorbital 1 large, ventral laminar expansion moderately developed ( Fig. 3b ); anterior portion with moderately developed expansion; infraorbital 2 small, posteroventral margin contacting posterodorsal ridge of hyomandibula, dorsal tip slender, contacting only sphenotic ( Fig. 3b ). Posterodorsal ridge of hyomandibula close to its articulation with opercle oblong; exposed, slightly thickened and bearing small odontodes; dorsal ridge of hyomandibula between compound pterotic and opercle covered by a thick layer of skin. Interopercle covered by thick layer of skin, somewhat triangular, anterior projection well developed. Preopercle slender, elongated, minute odontodes sparse on external surface. Opercle dorso-ventrally elongated, width equal or smaller than half of its length; free margin rounded, not angulated; few specimens with smooth uncinate expansion; covered by small odontodes. Anteroventral portion of cleithrum exposed; Posterolateral portion of scapulocoracoid exposed; minute odontodes sparse on exposed areas. Vertebral count 22 (3); ribs 6 (3), first pair conspicuously large; complex vertebra compact in shape. Neural and haemal spines with distal portion expanded.

Four branchiostegal rays decreasing in size posteriorly. Hypobranchial 2 somewhat triangular, tip ossified and directed towards anterior portion, posterior margin cartilaginous; ossifiedportionwelldeveloped,abouttwicesize 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, 30 to 37 (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 large triangular process on posterior margin. Upper tooth plate oval; 38 to 42 (3) teeth aligned in two rows on posteroventral 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 enteringfrontalthroughsupraorbitalcanal.Supraorbitalcanal 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 roughly triangular, located just posterior to second dorsolateral body plate. Dorsal-fin rays II,7 (1), II,8* (31), posterior margin of dorsal-fin spine with 17 to 18 serrations along entire posterior margin of spine; serrations directed towards dorsal-spine tip; nuchal plate exposed with minute odontodes; spinelet short; spine relatively long, adpressed distal tip slightly surpassing base of last branched dorsal-ray, anterior margin with small odontodes. Pectoral fin triangular, its origin just posterior to gill opening. Pectoral-fin rays I,8; posterior margin of pectoral spine with 20-22 well developed serrations along its entire length; serrations directed towards pectoral-spine tip; presence of bifid perpendicularly directed serrations on proximal region of spine ( Fig. 4b ). Pelvic fin oblong or rounded, located just below first ventrolateral body plate, and at vertical through first branched dorsal-fin ray. Pelvicfin 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 plate, and at vertical through anterior margin of adipose-fin spine. Anal-fin rays i,6. Caudal-fin rays i,12,i, generally four dorsal and ventral procurrent rays; bilobed, lobes with similar size.

Threelaterosensorycanalsontrunk;firstossicletubular, second ossicle laminar and last lateral-line 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 23 (11), 24* (21); ventrolateral body plates 20 (4), 21 (21), 22* (7); dorsolateral body plates along dorsal-fin base 5* (12), 6 (20); dorsolateral body plates between adipose- and caudal-fin 7 (9), 8* (23); preadipose platelets 2 (9), 3* (20), 4 (3), adipose spine opposed to anal-fin insertion; 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 with platelets, above posterior portion of lateral ethmoid and above junction of frontal and lateral ethmoid; in some specimens ventral margin of nasal capsule, above mesethmoid, with platelets. Ventral surface of trunk without platelets.

Color in alcohol. Ground color of body yellowish, with top of head black. Presence of striated black spots from tip of snout to nuchal plate region. Opercle with yellowish border; anterior portion dark brown. Dorsal series of four black blotches, first on anterior portion of dorsal-fin base, second on posterior portion of dorsal-fin base, third on adipose-fin base and fourth on caudal-fin base. Dorsal portion of dorsolateral plates generally with dark chromatophores scarcely scattered. Midline of flank with longitudinal series of three large black blotches; anterior and middle blotches conspicuously rectangular; posterior ellipsoid. Dorsal fin generally with transversal black bar on its middle portion. Pectoral fin with diffuse spots; hyaline in some specimens. Pelvic fin generally hyaline; with black spots in few specimens. Adipose fin hyaline; with black area on distal portion of membrane in some specimens. Anal fin with transversal black bar; hyaline in some specimens. Middle portion of caudal-fin base with small black dot. Caudal fin with generally three transversal black bars; hyaline portion of caudal fin with same width as bars; transversal bars conspicuously larger in width.

Sexual dimorphism. Male specimens of Corydoras froehlichi also present lanceolate genital papilla (see Nijssen & Isbrücker, 1980; Britto, 2003). As C. paleatus , males of the new species also present dorsal-fin spine and odontodes more developed than females, and first and second dorsal-fin branched rays slightly surpassing dorsal-spine tip. Females are generally larger than males. In addition, presence of elongated pelvic fin in males ( Fig. 9a ); females with shorter and rounded pelvic fin ( Fig. 9b ). The rounded pelvic fin of the females is used to make a ventral pouch to hold the eggs during spawning (H. Evers, pers. comm.).

Distribution. Corydoras froehlichi is known from the upper rio Uruguai basin, from the rivers Canoas, do Peixe and Pelotas ( Fig. 6 ).

Etymology. Corydoras froehlichi is named in honor and memory of Dr. Otávio Froehlich (1958-2015), UFMS (Universidade Federal de Mato Grosso do Sul), great teacher, mentor and dear friend, for generously sharing his knowledge with several colleagues, besides contributing to the development of LFCT as researcher and person.

Conservation status. Despite Corydoras froehlichi is known only from the rio Pelotas and two of its tributaries, Canoas and do Peixe rivers, it is probably widespread in other tributaries to the rio Pelotas. Additionally, no imminent threat is suspected, therefore, according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Subcommittee, 2014), C. froehlichi can be classified as Least Concern (LC).

Figures

Fig. 3. Lateral view of the head of cleared-and-stained specimens of (a) Corydoras paleatus, UFRGS 1722, 37.6 mm SL, and (b) Corydoras froehlichi, MCP 13388, 40.2 mm SL, paratype.Abbreviations: io1: infraorbital 1, io2: infraorbital 2, sph: sphenotic, cpt: compound pterotic. Scale bar = 1.0 mm.

Fig. 4. Pectoral-fin spine of cleared-and-stained specimens of (a) Corydoras paleatus, UFRGS 1722, 37.6 mm SL, and (b) Corydoras froehlichi, MCP 13388, 40.2 mm SL, paratype. Scale bar = 1.0 mm.

Fig. 8. Holotype of Corydoras froehlichi, MCP 48433, 51.5 mm SL, Brazil, Rio Grande do Sul State, Esmeralda, rio Pelotas, upper rio Uruguai basin. Dorsal, lateral and ventral views.

Fig. 9. Sexual dimorphism in Corydoras froehlichi, showing (a) the slender and more elongated pelvic fin on males, MCP 12945, 42.4 mm SL, paratype, and (b) the shorter and rounded pelvic fin on females, MCP 12945, 44.4 mm SL, paratype. Scale bar = 1.0 mm.

Fig. 6. Map showing the geographical distribution of Corydoras paleatus (stars) and Corydoras froehlichi (squares). The red star represents the Laguna del Diario, Maldonado, Uruguay, one of the plausible places that may be the type-locality of C. paleatus. The red square represents the type-locality of C. froehlichi, rio Pelotas, Rio Grande do Sul, Brazil. Each symbol may represent more than one locality.