Heptapterus mbya, Azpelicueta & Aguilera & Mirande, 2011

Azpelicueta, Maria De Las Mercedes, Mirande, Juan Marcos & Aguilera, Gastón, 2011, Heptapterus mbya (Siluriformes: Heptapteridae), a new species of catfish from the Paraná river basin, in Argentina, Revue suisse de Zoologie 118 (2), pp. 319-327 : 320-325

Heptapterus mbya , sp. n. Figs. 1-3, Tables 1, 2

HOLOTYPE: CI-FML 4008, 136.0 mm SL, Argentina, Misiones, río Paraná basin, arroyo Moreno at Ruta Provincial 202 (26° 54' 24'' S- 54° 54' 50'' W) headwaters of arroyo Garuhapé, October 21, 2004, M. Azpelicueta, D. Aichino, D. Méndez (Fig. 1).

PARATYPES: All specimens come from Argentina, province of Misiones. AI 247, 4 ex. (1 C&S), 88. 0-116.5 mm SL, arroyo Azul (200 m downstream from Puente Quemado , 27° 00' 46'' S- 54° 57' 06'' W), October 21, 2004, M. Azpelicueta, D. Aichino, D. Méndez; AI 269, 2 ex., 85. 0-116.3 mm SL, arroyo Cuña-Pirú (26° 30’ 20” S- 54° 48’ 03” W), March 10, 2005, M. Azpelicueta; CI-FML 4009, 2 ex., 136.6-165.8 mm SL, same collecting data; CI-FML 4010, 2 ex., 126.8-136.6 mm SL, arroyo Azul (27° 00' 46'' S- 54° 57' 06'' W), October 21 2004, coll. M. Azpelicueta, D. Aichino, D. Méndez. MHNG 2722 .092, 4 ex., 85-129.4 mm SL, same collecting data .

DIAGNOSIS: Heptapterus mbya sp. n. is distinguished from other species of the genus by the following combination of characters: adipose and caudal fins confluent, largest specimen less than 170 mm SL (maximum length 166.0 mm), dark plumbeous body, low number of anal-fin rays that are branched (11-12) out of a total number of 15-17 anal fin rays, a large eye 13.8-17.9 % of HL, prepectoral distance 31.9-37.8 % of SL, distance between last dorsal-fin ray and adipose-fin origin 5.24-8.33 % of SL, adipose-fin base 47.4-58.5 % of SL, 10-13 gill rakers on first branchial arch, 13 principal branched caudal rays, and 56-58 vertebrae. Heptapterus qenqo ( Aguilera et al., 2011) has the same number of anal-fin rays but it is distinguished by the presence of rudimentary serrae at base of the pectoral-fin spine (absent in H. mbya sp. n.).

DESCRIPTION: Morphometric data of the holotype and 14 paratypes are presented in Table 1. Heptapterus mbya sp. n. has a maximum of 166.0 mm SL (Figs. 1, 2). The body is covered by a deep layer of mucus; numerous sensory pits (pit organs) are distributed all over the body and fins. There are rare minute black soft structures, very fine, spiniform, embedded in soft tissues of the caudal fin, dorsal surface of pectoral and pelvic fins of females and males, independent of body size but with low number in young specimens. Spine-like structures form parallel rows, specially notably on caudal membrane (Fig. 3).

Dorsal profile of body nearly straight from snout tip to posterior region of head, scarcely convex from this point to dorsal-fin origin, straight from dorsal-fin origin to adipose-fin origin, then slightly tapering to end of caudal peduncle. Ventral profile slanting ventrally or straight from snout tip to pectoral-fin origin, straight or convex between pectoral and pelvic fins, straight between pelvic and anal fins, and scarcely slanting dorsally to end of caudal peduncle. Maximum body width at level of pectoral fins; posterior half of body increasingly laterally compressed to caudal peduncle. Maximum body depth at dorsal-fin origin, contained 8.2-10.2 times in SL.

Head relatively small contained 4.9-6.2 times in SL; head dorsoventrally depressed (depth of head between eyes 2.3-2.9 times into HL; depth of head at supraoccipital 1.8-2.2 into HL). Head covered by thick skin and a layer of mucus, head surface smooth with many sensory pits. Snout of moderate length (contained 2.6-3.0 in HL), rounded in dorsal view. Upper jaw scarcely projecting (projection 4.3-8.2 % of HL); premaxillary teeth covered by lower jaw when mouth closed. Anterior nostril with a very well developed tubular rim. Posterior nostrils preceded by large semicircular membrane. Distance between posterior nostrils and eye shorter than internarial distance. Eye placed dorsally, covered by skin, small (its length 5.5-7.2 times in HL); interorbital relatively wide and straight, containing eye diameter 0.6-1.3 times (13.4- 18.1 % of HL). Width of head at eye level 1.3-1.6 times into HL (71.8-78.7 % of HL). Mouth subterminal, opening anteriorly, wide; lips thin. Premaxilla with slightly rounded posterolateral corners; its anteroposterior length 3.6-4.2 times in premaxillary width (6 specimens measured). All teeth conical and fine, placed in 8-10 irregular rows in premaxilla, larger specimens with more rows; 6-8 tooth rows on dentary at

FIG.. 1 Heptapterus mbya sp. n., holotype, CI-FML 4008, 136.0 mm SL, lateral view. FIG. 2 Heptapterus mbya sp. n., holotype, CI-FML 4008, 136.0 mm SL, dorsal view.

FIG. 3

Heptapterus mbya sp. n. Spiniform structures embedded on most superficial mucous layer of the caudal fin. CI-FML 4008, detail of the holotype, 136.0 mm SL. Bar= 1 mm.

TABLE 1. Measurement data for Heptapterus mbya sp. n. expressed in percentages of the standard dimensions given above measurements. SL in mm.

Holotype Mean Min Max Standard Length 136.0 85.0 165.8 Percent of SL Predorsal-fin length 34.7 34.5 30.6 37.1 Preadipose-fin length 50.8 50.2 43.4 54.8 Prepectoral-fin length 17.6 17.2 15.0 18.9 Prepelvic-fin length 35.7 35.1 31.9 37.8 Preanal-fin length 58.8 60.2 55.2 64.9 Body depth at dorsal-fin origin 12.9 11.9 8.8 13.9 Caudal peduncle depth 6.3 6.4 5.8 7.2 Caudal peduncle length 20.9 20.6 17.9 24.2 Head length 19.1 18.8 16.1 20.4 Body width 13.8 13.9 11.8 15.4 Second dorsal ray 7.3 7.8 5.9 9.4 Second dorsal-fin ray 9.6 9.9 7.6 12.1 Dorsal-fin base 10.0 9.4 8.5 10.0 Last dorsal-fin ray to adipose-fin origin 6.9 6.9 5.2 8.3 Adipose-fin length 50.5 51.3 47.4 58.5 Adipose-fin depth 3.6 3.4 2.9 4.6 First pectoral-fin ray 10.2 10.6 9.0 11.8 Second pelvic-fin ray 11.4 11.0 9.4 12.7 Anal-fin base 19.8 18.8 14.5 21.6 Anal-fin height 3.0 4.5 3.0 6.0 Dorsal-fin origin to caudal-fin base 67.6 66.9 64.3 70.9 Pelvic-fin origin to caudal-fin base 62.7 65.1 62.7 67.2 Anal-fin origin to caudal-fin base 39.1 39.3 36.2 42.1 Pectoral-fin to pelvic-fin origins 20.5 19.9 17.8 21.8 Pelvic-fin to anal-fin origins 25.0 26.3 24.8 28.7 Percent of head length Snout length 32.6 35.2 32.6 37.6 Horizontal eye diameter 16.5 15.4 13.8 17.9 Eye to posterior margin of head 52.6 51.0 48.6 52.8 Bony interorbital 15.3 15.4 13.3 18.0 Head depth at occiput 53.0 49.2 45.4 53.8 Head width 74.2 74.9 71.8 78.7 Gape width 43.8 43.7 40.0 47.5 Anterior tip to anterior nostril 11.5 12.5 10.4 14.1 Distance between nares 12.6 11.6 9.5 13.3 Posterior naris to anterior eye margin 11.9 10.5 8.2 12.2 Percent of peduncle length Caudal peduncle depth 30.5 31.5 26.6 37.4

symphysis and fewer posteriorly. Origin of maxillary barbel close to anterior nostril, above rictus; basal third of maxillary barbel resting in a deep sulcus. Maxillary barbel usually reaching a vertical through mid of pectoral fin and scarcely surpassing pectoral-fin origin in few specimens. Tip of outer mental barbel usually reaching pectoral-fin origin, scarcely reaching branchiostegal membrane in two specimens. Tip of inner mental barbel scarcely reaching branchiostegal membrane.

Dorsal fin with one soft segmented ray and six branched rays; first dorsal-fin ray small, about two thirds of first branched ray. Second branched dorsal-fin ray longest, about twice of last branched ray. Dorsal-fin origin anterior to a vertical through pelvic-fin insertion; in small specimens, dorsal-fin origin located scarcely anterior or at same level of pelvic-fin origin. Last adpressed dorsal-fin ray close to adipose-fin origin, increasingly so in smaller specimens. Adipose-fin origin located at a vertical through tip of pelvic fins or little posterior. Adipose fin long, confluent with caudal fin; adipose fin low, 12-18 times in its base.

Caudal fin rounded, its upper lobe longer and broader than lower lobe. Principal caudal-fin rays 1+(6-7)+1. Dorsal procurrent caudal-fin rays 12-14, ventral procurrent caudal-fin rays 17-21 (counted in 6 specimens). Anal fin short, low, its origin at a vertical through anterior fourth of adipose fin; in small specimens, anal-fin origin placed at anterior third of adipose fin. Distal margin of anal fin straight or slightly convex. Tips of last anal-fin rays close to or surpassing origin of caudal fin. Anal-fin with 15- 17 rays (iii-v, 11-13; 2 with 11 branched rays; 9 including holotype with 12; 4 with 13). Pectoral fin i,6-8 (1 with 6 branched rays; 10 with 7 including holotype; 4 with 8); first pectoral-fin ray soft and segmented. Distal margin of pectoral fin rounded. First ray short, 1.2-1.7 times in fin length; third ray longest. Tip of pectoral fin reaching half length between pectoral and pelvic fin origins. A large axillary gland pore, above pectoral-fin insertion, close to posterior angle of opercle. Pelvic fin with i,6 rays; second branched ray longest; its distal margin rounded. Tip of pelvic fin reaching one third of distance between pelvic and anal fin origins. Inner pelvic-fin ray surpassing anus and urogenital papillae.

Urogenital papillae located immediately behind anus, somewhat tubular in males. Gonads of males with broad, finger-like projections.

Lateral line complete, ending on caudal peduncle; anterior lateral line ossicles without small plate-like expansions. Pores of cephalic sensory canals distributed as follows: supraorbital branch with four pores, infraorbital branch with six pores, mandibular branch with five pores, preopercular branch with six pores, and pterotic branch with 3 pores.

Swim bladder small, bilobed in shape (as an eight) transversely placed. Gill rakers somewhat short, slightly laterally compressed. Ten to thirteen gill rakers on first arch, distributed as follows: 0-3 on epibranchial, 1 on cartilage between epibranchial and ceratobranchial, 8-9 on ceratobranchial.

In two specimens, total number of vertebrae 56-58 (29-31 precaudal, 27 caudal); 9-10 pairs of ribs.

COLOR UPON CAPTURE: Background dark gray, whitish only on vent; a very slender lateral stripe from opercle to end of caudal peduncle. All unpaired fins dark gray with a notably darker margin on anal fin; pectoral and pelvic fins yellowish. Transverse dorsal bands barely visible.

COLOR IN ALCOHOL: Dark gray on dorsum, gray on sides of body and very light gray on ventral surface; head dark gray. Four transverse bands almost black, first one over supraoccipital region, second one at level of pectoral fins; third one at dorsal-fin origin, many times continued with an oval spot around dorsal-fin base; fourth band at adipose-fin origin. A very slender stripe developed from a dark area posterior to opercle to end of caudal peduncle. A light area on cheek. All fins dark gray, especially FIG. 4

Type locality, arroyo Moreno at Ruta Provincial 202, province of Misiones, Argentina (26° 54' 24''S- 54° 54' 50'' W) .

caudal fin. Dorsal fin with a light stripe near its base; anal fin with a dark band along its margin. Minute black rounded chromatophores scattered all over body, at different depths of skin. Large black, deep and star-like chromatophores spread on body. Chromatophores on myosepta, making myomeres very evident.

ETYMOLOGY: The Guaraní word mbya is the name of the aborigines that live in the Cuña-Pirú Valley and the Parque Provincial Salto Encantado. The name is applied as a noun in apposition.

DISTRIBUTION AND HABITAT: Heptapterus mbya sp. n. is found in the Cuña-Pirú, Moreno (Fig. 4), and Azul streams. The three streams are located in the río Paraná basin in Misiones, Argentina; the latter two, though, are headwaters of the Garuhapé stream. The largest number of specimens were collected in a pond about 1 m deep, with a slow current, and a sandy bottom; the place was bordered by dense vegetation, completely covered by shadow. The parameters measured were temperature at 18-20 °C, conductivity= 81µS/cm, and pH= 6.3.