Auchenipterichthys thoracatus ( Kner, 1857 )

Ferraris Jr, Carl J., Vari, Richard P. & Raredon, Sandra J., 2005, Catfishes of the genus Auchenipterichthys (Osteichthyes: Siluriformes: Auchenipteridae); a revisionary study, Neotropical Ichthyology 3 (1), pp. 89-106 : 101-104

Auchenipterichthys thoracatus ( Kner, 1857) Figs. 10-11

Auchenipterus thoracatus Kner, 1857: 425 , pl. 7, fig. 22 [type locality: rio Guaporé ; syntypes: NMW 47454 (2)].

Auchenipterus thoracicus Günther, 1864: 194 [based on Kner, 1857; unjustified emendation of Auchenipterus thoracatus ].

Auchenipterichthys thoracatus, Eigenmann & Eigenmann, 1888: 154 [in listing of SouthAmerican catfishes; not cited presence at Coary (=Coari) and Hyavary (=Javari), Brazil]. – Eigenmann & Eigenmann, 1891: 34 [in listing of fresh water fishes of South America; not cited occurrence in Solimoens (=Solimões) and tributaries]. – Eigenmann, 1910: 396 [in listing of South American fresh water fishes; not cited presence at Coary (=Coari) and Hyavary (=Javari), Brazil]. –Miranda-Ribeiro, 1911: 372 [description and distribution information based on Günther, 1864, and Eigenmann & Eigenmann, 1891; not citations of species at Coary (=Coari) and Hyavary (=Javari), Brazil]. – Fisher, 1917: 424 [Maciél, rio Guaporé; San Joaquin, Bastos, rio Alegre into R. Guaporé; not cited specimen from Manáos (=Manaus)]. – Pearson, 1937: 110 [Río Mamoré basin]. – Fowler, 1940: 96 [ Bolivia, San Joaquin; based on Fisher, 1917]. – Fowler, 1951: 458 [in part, citations of species in the upper rio Madeira]. –Miranda-Ribeiro, 1968: 8, pl. 7 [body, head, and anal-fin form illustrated]. – Mees, 1974: 34 [literature in part, citations of species from upper rio Madeira basin; not synonymy of Trachycorystes coracoideus into Auchenipterichthys thoracatus ; not cited specimen from Peru]. – Lauzanne et al., 1991: 68 [ Bolivia: Trinidad, Itenez (Guaporé)]. – Sarmiento, 1998: 364 [ Bolivia, Parque Nacional Noel Kempff Mercado]. – Sarmiento et al., 1999: 91 [ Bolivia, Pando, upper Río Othon basin]. – Chernoff et al., 1999: 59 [ Bolivia, riverine habitats]. – Chernoff et al., 2000: 281 [ Bolivia, Amazon]. – Ferraris, 2003: 473 [checklist].

Auchenipterichthys cf. thoracatus, Mendes dos Santos et al., 1984: 78 [ Brazil, rio Tocantins].

Diagnosis. A species of Auchenipterichthys with the coracoid bone covered with a thin layer of integument and exposed ventrally ( Fig. 1b ), an obliquely truncated caudalfin margin, typically 26 or more (rarely 25) branched analfin rays ( Table 1), eight (rarely nine or ten) branched pelvic-fin rays ( Table 1), the anterior teeth on the premaxilla visible when the mouth is closed, and a body pigmentation not consisting of distinct dark spots on a gray background. Auchenipterichthys thoracatus is most similar in appearance to A. coracoideus , which typically has fewer than 25 (26 in one of 63 specimens) branched anal-fin rays ( Table 1). Furthermore, it appears not to have the elongated dorsal-fin spine that is found in nuptial males of A. coracoideus . Auchenipterichthys thoracatus is readily distinguished from its other two congeners, A. longimanus and A. punctatus , which have coracoids that are covered ventrally by a thick layer of integument ( Fig. 1c ), the anterior teeth on the premaxilla are not visible in the closed mouth and, typically, have nine (very rarely eight) branched pelvic-fin rays ( Table 1).

Description. Body depth at dorsal-fin origin 0.25–0.29 of SL and slightly greater than width at cleithrum. Body depth at anal-fin origin 0.27 of SL. Body compressed, with width at anal-fin origin 0.38–0.40 of body depth at that point. Ventral surface of coracoids exposed on ventral surface of body (see Fig. 1b ). Lateral line complete and midlateral. Canal having irregular zigzag pattern, with oblique, posteriorly-directed branches off main canal. Lateral line canal extending short distance onto, and directed obliquely-posterodorsally on, caudal-fin base.

Head depressed anteriorly; height of head at vertical through middle of orbit approximately equal to distance from middle of eye to dorsal midline of head. Dorsal profile of head broadly convex anteriorly and then slightly concave from vertical running through anterior margin of orbit to dorsal-fin origin. Distance from midpoint of snout to anterior margin of orbit approximately equal to horizontal diameter of orbit. Snout margin broadly rounded from dorsal view. Interorbital width approximately 0.65–0.70 of HL and approximately equal to distance from middle of eye to posterior margin of opercle. Eye large, lateral, and visible in both dorsal and ventral views. Orbit distinctly ovoid with horizontal axis longest.

Barbels slender and thread-like. Maxillary barbel long, extending posteriorly slightly past margin of opercle. Medial mandibular barbel originating immediately posterior of lower lip; adpressed barbel extending posteriorly only to vertical through transverse plane through lateral mandibular barbel. Lateral mandibular barbel originating in plane slightly anterior of vertical through middle of orbit and extending posteriorly approximately to anterior portion of exposed cleithrum.

Branchiostegal membrane broadly attached to isthmus; ventral margin of gill opening extending to anterior margin of exposed portion of cleithrum.

Mouth terminal, but with upper jaw extending very slightly beyond margin of lower jaw.Anterior teeth on premaxilla visible from ventral view in closed mouth. Teeth on premaxilla minute and arranged in band. Band consisting of approximately eight irregular series of teeth at symphysis and of ten irregular series laterally. Dentary teeth slightly larger than those on premaxilla, with approximately six series of teeth at symphysis that progressively decrease to one tooth row posterolaterally.

Dorsal-fin origin at 0.36–0.39 of SL. Length of dorsal-fin base approximately one-half of length of first branched dorsal-fin ray. Dorsal-fin spine pungent with slightly convexly curved anterior margin. Length of dorsal spine approximately equal to HL in specimens of both sexes. Basal one-half of anterior margin of dorsal-fin spine bearing two rows of small, blunt projections with spine margin smooth or finely serrated distally. Posterior margin of spine with few, short, medial, obliquely distally-directed serrae. Dorsal-fin rays II,6. Adipose fin relatively small.

Caudal fin obliquely truncate with dorsal most branched ray longest. Principal caudal-fin rays i,7,8,i.

Anal-fin base approximately 0.28–0.31 of SL.Anal-fin origin located distinctly posterior of middle of SL and slightly anterior of middle of TL. Anal-fin margin straight, with first ray longest and subsequent rays becoming progressively shorter. Last anal-fin ray without membranous attachment to caudal peduncle.Anal-fin rays iii,25 to iii,28 ( Table 1).

Distal margin of pelvic fin broadly convex with middle branched ray longest. Pelvic-fin insertion situated anterior of middle of SL. Tip of adpressed anal fin falling short of anal-fin origin. Pelvic-fin rays typically i,8, rarely i,9 or i,10 ( Table 1).

Pectoral fin with strong spine serrated along entire length of both margins with antrorse serrae along anterior margin and retrorse serrae along posterior margin. Anterior pectoralfin rays longest. Fin margin straight anteriorly and convex along posterior rays. Pectoral-fin rays typically I,8, infrequently I,7 ( Table 1).

Pigmentation pattern in alcohol. Overall ground coloration ranging from brown to dark brown, with coloration darker on dorsal portion of head and body and in some individuals on midlateral portion of body posterior of head in region overlapping swimbladder. Abdomen unpigmented. Snout, upper lip, and region ventral of margin of lower lip very dark. Patch of very dark pigmentation present anterior to base of dorsal fin. Lateral and dorsolateral surface of body with series of unpigmented spots of size approximately equal to one-quarter width of pupil or smaller. Unpigmented spots arranged in several series. Midlateral surface of body with irregular longitudinal series of light spots extending from rear of head to posterior margin of caudal peduncle. Anterior portion of this midlateral series overlies several series of approximately vertically-aligned pairs of unpigmented spots. Dorsolateral surface of body with irregularly spaced, vertically-aligned series of unpigmented spots; these series begin under, or posterior of, base of dorsal fin and typically extend posteriorly to beyond base of adipose fin, but in some individuals continue posteriorly to rear of caudal peduncle.

Dorsal fin-rays dark distally. Adipose fin with dark basal spot continuous with dark pigmentation of body. Caudal fin dark basally with pigmentation continuing that of body. Some specimens with small, unpigmented spots within dark basal pigmentation field in region overlying central caudal-fin rays. Darkly pigmented region with distinct, straight to slightly irregular, posterior margin; margin of dark pigmentation ranges from approximately vertical to somewhat anteroventrally inclined. Dark region at base of caudal fin followed posteriorly by hyaline region and then by band of less intense dark pigmentation along distal margin of fin. Anal fin with variably developed dark pigmentation basally. Distal margin of dark pigmentation usually of irregular form, but sometimes smoothly convex. Dorsal surface of basal portion of pelvic fin with variably dark patch of pigmentation. Distal portion of fin with dark pigmentation in most individuals; pigmentation intense in well pigmented specimens. Margins and sometimes dorsal surface of pectoral fin spine dark; fin rays variably outlined with dark chromatophores.

Maxillary barbel dark. Mandibular barbels pale, with scattered, dark chromatophores.

Sexual dimorphism. Although a number of mature males of Auchenipterichthys thoracatus of 94 to 109 mm SL (as indicated by the possession of an elongated urogenital tube adhering to the anterior margin of the anal fin) were examined, none demonstrated an elongation of the dorsal-fin spine beyond the condition present in females of comparable sizes. It is uncertain whether this observation reflects the absence of sexual dimorphism in the species or the lack of nuptial males in the available samples. Serrae on the posterior surface of the distal one-half of the dorsal-fin spine are proportionally longer in mature males than they are in juveniles and females of the species.

Distribution. Upper portions of the Madeira River basin in Bolivia and Brazil ( Fig. 10 ; dots).

Remarks. The catalog number for the syntype series of Auchenipterus thoracatus, NMW 47454, was incorrectly reported as NMW 47452 in Eschmeyer (1998: 1674) and Ferraris (2003:473).

Various authors have misidentified samples of Auchenipterichthys coracoideus as A. thoracatus as is well exemplified in the synonymies for both of these species. One of the major consequences of the failure to discriminate these two species was the erroneous broad purported range for A. thoracatus that was thought to range across major portions of the Amazon River basin. Our results rather indicate that A. thoracatus is limited to the upper portions of the Madeira River basin in southwestern Brazil and eastern Bolivia ( Fig. 10 , dots); with A. coracoideus having an extensive distribution along the length of the Amazon River basin into the Tocantins River system and upper portions of the Essequibo River basin in Guyana ( Fig. 5 ).

As noted under Remarks for Auchenipterichthys coracoideus , that species and A. thoracatus differ in the shape of the head and angle of the divergence of the exposed portion of the coracoids (see Figs. 1 a-b). We have, however, been unable to unambiguously quantify those differences.

Material examined. BRAZIL. “Guaporé” (= rio Guaporé ), NMW 47454, 2 (91–108; syntypes of Auchenipterus thoracatus ) . Mato Grosso: rio Alegre, tributary of rio Guaporé, approximately 30 km from Vila Bela da Santíssima Trindade (15°30’S, 59°20’W), MZUSP 37485 , 186 (91–109) ; MZUSP 36934 , 22 (86–98) . rio Guaporé, Vila Bela da Santíssima Trindade , MZUSP 37518 , 11 (90–98) . Rio Guaporé, Vila Bela da Santíssima Trindade, near bairro do Aeroporto (15°01’17"S, 59°57’90"W), MZUSP 63034 , 23 (71–100) . Bastos, rio Alegre, upper rio Guaporé basin (approximately 15°06' S, 59°57’W), FMNH 58011 , 1 (105) . Rondônia: rio Jaciparana, approximately 3 km upstream from town of Jaci Paraná (9°15’S, 64°23’W), rio Madeira basin, UF 100659, 1 (91) . Inexact locality: Maciel, rio Guaporé basin, FMNH 57798 , 8 (45–93) . BOLIVIA. Beni: San Joaquín (= San Joaquín on Río Machupo ; see Eigenmann, 1911: 311; approximately 13°03’59"S, 64°48’59"W), FMNH 58016 , 2 (61–70) . Río Itenez at mouth of dry run, 2 km SE of Costa Marques, tributary of río Mamoré, río Madeira basin (approximately 12°28’S, 64°16’W), UMMZ 204300 , 1 (52) . Pando: río Manuripi , approximately 13 km by river above Puerto Rico (latter locality at 11°04’59"S, 67°37’59"W), FMNH 106716 , 2 (36–39) . Pando , approximately 9 km from Puerto Rico (latter locality at 11°04’59"S, 67°37’59"W), FMNH 106717 , 1 (39).

Figures

Fig. 10. Map of central and northern South America showing distribution of Auchenipterichthys punctatus (triangles; holotype locality inexact = “probably Brazil”, 1 = holotype locality of Auchenipterichthys dantei), and A. thoracatus (dots; 2 = Guaporé, presumably = rio Guaporé, the type locality of species) (some symbols represent more than one locality or lot of specimens).

Fig. 11. Auchenipterichthys thoracatus, FMNH 57798, 89 mm SL; Brazil, Maciel, rio Guaporé basin.

Fig. 1. Ventral view of anterior portion of body of (A) Auchenipterichthys coracoideus, ANSP 178446, 94 mm SL; (B) A. thoracatus, FMNH 57798, 89 mm SL; and (C) A. longimanus, INHS 61570, 67 mm SL; showing different degrees of exposure of coracoid in that region. Line points to exposed coracoids.

Fig. 5. Map of central and northern South America showing distribution of Auchenipterichthys coracoideus (1 = holotype locality; some symbols represent more than one locality or lot of specimens).