Sorubim lima (Bloch & Schneider 1801)

Michael W. Littmann, 2007, Systematic review of the neotropical shovelnose catfish genus Sorubim Cuvier (Siluriformes: Pimelodidae)., Zootaxa 1422, pp. 1-29 : 8-13

Sorubim lima (Bloch & Schneider 1801)

Chiripira, Chucharón, Pico de pato, Lima Shovelnose, Duckbill Catfish

Fig. 5 (Holotype), Fig. 6

Silurus lima Bloch and Schneider 1801 , p. 384. Type locality: in flumine Maranham Brasiliae ( Brazil). Holotype: ZMB 3185 (stuffed).

Sorubim infraoculare Spix in Spix and Agassiz, 1829 : 24, pl. 15. Type locality: Brazil. Not available, first published in the synonomy of Platystoma lima (Bloch & Schneider 1801) .

Silurus gerupensis Natterer in Kner, 1858 : 399. Type locality: stemmen von Rio Guaporé, Rio Branco und Rio Negro. Holotype: whereabouts unknown. Not available, first published in synonomy under Platystoma lima .

Platystoma luceri Weyenbergh, 1877 : 10, pl. 3 (figs. 1-3). Type locality: Argentina, Santa Fe. Holotype: whereabouts unknown. Junior subjective synonym (herein).

Sorubim latirostris Miranda-Ribeiro, 1920 : 14, pl. 12. Type locality: Amazonas ( Brazil). Holotype: MNRJ 631. Junior subjective synonym (herein).

Diagnosis: A species of Sorubim distinguished from S. elongatus by having modally nine pectoral rays; 21 anal-fin rays; 16 gill rakers; large vomerine tooth patches, almost always fused (Littmann et al. 2000, fig. 4a); a more robust, deeper head and body; body somewhat compressed laterally; mental barbels equal or anterior to gular apex (Littmann et al. 2001b, fig. 4a). Differs from S. cuspicaudus in having rounded caudal fin lobes and more robust body. Distinguished from S. trigonocephalus by premaxillary tooth patch length being 1.5 to 2.5 times its width. Trenchantly differs from S. maniradii having only 13-18 gill rakers. Additional characteristics distinguishing S. lima from congeners include pelvic fins that contact or nearly reach anal fin origin when depressed and presence of thin plates or ossicles (highly variable in shape) extending vertically on anterior lateral line in most large adults.

Description: Mensural and meristic data are given in Tables 1-5. Largest individual 505 mm SL (BMNH 1895.5.17.16, Río Paraguay). Dorsal-fin rays II,6 (n=196); pectoral-fin rays I,9 (8-10); anal fin rays 21 (19- 22); pelvic-fin rays 6, 1 unbranched and 5 branched (n=196); principal caudal rays on upper lobe always 8, lower rays variable, 8-13; gill rakers on first pharyngeal arch 16 (13-18), 3-4 (usually 4) on epibranchial. Body-shape and form shown in Figs. 5, 6. Head, body, and caudal peduncle deeper than in other species of Sorubim . This is based on unpublished data from my graduate thesis that included a sheared principal components analysis (PCA) of S. lima vs. congeners. A sheared PCA used to compare head and body shape of S. lima vs. S. elongatus can be found in Littmann et al. (2001b).

Head length approximately 3 times gape width (n=80, range 2.61-3.65, mean 3.00), interorbital distance 3 times or more than eye diameter (n=81, range 2.34-5.42, mean 3.58), anal- fin length 1.75-2.25 times adipose fin length (n=46, range 1.59-2.63, mean 2.08), premaxillary tooth patch width approximately 2 times its length (n=58, range 1.44-2.79, mean 2.06). Eyes positioned laterally on the head, visible ventrally. Three pairs fleshy barbels on head, ovate or flat in cross-section. Maxillary barbels long, sometimes reaching beyond pelvic-fin origin. Outer mental barbels extend beyond posterior cleithral process. Inner mental barbel insertion anterior to or even with gular apex (Littmann 2001b, fig. 4,) and short, not reaching beyond bony operculum.

Color in alcohol: Dorsal surface on freshly preserved specimens dark black or brown above, black or dark brown lateral stripe originating from area proximal to or completely through eye and reaching posterior tip of lower lobe of caudal fin on inferior margin. Area between darkened dorsum and lateral stripe intersected by a lighter area of white, gray, light tan or brown. In live specimens, lighter areas may appear golden or slate gray, often appearing iridescent. Some individuals may also display dark blotches or spots on dorsal part of body. Ventral part of body white or cream colored. Preserved specimens usually light brown or gold above, tan below.

Juveniles more heavily pigmented than adults. Posterior-most rays on dorsal, anal, and pelvic fins heavily speckled with chromatophores, speckling reduced in adults. Some individuals exhibit dark chromatophores on all fin-rays. During development, relative length and amount of pigmentation is reduced on lower caudal lobe until specimen reaches ~100 mm SL (Reid 1986). The degree of barbel pigment is highly variable. Maxillary barbels black, outer mental barbels black, clear or white. Inner mental barbels clear, white, or cream colored. Fin-rays in live specimens transparent, lemon yellow in preserved specimens.

Etymology: The name lima, meaning a file in Latin, refers to the ventrally exposed premaxillary tooth patch.

Distribution: Sorubim lima is widely distributed throughout most of South America east of the Andes mountain range (Fig. 7), including the Amazon, Orinoco, Paraná and Parnaíba river drainages. It is syntopic with S. elongatus in the Orinoco basin and with S. elongatus and S. maniradii in the upper Amazon drainage of Brazil, Ecuador, Peru, and Bolivia.

Remarks: Bleeker (1862) designated Silurus lima Bloch and Schneider 1801 as the type species of Sorubim , subsequently fixing “Maranham Brasiliae,” as the type locality. Weyenbergh (1877) described Platystoma luceri from a single specimen taken from the waters of Sante Fe, Argentina ( Río Paraná drainage). The illustration of this type is an accurate depiction of the genus, however it only serves as a representative and could not be identified further. The description also does not differ substantially from Bloch and Schneider's (1801) original description of Silurus lima . Eschmeyer (1998) reported the possibility that syntypes of S. luceri belonging to the Weyenbergh collection were originally housed in Santa Fe, Argentina, and were subsequently transferred to MSNG, Genova, Italy. I was unable to locate these specimens or find any other information confirming this. After a careful inspection of Weyenbergh's description (1877), Eigenmann and Eigenmann (1890), Gosline (1945), and Fowler (1951), S. luceri is treated herein as a junior subjective synonym of S. lima . Whitehead and Myers (1971) also judged S. infraoculare to be a junior subjective synonym of S. lima .

The name S. lima has long been confused with S. latirostris Miranda-Ribeiro 1920 . Miranda-Ribeiro (1920) described S. latirostris and S. trigonocephalus from single specimens from the Brazilian Amazon and the Río Madeira drainage, respectively. His paper included the first published key to Sorubim . Gosline (1945) recognized three nominal species of Sorubim : S. lima , S. trigonocephalus , and S. latirostris , listing S. infraoculare and S. luceri as junior synonyms of S. lima , but provided no justification for this action. Fowler (1951) recognized S. lima , S. latirostris , and S. trigonocephalus as valid and listed S. gerupensis Natterer in Kner (1858) to be a synonym of S. lima (Nass 1988).

Littmann et al. (2000) concluded that S. latirostris was a junior synonym of S. lima for several reasons. Color transparencies of the holotype of S. lima (Fig. 5) show a stout-shaped Sorubim with inner mental barbels inserted anterior to the gular apex at the isthmus. In addition, measurements made on the head of the holotype of S. lima fall within the ranges given in the description of S. latirostris . Miranda-Ribeiro (1920) examined little material (only two specimens of S. lima ), and diagnosed S. latirostris from only a few unreliable characters (i.e., ratios of head and body measurements). Proportional measurements made on the head are extremely variable. Furthermore, he did not provide any diagnostic characters to distinguish it from S. lima . There is insufficient evidence to support recognizing S. latirostris as distinct from S. lima .

Similar species: Although superficially similar to all congeners, the head shape of Sorubim lima is most similar in physical appearance to S. cuspicaudus . It differs from S. cuspicaudus in the following ways ( S. cuspicaudus in parentheses): lower lobe of caudal fin rounded (pointed and straight); body short and stout (elongated), no posterior fontanelle groove on the supraoccipital bone (groove present) (Fig. 5B vs. Fig. 8B). Results of a sheared PCA showed that S. lima has a slightly shorter head and much stouter body (Littmann et al. 2000) compared to S. cuspicaudus . The two species are allopatric.