A New Species of Whiptail Catfish, Genus Loricaria (Siluriformes: Loricariidae), from the Rio Curuá (Xingu Basin), Brazil

Loricaria birindellii, new species, is described based on two specimens from the Rio Curuá, a tributary of the Rio Iriri in the lower Xingu basin of Brazil. In adults the new species is distinguished from all other congeners by having a combination of an elongate dorsal-fin spine (36.0% SL, based on the holotype vs. 16–29%, usually less than 26% SL) that is supported throughout most of its length by the first branched ray, and an inconspicuous (vs. prominent) post-orbital notch with minimum orbital diameter 95.4–97.2% (vs. 71.8–91.5%) of maximum orbital diameter. It is further distinguished from similar and geographically proximate species, L. lata and L. simillima, by having a more slender body, particularly head width (13.9–14.9% SL vs. 15.2–19.4% SL in L. simillima and 16.4–20.1% SL in L. lata). The larger specimen of L. birindellii exhibits male breeding characteristics known in other species of Loricaria, including expanded membranous portions of the lower lip, an increase in development of globular papillae on lip surfaces, rounded premaxillary- and dentary-tooth cusps, and slight thickening of the pectoral spine. The smaller specimen of L. birindellii exhibits a different caudal fin pigment pattern and lacks an elongate dorsal spine, suggesting that the species either undergoes ontogenetic transformation or exhibits sexual dimorphism in these characters. Two juvenile specimens (95.6 and 98.0 mm SL) from the Rio das Mortes (Araguaia-Tocantins basin) are tentatively regarded as L. aff. birindellii, based on shared morphological characters and geographic proximity.

Fig. 1

Measurements used in morphometric analyses, as listed in Table 1. Figure modified from Thomas and Rapp Py-Daniel (2008).

Fig. 2

Loricaria birindellii, new species: (A) holotype, MZUSP 97210, 231.9 mm SL, dorsal, lateral, and ventral views; (B) paratype, ANSP 189318, 165.1 mm SL, dorsal view. Scale bars = 1 cm.

Fig. 3

Head in lateral view comparing post-orbital notch (shaded) development: (A) Loricaria simillima, INHS 39968, 217.7 mm SL, with deep and angular notch, also observed in L. cataphracta, L. clavipinna, and L. lata; and (B) L. birindellii, ANSP 189318, paratype, 165.1 mm SL, with shallow notch, also observed in L. aff. birindellii.

Fig. 4

Abdominal plate development and configuration in (A) Loricaria aff. birindellii, MNRJ 25209, 98 mm SL; and L. birindellii (B) paratype, ANSP 189318, 165.1 mm SL, and (C) holotype, MZUSP 97210, 231.9 mm SL. Scale bars = 1 cm.

Fig. 5

Variation in caudal fin pigmentation in Loricaria birindellii, new species. (A) Holotype, MZUSP 97210, 231.9 mm SL and (B) paratype, ANSP 189318, 165.1 mm SL. Scale bars = 1 cm.

Fig. 6

Loricaria birindellii, new species, holotype, MZUSP 97210, 231.9 mm SL, dorsal and ventral views of adult male in life.

Fig. 7

Geographic distribution of Loricaria birindellii (closed circle, type locality shared with that of Doras higuchii and occurrence of Hassar cf. affinis) and L. aff. birindellii (open circle), and type locality of Apteronotus camposdapazi (open square). 1 = large falls separating upper from lower Rio Curuá, 2 = Rio Amazonas, 3 = lower Rio Xingu, 4 = Rio Tocantins. Scale bar ca. 100 km.

Contributor Notes

Associate Editor: C. J. Ferraris.

¹ Department of Zoology and Center for Systematic Biology, Southern Illinois University, Carbondale, Illinois 62901, E-mail: matt.thomas@ky.gov. Send reprint requests to this address.

² Department of Ichthyology, The Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, Pennsylvania 19103, E-mail: sabaj@ansp.org.

Received: 22 May 2009

Accepted: 07 Dec 2009