Corymbophanini Armbruster 2004

Corymbophaes Eigenmann, 1909

Click on image to go to species descriptions.


Corymbophanes andersoni, photo by J.W. Armbruster

Corymbophanes kaiei, photo by J.W. Armbruster
TAXA LIST

In 1908, Carl Eigenmann completed a remarkable survey of the fishes of Guyana (Eigenmann, 1912).  Included in the survey were parts of the Potaro River drainage above Kaiteur Falls, the largest single-drop waterfall in the world.  Until recently, no other ichthyologists had collected above Kaiteur Falls, and several species described by Eigenmann had been known only from the types.  In 1998, a team consisting of researchers from the Illinois Natural History Survey, Auburn University, and the University of Guyana, along with a photographer and writer from National Geographic magazine, repeated much of Eigenmann’s journey and surveyed the Potaro River and some of its tributaries above Kaiteur Falls.

Among the recent collections are specimens representing two species of the loricariid catfish genus Corymbophanes.  Eigenmann (1909, 1912) described Corymbophanes andersoni as a new genus and species based on a single individual from Aruataima Falls, a cataract on the Potaro River above Kaiteur Falls that has since been renamed Chenapou Falls (Fig. 1).  Corymbophanes is nearly unique among loricariids in the replacement of the adipose fin by a series of raised, median, unpaired plates between the dorsal and caudal fins, hereafter referred to as a postdorsal ridge.  Currently, C. andersoni is the only species recognized in Corymbophanes; however, Chaetostoma venezuelae (Schultz) and Hemipsilichthys bahianus (Gosline) were originally described in Corymbophanes (Isbrücker, 1980; Armbruster, 1997).

 In the 1998 survey, we collected additional specimens of Corymbophanes andersoni from the type locality.  We also collected specimens of an undescribed species of Corymbophanes in Oung Creek, a small tributary of the Chenapou River that empties into the Potaro River across from the village of Chenapou (Fig. 1).  The information above and the description below is from Armbruster et al. (2000).  Links above are to descriptions of the two known species of Corymbophanes.



SPECIES


DIAGNOSIS

Based on Armbruster (1997), characteristics considered to be synapomorphies for Corymbophanes are the bladelike ventral surface of the first epibranchial, an elongate anterior process on the fourth epibranchial, preoperculo-hyomandibula ridge deflected beyond the posterior margin of the hyomandibula such that it is visible when the suspensorium is viewed mesially, a spoon-shaped anterior process of the metapterygoid, bony contact of the canal plate with the suspensorium, the suprapreopercle absent, a postdorsal ridge present, loss of the adipose-fin membrane and spine, and loss of the dorsal flap of the iris.  All of these characteristics are found elsewhere in Loricariidae, but they appear to have been uniquely derived in Corymbophanes based on Armbruster (1997).



DESCRIPTION

Corymbophanes is a member of the Hypostominae as diagnosed by Armbruster (1997).  Medium-sized species (largest specimen = 70.0 mm SL) morphologically similar to Chaetostoma and the neoplecostomines Pareiorhaphis.  Adipose fin replaced by postdorsal ridge of raised, median, unpaired plates.  23-26 lateral-line plates; three rows of plates on caudal peduncle (excluding median dorsal row); 4-6 predorsal plates; 6-8 dorsal-fin plates; 1-4 interdorsal plates; 10-12 adipose-caudal plates; 13-17 postdorsal ridge plates; 10-12 postanal plates; 3-5 adpressed pectoral-fin plates; 7-10 adpressed pelvic-fin plates.  Odontodes on lateral plates form distinct longitudinal rows; no keels present on lateral plates.  Area of ventral plates around anal fin not supporting odontodes.  Large plateless area between pterotic-supracleithrum and first lateral line plate.  No plates on abdomen.

 Body dark brown to black with white to cream-colored markings.  Dorsal surface fairly flat, depth increasing little from end of head to dorsal fin, and decreasing little from anterior end of dorsal fin to caudal fin.  Contours of head smooth; eye slightly raised above head with rounded ridge from anterior of orbit to anterolateral corner of nare.  Supraoccipital not pointed posteriorly.  Frontal forming dorsal border of orbit.  Frontal, opercle, preopercle, sphenotic, nasal, and infraorbitals supporting odontodes.  Suprapreopercle absent.  Canal plate small, not deflected ventrally.  Eye small, without dorsal flap of iris (See below).  Mouth with small, median buccal papilla.  Lips strongly papillose.  Maxillary barbel short, separate at tip from lip.  Teeth villiform, bicuspid, lateral cusp shorter than medial cusp.

Dorsal fin short, either not reaching postdorsal ridge, or slightly in contact with postdorsal ridge when adpressed; spinelet V-shaped, supporting odontodes; dorsal-fin spine lock functional. Pectoral-fin spine dorsal to and not in contact with pelvic-fin when adpressed parallel with long axis of body.  Pectoral-fin spine with fleshy tip; first pectoral-fin ray longer than spine.  Pelvic-fin spine about as long as pectoral-fin spine or longer, reaching anal fin; pelvic-fin spine wide.  Caudal fin short; posterior edge straight to slightly emarginate, lower lobe longer than upper.  Dorsal fin II7.  Pectoral fin I6.  Pelvic fin I5.  Anal fin I4 or I5 (see species descriptions).  Caudal fin I14I.

A) Eye of a typical loricariid, arrow points to dorsal flap of iris.  B) Eye of Corymbophanes, lacking dorsal flap of iris



COMPARISONS

Corymbophanes can be identified from all other loricariids by a combination of a postdorsal ridge, lack of an adipose-fin membrane, lack of the dorsal flap of the iris of the eye, lack of evertible cheek plates, lack of hypertrophied cheek odontodes, loss of the suprapreopercle, and three rows of plates on the caudal peduncle.  Among loricariids, the only species with a postdorsal ridge and no adipose-fin membrane are species of Leptoancistrus Meek and Hildebrand and some Chaetostoma. Leptoancistrus and the Chaetostoma can be separated from Corymbophanes by the presence of evertible cheek plates and hypertrophied odontodes, presence of a dorsal flap of the iris, five rows of plates on the caudal peduncle, and the loss of the anal fin.  Some species of Hemipsilichthys also have a large number of median, unpaired, postdorsal plates, but the plates do not form a ridge.  Delturus and Upsilodus have a postdorsal ridge, but an adipose-fin membrane is present.



ECOLOGY

Found in swift riffles.



DISTRIBUTION

Known only from the Potaro River and tributaries above Kaiteur Falls.  Red star = C. andersoni, Blue circle = Corymbophanes kaiei, 1 = the village of Chenapou, 2 = the former location of Holmia, 3 = Chenapou (Aruataima) Falls.



KEY
 
1a. 5 plates below the adpressed pectoral-fin spine.  No light bands on caudal fin.  Abdomen lightly colored, no vermiculations. Corymbophanes andersoni
1b. Anal fin I5.  3-4 plates below the adpressed pectoral-fin spine.  Bands on caudal fin.  Abdomen darkly colored, with light vermiculations in adults. Corymbophanes kaiei


LITERATURE CITED

Armbruster, J.W. 1997. Phylogenetic relationships of the sucker-mouth armored catfishes (Loricariidae) with particular emphasis on the Ancistrinae, Hypostominae, and Neoplecostominae. Unpubl. Ph.D. dissertation. University of Illinois, Urbana-Champaign. 409 pp.

Armbruster, J.W., M.H. Sabaj, M. Hardman, L.M. Page, and J.H. Knouft. 2000. The Loricariid Catfish Genus Corymbophanes with Description of One New Species: C. kaiei. Copeia.

Eigenmann, C. H. 1909. Reports on the Expedition to British Guiana of the Indiana University and the Carnegie Museum, 1908. Report No. 1.  Some new genera and species of fishes from British Guiana.  Ann. Carnegie Mus. 6:4-54.

Eigenmann, C. H.1912. The freshwater fishes of British Guiana, including a study of the ecological grouping of species and the relation of the fauna of the plateau to that of the lowlands. Mem. Carnegie Mus. 5:1-578.

Isbrücker, I. J. H. 1980. Classification and catalogue of the mailed Loricariidae (Pisces, Siluriformes). Verslagen en Technische Gegevens, Universiteit van Amsterdam No. 22, 1-181 pp.


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