Corymbophanes kaiei, Armbruster & Sabaj, 2000

Lujan, Nathan K., Armbruster, Jonathan W., Werneke, David C., Teixeira, Túlio Franco & Lovejoy, Nathan R., 2020, Phylogeny and biogeography of the Brazilian-Guiana Shield endemic Corymbophanes clade of armoured catfishes (Loricariidae), Zoological Journal of the Linnean Society 188, pp. 1213-1235 : 1222-1228

CORYMBOPHANES KAIEI – LUJAN ET AL., 2017: 323

[molecular phylogeny]

CORYMBOPHANES KAIEI – FISCH-MULLER ET AL., 2018: 11, 18

[molecular phylogeny, data from GenBank]

Holotype: CSBD F1721 , ex. ROM 89895 , 89.3 mm SL; GUYANA, Region 8 (Potaro–Siparuni), Kuribrong River , Potaro River –Essequibo River drainage, at rapids ~15 min upstream of upstream Kuribrong Camp; 05.33766°, -059.56615°, 454 m a.s.l.; 19–20 March 2011; N. K. Lujan, F. C. T. Lima, T. C. Pessali, T. F. Teixera, P. Bernardo, A. Khan, G. Savory and K. Andrew.

Paratypes: All collections GUYANA, Region 8 ( Potaro–Siparuni ), Kuribrong River, Potaro River – Essequibo River drainage . AUM 53676 , 1, 100.6 mm SL, tributary of Kuribrong River , above Amaila Falls , 05.36637°, -059.54324°, 29 March 2011, B. Noonan ; AUM 62704 , 2 , 72.5–99.6 mm SL, Amaila River , at campsite near confluence with Kuribrong , 05.37626°, -059.55114°, 5–6 March 2014, E. A. Liverpool and D. C. Taphorn ; AUM 62732 , 1 , 84.6 mm SL, Amaila River , mouth, 05.37608°, -059.55053°, 8 Mar 2014, D.C. Taphorn, E. A. Liverpool and L. Benjamin ; AUM 62741 , 1 , 55.8 mm SL, Amaila River , just upstream from mouth, 05.37608°, -059.55053°, 7–8 March 2014, D. C. Taphorn, J. W. Armbruster, D. C. Werneke, E. A. Liverpool and D. P. Fernandes ; MZUSP 110846 , 3 , 81.6–88.3 mm SL, same data as holotype ; ROM 89856 , 1 , 73.6 mm SL, same locality of holotype, 16 March 2011, N. K. Lujan, F. C. T. Lima, T. C. Pessali and T. F. Teixera ; ROM 89895 , 3 , 86.4–93.8 mm SL, same data as holotype ; ROM 89897 , 3 , 80.7–92.7 mm SL, same locality as holotype , 20–22 March 2011, T. C. Pessali and T. F. Teixera ; ROM 91390 , 1 , not measured, upper Kuribrong River at right (south) bank tributary mouth, 05.32438°, -059.57321°, 15–17 October 2011, D. Abraham and N. K. Lujan ; ROM 91506 , 2 , not measured, small right (south) bank tributary of upper Kuribrong upstream upper rapids (rapid 3), 05.33458°, -059.56738°, 15, 16 and 18 October 2011, D. Abraham and N. K. Lujan ; ROM 91402 , 1 , not measured, upper Kuribrong River at upper rapid (rapid 3), 05.34109°, -059.56474°, 24 October 2011, N.K. Lujan, D. Abraham, D. Stoby, D. Gordon and O. Williams ; ROM 94980 , 2 , not measured, rapid 6, tributary of upper Kuribrong , Itabu Creek, 05.29113°, -059.71923°, 28 March 2014, D. C. Taphorn, E. Liverpool, H. Lopéz-Fernández, M. Benjamin and G. Pablo .

Non-types: All collections GUYANA, Region 8 (Potaro– Siparuni), Kuribrong River, Potaro River–Essequibo River drainage. AUM 62801, 1, Kuribrong River, above Amaila Falls in rapid 1, 05.37608°, -59.55053°; AUM 62811, 1, Kuribrong River, at riffle midway between rapid 1 and 2, 1.58 km SSE of Amaila River confluence, 05.36405°, -59.54318°. These specimens are small juveniles whose identity cannot be confirmed.

Diagnosis: Corymbophanes ameliae can be distinguished from C. andersoni by having dark and light vermiculations on the ventral surface and bands in the caudal fin (vs. white spots on the caudal fin and ventral surface white to grey) and by generally having the anal fin i,5 (vs. i,4; two specimens of C. ameliae are i,4). Corymbophanes ameliae can be separated from C. kaiei by having a longer head ( Fig. 7) that is more rounded (vs. straight), by having a narrow caudal peduncle, visible dorsally by being nearly flat at end and ventrally by having the minimum caudal peduncle width 10.1–12.2% HL (vs. 12.3–13.0% HL; Fig. 7). Corymbophanes ameliae can be separated from the new genus Yaluwak by lacking hypertrophied cheek odontodes and evertible cheek plates. The only other loricariid with which Corymbophanes ameliae is sympatric is Hypostomus hemiurus , from which it can be distinguished by lacking an adipose fin.

Description: Morphometrics in Table 4; meristics in Table 5. Counts and measurements based on 16 specimens. It is a member of subfamily Hypostominae , tribe Ancistrini sensu Lujan et al. (2015) . Small to medium-sized loricariids, largest specimen examined 100.6 mm SL. Body narrow, subcylindrical with ventral surface completely flat, dorsal surface flattened from dorsal to adipose origins and tapering from cleithrum to caudal fin. Head gently sloped to dorsal fin. Parieto-supraoccipital not higher than nuchal region. Dorsal slope decreasing in straight line to insertion of dorsal procurrent caudal-fin rays then ascending to caudal fin. Body depth greatest at origin of dorsal fin. Ventral profile flat to caudal fin. Caudal peduncle almost triangular in cross section: flattened laterally, becoming transversely pointed dorsally and flattened ventrally. Body widest at origin of pectoral fins, narrowest at origin of caudal fin. Snout rounded.

Eye small (orbit diameter 15.3 ± 1.0% of head length), dorsal rim of orbit slightly higher than interorbital space. Iris operculum absent. Interorbital space with slight, rounded, median hump. Parieto-supraoccipital straight posteriorly with no crest. Infraorbitals, frontal, nasal, compound pterotic and parieto-supraoccipital supporting odontodes. Preopercle without odontodes. Exposed portion of opercle oval (long axis in anteroventral to posterodorsal angle) covered with odontodes (those along ventral margin slightly longer).

Lips covered with short papillae with circular bases. Lower lip wide, reaching just to, or slightly short of, pectoral girdle; upper lip narrow. Edge of lower lip smooth. Maxillary barbel reaching about half distance to gill opening from base of barbel.

Median plates 22(1), 23(11) or 24(4). Plates unkeeled, but first three or four plates of mid-ventral series bent to form a slight ridge and ventral plates posterior to pelvic fin with concave dorsal halves forming ventral ridge; ventral ridge most pronounced posteriorly. Mid-dorsal plate row consisting of just three plates anteriorly; mid-ventral plate row ends ventral to anterior portion of postdorsal ridge; dorsal and median plate rows complete, ventral row beginning dorsal to pelvic-fin origin; three caudal peduncle plate rows. Plates on all dorsolateral surfaces of body; ventral surface of head and abdomen naked. Cheek plates not evertible; cheek dontodes slightly longer than average body odontodes present along dorsal-, adipose-, pelvic-, caudal- and pectoral-fin spines; larger individuals with somewhat larger odontodes at tip of pectoral spine.

Dorsal fin ii,7; dorsal spinelet V -shaped, dorsal-fin locking mechanism present, spinelet ranging from covered in skin to just slightly exposed; last ray of dorsal fin almost reaching postdorsal ridge when adpressed. Adipose fin absent, replaced by postdorsal ridge of 12(2), 13(3), 14(3), 15(3), 16(4) or 18(1) median, azygous plates. Caudal fin i,14,i (one specimen i,13,i); caudal fin slightly forked, ventral lobe longer than dorsal lobe. Pectoral fin i,6; pectoral-fin spine reaching almost to pelvic fin when adpressed. Pelvic fin i,5; pelvic-fin spine extending almost to anal fin when adpressed. Anal fin i,4(2) or i,5(14); unbranched anal-fin ray slightly shorter than first branched ray.

ILM, Inter-Landmark.

Teeth bicuspid with lateral cusp one-half to threequarters length of medial cusp and lateral cusp half width of medial cusp; 38–70 left dentary teeth (mode 54; one specimen damaged); 44–76 left premaxillary teeth (mode 44; one specimen damaged).

Coloration: Dorsal surface and sides of head and body dark brown to black with small white to cream-colored spots (most spots smaller than eye size; Figs. 4, 5). Light spots smallest and most tightly spaced on head, becoming slightly larger and more irregularly spaced towards caudal peduncle; combining to form bars and/or vermiculations in some larger specimens. Ventral surface brown with distinct white vermiculations (light and dark vermiculations of approximately equal width); centre of dark vermiculations often fade towards middle of abdomen. Fin spines and rays tan to cream with dark spots forming bands (interradial membranes grey to brown); light areas generally narrower than intervening dark bands. Juveniles more uniformly coloured; appear medium to dark brown overall except for faint light spots on head, faint light bands on caudal fin and lightly pigmented abdomen; sides of body slightly darker midlaterally, forming broad, diffuse, dark brown stripe.

Fig. 4). Specimen has slightly thickened skin over dorsal and lateral surfaces of body and posterior part of head. Skin greatly thickened in circular patch anterior to nares with fleshy area extending over snout tip. Skin in this patch rugose with greatly elongated odontodes distributed along the periphery of the naked area. Some hypertrophied odontodes in the centre of the circle, but the soft tissue is damaged due to rot. Longest odontodes at anterior corners of snout with largest much longer than head (38.7 mm long, 116% of head length). Odontodes also considerably longer along back of circle (longest 16.8 mm long, 47.8% of head length). Damage caused by rot means odontodes are loosely held in flesh and some are pushed inward, making exposed length difficult to ascertain. Pectoral-spine odontodes barely, if any, greater than other specimens. Out of the

> 40 specimens of Corymbophanes that have been deposited in collections, this is the only individual to show any sign of sexual dimorphism.

Range: Known only from the Kuribrong River drainage upstream of Amaila Falls , and within this drainage only from regions adjacent to four rapids habitats (rapids 1, 3, 4 and 5; Figs. 1, 3).

Sexual dimorphism: Only nuptial male specimen known was found dead in a stream (AUM 53676, 100.6 mm SL, sex determined by examining gonads; Etymology: Named for Amelia, a Patamona Amerindian girl who disappeared near Amaila Falls in the late 19 th century. The falls are named for her, but her name was misspelled.

Haplotype diversity: Within Corymbophanes ameliae, ND 2 provided the most geographically associated variation ( Fig. 3), although Cytb also exhibited multiple haplotypes that corresponded with geography. 16S was variable but geographically uninformative, and no fixed polymorphisms were observed within the nuclear RAG1 or RAG2 regions. The phylogenetic analysis ( Fig. 2, Node 5: BI:

0.97, ML: 64) and ND2 haplotype network ( Fig. 3) both supported a sister relationship between the C. ameliae population in tributary 4 (rapid 5) and those in the remainder of the upper Kuribrong River watershed (rapids 1–4; see Fig. 3 inset map). Some population structure was also detected within the upper Kuribrong River main channel, with a few individuals from rapid 1 immediately upstream of Amaila Falls being distinguished from both syntopic individuals and more upstream populations by a single ND2 polymorphism ( Fig. 3).