Comprehensive DescriptionRead full entry
Holotype : GUYANA : Rupununi (Region 9) , Essequibo River Dr. , UG/CSBD 11041 (ex. AUM 35555) . 115.8 mm SL. Rupununi R 5.9 km WSW village of Sand Creek , 02.96656° , -059.56943° , D.C. Werneke, C.L. Allison, M.R Thomas, C.J. Chin, D. Arjoon, M.H. Sabaj, J.W. Armbruster , 4 November 2002 .
Paratypes : All localities GUYANA , Essequibo River Dr. : Upper Demerara-Berbice (Region 10) : AUM 35546 , 1, 169.4, Essequibo River at Kurukupari, east bank , 04.66149° , -058.67519° , J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, S.M. James , 4 November 2002 . Rupununi (Region 9) : AUM 35521 , 2, 18.9-29.6 and UG/CSBD 11042 , 1, 40.3, Simoni River - 4 sites from 6.6 km SE to 3.2 km W Karanambo , 03.71917° , -059.26121° , J.W. Armbruster, M.H. Sabaj, C.L. Allison, M.R. Thomas, R. Francis , 29 October 2002 ; ANSP 179211 , 3, 32.9-94.2, AUM 35537 , 2, 45.6-78.1, and SIUC 49166 , 2, 36.4-74.6, Rupununi River 4.6 km NW Massara , 03.92603° , -059.28037° , J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon, S.M. James, S. Mario , 4 November 2002 .
Nontypes: GUYANA : Takutu River - Rio Branco - Rio Negro Dr. , Rupununi (Region 9) , AUM 35733 , 5, 109.5-155.2, Takutu River ca. 2.75 km W Saint Ignatius , 03.35500° , - 059,83077° , J.W. Armbruster, M.H. Sabaj, D.C. Werneke, C.L. Allison, M.R. Thomas, C.J. Chin, D. Arjoon , 5- 6 November 2002 . VENEZUELA , Rio Cinaruco - Rio Orinoco Dr. , Apure , MCNG 20164 , 1, 197.7, Rio Cinaruco in Laguna Larga , 6°31’N , 67°21’W , D.C. Taphorn et al. , 25 April 1989 . VENEZUELA : Rio Siapa - Rio Casiquiare - Rio Negro Dr. , Amazonas , MCNG 37043 , 2 +1 cs. 116.3-149.0, Rio Siapa immediately below Raudal Gallineta , Departmento Río Negro , 1°49’N , 65°47’W , L. Nico, S. Walsh, and A. Arrington , 14 January 1998 .
Diagnosis: Peckoltia sabaji ZBK is diagnosable from nearly all other members of the Ancistrini based on coloration: small spots on the head with spots becoming very large on the caudal peduncle and caudal fin (Figs. 2-4). Only an undescribed Peckoltia ZBK among the Ancistrini examined has such large spots on the caudal peduncle. Peckoltia sabaji ZBK can be separated from the similarly colored undescribed species of Peckoltia ZBK by having a very long caudal peduncle (no specimens of the undescribed species have been examined for a precise measurement) and by having a much greater number of spots on the body (the undescribed species has fewer than ten spots present on the body posterior to the nape whereas P. sabaji ZBK has more than ten in adults). Peckoltia sabaji ZBK can be further separated from all other Ancistrini except Hemiancistrus ZBK , Panaque ZBK , and other Peckoltia ZBK by lacking (or rarely having) odontodes on the opercle in adults. Species of Panaque ZBK have widened, spoon-shape teeth (vs. villiform teeth). Sympatric Hemiancistrus ZBK and Peckoltia ZBK are without spots and have fewer than 27 lateral-line plates (vs. 27, rarely 26). Sympatric Ancistrus ZBK , Dekeyseria ZBK , Hypancistrus ZBK , Pseudancistrus ZBK , and Pseudolithoxus ZBK do not have plates on the abdomen (vs. some plates present in all adults). Sympatric Lasiancistrus have three rows of plates on the caudal peduncle (vs. 5). Pseudacanthicus ZBK has large keel odontodes on the lateral plates (vs. keels absent). Some species of Hypostomus ZBK (Hypostomini) have a similar color pattern to that of P. sabaji ZBK , but lack the evertible cheek plates and associated hypertrophied odontodes characteristic of the Ancistrini, and have odontodes on the opercle.
Description: A member of the Hypostominae: Ancistrini. Morphometrics in Table 2. Body low, narrow, and elongate. Body depth increases curvilinearly from snout tip to origin of dorsal fin, decreases to near end of caudal peduncle, and then increases at a steep angle until caudal fin. Ventral surface flat. Body widest at insertion of pectoral fins, narrowest at end of caudal peduncle. Snout rounded. Caudal peduncle oval in cross section with dorsal and ventral surfaces flat.
Dorsal margin of orbit forming ridge higher than interorbital space. Dorsal surface of head between orbits concave laterally and convex medially. Supraoccipital pointed posteriorly; point of supraoccipital slightly raised and with odontodes slightly larger than those of surrounding bones and plates. Following head bones supporting odontodes: infraorbitals, frontal, nasal, pterotic-supracleithrum, and supraoccipital. Preopercle and opercle rarely supporting odontodes. Posterodorsal margin of opercle often covered by plate.
Lower lip wide, covered with short, wide papillae. Upper lip narrow, spotted ventrally, and with very small papillae posteromedially and larger, wider papillae anteriorly and laterally. Only maxillary barbel present, typically reaching about three quarters of way from its origin to gill opening. Some individuals with one or both barbels bifurcated or trifurcated, split barbels are shorter than unsplit barbels. Mouth with small, narrow buccal papilla. Iris with small dorsal flap, not reaching ventral to center of pupil.
Usually 27 lateral plates (one of 14 individuals with 26 and one with 28). Plates unkeeled. Five rows of plates on caudal peduncle. Plates covering almost all surfaces of body except for anterior margin of snout and between mouth and pectoral girdle. Abdominal plates variable. Most individuals with some small, deeply embedded plates ventral to pectoral girdle, medially on abdomen, ventral to pelvic girdle, near anus, and along sides; however, any abdominal area may be naked. Extent of abdominal plating only partially correlated with size, most small individuals with fewer plates, but some adults with few plates on abdomen.
24-53 (mode = 48) evertible cheek odontodes Longest evertible cheek odontode does not reach posterior to cleithrum. Evertible cheek odontodes supported by plates than can be everted to approximately 90° from the head. Hypertrophied cheek odontodes relatively weak. Slightly longer odontodes present along dorsal-, adipose-, and pectoral-fin spines; largest individual examined with modestly hypertrophied odontodes at tip of pectoral-fin spine.
All fin spines and rays supporting odontodes. Dorsal fin II7 ; dorsal-fin spinelet V- shaped, dorsal-fin lock functional; dorsal-fin spine elongated relative to other fin rays in some specimens; dorsal fin reaching adipose fin when adpressed in juveniles, but not in adults. Adipose fin with single median preadipose plate and fairly long curved spine. Caudal fin I14 I; caudal fin forked, lower lobe longer than upper; usually 5 dorsal and ventral procurrent caudal-fin rays (one of 14 individuals with 7 dorsal and 6 ventral). Pectoral fin I6 ; pectoral fin spine reaching beyond base of pelvic fin when adpressed ventral to pelvic fin. Pelvic fin I5 ; pelvic-fin spine reaching at least to end of base of anal fin when adpressed. Anal fin I4 ; anal-fin spine slightly shorter than first ray.
Teeth bicuspid with a longer, slightly wider median lobe and a thicker, shorter, darkeryellow lateral lobe. Most teeth are worn such that the two lobes are approximately equal in length. 27-57 dentary teeth (mode = 38). 31-58 premaxillary teeth (mode = 49).
Considerable ontogenetic change in shape. Juveniles more dorsoventrally flattened and not as elongate as adults.
Coloration: In life, the base color is light tan (almost yellow), tending to orange on the fins (Fig. 1). In alcohol, the base color is darker tan (Fig. 3). Small- to medium-sized dark spots on the head becoming much larger posteriorly; corresponds with decrease in numbers of rows of spots. Size of spots varies, even between specimens collected together, but spots always largest on caudal peduncle and fin. Dorsal-fin spine either without spots or spots present distally. Dorsal fin with spots centered on the membranes, rays typically without spots; dark wash present between dorsal-fin spine and first ray and between the distal branches of the first ray; dorsal fin generally with a black margin. Adipose fin with spot present on preadipose plate and one or two large spots along spine; adipose-fin membrane mottled. Spots on caudal fin largest on body, often combining to form bands (particularly ventrally); caudal-fin spots centered on fin rays; spots present along dorsal margin of dorsal and ventral caudal-fin spines, but ventral margin of ventral caudal-fin spine tan. Pectoral fin spots smallest, centered on either side of the pectoral-fin rays and dorsally along the pectoral-fin spine; spots fade distally. Pelvic fin with large spots dorsally, centered on rays and spine, spots fading posteriorly and distally. Anal fin spotted randomly with spots centered over membranes. Ventral surface behind mouth much lighter than sides, occasionally with slight mottling. Upper lip with small dark spots. Barbels mottled. Eye with dark spots dorsally, mottled ventrally.
Considerable ontogenetic change observed in coloration (Figs. 3 & 4). The smallest individual examined with mottled head and spots that appear to form dorsal saddles posteriorly; large spots present on all fins. Slightly larger individuals with spots on the head, but posterior body spots still forming saddles; dorsal and caudal fins with bands. As individuals grow, the spots become more numerous and the relative size of the spots decreases.
Ecology: Uncommon. Found in medium to large rivers among boulders. Usually in runs and riffles, but small individuals may be found hidden in the holes of lateritic rocks in pools. Most specimens I collected were collected at night. The largest individual was captured in a gill net in the main stem Essequibo and it appeared to be moving from deeper water into the shallows where there were exposed boulders.
Range: Currently known from the Rupununi, Essequibo, and Takutu River drainages of Guyana, and from single localities in the Río Casiquiare - Río Negro and the Río Cinaruco - Río Orinoco drainages of Venezuela (Fig. 5).
Etymology: Named for Dr. Mark Henry Sabaj, Collection Manager of Ichthyology, Academy of Natural Sciences of Philadelphia, for his tremendous help in collecting specimens throughout South America, and because he collected the first live specimen that I ever saw. Pronounced sah-bay’-i.
Some variation was found in PCA among the three populations (Fig. 6, most strongly weighted characters shown along axes); however, there are far too few collections available at this time to determine if these morphometric differences represent interspecific differences. Color and meristics did not vary significantly among populations. Type specimens were restricted to the Essequibo River drainage because future effort might determine that the three known populations (Essequibo, Negro, Orinoco) should be separated.
The distribution of Peckoltia sabaji ZBK can be explained by current (seasonal and permanent) connections between the Orinoco, Negro, and Essequibo River drainages. The seasonally flooded Rupununi Savannah allows movement between the watersheds of the Rupununi River (Essequibo Dr.) and Takutu River (Branco-Negro-Amazon Dr.), and the Río Casiquiare allows movement of upper Río Negro fauna into the upper Río Orinoco. The lack of strong geographic variation in the morphology of P. sabaji ZBK suggests that this species may frequently disperse via these passageways. The large specimen from Kurukupari on the Essequibo River ( AUM 35546) was collected at night in a gill net and appeared to be moving from deeper water into the shallows suggesting that the species may make diurnal migrations.