Lasiancistrus is a medium-sized genus (ca. 16 species) of the Loricariidae from the Amazon, Essequibo, Orinoco, Magdalena, San Juan, Atrato, Tuyra, and Bayano River drainages and the Lake Maracaibo drainage.  Lasiancistrus was described by Regan (1904) as a subgenus of Ancistrus for those species of loricariids that have hairlike odontodes as part of the evertible cheek odontodes (later called whiskerlike odontodes; Armbruster, 2004).  The whiskerlike odontodes are unique among the Loricariidae (Armbruster, 2004).  These odontodes are very narrow, but appear to be made out of the same material as the rest of the odontodes (enamel and dentin).  Later, Lasiancistrus was raised to genus level, and many unrelated species were placed into it (Isbrückercker, 1980; Heitmans et al. 1985; Armbruster and Provenzano, 2000).  The genus was diagnosed by Armbruster (1997; 2004), and the taxonomy was greatly updated by Fisch-Muller (2003).

            Several taxonomic problems are still inherent in Lasiancistrus due to the fact that most species were described from few, and in one case no, specimens, and localities are imprecise.  An examination of the type specimens, the original descriptions, and a little detective work has led to this revision of the genus.  Based on this study, four of the 16 described species are considered valid: L. heteracanthus (Günther, 1869) (type of the genus), L. schomburgkii (Günther, 1864), L. caucanus Eigenmann, 1912, and L. guacharote (Valenciennes, 1840).  In addition, two new species are described (L. saetiger and L. tentaculatus). Lasiancistrus maracaiboensis Schultz 1944, and L. mystacinus (Kner, 1854) are synonyms of L. guacharote. Lasiancistrus castelnaui (Miranda Ribeiro 1911) was originally published as a replacement name for L. pictus (Castelnau, 1855) which was preoccupied by Ancistrus pictus Kner 1854 when both species were in Hemiancistrus (Miranda Ribeiro, 1911).  Lasiancistrus castelnaui, L. caquetae (Fowler, 1945), L. guapore Knaack, 2000, L. multispinis Holly, 1929, L. pictus, and L. scolymus Nijssen and Isbrückercker 1985, are synonyms of L. schomburgkii.  Lasiancistrus planiceps Meek and Hildebrand, 1913, L. mayoloi (Eigenmann, 1912), and L. volcanensis Dahl, 1942, are synonyms of L. caucanus. Chaetostomus trinitatus G nthenther, 1864, is occasionally recognized in Lasiancistrus, but there were no types designated for the species.  The species cannot be placed to genus based on the original description and C. trinitatus is recognized as incertae sedis in the Loricariidae.  In addition, Lasiancistrus nationi was found to be a species of Ancistrus.  In this paper, Lasiancistrus and its species are described and diagnosed.

 

Diagnosis. Lasiancistrus is diagnosed by two unique synapomorphies from Armbruster (2004): presence of a posteriorly directed strut of the pterotic leading from the anterior process of the pterotic to the main body of the pterotic, which is visible from below and which causes the dilatator operculi chamber to be open posteriorly (114:1; Fig. 1; originally described by Schaefer, 1986) and presence of whiskerlike odontodes on the cheek (186:1, Fig. 2).  Lasiancistrus is also diagnosed by the following homoplastic synapomorphies: three branchiostegals (5:1), presence of a posteromedial invagination of the fifth ceratobranchial (11:1), presence of a ventral process on the quadrate for articulation with the canal plate (65:1), infraorbital six forming the entire ventral border of the orbit (89:1), loss of a deep pouch posteroventrally on the lateral ethmoid (98:0), loss of contact of the sphenotic and infraorbital six (117:1), and distal margin of rib of sixth vertebra flared distally so that the tip is much wider than the shaft (128:1).

                                                                                                                                       

            Adult Lasiancistrus can be separated from all other loricariids by the presence of whiskerlike odontodes on the cheek.  In addition, Lasiancistrus can be separated from all other loricariids except members of the Pterygoplichthini and Ancistrini by the presence of evertible cheek odontodes; from the Pterygoplichthini by having three rows of plates on the caudal peduncle (vs. five) and a modified, bar-shaped opercle (vs. a triangular opercle); from all except Ancistrus, Dekeyseria, Exastilithoxus, Lithoxus, Neblinichthys, and Pseudolithoxus of the Ancistrini by having three rows of plates on the caudal peduncle (vs. five, rarely four); from all but Ancistrus by having nuptial males with tentacules on the pectoral-fin spines longer than their associated odontodes; from Ancistrus by having plates along the edge of the snout (vs. snout plates absent) and by maximally having transluscent tentacules on the snout that have odontodes associated with them (vs. larger tentacles without associated odontodes colored the same as the head; even female and juvenile Ancistrus have some tentacles along the snout margin); from Dekeyseria by lacking keels on the lateral plates; from Exastilithoxus and Lithoxus by having greater than 30 teeth per jaw ramus (vs. less than 10) and by having oval lips (vs. round); from Neblinichthys by lacking hypertrophied odontodes on top of the head in nuptial males; and from Pseudolithoxus by lacking long, bristle-like odontodes on the leading edge of the pectoral-fin spine.

            Description. Member of Ancistrini as diagnosed by Armbruster (2004). Medium-sized loricariids, largest specimen 190.4 mm SL. Body strongly dorsoventrally compressed and moderately wide. Head and nape gently sloped to insertion of dorsal fin. Dorsal profile very slightly sloped ventrally to dorsal procurrent caudal-fin spines, then rising slightly to caudal fin. Ventral profile flat to caudal fin. Supraorbital ridge almost absent with interorbital space slightly concave, almost flat.  Supraorbital ridge continues as slightly higher, rounded ridge from anterior of orbit to slightly anteroventral of anterior nare. Mesethmoid raised slightly above lateral surface of snout to form slight ridge. Head contours smooth. Eyes small to medium.

            Keels absent.  All plates slightly convex medially to produce cylindrical body. Mid-dorsal and mid-ventral plate rows incomplete, generally ending below adipose fin; three rows of plates on caudal peduncle. Abdomen either naked, with few small plates near insertion of pectoral-fin spine, or with very small, embedded plates from pectoral girdle to anterior of pelvic girdle. First anal-fin pterygiophore not exposed to form platelike structure. 21-25 (mode = 24) plates in the median series.

            Frontals, infraorbitals, nasals, opercles, pterotics, sphenotics, and supraoccipital supporting odontodes.  Opercular odontodes occasionally moderately hypertrophied, thick, and sharp; whiskerlike odontodes rarely present on opercle. Whiskerlike odontodes present in evertible cheek mass and occasionally at anterolateral corner of snout; 0-35 whiskerlike odontodes in evertible cheek mass with number of whiskerlike odontodes increasing with size; 12-76 (mode = 25, N=159) total hypertrophied odontodes in cheek mass. Cheek plates evertible to approximately 90¡ from head, hypertrophied cheek odontodes folded under opercle when relaxed. Odontodes on tip of pectoral-fin spine slightly hypertrophied.  Odontodes on lateral plates not enlarged to form keels.

            Dorsal fin not reaching preadipose plate when adpressed; dorsal-fin spine not elongate, edge of dorsal fin straight. Dorsal-fin spinelet V-shaped, dorsal-fin spine lock functional. Dorsal fin II7 (one of 280 individuals II6). Adipose fin with one preadipose plate and moderately long spine. Caudal fin slightly emarginate to forked, lower lobe longer than upper, I14I (one of 286 individuals I11I, two I12I, and four I13I) with three to five (mode five, N=157) dorsal procurrent caudal-fin rays and three to five (mode 4, N=157) ventral procurrent caudal-fin rays. Anal fin short with unbranched ray weak and usually about three quarters length of first branched ray. Anal fin I5 (one of 307 specimens I1, five I4, and one I6), Pectoral-fin spine reaching slightly posterior to insertion of pelvic fin when adpressed ventral to pelvic fin. Pectoral fin I6 (three of 307 individuals I5). Pelvic fin reaching to posterior of anal-fin when adpressed. Pelvic fin I5 (N=307).

            Dorsal flap of iris present. Flap between anterior and posterior nares short. Lips wide, fairly thin. Upper lip with small, round papillae. Lower lip with medium-sized papillae anteriorly and smaller ones posteriorly. Maxillary barbels very short, not reaching behind lower lip, occasionally completely adnate. Buccal papilla small. Jaws moderately wide, dentaries forming very oblique angle; premaxillaries forming a very shallow arc with an overall angle just slightly less than 180¡. Teeth with fairly long, narrow cusps; lateral cusp approximately half-length of medial cusp, stalks of teeth long; 39-101 dentary teeth (mode = 74, N=137) and 29-97 premaxillary teeth (mode = 60, N=141).

           

Sexual dimorphism. Snout of nuptial males almost square (vs. rounded in females and juveniles). Adult males of most species (except Lasiancistrus tentaculatus) with whiskerlike odontodes at anterolateral corner of snout (Fig. 2a); males of L. tentaculatus with tentacules instead of whiskerlike odontodes along anterior margin of snout (Fig. 2b).  Nuptial males with tentacules longer than their associated odontodes on the pectoral-sin spine (Sabaj et al., 1999).

           

Range. Found throughout the Amazon River basin, the upper and middle of the Orinoco River basin, the Rupununi River basin (Essequibo River drainage), the Lake Maracaibo drainage, and drainages west of the Andes in Colombia and Panama to the Bayano River. Square - L. caquetae, Upsidedown triangle - L. guacharote, Diamond - L. heteracanthus, Plus - L. saetiger, triangle - L. schomburgkii, Dot - L. tentaculatus; open symbols type localities except in L. heteracanthus where the precise type locality is unknown.

Key to the Species of Lasiancistrus

 

1a.  .... Dorsal fin with either white spots in the dorsal fin or dorsal fin plain.  Body typically with small or large light spots or entirely dark............................................................................................................................................. 2

1b....... Dorsal fin with black spots.  Body with dark markings, light markings (if present) usually present as blotches or thick lines (except in r’o Bayano population in Panam‡), body never completely dark...................................... 3

 

2a....... Body and fins with small white spots (although spots may be faded).  Plates entirely dark or with small spots.        L. schomburgkii

2b....... Body and paired fins with large white spots, dorsal fin without spots.  Plates outlined in black         L. saetiger

 

3a....... Abdomen without plates...................................................................................................... 4

3b....... Abdomen with plates in at least a small patch medial to the insertion of the pectoral-fin spines.         5

 

4a....... Nuptial males with whiskerlike odontodes at the corners of the snout (Fig. 2a).  Caudal fin emarginate.       L. caucanus

4b....... Nuptial males with tentacules along the anterior margin of the snout (Fig. 2b).  Caudal fin forked.   L. tentaculatus

 

5a....... Abdomen with plates underneath entire pectoral girdle and on abdomen.

................................................................................................................................ L. heteracanthus

5b....... Abdomen with only a couple of plates medial to insertion of pectoral-fin spines.

..................................................................................................................................... L. guacharote

 

Lasiancistrus caucanus Eigenmann 1912

                                                                                                                                                      F4

Synonymy:

Lasiancistrus caucanus Eigenmann 1912:11.

Hemiancistrus mayoloi Eigenmann 1912:10.

Ancistrus planiceps Meek and Hildebrand 1917:79.

Lasiancistrus volcanensis Dahl 1942: 83

 

Diagnosis. Lasiancistrus caucanus is distinguished from all other species of Lasiancistrus except L. saetiger, L. tentaculatus, and some L. schomburgkii by the absence of plates ventrally in front of the anus and from all Lasiancistrus except some L. guacharote by having the caudal fin slightly emarginate (vs. forked; Fig. 4).  Additionally, L. caucanus can be separated from L. schomburgkii and L. saetiger by having dark spots in the dorsal fin (vs. dorsal fin all gray or with white spots); from L. tentaculatus by having tentacules along the snout that are shorter than their associated odontodes in nuptial males (vs. longer in nuptial males), and by having whiskerlike odontodes at the anterior corner of the snout in nuptial males (vs. whiskerlike odontodes absent, Fig. 2a).

Description. See genus description for more information. Morphometrics in Table 1.  Largest specimen 190.4 mm SL. Abdomen naked.  21–25 (mode = 24) plates in the median series.  4-35 whiskerlike odontodes in evertible cheek mass (mode = 11, N = 49); 21-76 (mode = 39, N = 57) total hypertrophied odontodes in cheek mass.

                                                                                                                               

Color. Color variable.  Body typically light brown with dark, wavy stripes that may break up into dashes or spots posteriorly. Light areas occasionally exist as spots rather than background color.  The head may be mottled or have light spots.  The body and head may also be uniformly dark. Abdomen uniformly light tan, lower surface of caudal peduncle darker than abdomen. Dorsal fin with large, rectangular spots centered and darkest on fin rays, almost combing to form bands.  Paired, caudal, and anal fins with narrow bands.  Lower half of caudal fin slightly darker than upper.  Adipose fin uniformly dark.  Color darkens with size.

           

Sexual dimorphism. Nuptial males with whiskerlike odontodes at the anterolateral corner of the snout, else as in genus description.

 

Range. Lasiancistrus caucanus has a trans-Andean distribution in the r’os Magdalena, Atrato, San Juan, Tuyra, and Bayano drainages of Colombia and Panama.

 

Comments: Lasiancistrus caucanus and L. mayoloi were both described by Eigenmann (1912); however, L. mayoloi was described in Hemiancistrus.  Because L. caucanus was described in the correct genus and L. mayoloi was not, L. caucanus was chosen as the valid species.

            Most specimens available have the colors faded, but those that do have color left show little variation across the trans-Andean region they occupy and no other characteristics could be found to support any of the species listed above as synonyms.  The only difference in color pattern is from specimens collected from the r’o Bayano, the furthest west river in the range of L. caucanus in Panama.  These specimens have the light areas of the body as spots instead of forming a light background; however, the other elements of the color pattern are as in the rest of the species.  Few specimens are available from the Bayano to make comparisons, so it is unknown if this population would require separate species status.

 

Lasiancistrus guacharote Valenciennes 1840

                                                                                                                                              

Synonyms

Hypostomus guacharote Valenciennes in Cuvier & Valenciennes 1840: 508.

Ancistrus mystacinus Kner 1854: 276.

Lasiancistrus maracaiboensis Schultz 1944: 314.

 

Diagnosis. Lasiancistrus guacharote can be separated from all other species of Lasiancistrus except for some L. schomburgkii by having a single to a small patch of platelets ventromedially from the insertion of the pectoral-fin spine (Fig. 5) and nowhere else ventrally, and from L. schomburgkii by having black spots in the dorsal fin (vs. no or white spots) and black bands in the paired and caudal fins (vs. bands absent).

 

Description. See genus description for more information. Morphometrics in Table 1.  Largest specimen 119.5 mm SL. Abdomen naked.  23-25 (mode = 24) plates in the median series.  4-24 whiskerlike odontodes in evertible cheek mass (mode = 16, N = 26); 17-43 (mode = 25, N = 26) total hypertrophied odontodes in cheek mass.

 

Color. Small, white spots on head, fading on nape.  Body mottled with faint hint of dorsal saddles.  Abdomen light tan, ventral surface of caudal peduncle slightly darker. Dorsal fin with large, rectangular spots centered and darkest on fin rays, almost combing to form bands.  Paired, caudal, and anal fins with narrow bands.  Lower half of caudal fin slightly darker than upper.  Adipose fin uniformly dark.  Color darkens with size.

           

Sexual dimorphism. Nuptial males with whiskerlike odontodes at the anterolateral corner of the snout, else as in genus description.

 

Range. The Lago Maracaibo basin of Venezuela and Colombia.

 

Comments: The holotype of Lasiancistrus guacharote is said to be from Puerto Rico (Cuvier and Valenciennes, 1840), but it is highly unlikely that loricariids could have arrived naturally on this northern Caribbean island.  The holotype was collected by Augustus Pl e, ae, a young adventurer-naturalist who collected fish specimens from around the Caribbean and the Gulf of Mexico in the 1820's, and who did collect in Puerto Rico (Pietsch, 1995).  Plee also collected in the Maracaibo basin of Venezuela.  Specimens of upland fishes that are known to be sympatric with Lasiancistrus such as Parodon and Piabucina were collected by Plee in the Maracaibo basin according to the MNHN catalog on the internet.  Examination of the type reveals that it has the characteristic used to diagnose the species from the Maracaibo Basin.  In all likelihood, the locality was somehow misplaced.  Pl e wae was not around to correct the error because he died on the day he was to return to France (Pietsch, 1995).

            Lasiancistrus mystacinus was described by Kner (1854) based on a single specimen with the stated locality of "Caracas".  The drainage in Caracas is the r’o Tuy, and no Lasiancistrus have been reported from the Tuy.  It is believed that the locality "Caracas" in Kner's work simply means where the specimens left Venezuela (R. P. Vari, pers. comm.), and that these specimens could have come from anywhere in Venezuela.  The type of L. mystacinus has the plates only in the corners of the pectoral girdle as is used to diagnose L. guacharote and is considered a synonym.  The only other species of Lasiancistrus in Venezuela is L. tentaculatus, which lacks plates on the abdomen and L. schomburgkii, which has more plates on the abdomen.

Lastly, Schultz (1944) described Lasiancistrus maracaiboensis as the first species of Lasiancistrus in Venezuela with an accurate type locality.  These specimens also have a small patch of platelets near the insertion of the pectoral-fin spine.  Kner (1854) and Schultz (1944) both mention the resemblance of L. mystacinus and L. maracaiboensis, respectively, to L. guacharote, and suggest that because of the poor description, the identity of L. guacharote was uncertain and that a new species should be described.  Schultz (1944) was further restricted from viewing the types of L. guacharote and L. mystacinus by the events of World War II.

            Lasiancistrus guacharote occurs in one river in the río Meta - río Orinoco drainage of Colombia.  These specimens are clearly L. guacharote as they have a patch of platelets ventrally near the insertion of the pectoral-fin spines, whiskerlike odontodes at the edge of the snout, and dark spots in the dorsal and caudal fins.  Two other species are known from the r’o Orinoco, drainage: L. schomburgkii and L. tentaculatus.  Lasiancistrus schomburgkii has white spots in the dorsal and caudal fins (vs. having dark spots in the fins), and L. tentaculatus has no abdominal plates and has tentacules along the snout instead of whiskerlike odontodes.  The collection of these fishes (ANSP 128695) is from around Villavicencio, a town well connected with the aquarium export business.  It is likely that these fishes result from having been introduced from the aquarium trade.  It is unknown if this population is extant.

 

Lasiancistrus heteracanthus Günther 1869

                                                                                                                                               

Chaetostomus heteracanthus Günther 1869.

 

Diagnosis. Lasiancistrus heteracanthus can be separated from L. caucanus, L. saetiger, and L. tentaculatus by having abdominal plates (vs. abdominal plates absent), from L. schomburgkii and L. saetiger by having dark spots in the dorsal and caudal fins (vs. white spots or all dark), and from L. guacharote by not having the abdominal plates restricted to a region near the insertion of the pectoral-fin spine.

 

Description. See genus description for more information. Morphometrics in Table 2.  Largest specimen 149.2 mm SL. Abdomen with small platelets anteriorly.  23-25 (mode = 24) plates in the median series.  10-19 whiskerlike odontodes in evertible cheek mass (N = 3); 24-32 (N = 3) total hypertrophied odontodes in cheek mass.

                                                                                                                                                T2

Color. Large, light spots barely visible on brown head, becoming mottling on dorsal and lateral surfaces of body.  Distinct, midlateral stripe in larger specimen with a more diffuse stripe located down middle of dorsal plates, both stripes beginning at vertical through dorsal-fin spine.  Small spots present along dorsal spine and rays, spots not extending onto membrane.  Medium spots on paired-fin rays and spines combining to form bands, but spots lighter on membranes.  Lower lobe of caudal darker than upper lobe.  Large spots on lower lobe of caudal combining to form bands that angle anteroventrally in upper half of lower lobe and posteroventrally in lower half.  Small spots only on rays of upper caudal lobe, spots not connected to form bands, but if bands were formed, they would be angled posteroventrally.  Abdomen a slightly lighter tan than sides.  Color of the larger recently collected specimen (FMNH 111719) more intense than that of smaller (SIUC 27970).  Smaller specimen faded because it was collected from muddy waters of the lower r’o Napo (pers. obs.).  Color of holotype gone except for some faint, dark spots in the dorsal and caudal fins.

 

Sexual dimorphism. So sexual dimorphism observed; specimens might not be mature.  The holotype appears to be developing whiskerlike odontodes on the snout.

 

Range. The type locality of Lasiancistrus heteracanthus is stated as the upper Amazon of Peru.  Only two specimens are available with good localities (FMNH 111719 and SIU 27970) from the upper r’o Napo of Ecuador and the lower rio Napo of Peru (Fig. 3).  No other specimens of L. heteracanthus have been examined.

 

Comments: Lasiancistrus heteracanthus appears to be very rare, and only three specimens were examined.  The type of L. heteracanthus has the color almost absent; however, some faint, dark spots are visible on the dorsal and caudal fins.  The only specimens examined from the Amazon drainage that have dark spots are FMNH 111719 and SIU 27970, and these two specimens were used for the color description.

 

Lasiancistrus saetiger Armbruster 2005

                                                                                                                                               

Diagnosis. Lasiancistrus L. saetiger can be separated from L heteracanthus, L. guacharote, and some L. schomburgkii by having no plates on the abdomen, from L. schomburgkii by having large white spots on the head (vs. small white spots), by having the plates of the body outlined in black (vs. entire body uniformly dark), and by having no spots in the dorsal and caudal fins (vs. usually with small white spots), and from L. tentaculatus by having whiskers on the snout of nuptial males (vs. tentacules longer than their associated odontodes) and by lacking dark spots in the dorsal and caudal fins (vs. with dark spots).

 

Description. See genus description for more information.  Morphometrics in Table 2.  Largest specimen 100.1 mm SL. Abdomen naked.  24 plates in the median series.  7-15 whiskerlike odontodes in evertible cheek mass (N = 4); 30-39 (N = 4) total hypertrophied odontodes in cheek mass.

 

Color. Body gray-brown with lighter spots.  Medium-sized light spots on tip of snout, becoming very large posteriorly on head.  Plates of nape and anterior body light gray-brown with dark edging giving appearance of large, light spots.  Posteriorly on body, dark edges of plates most intense on anterior and posterior margins of plates forming oblique bars.  Median fins without spots.  Lower lobe of caudal darker than upper.  Paired fins with medium-sized, round, light spots centered on rays.  Pectoral-fin spines without spots; pelvic-fin spines with spots posteriorly, often faded.  Abdomen slightly lighter than sides, with small, light spots laterally between posterior pectoral-fin insertion and insertion of pelvic-fin spine.  Lower lobe of caudal fin darker than upper lobe.

 

Sexual dimorphism. No sexual dimorphism observed; specimens might not be mature.

 

Range. Lasiancistrus L. saetiger is known from a single collection of fishes from the rio Guama, a tributary of the rio Capim - rio do Para, a drainage that enters the Atlantic just southeast of the mouth of the Amazon (Fig. 3).

 

Lasiancistrus schomburgkii (Günther 1864)

Chaetostomus schomburgkii G nthenther 1864: 245

 

Synonyms:

Hypostomus pictus Castelnau 1855: 44 Pl. 22 (Fig. 2).

Hemiancistrus castelnaui Miranda-Ribeiro 1911:58.

Ancistrus multispinis Holly 1929:119-120.

Hemiancistrus caquetae Fowler 1945:115, Figs 17-20.

Lasiancistrus scolymus Nijssen & Isbrücker 1985: 242, Figs. 1-3.

Lasiancistrus guapore Knaack 2000: 57, Fig. (unnumbered).

Diagnosis. Lasiancistrus schomburgkii can be separated from all other Lasiancistrus by having a dark body usually with small white spots (vs. large white spots; spots are occasionally absent in preserved L. schomburgkii, but no other Lasiancistrus will be entirely dark) and by having the dorsal fin either uniformly dark or with light spots (vs. with dark spots) and by lacking dark spots on any of the fins (vs. dark spots present on dorsal, caudal, and paired fins in all accept L. saetiger).  Lasiancistrus schomburgkii can additionally be separated from L. saetiger by having the plates not outlined with dark pigment.  

Description. See genus description for more information. Morphometrics in Table 3.  Largest specimen 161.7 mm SL. Abdomen ranging from having no plates, to just a few plates laterally under the pectoral girdle, to having much of the anterior two thirds of the abdomen with small plates (see Comments).  23-25 (mode = 24) plates in the median series.  2-36 whiskerlike odontodes in evertible cheek mass (mode = 18, N = 61; 17-81 (mode = 21, N = 61) total hypertrophied odontodes in cheek mass.

Color. Body and head dark brown to dark gray (almost black) with small to medium light spots. Abdomen light tan to gray, ventral surface of caudal peduncle slightly darker. Dorsal fin dark brown to gray with the fin rays darker, usually with small white spots.  Caudal fin with lower half dark, upper half sometimes very light, always lighter than lower half except along upper caudal-fin spine, which may be very dark; caudal fin occasionally with small light spots on the darkened lower lobe. Paired fins with small light spots centered on the rays.  Adipose and anal fins uniformly dark. Light spots much more intense and usually larger in living specimens, and may fade completely in preserved specimens.

Range. Lasiancistrus schomburgkii is found throughout much of the Amazon basin and the Upper Orinoco and Essequibo River basins (Fig. 3).

Comments. The types of Chaetostomus schomburgkii are in poor condition and are too small to have developed whiskerlike odontodes.  The species was placed in Guyanancistrus by Isbrücker ckercker et al. (2001) and later transferred to Pseudancistrus with the rest of Guyanancistrus (Armbruster, 2004).   The poor condition of the smaller of the two syntypes is actually a good thing because it can be verified that the specimen has the two other synapomorphies for Lasiancistrus: three branchiostegals and an open dilatator operculi chamber can be observed in the smaller of the two syntypes.  In addition, the specimens have three rows of plates on the caudal peduncle vs. four or five in Pseudancistrus.

Hemiancistrus castelnaui was described by Miranda Ribeiro (1911) as a replacement for Hypostomus pictus Castelnau 1855 that was secondarily preoccupied in Hemiancistrus by Ancistrus pictus Kner 1854 (now Dekeyseria picta).  The color pattern of the holotype of L. pictus is mostly gone; however, there are a few small white spots in the dorsal fin, and I have examined only one species of Lasiancistrus from the upper Amazon of Peru (excluding the r’o Napo) making it most likely that the common species of the upper Amazon is L. schomburgkii.

            Two species of Lasiancistrus have been described in the past 20 years, L. scolymus and L. guapore (Nijssen and Isbrücker, 1985; Knaack, 2000).  Lasiancistrus scolymus was based on a single individual and L. guapore was based on a single collection, and both species were described from the rio Madeira drainage of Brazil.  Lasiancistrus scolymus was compared only to the holotype of L. heteracanthus and L. guapore only to the descriptions of L. scolymus and L. heteracanthus.  Although some measurements were given as differences between the species in both descriptions, the results of the morphometric analysis in this study suggest that measurements cannot separate species of Lasiancistrus.  The only other characteristic mentioned is the absence of plates on the abdomen in L. scolymus and the near absence of plates on the abdomen in L. guapore vs. a partially plated abdomen in L. heteracanthus.  No comparisons were made with L. castelnaui or L. schomburgkii whose types are also without plates on the abdomen.

Specimens of Lasiancistrus schomburgkii from northern tributaries of the Madeira, tributaries of the Amazon upstream of the Madeira, and northern tributaries of the Amazon, the Orinoco, and the Essequibo tend to have many small, embedded plates on the abdomen, although the number of plates varies considerably, and plates are absent at least in the holotype of L. pictus. Two specimens from the r’o Ucayali basin (MUSM 14313) exhibit almost the entire range of variation in abdominal plating in L. schomburgkii.  One specimen (92.6 mm SL) has a single plate medial to the insertion of the right pectoral-fin spine and two medial to the left pectoral-fin spine and none in the center of the body.  The other specimen (91.1 mm SL) has many small plates below the pectoral girdle and a large patch in the center of the body behind the pectoral girdle.  Specimens from southeastern tributaries of the Madeira and southern tributaries of the Amazon downstream of the Madeira have no plates on the abdomen.  Specimens upstream of the rio Aripuana (a southeastern tributary of the Madeira) are variable with specimens ranging from having no abdominal plates to a moderate amount.  Based on the tree in Armbruster (2004), the absence of abdominal plates in Lasiancistrus is the plesiomorphic condition.  Because of the variability of abdominal plating in L. schomburgkii, it is impossible to use the degree of plating to recognize any of the other described species.

The type of Ancistrus multispinis is lost, and there is no information to confirm that the species is a Lasiancistrus.  The type locality is stated as 'Mercado Blein' (Holly, 1929:120), which is likely to be the Belem market.  The original description describes a 148 mm long fish with 39 hypertrophied odontodes on the cheek, plates on the edge of the snout, and no tentacles, which are consistent with Lasiancistrus (Holly, 1929), however, the specimen is described as having an anal-fin ray count of I4 while most Lasiancistrus are I5.  A count of I4 is rare in Lasiancistrus, but is occasionally present.  The species could be considered incertae sedis in the Ancistrini; however, the description is consistent with a Lasiancistrus, and I prefer to leave it as a Lasiancistrus.  Both the rio Tocantins and the rio Capim have their mouths near Belem making it possible that the species is either L. schomburgkii, which is from the Tocantins or the population described below as L. saetiger, which is described from the Capim.  Holly (1929) describes the color as light brown with a darker back and brown fins.  The specimens of L. saetiger are clearly spotted whereas L. schomburgkii is often entirely brown.  Based on color, range, and that the description of the species is not inconsistent with L. schomburgkii, I am recognizing A. multispinis Holly as a synonym of L. schomburgkii.

            The type of Lasiancistrus caquetae is very small (41.9 mm SL) and in poor condition.  The specimen is entirely dark brown, seemingly the same as when it was described (Fowler, 1945).  The only other described species that would likely be found the area where L. caquetae was collected are L. heteracanthus (which has dark spots on the fins) and L. schomburgkii.  The original color description suggests that the species is not L. heteracanthus.  Unfortunately, I have examined no other specimens from the Caqueta River; however, based on the original description of the lack of spots on the fins, it is most likely that L. caquetae is also a synonym of L. schomburgkii.

            Some of the specimens examined from southern Amazonian tributaries have a couple of the teeth replaced by whiskerlike odontodes.  Armbruster and Page (1996) speculated that the elongate, unicuspid teeth of nuptial male Hypostomus ammophilus were the result of a pleiotropic affect of the elongation of the body odontodes in nuptial males.  Thus, there may be some correlation between the development of the integumentary teeth and the oral teeth.  This correlation may also explain why some of the teeth in Lasiancistrus schomburgkii may be replaced by whiskerlike odontodes.

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Lasiancistrus tentaculatus Armbruster 2005

Diagnosis. Lasiancistrus tentaculatus is diagnosed by one unique synapomorphy, the presence of small tentacles (tentacules sensu Sabaj et al., 1999) on the snout of nuptial males that are larger than the supporting odontodes.  All other Lasiancistrus whose nuptial males have been observed have whiskerlike odontodes at the anterolateral corners of the snout.  In addition, L. tentaculatus can be separated from L heteracanthus, L. guacharote, and some L. schomburgkii by having no plates on the abdomen, from L. schomburgkii and L. saetiger by having black spots in the dorsal, caudal, and paired fins fin (vs. no or white spots or entirely gray, respectively), and from L. caucanus by having a forked caudal fin (vs. emarginate).

Description. See genus description for more information. Morphometrics in Table 3.  Largest specimen 147.6 mm SL. Abdomen naked.  23–25 (mode = 24) plates in the median series.  1-26 whiskerlike odontodes in evertible cheek mass (mode = 5, N = 29); 12-60 (mode = 36, N = 31) total hypertrophied odontodes in cheek mass.

Color. Body and head almost uniformly brown with slight mottling. Abdomen light tan, ventral surface of caudal peduncle slightly darker. Dorsal, caudal, and paired fins with dark spots centered on the fin rays and that may form incomplete or wavy bands.  Adipose and anal fins uniformly dark.  Lower half of caudal fin generally darker than upper half.

Range. Lasiancistrus tentaculatus is found in the Orinoco River basin of Colombia and Venezuela and in the lago Valencia drainage of Venezuela (Fig. 3).

Comments. Lasiancistrus nationi was described by Fernandez Yepez (1972) for specimens from the r’o Yaracuy of northern Venezuela.  No Lasiancistrus are present from recent collections from this region at INHS and MCNG, and the photograph in Fernandez Yepez (1972) is of an Ancistrus as the snout is clearly lacking plates.  Lasiancistrus nationi is therefore referred to as Ancistrus nationi (Fernandes Yepez), new combination.

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Discussion

            Lasiancistrus guacharote, L. schomburgkii, and L. trinitatus were placed in Guyanancistrus by Isbrücker ckercker et al. (2001), and Guyanancistrus was placed in the synonymy of Pseudancistrus by Armbruster (2004).  Lasiancistrus guacharote and L. schomburgkii are clearly members of Lasiancistrus.  The description of L. trinitatus is poor; however, Günther (1864) states that it has four total anal-fin rays while Lasiancistrus almost always has six.  There are no known specimens of Lasiancistrus or Pseudancistrus from Trinidad, and the only loricariids known from the island are Hypostomus robinii and a species of Ancistrus.  Because there are no types of the species, the species should be listed as Chaetostomus trinitatus Günther 1864, incertae sedis.

            Contrary to the case presented by many other members of the Ancistrini being examined, the ranges of most of the species of Lasiancistrus are quite broad.  The species with the greatest range is L. schomburgkii, which occupies most of the Amazon basin and the upper Orinoco and Essequibo basins as well.  The species of Lasiancistrus are most commonly found in small creeks, typically in swift flow.  However, some of the streams where Lasiancistrus can be found are in the lowlands, and hypoxia has been observed in one such stream (cano Maraca, rio Portuguesa - rio Orinoco drainage).  This suggests that lowlands are not a barrier to the movement of the species.

            The biogeography of Lasiancistrus suggests that lowland fishes can fairly easily breach the barriers between the Orinoco and Essequibo and the Amazon.  The range of L. schomburgkii is similar to Hypostomus hemicochliodon, which also makes it into the upper Orinoco (but not into the Essequibo).  The two species have similar habitat preferences, occurring in the swift sections of otherwise lowland streams.

            Also curiously within Lasiancistrus schomburgkii is that those populations with the presence of plates on the abdomen (likely the derived condition based on Armbruster, 2004) are found in an arc that includes the northern Amazonian tributaries, the upper Orinoco and the Essequibo rivers while the plesiomorphic populations are from the southern Amazonian tributaries.   Lasiancistrus are most common in lower piedmont streams.  Due to the range of the plated and unplated populations of Lasiancistrus, it is likely that L. schomburgkii dispersed via stream capture events of these piedmont streams rather than crossing the lowlands and the Amazon.

             The function of tentacules on the snouts of nuptial male Lasiancistrus tentaculatus and the pectoral fins of all Lasiancistrus and Ancistrus is unknown.  Sabaj et al. (1999) speculated that the tentacles of Ancistrus are larval mimics that could potentially trick females into believing that males have larvae in the nest when they do not.  Indeed, male Ancistrus are often found with larvae the size of their tentacles in their nests (see Sabaj et al., 1999 for review).  Spawning in Lasiancistrus has not been reported, and members of Lasiancistrus are rarely found in the aquarium trade; however, it would be reasonable to speculate that the tentacules are mimicking a younger larva than the tentacles of Ancistrus.  Although the larval mimicry hypothesis for Ancistrus and Lasiancistrus has not been tested, it is likely that the behavioral ecology of these species is quite interesting.

            No morphometric, meristic, or skeletal differences could be found among the species of Lasiancistrus.  The only differences between the species are the degree of abdominal plating (itself a characteristic that is likely to be very homoplastic) and coloration.  The difficulty in using abdominal plating is underscored by L. schomburgkii, which has all of the observed character states for the genus.  The only major difference between L. caucanus and L. guacharote is that L. caucanus has a naked abdomen and L. guacharote has a few small plates at the insertion of the pectoral-fin spine.  Although this character was not useful in separating populations of L. schomburgkii, it was used to separate L. caucanus and L. guacharote because there was also geographic concordance.

            The only major characteristic to be found other than color and abdominal plating between the species is the nuptial male condition of Lasiancistrus tentaculatus.  Males of L. tentaculatus develop tentacules along the anterior margin of the snout while all other Lasiancistrus develop whiskerlike odontodes at the anterior corners of the snout.  It is unknown how the tentacules or the whiskerlike odontodes are used.  Presence of whiskerlike odontodes on the cheek does not appear to be sexually dimorphic, although males may have longer ones.

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