Isorineloricaria villarsi ( Lütken 1874 ), Lutken, 1874

Ray, C. Keith & Armbruster, Jonathan W., 2016, The genera Isorineloricaria and Aphanotorulus (Siluriformes: Loricariidae) with description of a new species, Zootaxa 4072 (5), pp. 501-539 : 534-536

Isorineloricaria villarsi ( Lütken 1874)

( Fig. 18 )

Plecostomus villarsi Lütken, 1874a: 211 . Type locality: Caracas. Syntypes: ZMUC P 30149 (1), ZMUC P 30150 (1).

Material examined. Venezuela: AUM 22584 (1); Zula, Lago Maracaibo, Southern part of lake, Santa Barbara fish market, 20 December 1999. FMNH 6338 (4); Encontrados, N. Dearborn, February 1908. MCNG 33523 (2); USNM 121019 (1); Rio Apon about 35km. south of Rosario in Maracaibo basin, col. by L. Shultz, 26 February 1942. USNM 12120 (3); Rio Socuy 3km above mouth, Maracaibo Basin, col. by L. Shultz, 24 February 1942. USNM 121021 (1); Rio Negro, 75km west of Rosario, col. by L. Shultz, 2 March 1942. USNM 121022 (1); Cienaga del Guanavana about 10km. north of Sinamaica, col. by L. Shultz, 11 March 1942. USNM 121031 (2); Lago Maracaibo, near mouth of Rio Concha, col. by L. Schultz, 2 May 1942.

Diagnosis. Isorineloricaria villarsi can be diagnosed from all other members of Isorineloricaria by having distinct raised ridges on the compound pterotics (vs. rounded ridges). Isorineloricaria villarsi can be further separated from Aphanotorulus ammophilus and A. unicolor by a single, large buccal papillae (vs. multiple buccal papillae) and from A. emarginatus and A. horridus by distinct raised ridges on the compound pterotics (vs. compound pterotics flat).

Description. Morphometric data given in Table 6 . Head moderately deep with prominent supraoccipital crest; crest often ending abruptly, with posterior edge perpendicular to head. Ridges formed on compound pterotics; compound pterotic ridges align with keel of mid-dorsal plate row to form continuous series. Nape flat.

Caudal fin highly forked with lower lobe longer than upper. Pectoral-fin spine reaches past point of insertion onpelvic fin. Pelvic-fin spine reaches anal-fin insertion. Adipose fin spine pointed; adipose-fin membrane extending to end of third adipose base plate (two plates separate adipose-fin membrane and first dorsal procurrent caudal-fin spine).

Lateral line plates 28 (mode 28; n= 15); dorsal-fin base plates seven to nine (mode eight; n= 15); folded dorsal plates 12–13 (mode 12; n= 15); plates between dorsal and adipose fins seven to nine (mode eight; n= 15); adipose fin plates two to four (mode three; n= 15); anal-fin base plates two (mode two; n= 15); plates from anal fin insertion to last plate on caudal peduncle 16–18 (mode =17; n= 15); plates in folded pectoral fin five to seven (mode six; n =151); number of teeth on dentary 24–36 (mode =36; n= 15); number of teeth on premaxilla 20–38 (mode =26; n= 15).

Sexual dimorphism. Breeding males with hypertrophied odontodes on pectoral fin spines, which increase in length and density distally. Adipose-fin spine and caudal-fin spines also covered with hypertrophied odontodes. Caudal-fin rays also with odontodes in same manner, though not as large as on caudal-fin spines. Hypoertrophied odontodes also covering posteromedial edge of most plates along body. Longest plate odontodes occur on middorsal, median, and mid-ventral plate rows. Hypertrophied odontodes also present on opercle, along snout, cleithrum, posterior edges of head, and dorsal-fin spine.

Color in alcohol. Body base color light brown or tan. Base color darkens in largest specimens (breeding males). Spots oblong (not perfectly circular) on head and body. Greatest density occurs on head, with spots increasing in size posteriorly. Spots on head centered on anterior end of supraoccipital crest and radiate outward. Abdominal spots observed in some specimens and range from small spots with random distributions to large spots in columns. Paired fin spines with bands, with paired fins having random spots that are often fused together. Dorsal-fin spine with dark spots anteriorly; interradial membrane of dorsal fin with two rows of spots between each fin ray. Caudal fin with random spotting. Lower caudal fin lobe with dark coloration in large adults, with spots apparent.

Juveniles have no spots on abdomen. Spots appear to form bands on paired fins and caudal fin when it is depressed in juveniles.

Ecology. Unknown.

Distribution. Isorineloricaria villarsi is restricted to the Maracaibo basin in northwestern Venezuela and extreme eastern Colombia (Fig. 10).

Comments. There are two color morphs in the Maracaibo basin, one with small spots on the abdomen, and the other with large spots.

Figures

FIGURE 18. Lateral, dorsal, and ventral views of Isorineloricaria villarsi, USNM 121031, 301.5 mm SL. Scale = 1 cm.