Lithoxus jariensis, Silva & Covain & Oliveira & Roxo, 2017

Silva, Gabriel S. C., Covain, Raphael, Oliveira, Claudio & Roxo, Fábio F., 2017, Description of two new species of Lithoxus (Hypostominae: Loricariidae) from rio Jari and rio Amapá basins, Brazilian Guiana Shield, Zootaxa 4347 (1), pp. 151-168 : 154-161

Lithoxus jariensis , sp. n.

Fig. 2 ; Table 1

Holotype. MZUSP 123131, 60.7 mm SL, municipality of Laranjal do Jari, Amapá State, rio Itapuru, cachoeira de São Raimundo, rio Jari, rio Amazonas basin, 00°33’59” S, 52°34’40” W, 20 February 2009, J.L Birindelli, L.S. Sousa, & M. Soares.

Paratypes. All specimens from Brazil: Amapá State: rio Jari: rio Amazon basin: LBP 19553 (3, 33.8–45.5 mm SL, 1 c&s, 47.1 mm SL), collected with holotype . LBP 20468 (1, 32.2 mm SL), municipality of Laranjal do Jari, igarapé Iratapuru , 00°32’01”S, 52°35’05”W, 26 September 2015, C. Oliveira & B.F. Melo . LBP 20512 (10, 29.3– 48.1 mm SL, 1 c&s, 45.6 mm SL), municipality of Laranjal do Jari, rio Jari , rio Amazonas basin, 00°38’33”S, 52°30’27”W, 28 September 2015, C. Oliveira & B.F. Melo . MHNG 2767.051 (2, 48.1–48.9 mm SL), municipality of Almeirim, rio Jari , rio Amazonas basin, 00°37’25”S, 52°32’48”W, 19 February 2009, J.L Birindelli, L.S. Sousa, & M. Soares . MZUSP 103396 (24, 30.0– 50.7 mm SL), municipality of Almeirim, rio Jari , rio Amazonas basin, 00°37’25”S, 52°32’48”W, 19 February 2009, J.L Birindelli, L.S. Sousa, & M. Soares . MZUSP 103491 (40, 19.5– 53.2 mm SL), collected with holotype . MZUSP 101528 (17, 29.2–53.3 mm SL), municipality of Laranjal do Jari, rio Jari , rio Amazonas basin, 00°38’44”S, 52°30’34”W, 19 September 2008, C. Moreira & A. Akama.

Diagnosis. Lithoxus jariensis differs from L. surinamensis and L. pallidimaculatus by the presence of an adipose fin (vs. adipose fin absent); from L. bovallii by the absence of an irregular concentration of chromatophores around the anal-fin origin and adjacent region (vs. presence), and by the coloration pattern of caudal fin with three dark bands (vs. five dark bands); from L. lithoides and L. jantjae by the presence of five branched anal-fin rays (vs. four); from L. pallidimaculatus and L. raso by absence of light spots on the body (vs. presence of light spots on the body); from L. jantjae by having 14 branched caudal-fin rays (vs. 12); and from L. stocki by having medial premaxillary teeth with an enlarged and widened cusp (vs. cusps of all premaxillary teeth similar in size, not enlarged), and by a small number of dentary teeth 5–8 (vs. 10–12). Moreover, the new species differs from L. boujardi by having a greater adipose–spine length, 6.2–10.1% SL (vs. 3.6–4.7% SL), and by having a greater dorsal adipose-caudal distance, 12.0–16.5% SL (vs. 10.3–11.7% SL); from L. planquettei by smaller caudal peduncle depth, 7.6–8.7% SL (vs. 9.7–10.5% SL), and by having a straight adipose-fin spine (vs. a curved adiposefin spine); and from L. stocki by having a shorter cleithral width, 27.8–31.2% SL (vs. 32.6–34.2% SL), and a greater dorsal–anal distance, 10.4–13.7% SL (vs. 8.8–10.4% SL).

Description. Morphometric data presented in Table 1. Medium sized loricariids (41–60 mm SL). In lateral view, dorsal profile convex from snout tip to dorsal-fin origin; straight and gradually descending from dorsal-fin origin to end of caudal peduncle insertion. Ventral profile slightly concave from snout tip to pectoral-fin origin; convex from pectoral-fin origin to pelvic-fin origin; concave from pelvic-fin origin to insertion of lower caudal-fin spine.

Head and snout broadly rounded. Snout elongated (49–57% HL); anterior region slightly depressed. Posterior nostril small, almost reaching same diameter of eyes; no concavity between nostrils. Eyes small (orbit diameter 11– 15% HL), dorsally positioned. Superior margin of orbits not elevated. Oral disk occupying entire ventral surface of head. Ventral surface of disk covered with low and wide papillae; margin of disk fringed with low triangular papillae. Maxillary barbel relatively long and projected anterolaterally to upper lip. Teeth bicuspid with deep division between cusps; four to five left premaxillary teeth, five to eight left dentary teeth; premaxillary tooth cusps increasing in size from lateralmost to medialmost tooth; medialmost tooth cusp two to four times larger than lateralmost tooth cusp. Lateralmost premaxillary tooth cusps similar in size to dentary tooth cusps; dentary teeth all similar in size.

Percents of HL Holotype Min Max Mean SD Holotype Min Max Mean SD ......continued on the next page

Continued.

L. boujardi , n = 6 L. gr. bovallii , n = 8 ......continued on the next page

Continued.

L. planquettei , n = 13 L. stocki, n = 5 Body dorsoventrally depressed. In dorsal view, greatest body width at cleithral region and greatest body depth at dorsal-fin origin. Body progressively narrow from opercular region to caudal fin. Cross-section of body between pectoral and pelvic fins rounded dorsally and flat ventrally. Body almost entirely covered by plates, except at ventral portions of head, abdomen and along dorsal-fin base. Dorsal surface of body entirely covered by plates; three to four predorsal plates; five interdorsal plates, eight plates below dorsal-fin base; four plates between dorsal fin and adipose fin. Lateral surface of body entirely covered by plates; mid-dorsal plate series developed, reaching end of adipose fin; lateral median plates 23−24; mid-ventral plate series developed (six plates), reaching end of adipose-fin base. Body plates with minute odontodes. Odontodes slightly hypertrophied on pectoral-fin spines, becoming gradually larger distally. Longest odontodes on posteriormost evertible cheek plates.

Dorsal-fin II,7; dorsal-fin spinelet V -shaped, locking mechanism present; dorsal-fin origin approximately at midpoint between pectoral- and pelvic-fin origins; last dorsal-fin ray not reaching adipose fin when depressed. Pectoral-fin I,6; pectoral-fin spine reaching slightly beyond base of pelvic-fin spine when depressed. Pelvic-fin I,5; reaching anal-fin origin when depressed. Anal-fin I,5. Adipose-fin present, with single azygous preadipose plate; posterior margin of adipose-fin membrane convex, extending posteriorly beyond adipose-fin spine. Cross-section of caudal peduncle ellipsoid, flat dorsally and ventrally. Three lateral plate rows at base of caudal peduncle. Caudal-fin I, 7−I,7; obliquely forked, lower lobe longer than upper.

Color in alcohol. Background color dark brown dorsally and laterally, and light brown ventrally. Four dark saddles along dorsal portion of body: first at dorsal-fin origin, second at end of dorsal-fin base, third at the middle of caudal peduncle, and fourth reaching anteriormost caudal procurrent ray. Fins with irregular and poorly defined bars: three or four on anal-, pectoral-, dorsal- and pelvic-fin rays. Caudal-fin dark with a large hyaline bar in middle portion of rays. Hypertrophied odontodes on posteriormost evertible cheek plates and on pectoral-fin spines yellowish.

Sexual dimorphism. Males possess a papilla posterior to urogenital opening (absent in females).

Etymology. The specific epithet jariensis is in reference to the type-locality, the rio Jari, a large tributary of the rio Amazon basin.

Distribution. Lithoxus jariensis is only known from rio Jari and small tributaries, at municipality of Almerim and Laranjal do Jari, Amapá State, Brazil (see Fig. 3 ).

Habitat. The new species L. jariensis is found in the bottom of a fast-flowing clear-water rivers of median to large size, such as rio Jari ( Fig. 4 ). The bottom of the rivers was composed of small to large-sized rocks, loose stones, and sand.

Figures

FIGURE 2. Lithoxus jariensis, holotype, MZUSP 123131, male 60.6 mm SL, from rio Jari (rio Amazon basin), municipality of Laranjal do Jari, Amapá State, Brazil.

FIGURE 3. Map showing the type locality of (A) L. jariensis, rio Jari basin, rio Amazonas basin, Amapá State, Brazil; and (B) Lithoxus raso in igarapé Balneário Raso, rio Amapá basin, Amapá State, Brazil.

FIGURE 4. Upper picture showing the habitat of the type locality where the species Lithoxus jariensis lives at cachoeira de São Raimundo, 00 ° 33 ’ 59 ” S, 52 ° 34 ’ 40 ” W. Lower picture showing the habitat of the type locality where the species of L. raso lives at igarapé Balneário Raso, 02 ° 05 ’ 25 ” N, 50 ° 53 ’ 20 ” W.