Laemolyta fernandezi ( Myers, 1950 )

Mautari, Kelly Cristina & Menezes, Naércio Aquino, 2006, Revision of the South American freshwater fish genus Laemolyta Cope, 1872 (Ostariophysi: Characiformes: Anostomidae), Neotropical Ichthyology 4 (1), pp. 27-44 : 31-33

Laemolyta fernandezi ( Myers, 1950)

Fig. 4

Laemolyta fernandezi Myers, 1950: 197 , 198, [original description, type locality: upper Orinoco]; Géry, 1964: 466 [key to species]; Géry, 1974: 157–159, Fig. (3), p. 158 [complementary description, key to species]; Böhlke, 1953: 197 [catalog of types]; Eschmeyer, 1998: 574 [catalog]; Garavello & Britski, 2003: 73 [catalog]; Taphorn et al., 1997:55–100 [catalog]; Lasso et al., 2004:105–195 [list of species and distribution].

Laemolyta petiti Géry, 1964: 464 , plate IV b [type locality: ilha do Bananal, upper rio Araguaia]; Santos & Jégu, 1989: 166, Fig. p. 196 [redescription]; Santos et al., 1984: 33 [lower rio Tocantins]; Eschmeyer, 1998: 1326 [catalog]; Garavello & Britski, 2003: 73 [catalog].

Anostomus (Laemolyta) fernandezi: Géry, 1977: 180 [key to species, distribution].

Material examined. 93 specimens (63.6–212.9 mm SL). Venezuela. Río Orinoco system, upper Orinoco, 1925, C. Ternetz, CAS 116126 , holotype, 73.1 mm SL. Anzoategui, río Orinoco basin, ANSP 166730 , 5 , 80.2–152.6 mm SL. Bolivar, río Orinoco basin, San Pedro de Tauca , ANSP 166532 , 1 , 137.0 mm SL. Bolivar, laguna Aricagua , floodplain, río Caura , Vispo Conrad , MHNLS 13061 , 1 of 2, 110.9 mm SL. Bolivar, laguna Guaiparo , San Felix , MHNLS 7063 , 1 of 3, 102.6 mm SL. Delta Amacuro, caño Guarguapo , in small tributary, approximately 500 m from mouth in río Orinoco , MZUSP 62448 , 2 , 80.6–109.8 mm SL. Brazil. Tocantins: upper rio Araguaia , ilha do Bananal , MHNG 2229.01 , 1 , 74.8 mm SL. Pará: Itupiranga , Tocantins, INPA 1546 , 4 , 136.1 – 166.6 mm SL, INPA 1548 , 5 , 137.8 – 156.7 mm SL, INPA 1888 , 1, 141.5 mm SL. Rio Tocantins, Icangui , Projeto Tucuruí , INPA 1547 , 7 , 95.1 – 141.7 , INPA 12234 , 14 , 81.8–136.5 mm SL, INPA 15350 , 6 , 110.8 – 162.2 mm SL. Rio Tocantins below dam, Tucuruí , INPA 1549 , 4 , 168.3 – 191.1 mm SL, INPA 16176 , 2 , 134.1 – 164.2 mm SL. Rio Tocantins, poço do Paulo , below Tucuruí Dam , INPA 1889 , 2 , 87.5–89.3 mm SL. Rio Tocantins, Jatobal , above Tucuruí Dam , INPA 1890 , 2 , 183.2 – 183.8 mm SL. Rio Tocantins, Tucuruí market, INPA 1891 , 2 , 193.4 – 201.3 mm SL. Rio Tocantins, INPA 15295 , 2 , 152.9 – 191.3 mm SL. Rio Tocantins, reservoir above Tucuruí Dam , INPA 16176 , 2 , 134.1 and 164.2. Rio Tocantins, lago Tauá below Tucuruí , INPA 16177 , 7 , 132.5 – 156.3 mm SL. Base I of Tucuruí reservoir, INPA 16178 , 5 , 161.7 – 193.7 mm SL. Base IV of Tucuruí reservoir, INPA 16179 , 2 , 198.3 – 208.7 mm SL. Rio Xingu , Belo Monte , MZUSP 60180 , 3 , 172.8 – 212.9 mm SL, MZUSP 60181 , 4 , 163 – 178.7 mm SL. MZUSP 61947 , 1, 164.9 mm SL. Mato Grosso: rio Araguaia , Santa Terezinha , MZUSP 20842 , 7 , 63.6–110.3 mm SL .

Diagnosis. Laemolyta fernandezi is distinguished from all congeners by its deeper body (22.9–31.6 % vs. 17.2–29.8 %, respectively, Fig. 5 ). It can be further distinguished from all Laemolyta species , except L. orinocensis , by having more lateral line scales (49–58 vs. 40–47). Although L. fernandezi cannot be separated from L. orinocensis on the basis of this character, the latter species has a very conspicuous midlateral dark stripe, whereas in L. fernandezi this stripe is inconspicuous and the transverse dark spots are much more evident than in L. orinocensis .

Description. Morphometric and meristic data presented in Table 1. Body moderately large (SL = 63.6–212.9 mm). Dorsal profile of body straight or slightly concave from snout tip to end of supraoccipital spine, slightly convex from that point to origin of dorsal fin, straight and posteroventrally aligned along dorsal-fin base and straight or slightly convex from base of posterior most dorsal-fin ray to caudal peduncle. Ventral profile of body straight or slightly convex from anterior tip of lower jaw to region near isthmus and slightly convex from that point to anal-fin origin and slightly concave at region of pelvic-fin insertion. Upper limb gill-rakers 9–12 on first gill arch and 11–15 on lower limb.

Scales small, 49–58 (51*, usually 53, Table 2) perforated along all of lateral line. Longitudinal scale rows from lateral line to dorsal-fin origin 7–8 (8*, usually 8), scale rows from lateral line to anal-fin origin 5–7 (7*, usually 6). Predorsal scales irregularly arranged. Scales rows around caudal peduncle 17–20 (19*, usually 18).

Dorsal fin rays ii,10–12 (10*, usually 11); distal margin of fin slightly rounded. Anal fin short, slightly falcate, with ii–iii (iii, rarely),8–10 (8*, rarely 10) rays. Pectoral fin rays i,11–15 (14*, usually 14). Pelvic fin rays i,8; distal margin of fin truncate. Vertebrae 39–42 (42*, usually 39, N=30).

Color in alcohol.Adult specimens usually with dark, but sometimes very inconspicuous, longitudinal stripe, covering 1.5

to almost 3 longitudinal scale rows. Stripe extends from posterior region of opercle to caudal peduncle where it usually ends in form of darker triangular or oval spot. Upper region of body usually dark, with dark coloration extending ventrally to below midlateral dark stripe. Ventral region of body unpigmented from ventral limit of dark midlateral stripe on body to midventral one. Body with 4 transverse dark but sometimes inconspicuous bars or blotches, sometimes inconspicuous. First series situated between opercle and dorsal fin, but closer to opercle; second below dorsal fin, and usually more conspicuous; third located between pelvic and anal fins and last, anterior to adipose fin. First and second series usually more conspicuous and last series usually diffuse ( Fig. 6 ).

Young specimens ( Fig. 7 ) with midlateral longitudinal stripe indistinct, extending from anterior part of snout to rear of caudal peduncle and usually finishing in form of triangular spot. Four transverse bars or blotches present in adults absent. Upper part of body sometimes with approximately 14 narrow transverse dark bars extending ventrally to near lateral line. Adult specimens sometimes retain faded transverse bars. Adult specimens from río Orinoco basin ( Fig. 8 ) with bars faded and midlateral longitudinal stripe on body very conspicuous.

Dorsal, pectoral, and ventral fins hyaline with scattered dark chromatophores. Dark chromatophores also scattered along fin margin and over median rays of caudal fin. Adipose fin usually dark.

Some specimens with 4 transverse dark bars quite evident, with dark blotch present on caudal peduncle and dark midlateral stripe on body faded ( Fig. 9 ).

Common name: Venezuela: Mije ( Lasso, 1992).

Distribution: Río Orinoco and Amazon basin (rios Xingu, Tocantins and Araguaia) ( Fig. 10 ).

Remarks. Laemolyta fernandezi Myers, 1950 , was described based on a young specimen (73.1 mm SL), that was considered to be a new species in having a compressed body and more longitudinal scale rows (8/7) than L. garmani , L. proxima and L. taeniata (4–6/4–7). According to Myers the specimen was collected in the upper río Orinoco, but the precise locality was not provided.

The description of L. petiti Géry, 1964 , is also based on a young specimen (76.4 mm SL), collected in the rio Araguaia. When Géry (1964) described his new species he recognized its similarity with L. fernandezi , but noted that a comparison between the two nominal forms was impossible because of the succinct description and lack of illustration of L. fernandezi . Later on Géry (1974) redescribed L. fernandezi and compared the data he obtained with those of L. petiti and found that L. fernandezi has fewer longitudinal scale rows (7–7 ½ / 6–6 ½), more lateral line scales (55) and a deeper caudal-peduncle than did L. petiti .

The comparison of meristic and morphometric data among specimens of L. fernandezi from the Orinoco, Tocantins / Araguaia and rio Xingu basins revealed no significant differences between these populations. The number of vertebrae in a sample from the río Orinoco is 41 (10 specimens) and 42 (1 specimen - holotype) and from the rios Tocantins /Araguaia 39 (15 specimens), 40 (3 specimens) and 41 (1 specimen). The number of vertebrae in 4 specimens from the rio Xingu basin is 39 (1 specimen), 40 (2 specimens) and 41 (1 specimen). The comparison of body depth, that seemed to be visually different among the populations originating from the three basins mentioned, also did not show any significant difference ( Fig. 11 ) .

In spite of the slight difference in number of vertebrae we prefer to recognize just one widely distributed species represented by allopatric populations, especially because no other meristic or morphometric differences were found to distinguish the populations.

Laemolyta fernandezi was recorded from the rios Tocantins and Araguaia by Santos & Jégu (1989) and is the most common anostomid species in the lower rio Tocantins ( Santos et al., 1984). It is to date the only species of Laemolyta found in the central portion of the rio Araguaia basin. In the lower rio Araguaia it occurs in sympatry with L. garmani .

Laemolyta fernandezi reaches 25 cm SL and eats small invertebrates (Santos & Jegú, 1989), vegetable material and periphiton ( Santos et al., 1984). Sexual maturity seems to occur in specimens at approximately 130 mm SL judging from direct observation of the gonads. Reproduction seems to occur during the flood season ( Santos et al., 1984).

Figures

Fig. 4. Laemolyta fernandezi, CAS 116126, holotype, 73.1 mm SL; Venezuela, upper río Orinoco.

Fig. 5. Scatter plot of body depth on standard length for all species of Laemolyta.

Fig. 6. Adult specimen of Laemolyta fernandezi, INPA 16178, 173.4 mm SL; Brazil, Pará, Base I Tucuruí Reservoir.

Fig. 7. Young specimen of Laemolyta fernandezi, MZUSP 20842, 63.6 mm SL; Brazil, Mato Grosso, rio Araguaia, Santa Terezinha.

Fig. 8. Adult specimen of Laemolyta fernandezi,ANSP 166532, 137 mm SL; Venezuela, Bolivar, rio Orinoco basin, San Pedro de Tauca, L. Madera.

Fig. 9. Adult specimen of Laemolyta fernandezi, INPA 16177, 156.3 mm SL; Brazil, Pará, rio Tocantins, Lago Tauá below Tucuruí.

Fig. 10. Geographic distribution of Laemolyta taeniata (black dots; open circle = type-locality) and of Laemolyta fernandezi (black squares; open squares = type-locality).

Fig. 11. Scatter plot of body depth on standard length for populations of Laemolyta fernandezi.