Myloplus lucienae, Andrade, Marcelo C., Ota, Rafaela P., Bastos, Douglas A. & Jégu, Michel, 2016

Andrade, Marcelo C., Ota, Rafaela P., Bastos, Douglas A. & Jégu, Michel, 2016, A new large Myloplus Gill 1896 from rio Negro basin, Brazilian Amazon (Characiformes: Serrasalmidae), Zootaxa 4205 (6), pp. 571-580: 572-578

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Myloplus lucienae

new species

Myloplus lucienae  , new species

( Figs. 1‒4View FIGURE 1View FIGURE 2View FIGURE 3View FIGURE 4)

Myleus rhomboidalis  (non Cuvier): Toledo-Piza, 2002: 168, fig. 53 [rio Negro basin, listed; brief description; drawing of specimen by A.R. Wallace].

Myleus  sp.: Toledo-Piza, 2002: 180, fig. 59 [rio Negro basin, listed; brief description; drawing of specimen by A.R. Wallace]. Myleus  sp. A: Goulding, 1980: 115 (in part) [feeding behavior]; Borges, 1986: 106, figs. 3‒5 [short description; distribution].

Holotype. INPA 30717, 130.7 mm SL; Brazil: Amazonas: Novo Airão: rio Carabinani , 2°01'25"S 61°32'35"W; L. N. Carvalho, 25 Oct 2004.GoogleMaps 

Paratypes. All from Brazil, Amazonas. INPA 915, 1, 230.0 mm SL; and INPA 10215, 1, 315.7 mm SL; São Gabriel da Cachoeira: rio Negro , 0°08'08"S 67°05'29"W; M. Goulding, 18 May 1979GoogleMaps  ; INPA 916, 4, 279.9‒320.0 mm SL; São Pedro: rio Negro, confluence with igarapé Ibará , 0°24'50"S 65°01'09"W; M. Goulding, 23 May 1979GoogleMaps  ; INPA 917, 2, 286.5‒ 334.3 mm SL; and INPA 3877, 4, 266.2‒ 337.5 mm SL; Santa Isabel do rio Negro: rio Daraá , cachoeira do Aracu , 0°25'21"S 64°46'27"W; M. Goulding, 10 Feb 1980GoogleMaps  ; INPA 3682, 1, 317.0 mm SL; and INPA 3685, 1, 263.4 mm SL; São Gabriel da Cachoeira: rio Negro, cachoeira do Caranguejo , 0°03'15"S 67°08'56"; W. R. P. Ribeiro & R. Sotero, 7‒8 Mar 1990  ; INPA 10213, 1, 286.8 mm SL; Manaus: rio Negro, ilha de Tamaquaré , 2°52'59"S 60°31'00"W; M. Goulding, 10 Nov 1979GoogleMaps  ; INPA 10214, 2, 302.7‒ 312.3 mm SL; Barcelos: rio Arirará , 0°30'00"S 63°33'00"W; M. Gouding, 28 May 1979GoogleMaps  ; INPA 10216, 4, 260.9‒ 331.3 mm SL; Barcelos: rio Negro confluence with rio Cuiuni , 0°53'41"S 62°58'21"W; M. Goulding, 3 Jun 1979GoogleMaps  ; INPA 42972, 1, 74.9 mm SL (c&s); São Gabriel da Cachoeira: rock outcrops on rio Negro , 0°08'27''S 67°04'58''W; L. R. Py-Daniel et al., 6 Dez 2013GoogleMaps  ; INPA 49881, 4, 211.9‒ 248.5 mm SL (234.9 mm SL, 1 skel.); São Gabriel da Cachoeira: street market (probably fished at Balaio community, rio Iá ), 0°23'22'' N 66°38'53'' W; D. A. Bastos, 20 Feb 2015GoogleMaps  ; INPA 50849, 1, 90.2 mm SL; same data of holotypeGoogleMaps  . INPA 52894, 2, 122.5‒ 123.4 mm SL; and MZUEL 14704, 1, 137.4 mm SL; Novo Airão: Igapó no rio Negro , Parque Nacional de Anavilhanas , 2°43'10"S 60°45'18"W; J. Birindelli et al., 3 May 2016GoogleMaps  .

Diagnosis. Myloplus lucienae  differs from all congeners, except M. planquettei  and M. zorroi  , by having anteriormost spine of prepelvic serra reaching only the middle of the abdomen between the verticals through pectoral and pelvic-fin origins (vs. reaching the vertical through pectoral-fin origin or almost so). Myloplus lucienae  is distinguished from M. asterias  , M. lobatus  , M. planquettei  , M. rhomboidalis  , M. rubripinnis  , M. ternetzi  and M. zorroi  , by having fewer scale rows between lateral line and dorsal-fin origin (30‒35 vs. 36‒61), and between lateral line and pelvic-fin origin (27‒31 vs. 32‒63). It is distinguished from M. asterias  , M. levis  , M. tiete  and from M. torquatus  , by having 18‒22 branched dorsal-fin rays (vs. 24‒27). Myloplus lucienae  differs from M. arnoldi  by having a relatively elongate body (body depth 53.0‒64.5% of SL vs. 69.0‒76.9% of SL). Myloplus lucienae  still differs from M. ternetzi  by the presence of a pair of symphyseal teeth on dentary (vs. absence), and from M. schomburgkii  by the absence of a vertical black stripe on middle portion of flank (vs. presence).

Description. Morphometric data presented in Table 1. Large-sized serrasalmid, maximum SL recorded 337.5 mm SL. Body relatively elongated. Greatest body depth at dorsal-fin origin. Snout blunt and rounded. Dorsal profile of head gently concave or straight from vertical through nostrils to tip of supraoccipital process, slightly convex from this point to dorsal-fin origin. Ventral profile of head and body slightly convex. Base of dorsal- and anal-fins gently convex.


Mouth terminal to slightly upturned. Two rows of premaxillary teeth with 5 (28) molariform teeth in labial row, and 2 (28) in lingual row. Labial and lingual premaxillary rows interspaced by gap. First and second teeth of labial row with wide and rounded basis, more elongated anteroposteriorly, and edge with cutting crown. Dentary with 5* (26) or 6 (2) molariform teeth decreasing posteriorly in size. Pair of conical teeth at dentary symphysis. Symphyseal tooth with cutting edge on anterior margin. Maxilla edentulous.

Scales cycloid, relatively large sized for serrasalmid species. Perforated scales on lateral line imbricated on supracleithrum, and juxtaposed from humeral region to base of median caudal-fin rays. Perforated scales from supracleithrum to hypural plate end 66 (1), 67 (3), 68* (10), 69 (9), 70 (3) or 71 (2); and total perforated scales on lateral line from supracleithrum to base of median caudal-fin rays 71 (1), 72 (1), 73* (8), 74 (6), 75 (5), 76 (5) or 78 (2). Longitudinal scale rows between dorsal-fin origin and lateral line 30 (1), 31 (1), 32* (7), 33 (7), 34 (10) or 35 (2); and longitudinal scale rows between lateral line and pelvic-fin origin 27* (4), 28 (8), 29 (12), 30 (3) or 31 (1). Circumpeduncular scale rows 29* (1), 30 (7), 31 (9), 32 (9) or 33 (2).

Dorsal fin preceded by strong forward-oriented spine. Dorsal-fin rays ii* (25) or iii (3), and 18 (1), 19 (4), 20 (4), 21* (13) or 22 (6). Anal-fin rays iii* (24) or iv (4), and 31 (4), 32 (5), 33 (9) or 34* (10). Pectoral-fin rays i* (28), and 15 (1), 16* (16) or 17 (11). Pelvic-fin rays i,7* (28). Adipose fin with distal margin rounded to subrectangular. Caudal fin forked with two lobes of similar size.

Ventral keel with anteriormost spine of prepelvic serra located between verticals through pectoral- and pelvicfin origin, with series of 15 (1), 17 (1), 18 (3), 19* (5), 20 (7), 21 (5), 22 (5) or 23 (1) prepelvic spines; followed by 7* (9), 8 (14), 9 (2) or 10 (3) simple postpelvic spines; and 3 (2), 4 (19) or 5* (7) pairs of spines around anus. Total spines 28 (3), 29 (1), 31* (8), 32 (4), 33 (4), 34 (5), 35 (2) or 38 (1). First branchial arch with 24 (1), 25 (1), 27 (1), 28 (3) or 29 (1) total gill rakers; upper branch with 10 (1), 11 (1), 12 (2) or 13 (2) rakers; lower branch with 13 (2), 14 (2) or 15 (2) rakers; and 1 (6) at cartilage between upper and lower branches.

Gas bladder well-developed, two-chambered, total length 45‒50% SL, and with extrinsic muscle thin and poorly-developed (17 examined specimens). Anterior chamber smaller, cylindrical, horizontally positioned, with length 16‒19% SL. Posterior chamber larger, somewhat conical, posteriormost region narrower not very contracted, with length 26‒31% SL. Posterior chamber curved downward, lacking long appendix on its far end.

Ascending premaxillary process high, elongated with similar width from base to distal tip, and moderately inclined in relation to lateral premaxillary process ( Figs. 3View FIGURE 3 a, b). Premaxillary lacking interdigitations at symphysis and strongly attached on mesethmoid ( Fig. 3View FIGURE 3 b). Lateral premaxillary process lengthy, subrectangular, with dorsolateral process with concavity for maxillary insertion ( Figs. 3View FIGURE 3 a, b). Three replacement teeth trenches on premaxillary ( Fig. 3View FIGURE 3 b). Dentary rectangular ( Figs. 3View FIGURE 3 c, d), slightly arched with four bony lamellae at symphysis ( Fig. 3View FIGURE 3 d, f). Antorbital narrow and club-shaped. Supraorbital oval, narrow, with regular margins, not contacting infraorbital 6. Antorbital and supraorbital with unbranched sensory canal. Infraorbitals 1, 2, 3 and 5 with unbranched sensory canal, 4 and 6 with branched sensory canal, and 6 with Y shaped canal. Broad orbital region.

Neurocranium massif, high and triangular. Mesethmoid short, pointed and triangular anteriorly. Lateral ethmoid slender antero-posteriorly, positioned on anterior half of mesethmoid. Olfactory fossa with narrow aperture. Frontal short with oval fontanel slightly elongate and moderate concavity at epiphyseal bar. Parietal compact, narrower anteriorly, increasing slightly in width posteriorly. Supraoccipital spine well developed, its dorsal portion moderately curved posteriorly. Orbitosphenoid possessing two laterally compressed bony lamellae, anterior process wide distally and upturned, posteroventral process narrow and projecting ventrally with interdigitations on ventral margin not reaching parasphenoid. Parasphenoid lacking midventral keel with ventral aperture forming two projections parallel to each other along prootic and basioccipital ventral margins. Pterotic triangular with posterior process downward directed. Sphenotic with concave ventral margin, its anterior portion wider, narrowing posteriorly from middle portion of bone forming pointed tip.

Six (2) supraneurals, with 1st and 6th supraneurals positioned anterior to neural spine of 4th and 9th centrae, respectively. First dorsal-fin pterygiophore inserted posterior to neural spine of 11th (2) centrum. First anal-fin pterygiophore inserted behind haemal spine of 23nd (2) centrum. Forty-one (2) total vertebrae, with 20 (1) or 21 (1) precaudal and 20 (1) or 21 (1) caudal vertebrae.

Color in alcohol. Ground coloration silver-brownish hue. Dorsal portion of head and flanks darker than lower portion of head and flanks. Opercle, fourth infraorbital, and on third infraorbital cheek gap light brown. Postopercle membrane pale brown. Scales bordered distally by dark chromatophores forming overall faint reticulate pattern on body. Largest specimens with brown pectoral, pelvic, and caudal fins, posterior dorsal-fin rays and first anal-fin rays darker. Smaller specimens (131 mm SL or less) with overall coloration light brown, with pectoral and pelvic fins ranging from hyaline to hyaline with some melanophores distally. Smaller specimens with verticallyovoid dark spot on opercle, and dorsal, anal and caudal fins with distinct dark brown vertical stripe distally. Adipose fin light brown in all specimens.

Color in life. Based on freshly collected specimens (i.e. INPA 52894), the coloration in life ranging from flanks silvery with an olivaceous hue, with fins yellow reddish in young specimens ( Fig. 4View FIGURE 4) to flanks silvery gray with fins black in larger specimens. Scales silvery distally with darkly pigmented base. Flanks with scattered, shapeless rosy salmon colored blotches, more concentrated at humeral region. Scales on ventral surface of body and anal-fin base slightly dark pigmented. Dorsal, adipose, anal and caudal fins with distinctly dusky indigo to black brownish coloration. Pectoral and pelvic fins with pale dark pigmentation.

Sexual dimorphism. Males of Myloplus lucienae  can be distinguished from juveniles and females by having thin long filaments extending the branched dorsal-fin rays, an additional lobe formed by the projection of the middle anal-fin rays ( Fig. 2View FIGURE 2 a), and by the presence of stiff hooks laterally divergent on distalmost lepidotrichia of each anal-fin branched ray (scarcely developed and solely recorded in the largest specimen examined, 337.5 mm SL). From ten dimorphic males (248‒337 mm SL), only four specimens presented thin filaments on dorsal fin, but all males exhibit the additional anal-fin lobe centered at the 16th branched anal-fin ray. Males of M. lucienae  ( Fig. 2View FIGURE 2 a) show overall coloration somewhat darker than females ( Fig. 2View FIGURE 2 b). Juveniles and females lack dorsal-fin filaments or anal-fin hooks, and additionally, possesses anal fin with first 8 to 10 rays longer than posterior rays, forming a falcate anterior lobe ( Figs. 1View FIGURE 1, 2View FIGURE 2 b).

Variation on body shape along ontogenetic development. Subunits of head presenting high variability along ontogeny, with three measurements among smaller analyzed specimens (i.e. 75.0‒ 130.7 mm SL) are distinct from larger specimens (i.e. 212.0‒ 337.5 mm SL). Positive allometry in postorbital distance, ranging between 28‒30% HL in smaller specimens and 30‒37% of HL in larger specimens; negative allometry in eye vertical diameter, 40‒43% of HL in smaller specimens and 30‒37% of HL in larger specimens; and positive allometry in mouth width, 30‒31% of HL in smaller specimens and 34‒39% of HL in larger specimens.

Distribution. Myloplus lucienae  is so far only known from rio Negro and its main tributaries, such as the rio Arirará, rio Carabinani, rio Cuiuni, rio Curicuriari and rio Daraá, all belonging to the rio Negro basin, Amazonas State, Brazil ( Fig. 5View FIGURE 5). The species is apparently widespread throughout rio Negro basin and is restricted to its blackwaters tributaries. The species is typically found in rapids, but is also recorded for slow-flowing habitats such as backwaters and lakes.

Etymology. Myloplus lucienae  is named in honor of Luciene Maria Kassar Borges in recognition of her pioneer attempt to organize the knowledgement on the herbivorous Serrasalmidae  from the rio Negro basin.

TABLE 1. Morphometric data of Myloplus lucienae. Range, mean, and standard deviation (SD) include values for holotype and paratypes.

  130.7 29 75.0–337.5 261.7  
Percentage of standard length          
    28     2.5
    28     0.8
    28     2.1
    28     1.9
    28     1.7
    28     1.4
    28     0.7
    28     0.5
    28     1.0
    28     1.8
    28     1.5
    28     1.3
    28     1.5
    28     1.3
    28     0.5
    28     1.3
    27     0.9
    21     4.5
    27     3.0
    28     1.9
    28     1.6
    28     0.7
    28     3.4
    28     3.6
    27     3.5
    28     2.4
    28     1.3
    28     3.7
    28     1.4
    28     1.3
    28     1.3
    28     2.5

Instituto Nacional de Pesquisas da Amazonia














Myloplus lucienae

Andrade, Marcelo C., Ota, Rafaela P., Bastos, Douglas A. & Jégu, Michel 2016

Myleus rhomboidalis

Toledo-Piza 2002: 168


Toledo-Piza 2002: 180
Borges 1986: 106
Goulding 1980: 115