Mastiglanis yaguas, Faustino-Fuster & Ortega, 2020

Faustino-Fuster, Dario R. & Ortega, Hernán, 2020, A new species of Mastiglanis Bockmann 1994 (Siluriformes: Heptapteridae) from the Amazon River basin, Peru, Zootaxa 4820 (2), pp. 323-336 : 325-331

Mastiglanis yaguas , new species

( Figures 1 A−C, 2, 3, 4; Table 1)

urn:lsid:zoobank.org:act:F33BDFEC-872C-45D0-BCF8-700D28CDC999

Mastiglanis sp.: Hidalgo & Ortega-Lara, 2011: 98, 103, 106, 221, 227, 229, 324 (species list).

Mastiglanis sp1.: Faustino-Fuster, 2019: 11–17, Table 1. Fig.: 1–7 (taxonomic revision).

Mastiglanis sp5.: Almeida, 2019: 71–75. Fig. 22 (taxonomic revision).

Holotype. MUSM 66612 , 49.1 mm SL. Peru, Loreto Department, Putumayo Province, Yaguas District , Putumayo River basin, Yaguas River , 2°43’5.31”S; 70°31’42.12”W, 29 November 2010, M. Hidalgo & A. Ortega-Lara.

Paratypes. All from Peru: Nanay Province, Iquitos District , Nanay River : ANSP 167653 , 1 , 43.1 mm SL, beach downstream from Nina Rumi community, 3°44’0.00”S; 73°19’60.00”W, 8 September 1990, Dan & Pat Fromm ; ANSP 167654 , 1 , 37.9 mm SL, beach downstream from Nina Rumi community, 3°44’0.00”S; 73°19’60.00”W, 8 Sep. 1990, Dan & Pat Fromm ; ANPS 167715 , 5 , 30.3−37.2 mm SL, beach downstream from Minchana community, 3°53'0.00"S; 73°27'0.00"W, 10 September. 1990, Dan & Pat Fromm ; ANSP 178449 , 7 , 37.0− 55.4 mm SL, beach in Pampachica , 3°45'9.00"S; 73°16'60.00"N, 2 August 2001, M. Sabaj, M. Littmann, N. Lovejoy, C. Skelton, K. Elkin, M. Thomas & J. Stewart ; ANSP 180407 , 20 , 37.5−52.7 mm SL, beach upstream from Santa Clara community, 3°46'45.00"S; 73°22'6.00"W, 14 August 2003, M. Sabaj, N. Salcedo & B. Sidlauskas ; ANSP 181127 , 6 , 40.0− 43.4 mm SL, beach in Pampachica , 3°45'9.00"S; 73°16'60.00"N, 21 August 2005, M. Sabaj & C. Pérez ; ANSP 182474 , 7 , 38.6−47.7 mm SL, beach in Pampachica , 3°45'9.00"S; 73°16'60.00"N, 7 Aug. 2005, M. Sabaj, C. Perez, M. Arce & A. Bullard ; ANSP 182565 , 1 , 41.7 mm SL, beach in Pampachica , 3°45'9.00"S; 73°16'60.00"N, 3 August 2005, M. Sabaj, C. Pérez, A. Bullard, C. DoNascimiento, O. Castillo, S. Snyder ; ANSP 182750 , 1 , 46.8 mm SL, beach upstream from confluence with the Amazonas River , 3°42'49.00"S; 73°16'43.00"W, 15 August 2005, M. Sabaj, C. DoNascimiento & O. Castillo ; ANSP 191830 , 5 , 29.7−46.6 mm SL, beach upstream from Pampachica, 3°45'10.00"S; 73°16'60.00"W, 6 August 2010, M. Sabaj, B. Sidlauskas, C. Phillips, J. Tiemann & E. Correa. Loreto Department, Putumayo Province , Yaguas District : FMNH 140321 , 3 (all xr), 41.5–47.1 mm SL ; MCP 54155, 1 , 43.3 mm SL ; MUSM 61686 , 5 (1 c&s), 42.7−51.3 mm SL ; UFRGS 27250 , 1 , 38.0 mm SL, collected with the holotype . MUSM 61545 , 1 , 38.2 mm SL, Yaguas River , 2°43’5.31”S; 70°31’42.12”W, 27 November 2010, M. Hidalgo & A. Ortega-Lara .

Diagnosis. Mastiglanis yaguas differs from all its congeners by having eight branched anal-fin rays (vs. seven), longer pelvic fin, exceeding the origin of the adipose fin (21.2−26.1% SL) (vs. not exceeding the adipose-fin origin 17.7−19.1% SL in M. asopos and 16.0−18.4 % SL in M. durantoni ), 39 vertebrae (vs. 37−38 vertebrae in M. asopos and 38 in M. durantoni ), anterior process on posteriormost neural spines (vs. lacking of anterior process), process at symphysial region of premaxilla absent (vs. present), posterior fontanel two times wider than anterior fontanel (vs. one and a half), anterior process of premaxilla short (vs. long). Additionally M. yaguas is differentiated from M. asopos by having more epibranchial gill rakers (2 vs. 0), more ceratobranchial gill rakers (13 vs. 11), slender body (body width 12.9−14.9% SL vs. 15.6−17.2% SL), deeper head (59.5−67.9% HL vs. 38.5−47.8% HL), narrow head (44.7−50.9% HL vs. 57.9−70.9% HL), wider interorbital distance (30.3−36.4% HL vs. 22.3−24.6% HL), larger eye (21.4−24.7% HL vs. 18.6−20.5% HL), and wider posterior inter-narial distance (10.3−14.2% HL vs. 7.7−9.1% HL).

Description: Morphometric data presented in Table 1. Body slightly elongated, elliptical in anterior cross section at level of dorsal-fin origin, then gradually compressed along caudal peduncle ( Figure 1 ). Dorsal profile of body more convex than ventral profile; dorsal profile convex from snout tip to last dorsal-fin ray; almost straight from last dorsal-fin ray to adipose-fin origin, and slightly convex from adipose-fin origin to caudal-fin origin. Ventral profile of head slightly convex from snout tip to gill opening. Ventral profile of body slightly convex from gill opening to pelvic-fin origin, nearly straight from pelvic-fin origin to anal-fin origin, and slightly convex to caudal peduncle. Anus and urogenital pore close to each other.

Head short, narrow, depressed, and trapezoidal in dorsal view ( Figure 1B ). Anterior nostril near to upper lip and posterior nostril slightly closer to anterior edge of eye than to anterior nostril. Distance between anterior nostrils greater than distance between posterior nostrils, nostrils arranged as vertices of trapezoid. Mouth subterminal, with snout projected beyond lower jaw. Barbels very long, tapering distally. Maxillary barbel origin dorsally to upper lip and lateral to anterior nostrils, reaching half of adipose fin when adpressed along body axis. Mental barbel origin between anterior edge of lower jaw and gular fold. Outer mental barbel longer than inner mental barbel, tip reaching pelvic-fin origin when adpressed along body axis. Inner mental barbel origin closer to gular fold, tip surpassing pectoral-fin origin when adpressed along body axis. Eye large; horizontally elliptical; slightly anterior at midpoint between tip of snout and edge of opercular membrane; dorsal region slightly covered by skin, lens visible and pupil rounded. Branchiostegal rays seven (1). Gill rakers on first ceratobranchial 13 (1) (including one on angle formed with epibranchial), and two (1) on first epibranchial.

Dorsal fin with i+6 (11) rays; triangular; first dorsal-fin ray unbranched, with stiffened proximal region, approximately as long as first branched ray, and distal region soft and long, surpassing half-length of adipose fin when adpressed; followed by six branched rays; dorsal-fin origin anterior to vertical through pelvic-fin origin. First pterygiophore of dorsal fin inserted between bifid neural spines of vertebrae 6–7 (4).

Pectoral fin with i+9 (11) rays; triangular; proximal region of first ray stiffened, approximately as long as first branched ray, distal region soft and filamentous, reaching vertical through half-length of adipose fin when adpressed; second ray of pectoral fin (first branched ray) almost as long as third ray (second branched ray) followed by branched rays decreasing moderately in length.

Pelvic fin with i+5 (11) rays; rounded distal margin; first pelvic-fin ray, completely flexible and slightly shorter than second and third rays (first and second branched rays, respectively); origin of pelvic-fin anterior to vertical through half-length of body standard length, and between the verticals through fourth and fifth dorsal-fin branched rays; tip of adpressed pelvic-fin reaching vertical through anal-fin origin.

Anal fin with iii+8 (11) rays ( Figure 6 A–B); triangular in lateral profile; short (9.5−11.9% of SL). Anal-fin base origin anterior to vertical through adipose-fin origin, and reaching the vertical through half-length of adipose-fin when adpressed. First pterygiophore of anal-fin inserted between hemal spines of vertebrae 22–23 (3) or 23–24 (1).

Adipose fin slightly long (21.6−27.1 % of SL), convex in lateral profile; distance from last dorsal-fin ray to adi-pose-fin origin shorter than adipose-fin base length. Adipose-fin origin posterior to vertical through body midpoint (excluding caudal fin), posterior region of adipose fin slightly posterior to vertical through anal-fin tip.

Caudal fin bifurcated, dorsal and ventral lobes of same size. Dorsal caudal-fin lobe with seven (11) branched rays; ventral caudal-fin lobe with eight (11) branched rays. Caudal fin with 45 total rays; with 22 (1) rays on dorsal lobe and 23 (1) rays on ventral lobe. Dorsal caudal plate (hypurals 3, 4 and 5) with eight (4) rays; ventral caudal plate (parhypural plus hypurals 1 and 2) with nine (4) rays ( Figure 4 ).

Total vertebrae 39 (4). First complete hemal spine on vertebra 14 (4). 13 (4) pre-caudal vertebrae (including five vertebrae of Weberian apparatus) followed by 26 (4) caudal vertebrae. Posteriormost vertebrae 6–9 with anterior neural process; and last 2−3 vertebrae (except on pu1 + u1) with anterior hemal process ( Figure 4 ). Six (1) or seven (3) ribs.

Laterosensory canals of head with simple tubes ending in single pores. Supraorbital canal with seven branches: s1, s2, s3, s4, s6, s7 and s8; each one opening into its own pore, except branch s2 (fused with i2 into complex s2+i2 pore). Infraorbital canal with six branches i1, i2, i3, i4, i5 and i6; each one opening into its own pore, except branch i2 (fused with branch s2 into complex s2 + i2 pore). Preoperculomandibular canal with 10 branches; pm1, pm2, pm3, pm4, pm5, pm7, pm8, pm9, pm10 and pm11, all opening into its own pore except branch pm11, fused with branch po1 (into complex po1 + pm11 pore). Postotic canal with three branches; po1, po2 and po3, each one opening into its own pore except branch po1 (po1 + pm11 pore). Lateral line complete and continue until caudal fin base.

Color in alcohol. Body overall pale cream, with dark brown chromatophores distributed indistinctly on lateral region of body and head; ventral surface unpigmented ( Figure 1 ). Narrow and indistinct lateral strip, dark brown, clearer on posterior region, extending from adipose-fin origin to caudal-fin base. Dorsal region with six conspicuous blotches of dark brown chromatophores: first posterior to supraoccipital process, second anterior to dorsal-fin origin, third posterior to last dorsal-fin ray, fourth between last dorsal-fin ray and adipose-fin origin, fifth at adipose-fin origin, and sixth located at end of adipose-fin base. Dorsal surface of head (supraoccipital) covered with dark brown chromatophores fading laterally, and ventral surface pale. Maxillary barbel, outer mental barbel, and inner mental barbel slightly pigmented with dark brown chromatophores dorsally; and unpigmented ventrally. Dorsal, pectoral, pelvic, anal, and caudal-fin rays lightly pigmented with light brown chromatophores, inter-radial membranes hyaline. Adipose fin with dark brown chromatophores irregularly distributed, more concentrated at proximal region than distal region (hyaline).

Geographic distribution. Mastiglanis yaguas is distributed in the Yaguas River, tributary of the Putumayo river basin, and in the Nanay River tributary of the western Amazon River; in Putumayo and Maynas provinces, Loreto department, Peru, Upper Amazon basin. ( Figure 5 ).

Etymology. The species name, yaguas , is in reference to the Yaguas National Park (Parque Nacional Yaguas) in northeastern Peru; created recently as a conservation area to protect the flora and fauna, and the hidden Amazon biodiversity. The name is treated as a noun in apposition.

Figures

FIGURE 1. Mastiglanis yaguas, new species, MUSM 66612, holotype, 49.1 mm SL, (A) Lateral view of right side (image flipped), (B) Dorsal view, (C) Ventral view. Bar = 1 cm.

FIGURE 4. Lateral view of caudal skeleton of Mastiglanis yaguas, paratype, MUSM 61686, 42.7 mm SL. Abbreviations: epu = epural; hu1 + hu2 = hypurals 1 and 2; hu3 + hu4 + hu5 = hypurals 3, 4, and 5; ph = parhypural; pu1 + u1 = preural centrum 1 and ural centrum 1; pu2 = preural centrum 2; ur = uroneural. Arrows: anterior processes.

FIGURE 5. Geographical distribution of Mastiglanis yaguas (red circle), M. asopos (white triangle), and M. durantoni (yellow square). Stars represent the type localities of each species. Each symbol may represent more than one specimen.

FIGURE 6. Boxplot showing meristic variation among Mastiglanis. (A) Total number of unbranched anal-fin rays. (B) Total number of branched anal-fin rays.