Aspidoras marianae, Leão, Manuela D. V., Britto, Marcelo R. & Wosiacki, Wolmar B., 2015

Leão, Manuela D. V., Britto, Marcelo R. & Wosiacki, Wolmar B., 2015, A new species of Aspidoras Ihering (Siluriformes: Callichthyidae: Corydoradinae) from the Rio Xingu Basin, Pará, Brazil, Zootaxa 3986 (5), pp. 577-587 : 578-582

Aspidoras marianae , new species

( Fig. 1 ; Table 1 )

Holotype. MPEG 26409, 28.5 mm SL, Brazil, Pará, Castelo de Sonhos municipality, unnamed stream tributary to the Rio Curuá, itself a tributary to the Rio Iriri, Rio Xingu basin, 8º26’44.7”S, 55º09’25.0”W, 15 Aug 2012; M. B. Mendonça.

Paratypes. 12 specimens. All collected with the holotype: MPEG 26408, 3 + 3 cs, 17.8–28.5 mm SL. MNRJ 43440, 2, 18.7–21.2 mm SL. MCP 48790, 2, 19.0–19.6 SL. INPA 48537, 2, 18.8–21.7 mm SL.

Diagnosis. Aspidoras marianae differs from its congeners by the presence of minute odontode-bearing platelets scattered over surface of snout region ( Fig. 2 ; vs. absence). The new species can be distinguished from its congeners, except A. taurus , by the presence of infraorbital 1 and 2 covered by thick skin and not visible externally (vs. externally visible); and from A. taurus by the possession of minute platelets between parieto-supraoccipital process and nuchal plate (vs. absence).

Additionally, the new species can be distinguished from Aspidoras microgalaeus and A. belenos by the presence of three nasal pores (vs. two); from A. velites by presenting ventral laminar expansion of the first infraorbital conspicuously expanded ( Fig. 3 ; vs. very reduced, almost absent in some specimens); by the number of dorsal-fin rays, II,7,i (vs. II, 7–II,8); the reduced number of ventrolateral body plates, 22–23 (vs. 24–26); the greater depth of body, 28.0–31.0% SL (vs. 15.0–20.3%); the greater maximum cleithral width, 24.1–28.5% SL (vs. 12.5– 17.1%); the greater head depth, 68.2–83.0% HL (vs. 53.2–64.6%); the greater least interorbital distance, 49.9– 58.6% HL (vs. 30.3–38.3%); and the greater least internareal distance, 26.9–31.8% HL (vs. 11.1–17.9%). From A. microgalaeus it is easy to distinguish by the greater head length, 32.5–38.6% SL (vs. 25.4–28.7%); the greater horizontal orbit diameter, 18.9–23.5% HL (vs. 10.1–17.0%); the reduced number of total free vertebrae, 23 (vs. 25); the first infraorbital notoriously expanded ventrally ( Fig. 3 , vs. not expanded); and the anal fin with a diffuse blotch restricted to the base of the last two rays, and one blotch each over third and fourth branched rays (vs. two series of dots on all rays). From A. belenos and A. brunneus , it differs by the overall coloration in a roughly marbled pattern ( Fig. 1 ) (vs. characterized by stripes; Britto et al., 2002: figs. 1, 2, and/or solid, uniform coloration; Nijssen & Isbrücker, 1976: fig. 7). Also from A. belenos by conical serrations on the pectoral-fin spine (vs. bifid serrations).

Description. Small species, largest specimen 28.5 mm SL. Morphometric data presented in Table 1 . Head slightly compressed, with convex dorsal profile. Snout rounded in dorsal view. Dorsal profile of body convex from snout dorsal-fin base; slightly concave from last dorsal-fin ray to caudal peduncle. Ventral profile of body slightly convex from snout to pelvic girdle region; straight from this point to anal-fin origin; markedly concave from first anal-fin ray to caudal-fin base. Body roughly elliptical in cross-section at pectoral girdle, gradually more compressed toward caudal fin.

Eye rounded, dorsolaterally on head. Orbit delimited dorsally by frontal and sphenotic, anteriorly by lateral ethmoid, and ventral and posteriorly by infraorbitals. Anterior and posterior nares very close, separated by thin skin flap. Anterior naris tubular.

Small papillae on surface of snout. Mouth small and subterminal. One pair of maxillary barbels and two pairs of mental barbels. Maxillary barbel not reaching limit of gill opening ventrally. Maxillary barbel slightly longer than outer mental barbel. Inner mental barbel fleshy, nearly one-fourth of outer mental barbel length. Minute rounded papillae over all barbels and upper and lower lips. Minute odontode-bearing platelets scattered over surface of snout region ( Fig. 2 ).

Gill membranes united to isthmus. Four branchiostegal rays covered by thick layer of skin; distal two rays united at their tips by branchiostegal cartilage. Teeth on upper pharyngeal tooth plate 21(1), 24(1) or 25(1) in two rows, and on fifth ceratobranchial 22(1), 25(1) or 26(1) aligned in one row. Minute vermiculate platelets homogeneously scattered over entire surface between isthmus and pelvic region ( Fig. 4 ).

Nasal, frontal, sphenotic, parieto-supraoccipital and compound pterotic visible externally, all covered by thin layer of skin and bearing minute scattered odontodes. Two cranial fontanels; anterior small, ovoid, delimited by frontal bones, its posterior margin contacting anterior margin of parieto-supraoccipital; posterior rounded and smaller than anterior fontanel, restricted to middle of parieto-supraoccipital.

Nasal slender, slightly curved, inner margin contacting frontal. Frontal quadrangular, anterior extension contacting nasal bone. Posteriorly, frontal contacts sphenotic and parieto-supraoccipital. Sphenotic quadrangular, contacting parieto-supraoccipital dorsally, compound pterotic posteriorly and infraorbital 2 ventrally. Compound pterotic anterior portion contacting sphenotic anteriorly and parieto-supraoccipital dorsally; posterior portion contacting first dorsolateral body plate dorsally and first lateral line ossicle posteriorly. Ventrally, compound pterotic contacting opercle and cleithrum. Parieto-supraoccipital quadrangular, with elongated posterior process separated from nuchal plate by one dorsal body plate. Minute platelets between these elements (Fig. 5). Two infraorbital bones, both covered by thick skin and not visible externally; first infraorbital notoriously expanded ( Fig. 3 ). Opercle exposed, ovoid and roughly elongated. Preopercle externally visible, slender and covered by thin layer of skin. Interopercle quadrangular, covered by thin layer of skin.

Trunk lateral line composed of one perforated dorsolateral body plate (third) and two laterosensory canals, reduced to small ossicles. Lateral line canal entering neurocranium through compound pterotic, splitting into three branches before entering sphenotic: pterotic, preoperculomandibular, and postero-lateral, each with single pore. Postero-lateral branch open in compound pterotic itself, just above upper margin of opercle. Sensory canal continuing through compound pterotic, entering sphenotic as temporal canal, which splits into two branches: one branch giving rise to infraorbital canal, other branch entering frontal through supraorbital canal. Supraorbital canal with two branches: epiphyseal, opening near anterior fontanel; and anterior running through nasal bone. Nasal canal with one opening anteriorly and two posteriorly. Infraorbital canal running through entire second infraorbital, extending to infraorbital 1 and opening into two pores. Preoperculomandibular branch giving rise to preoperculomandibular canal, which runs through entire preopercle with three openings, corresponding to pores 3, 4 and 5, respectively.

Body plates with minute odontodes restricted to posterior margins. Nuchal plate exposed. Dorsolateral body plates 24(9) or 25(4*); ventrolateral plates 22(8) or 23(5*); dorsolateral body plates along dorsal-fin base 6(5*) or 7(8); dorsolateral body plates from adipose-fin to caudal-fin base 8(5) or 9(8*); preadipose platelets 4(4) or 5(9*). Precaudal vertebrae 8(3); caudal vertebrae 15(3); Six pairs of ribs, first pair conspicuously larger than others.

Dorsal fin rectangular; its origin just posterior to third dorsolateral body plate. Dorsal spine shorter than first five dorsal-fin rays and with smooth anterior and posterior margins; dorsal-fin rays II,7,i(13*). Adipose origin just posterior to 16th or 17th dorsolateral body plate; preceded by small curved well-ossified spine. Pectoral fin roughly triangular; origin just posterior to gill opening; ossified portion of pectoral spine shorter than all branched pectoralfin rays; anterior margin with small, scattered odontodes; posterior border of pectoral spine with 14–19 conical serrations, roughly perpendicularly oriented relative to main axis of spine ( Fig.6 ); pectoral-fin rays I,8(5) or I,8,i(8*). Pelvic fin ovoid; origin just below second ventrolateral body plate; pelvic-fin rays i,5(11*) or i,6(2). Anal fin roughly ellipsoid; origin just posterior to 13th or 14th ventrolateral body plate; anal-fin rays ii,5(13*). Caudal fin bilobed, lobes bluntly pointed and equal in size; principal caudal-fin rays i,6/6,i(13*); procurrent caudal-fin rays 5(4) or 6(9*) and 5(4) or 6(9*) on dorsal and ventral lobes, respectively. All fins with minute odontodes scattered on all rays.

Color in alcohol. Background coloration pale yellow. Presence of four large brown blotches along midline of flank: first located between pectoral and pelvic girdles; second between pelvic girdles and anal fin; third above anal fin; and last on caudal peduncle and caudal-fin base. First, second and third blotches chevron shaped, fourth roughly triangular. Tiny dark brown blotches on dorsal surface of head; more numerous and concentrated on parieto-supraoccipital region. Elongated, oblique, dark brown blotch on antorbital portion. Opercle with few brown saddles. Roughly rounded, brown blotch on base of dorsal fin, from base of spine to interradial membrane after third branched ray. Small brown patches scattered along dorsal fin, larger until third or fourth branched rays. Dark spot on base of adipose-fin spine and few diffuse chromatophores on medial portion. Pectoral spine with small, diffuse, light brown blotches on proximal and distal portions; with tiny chromatophores; small, light brown patches until fourth or fifth pectoral-fin rays. Pelvic fin hyaline. Anal fin with small, diffuse, light brown blotches restrict to base of last two rays, and one diffuse light brown blotch each over third and fourth branched rays. Three to four irregular, vertical series of small, brown blotches restrict to rays on caudal fin.

Distribution. Known only from its type locality, an unnamed stream tributary of the Rio Curuá, itself a tributary of the Rio Iriri, in the Rio Xingu basin ( Fig. 7 ).

Habitat notes. Aspidoras marianae was only collected in a slow-flowing stream with clear water and a sandy bottom with mud, leaf litter, submerged logs, and some aquatic macrophytes ( Fig. 8 ).

Etymology. The specific epithet marianae is a reference to Mariana P. Wosiacki, daughter of the third author. A genitive noun.

Figures

FIGURE 1. Aspidoras marianae, holotype, MPEG 26409, 28.5 mm SL, Castelo de Sonhos municipality, unnamed stream, Rio Xingu basin, Pará, Brazil. Left lateral, dorsal, and ventral views.

FIGURE 2. Dorsal view of the snout region of Aspidoras marianae, MPEG 26408, paratype. Arrows indicate minute odontodebearing platelets scattered over all surface of the snout. MAX = maxilla, AP = autopalatine, MES = mesethmoid, N = nasal, F = frontal. Scale bar = 1 mm.

FIGURE 3. Lateral view of the orbital region of Aspidoras marianae, MPEG 26408, paratype. N = nasal, IO 1, 2 = infraorbitals 1, 2, POP = preopercle, OP = opercle. Scale bar = 1 mm.

FIGURE 4. Detail of the isthmus region of Aspidoras marianae, MPEG 26408, paratype. Arrows indicate minute odontodebearing platelets. Left ventrolateral plates removed. Scale bar = 2 mm.

FIGURE 6. Dorsal view of left pectoral-fin spine of Aspidoras marianae, MPEG 26408, paratype. Odontodes on anterior margin not depicted. Scale bar = 1 mm.

FIGURE 7. Map of part of the upper Rio Xingu showing type localities of Aspidoras species. Star = Aspidoras marianae, circle = A. microgalaeus, triangle = A. brunneus. 1 = Rio Curuá; 2 = Rio Xingu; 3 = Rio Culuene; 4 = Rio Araguaia.

FIGURE 8. Type locality of Aspidoras marianae, in unnamed stream tributary to the Rio Curuá, itself a tributary to the Rio Iriri, Rio Xingu basin, 8 º 26 ’ 44.7 ” S, 55 º 09 ’ 25.0 ” W.

Tables

TABLE 1. Morphometric data of holotype and 12 paratypes of Aspidoras marianae. Ranges include the holotype.

	Holotype	Paratypes
Standard length	28.5	Mean Range 21.8 17.8–28.5
Percents of standard length
Depth of body	28.5	29.2 28.0–31.0
Predorsal distance	40.0	44.3 40.0–46.7
Prepelvic distance	43.8	47.0 43.8–50.1
Preanal distance	73.1	75.3 73.1–78.3
Preadipose distance	78.4	79.7 74.7–84.5
Length of dorsal spine	14.7	13.7 11.8–15.9
Length of pectoral spine	17.3	16.9 15.9–18.5
Length of adipose-fin spine	9.0	9.7 8.3–11.7
Depth of caudal peduncle	14.4	15.0 14.4–15.9
Dorsal to adipose distance	22.6	21.7 20.2–23.3
Length of dorsal-fin base	17.1	17.0 15.6–19.1
Maximum cleithral width	24.1	27.1 24.1–28.5
Head length	32.5	35.9 32.5–38.6
Length of maxillary barbel	14.7	16.2 14.5–18.7
Percents of head length
Head depth	83.0	75.4 68.2–83.0
Least interorbital distance	40.5	43.6 38.7–48.3
Horizontal orbit diameter	19.0	20.6 18.9–23.5
Snout length	42.5	44.0 35.4–51.7
Least internareal distance	28.3	29.2 26.9–31.8