Curculionichthys itaim, Roxo & Dias & Silva & Oliveira, 2017

Roxo, Fábio F., Dias, Angelica C., Silva, Gabriel S. C. & Oliveira, Claudio, 2017, Two new species of Curculionichthys (Siluriformes: Loricariidae) from the rio Amazonas basin, Brazil, Zootaxa 4341 (2) : -

Curculionichthys itaim , new species

Fig. 4 , Table 1

Curculionichthys sp. n. 2: Roxo et al. 2015: 116 (Fig. 8)

Holotype. MZUSP 123011 , 22.3 mm SL, Brazil, state of Pará, municipality of Itaituba, Igarapé Nambuaí, rio Tapajós basin, 04°37’28” S, 56°23’18” W, 15 June 2012, R. Britzke & Cepta’s Team.

Paratypes. All from Brazil, state of Pará, municipality of Itaituba, rio Tapajós basin. AUM 68655., 4, 19.3– 20.1 mm SL, Igarapé Presidente , 04°43’13” S, 56°44’24” W, 29 September 2011, R. Britzke & Cepta’s Team . LBP 13743, 1, 20.3 mm SL, rio Tracuá , 04°29’11” S, 56°17’22” W, 25 September 2011, R. Britzke & Cepta’s Team . LBP 13864, 13, 16.4–24.0 mm SL, 2 c&s, 21.6–22.1 mm SL, Igarapé Nambuaí , 04°37’28” S, 56°23’18” W, 25 September 2011, R. Britzke & Cepta’ s Team . LBP 14102, 6, 17.0– 22.3 mm SL, 2 c&s 19.9–21.5 mm SL, Igarapé Cipó , 04°52’14” S, 56°51’19” W, 29 September 2011, R. Britzke & Cepta’s Team . LBP 14227, 1, 22.6 mm SL, Igarapé Urubutu , 04°46’10” S, 56°46’46” W, 0 1 October 2011, R. Britzke & Cepta’s Team . LBP 14152, 20, 18.7– 20.3 mm SL, Igarapé Presidente , 04°43’13” S, 56°44’24” W, 29 September 2011, R. Britzke & Cepta’s Team . LBP 16159, 1, 20.8 mm SL, Igarapé Nambuaí , 04°37’28” S, 56°23’18” W, 15 June 2012, R. Britzke & Cepta’s Team . LBP 16249, 6, 19.5–24.6 mm SL, Igarapé São José , 04°30’28” S, 56°17’23” W, 14 June 2012, R. Britzke & Cepta’s Team . LBP 17485, 4, 17.7–23.6 mm SL, collected with holotype . NUP 19281, 4, 18.9–21.6 mm SL, Igarapé Presidente , 04°43’13” S, 56°44’24” W, 29 September 2011, R. Britzke & Cepta’s Team. ZUFMS PIS 0 5432, 2, 19.4–22.4 mm SL, collected with holotype .

Diagnosis. Curculionichthys itaim differs from all congeners, except C. coxipone , C. sabaji and C. tukana by having eight to ten plates in abdominal lateral plates series, Fig. 5A (vs. four to six plates in abdominal lateral plates series); from C. coxipone and C. oliveirai by having the anterior profile of the head pointed (vs. anterior profile of the head rounded); from C. insperatus , C. paresi , C. sabaji and C. tukana by having papillae randomly distributed throughout the lower lip (vs. the papillae aligned in series that extends from the distal portion of lower lip to dentary, see Fig. 4 in Silva et al. 2016 for both characters states); and from C. insperatus and C. oliveirai by absence of large conspicuous odontodes forming rows on head and trunk (vs. the presence of large, conspicuous odontodes forming rows on the head). Curculionichthys itaim can be further distinguished from C. coxipone and C. luteofrenatus by having 22–23 medial plates series on lateral portion of the body following the lateral line (vs. 25– 27 medial plates series); from C. sabaji by the absence of dark-brown spots scattered over the body (vs. the presence of dark-brown spots on the body); from C. oliveirai and C. tukana by having two or three irregular median plates series in abdomen (vs. one median plate series in abdomen); from C. karipuna by the absence of an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portion of the first unbranched anal-fin ray (vs. the presence of such pigmentation pattern); from C. paresi by having 11–18 dentary teeth (vs. 4–7), and the lack of contrasting dark spots at the anterodorsal region of body (vs. the presence of such pigmentation pattern at the anterodorsal region of body); from C. piracanjuba by having odontodes forming aligned rows, more evident in the dorsal portion of head and in the lateral portion of caudal peduncle (vs. odontodes not forming rows); and from C. sagarana by absence of one unpaired platelet on the dorsal portion of the caudal peduncle (vs. presence).

Description. Morphometric and meristic data are given in Table 1. Small-sized loricariid (17.6–24.9 mm SL). Snout slightly pointed (48–56% HL), completely covered with odontodes. Eyes of median size (13–16% HL), dorsolaterally positioned on head. Dorsal margin of orbit with small ridge. Interorbital space slightly concave. Buccal papilla absent. Lower lip of mouth reaching line between gill openings; lower lip inner surface covered with small papillae, increasing in size as it approaches to dentary. Maxillary barbel of small size, shorter than orbital diameter. Teeth tender and small, bicuspid; cusps asymmetrical, main cusp larger than lateral cusp. Premaxillary teeth 11–18 (mode 14). Dentary teeth 8–15 (mode 12). Lower surface of head naked, with small to moderate patches of platelets with odontodes immediately posterior to gill openings and coracoid in larger specimens.

Head broad, rounded, covered dorsolaterally with dermal ossifications, and small odontodes, except in insertion area of dorsal fin base. Lightweight longitudinal ridge on dorsal surface of head extending posterior to eye, on compound pterotic. Predorsal region without ridges. Odontodes not well developed in opercular region. Dorsal profile slightly concave and sloped upward from snout tip to supraocciptal; straight from that point to dorsal fin origin. In lateral view, dorsal profile of head and snout rising at approximately 45°. Ventral profile of head and trunk slightly descending at approximately 225° from snout tip to pectoral-fin origin, inclining upwards from this point to lower procurrent caudal-fin rays origin.

In dorsal view, elongated body, without conspicuous keels. Greatest body width at cleithral region (44–52% SL), narrowing posteriorly towards caudal peduncle and caudal fin insertion. Greatest body depth at unbranched dorsal-fin ray insertion (15–21% SL), slightly descending from that point to first upper procurrent caudal-fin ray origin, elevating posteriorly to insertion of caudal fin. Body lateral surface with five longitudinal series of bony plates, without keels. Dorsal series with slightly developed longitudinal rows of odontodes on caudal peduncle region, oriented from seventh to first upper procurrent caudal-fin rays origin. Mid-dorsal series poorly developed (six plates), reaching about middle of dorsal-fin base. Median series uninterrupted in median portion of body and sequentially bearing lateral-line pores (21–23 plates). Mid-ventral series developed (14), reaching middle of analfin unbranched ray. Ventral series of plates with rows of odontodes on caudal peduncle region, oriented from 11 to first lower procurrent caudal-fin rays origin.

Cleithrum and coracoid completely exposed in ventral view, covered by small odontodes. Abdomen completely covered by plate series, except for naked areas around pectoral and pelvic fin insertion. Lateral abdominal plates series larger, with regular series of eight elongate plates; anterior lateral plate series in abdomen smaller than posterior plates; one series of median plates, asymmetrical and irregularly arranged; anal plates series formed by three to four large plates ( Fig. 5A ).

Dorsal-fin ii,5; small size; originating posteriorly to pelvic-fin origin; distal margin slightly convex; when adpressed reaching anal-fin origin. Dorsal-fin spinelet small and V -shaped ( Fig. 5B ). Pectoral-fin i,6; distal rays longer than proximal rays; presence of pectoral fin axillary slit between pectoral fin insertion and posterior process of cleithrum; pectoral-fin spine concave and arrow-shaped, inflexible, not pungent, with poorly developed odontodes distally; when adpressed reaching approximately middle of pelvic-fin spine. Pelvic-fin i,5; similar-sized rays, distal border slightly convex; pelvic-fin unbranched ray flexible, slightly straight; when adpressed reaching anal-fin origin. Anal-fin i,5, distal margin slightly straight, with similarly-sized rays. Adipose-fin absent. Caudalfin i,7-7,i; forked; two lobes with unbranched rays of similar size. Caudal peduncle slightly compressed. Caudal peduncle elliptical in cross-section, rounded dorsally and ventrally.

Bony plates of neurocranium presented in Fig. 5C,D . In dorsal view ( Fig. 5C ), parieto-supraoccipital (soc) octagonal with posterior process moderate in size, bordered by one large single plate and two small lateral plates. Snout composed by two rostral rectangular-shaped plates (r); two prenasals square-shape plates (pn), two small triangular-shaped plates (pn) between nares, one prenasal elongate plate (pn) positioned posteriorly of rostral plate; and nasal bone (n) almost triangle-shaped bordered anteriorly by prenasal plates and posteriorly by frontals (f). Upper region of neurocranium composed by compound pterotic (cpt) bordered by sphenotic (sp), parietosupraoccipital (soc) and frontal (f), largest bones of head.

In lateral view ( Fig. 5D ), posterior rostrum plates larger, pr1 and pr3 triangular-shaped, and pr2 rectangularshaped. Infraorbital plate series complete (io1-io5), with laterosensory canal system bordered by posterior rostrum series; io1 io5 smallest, io2 largest; io3, io4 and io5 forming inferior orbital margin of eyes. Opercular series of bone small, preopercle (pop) and supraopercular plate (spop) reduced, rectangular-shaped, covered by laterosensory canal; two subocular cheek plates, cp1 largest, triangular-shaped, and cp2, bordering by cp1, preopercle and opercle (op) forming posterior lateral margin of head.

Color in Alcohol. In dorsal view, dark brown background. Three inconspicuous dark bars along dorsal portion of body: first at final portion of dorsal fin; second at middle portion of caudal peduncle; third located in lower procurrent caudal-fin rays origin. Unpigmented portion of lateral cleithral region and latero-anterior portion of head. Two hyaline parallel strips formless on snout, from rostral plate to nares. Pectoral fins hyaline, without chromatophores. In lateral view, body with a color gradient in dorsal and ventral region of body. Dark bar inconspicuous in median region of body following lateral line. Dorsal fin with dark chromatophores forming inconspicuous three sets of bands. Caudal-fin hyaline, except on anterior to middle region of rays, dark stains at posterior region of rays and chromatophores irregularly distributed. Yellowish body in ventral view; chromatophores irregularly distributed on anal-fin base.

Sexual dimorphism. Adults males possess a papilla covering urogenital opening, a long pelvic fin that extends beyond anal-fin origin, and an unbranched pelvic-fin ray supporting a dermal flap along its dorsal surface, features absent in all analyzed females.

Distribution. The new species C. itaim is known from six small streams of the rio Tapajós basin ( Fig. 3 ): Igarapé Cipó, Igarapé Nambuaí (type locality), Igarapé Presidente, Igarapé São José, Igarapé Urubutu and rio Tracuá.

Etymology. The specific name “ itaim ” came from Tupi-Guarani language and means itá = stones and im = diminutive. This name is related to the city Itaituba (itá'imtyba) where the new species is found and means “gathering of small stones”. A noun in apposition.

Figures

FIGURE 3. Map of north South America showing the distribution of Curculionichthys itaim— Red Diamond = type locality at Igarapé Nambuaí, municipality of Itaituba, state of Pará, Black Circles = paratypes specimens; and Curculionichthys tukana — Red Star = type locality at ribeirão Bofe, municipality of Estreito, state of Maranhão, Black Square = paratypes and non-type specimens. The green color in the map shows the rio Tapajós basin and the purple color the rio Tocantins-Araguaia basin.

FIGURE 4. Curculionichthys itaim, MZUSP 123011, holotype, 22.3 mm SL, state of Pará, municipality of Itaituba, Igarapé Nambuaí, rio Tapajós basin. Dorsal, lateral and ventral views.

FIGURE 5. Curculionichthys itaim, LBP 14102, 21.5 mm SL. A) Ventral view showing intraspecific variation in abdominal plates; B) Shape of the spinelet. Neurocranium in C) dorsal and D) dorsolateral views. Abbreviations are: f = frontal; io 1 – 4 = infraorbitals; cpt = compound pterotic; pr 1 – 3 postrostral plates; op = opercle; pf = prefrontal; n = nasal; pn = prenasal; r = rostral plate; pop = preopercle; cp 1 – 2 = subocular cheek plate; sp = sphenotic; soc = parieto-supraoccipital; spop = supraopercular plate. Scale bars: 0.5 mm (B); 1 mm (A, C, D).