Curculionichthys karipuna, Silva, Gabriel S. C., Roxo, Fábio F., Melo, Bruno F. & Oliveira, Claudio, 2016

Silva, Gabriel S. C., Roxo, Fábio F., Melo, Bruno F. & Oliveira, Claudio, 2016, New species of Curculionichthys (Siluriformes: Loricariidae) from the eastern Guiana Shield, Zootaxa 4175 (3), pp. 281-291 : 282-288

Curculionichthys karipuna , new species

Fig. 1 , Table 1

Holotype. MZUSP 120190 , female, 23.7 mm SL, Brazil, state of Amapá, municipality of Oiapoque, rio Cassiporé, Atlantic coastal river, small stream under the bridge of the road BR-156 at Campo Alegre farm, 3°04’49.7”N 51°28’50.7”W, 0 1 Dec 2015, B. F. Melo & C. Oliveira.

Paratypes. All from Brazil. LBP 21166, 15 females (19.9–21.5 mm SL), 25 males (19.4–21.8 mm SL), 2 c&s undetermined sex (tissues 83032–83036), same data as holotype . NUP 18739, 4 females (19.8–21.9 mm SL), 4 males (20.7–22.3 mm SL), same data as holotype .

Non-types. LBP 20434, 3 females (19.7–21.3 mm SL), 2 males (21.2–21.4 mm SL) (tissues 80723–80727), state of Pará, Monte Dourado-Almeirim, Amazon basin, rio Jari , small stream under the bridge, road to UHE Santo Antônio Jari , 0°45’07.3”S 52°34’30.6”W, 24 Sep 2015, B. F. Melo & C. Oliveira . LBP 21106, 1 male (18.3 mm SL), 4 females (19.4–20.0 mm SL), 1 c&s undetermined sex, state of Pará, Monte Dourado-Almeirim, Amazon basin, rio Jari , small stream under the bridge, road to UHE Santo Antônio Jari , 0°49’03.9”S 52°35’08.2”W, 25 Nov 2015, B. F. Melo & C. Oliveira.

Diagnosis. Curculionichthys karipuna differs from all congeners, except C. sabaji and C. paresi , by the presence of an irregular concentration of chromatophores that entirely cover the anal-fin origin and adjacent region, and distal portions of the first unbranched anal-fin ray ( Fig. 2a ) (vs. absence of such pigmentation pattern, Fig. 2 b). Curculionichthys karipuna differs from C. sabaji by the absence of dark-brown spots scattered over the body ( Fig. 3 ) (vs. presence); and it differs from C. paresi by the lack of contrasting dark spots at the anterodorsal region of body ( Fig. 3 ) (vs. presence of such spots). In addition, the new species differs from C. insperatus , C. sabaji , C. paresi and C. coxipone by having all papillae randomly distributed throughout lower lip ( Fig. 4 ) (vs. papillae aligned in series that extends from the distal portion of lower lip to dentary); it differs from C. insperatus and C. oliveirai by the presence of small, inconspicuous odontodes forming rows on head and trunk (vs. presence of large, conspicuous odontodes). Curculionichthys karipuna differs from C. coxipone and C. oliveirai by having a pointed profile of the anterior portion of the head (vs. rounded profile); it differs from C. paresi by having 10–16 premaxillary teeth (vs. 6–10) and 10–14 dentary teeth (vs. 4–7); it differs from C. sagarana by the absence of an unpaired platelet on dorsal portion of caudal peduncle (vs. presence). The new species also differs from C. coxipone by having 27–28 vertebrae (vs. 29–30). Finally, C. karipuna differs from C. oliveirai by the presence of 7–8 lateral abdominal plates (vs. 4–5).

Description. Morphometric and meristic data are summarized in Table 1. Small-sized loricariid; maximum standard length reaching 23.9 mm. Dorsal profile of body slightly convex from snout tip to interorbital region; slightly convex from this point to dorsal-fin origin and then slightly concave to origin of anteriormost caudal procurrent ray. Ventral surface of body convex from tip of snout to first anal-fin ray; slightly concave from this point to first anteriormost caudal procurrent ray. Greatest body depth at dorsal-fin origin. Greatest body width at opercular region; progressively narrowing towards snout and caudal fin. Trunk and caudal peduncle almost ellipsoid in cross section; rounded laterally and almost flat dorsally and ventrally.

Head elliptical in dorsal view; snout long, slightly pointed with rounded tip and flat between orbits. Dorsal and ventral series of odontodes completely covering anterior margin of snout; odontodes of snout larger in size than remaining ones found on head. Odontodes on head and trunk well defined, arranged in longitudinal rows, not always necessarily forming parallel series. Eye relatively small and rounded, situated dorsolaterally at midpoint of head. Iris operculum poorly developed. No ridge between eyes and nares. Nasal aperture small. Supraoccipital process not elevated and without tuft of odontodes in specimens of all sizes. Mouth wide; oral disk roundish with papillae randomly distributed. Lower lip larger than upper lip, not reaching cleithrum region; its border strongly fringed. Maxillary barbel short, slender and free distally. Teeth slender and bicuspid. Cusps symmetrical; central cusp larger than lateral cusps. Premaxillary teeth 11–17 (mode 15). Dentary teeth 10–15 (mode 13).

Dorsal fin rays ii,7. Dorsal-fin origin slightly posterior through pelvic-fin origin; distal margin of dorsal fin slightly convex. Tip of adpressed dorsal-fin rays surpassing terminus of anal-fin base. Dorsal fin spinelet short and V -shaped, Fig. 5 a; lock mechanism functional. Pectoral-fin rays i,6; its tip reaching beyond pelvic-fin insertion when adpressed. Presence of pectoral axillary slit between pectoral-fin insertion and posterior process of cleithrum. Pelvic-fin rays i,5; distal margin slightly convex; tip of adpressed pelvic fin reaching anal-fin origin in males, but not in females. Adipose fin absent. Anal-fin rays i,4; distal margin slightly convex. Caudal fin rays i, 7–i,7; slightly emarginated; unbranched rays of same size. Rays of all fins covered with pointed odontodes. Total vertebrae 27–28 (2 c&s).

TABLE]. Morphometric anđ meristic đata for new species of Curculionichthys. SD = stanđarđ đeviation.

C.karipuna , n = 36 C. karipuna , n = 25 (Cassiporé) C. karipuna , n = ]] (Jari) Body completely covered by bony plates, except on ventral part of head, around pectoral- and pelvic-fin origins and dorsal-fin base. Abdomen entirely covered by plates. Lateral abdominal plates larger and forming regular series of six to seven elongate plates on each sides; median abdominal plate smaller, irregularly arranged and formed by one series of plates; series of anal plates formed by three to four large plates ( Fig. 5 b). Lateral surface of body entirely covered by plates; mid-dorsal plate series poorly developed, almost reaching terminus of dorsal-fin base; median plate series uninterrupted in median portion of body and perforated by lateral line; midventral plates almost reaching middle of caudal peduncle. Cleithrum and coracoid completely exposed. Arrector fossae partially enclosed by ventral lamina of coracoids.

Bony plates of dorsal head presented in Fig. 3 . Snout tip formed by one or two rostral square-shaped plates (r); nasal (n) almost rectangular forming anterior medial nostril margin in contact posteriorly with frontals (f) and anteriorly and laterally with prenasals (pn) and second infra-orbital (io2). Prenasals (pn) positioned posteriorly of rostral plates (r) formed by two large and three small triangular-shaped plates between nares. Top of head composed by compound pterotic (cpt), parieto-supraoccipital (soc) and frontal (f), largest bones of head, and prefrontal (pf) and sphenotic (sp). Compound pterotic (cpt) fenestrate randomly distributed. Posterior rostrum plates pr1-pr2 small, rectangular shaped; pr3-pr4 largest, rectangular shaped. Infraorbital plate series complete (io1-io5), present just above posterior rostrum series, all covered by the laterosensory canal system; io2 largest and io5 smallest; io3, io4 and io5 forming inferior orbital margin of eyes; preopercle (pop) elongated and rectangular, covered by laterosensory canal; preopercle situated ventral to io4 and io5, and upper cp1, cp2. Supraopercular plate (spop) situated just above preopercle, covered by laterosensory canal. Subocular cheek plates (cp1–cp2) and opercle (op) form posterior lateral margin of head.

Color in alcohol. Ground color of dorsal region of head and trunk brown. Four dark saddles along dorsal portion of body: first at dorsal-fin origin, second at end of dorsal-fin base, third at middle of caudal peduncle, and fourth reaching anteriormost caudal procurrent ray. Unpigmented portion of snout appears as two hyaline parallel stripes from rostral plate to nares. Midlateral dark stripe extending from posterior margin of orbit to caudal peduncle. Ventral portion of the body entirely whitish, except the concentration of dark chromatophores at the analfin origin and adjacent region. Dorsal, pectoral, and pelvic fins with dark, irregularly distributed chromatophores. Caudal fin hyaline with dark stripe extending from caudal-peduncle base onto base of median caudal fin rays; dark chromatophores forming one irregularly diffuse band.

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

Distribution and habitat. Curculionichthys karipuna is known from two localities: a small stream of the rio Cassiporé, an Atlantic coastal river of northern Amapá (type locality) and a small stream reaching the rio Jari (non types) ( Fig. 6 ). These localities are composed of shallow, fast-flowing streams bordered with marginal vegetation ( Fig. 7 ). Portions of the stream of rio Cassiporé ( Fig. 7 a) contain large rocks and the vegetation has suffered high anthropic influence causing intense penetration of light. The stream of the rio Jari ( Fig. 7 b) is composed of 1-meter deep water in which C. karipuna lives associated to aquatic roots stuck on the border.

Etymology. The specific name “ karipuna ” is a reference to the Karipuna indigenous people that inhabit the region of the rio Oiapoque, northern Amapá, Brazil. A noun in apposition.

Remarks. Le Bail et al. (2000: 262) catalogued a “noveau genre (aff. Parotocinclus )” in the Marowijne river basin. Although that specimen, based on their photography, strongly resembles Curculionichthys karipuna , examination of that material is still necessary to confirm the identification.

Discussion. Curculionichthys karipuna is included within the recently described genus Curculionichthys by possessing four of five diagnostic features (see Introduction). However, C. karipuna does not possess the welldeveloped membrane at the anal opening in females and has variable morphology related to the rostral plates in some specimens. Yet, one counterstained specimen has a single rostral plate at the snout tip ( Fig. 5 c). Curculionichthys insperatus , type species of the genus, similarly has intraspecific variability in the rostral plates (see details in Roxo et al., 2014b). Notwithstanding, the character is useful to diagnose Curculionichthys from other Otothyrini genera. In addition to the five proposed diagnostic characters for Curculionichthys ( Roxo et al., 2015), we found two additional features related to external morphology present in all species of Curculionichthys: (1) the presence of a dark blotch of pigmentation on the caudal peduncle that extends onto the median caudal-fin rays and (2) the absence of hypertrophied odontodes covering snout tip.

Despite the fact that the species of Otothyrini have wide variation in color pattern of the caudal fin, only species of Curculionichthys have a dark blotch of pigmentation on the caudal peduncle that extends to the median caudal-fin rays ( Fig. 3 ; see also Roxo et al., 2015: 113), which is useful to diagnose species of this genus along with the lack of hypertrophied odontodes covering the snout tip. Schaefer (1998) proposed that the presence of enlarged odontodes covering the snout tip can diagnose species of Hisonotus . Recently, Silva et al. (2016) found that this character is exclusive to species related to the type species, H. notatus (e.g., H. armatus , H. laevior , H. leucofrenatus , H. nigricauda ). Conversely, species not related to H. notatus , such as H. acuen and H. chromodontus ( Roxo et al., 2014a; Silva et al., 2016) do not have such hypertrophied odontodes. Similarly, species of Curculionichthys previously included in Hisonotus ( C. insperatus , C. luteofrenatus , C. oliveirai , C. paresi and C. piracanjuba ) and those recently described ( C. coxipone , C. sabaji , C. sagarana and also C. karipuna ) do not have hypertrophied odontodes, which confirms the variable nature of this character within Otothyrini.

Figures

FIGURE 1. Curculionichthys karipuna, MZUSP 120190, holotype, female, 23.7 mm SL, Brazil, Amapá State, municipality of Oiapoque, rio Cassiporé, stream at road BR- 156 at Campo Alegre farm.

FIGURE 5. Curculionichthys karipuna, LBP 19017, 29.0 mm SL. A) Spinelet shape; B) Ventral view of abdominal plates; Neurocranium in C) dorsal and D) dorsolateral views. Abbreviations are: cpt = compound pterotic; f = frontal; io 1 - 5 = infraorbitals; n = nasal; op = opercle; pr 1 - 5 postrostral plates; pf = prefrontal; pn = prenasal; pop = preopercle; r = rostral plate; sp = sphenotic; cp 1 - 2 = subocular cheek plate; soc = parieto-supraoccipital; spop = supraopercular plate. Scale bars: 0.5 mm (A); 1 mm (B, C, D).

FIGURE 6. Northern South America showing the distribution of Curculionichthys karipuna. Star = rio Cassiporé, type locality; circle = rio Jari, locality of non-type specimens.

FIGURE 7. Habitats of Curculionichthys karipuna. A) Type locality, stream at road BR- 156 at Campo Alegre farm, tributary of rio Cassiporé, Atlantic coastal river; B) locality of non-type specimens, unnamed tributary of rio Jari of the Amazon basin.

FIGURE 2. A) Curculionichthys karipuna, MZUSP 120190, 23.7 mm SL, holotype, showing the diagnostic character of irregular concentration of chromatophores covering the anal-fin origin and adjacent region along with the distal portions of the first unbranched anal-fin ray. B) Curculionichthys sagarana, MZUSP 117381, 23.7 mm SL, holotype, showing the absence of that pigmentation on the anal-fin origin.

FIGURE 3. A) Curculionichthys sabaji, MZUSP 117379, holotype, 23.3 mm SL, with dark-brown spots over the body; B) Curculionichthys paresi, MZUSP 115062, holotype, 26.2 mm SL, with contrasting dark spots at the anterodorsal region of body; C) Curculionichthys karipuna, MZUSP 120190, holotype, 23.7 mm SL, lacking the pigmentation patterns as described above. The arrows in the figure indicate the presence of a dark blotch of pigmentation covering the caudal peduncle that extends onto median caudal-fin rays.

FIGURE 4. A) Curculionichthys insperatus, LBP 20130, 25.2 mm SL, with well-developed papillae aligned in series that extends from the distal portion of lower lip to dentary; B) Curculionichthys karipuna, MZUSP 120190, holotype, 23.7 mm SL, with papillae randomly distributed throughout the lower lip.