Leporinus oliveirai, Ito & Souza-Shibatta & Venturieri & Birindelli, 2023

Ito, Ian Solon Bortoloci, Souza-Shibatta, Lenice, Venturieri, Marcos & Birindelli, José L. O., 2023, A new species of Leporinus (Characiformes: Anostomidae) from the Serra do Cachimbo, Pará State, Brazil, Neotropical Ichthyology (e 230058) 21 (3), pp. 1-21 : 5-16

Leporinus oliveirai , new species urn:lsid:zoobank.org:act:3F715C2E-C60E-4CCC-A8DE-AFFE54531419

( Figs. 1–7 ; Tab. 2)

Holotype. MNRJ 34085 , 94.4 mm SL, Brazil, Pará, Novo Progresso, rio Braço Norte, a tributary of rio Peixoto de Azevedo , Teles Pires drainage, Amazon basin, below the CPBV-FAB power plant, 09°21’47.48”S 54°54’11.47”W, 1 Oct 2008, P. A. Buckup, J. L. O. Birindelli, F. C. Jerep, C. Chamon & J. A. Maldonado-Ocampo (AquaRios expedition).

Paratypes. All from Brazil, Pará, Novo Progresso . MNRJ 34085 , 2 alc, 96.3–107.6 mm SL, collected with holotype . MZUEL 23321 , 1 alc, 109.3 mm SL, collected with holotype . MZUSP 87068 , 1 alc, 92.2 mm SL, rio Braço Norte , near FAB-NDB, 09°21’46.32”S 54°54’11.18”W, 17 May 1955, L. P. Travassos . MZUSP 96833 , 1 alc, 23.5 mm SL, rio Braço Norte , BR-163 bridge, near FAB, 09°26’8.51”S 54°53’13.83”W, 18 Oct 2007, J. L. O. Birindelli, M. H. Sabaj, L. M. Sousa, A. L. Netto-Ferreira & N. K. Lujan (Pipe Expedition) . MZUSP 96836 , 14 , 38.9–53.5 mm SL, rio Braço Norte , BR-163 bridge, near FAB, 09°28’32.94”S 54°52’34.94”W, 18 Oct 2007, Pipe expedition . MZUSP 119371 , 18 alc, 2 c&s, 97.3–137.1 mm SL, rio Braço Norte , below the CPBV-FAB power plant, 09°21’46.13”S 54°54’11.07”W, 3 Aug 2015, W. M. Ohara & M. N. L. Pastana .

Non-types. MZUEL 20844, 2 alc (17.4–32.7 mm SL), specimens bred in captivity for ornamental purposes.

Diagnosis. Leporinus oliveirai can be distinguished from other anostomids, except Hypomasticus megalepis (Günther, 1863) , Leporinus amae Godoy, 1980 , L. bahiensis Steindachner, 1875 , L. bistriatus Britski, 1997 , L. guttatus Birindelli & Britski, 2009 , L. marcgravii Lütken, 1875 , L. melanopleura Günther, 1864 , L. microphthalmus Garavello, 1989 , Leporinus moralesi Fowler, 1942 , L. octofasciatus Steindachner, 1915 , L. octomaculatus , L. paranensis Garavello & Britski, 1987 , L. reticulatus Britski & Garavello, 1993 , L. sexstriatus Britski & Garavello, 1980 , L. striatus Kner, 1858 , L. taeniatus Lütken, 1875 , L. taeniofasciatus Britski, 1997 , L. tigrinus Borodin, 1929 , and Megaleporinus garmani (Borodin, 1929) , by having three unicuspid teeth on the premaxilla and four on the dentary (vs. four unicuspid teeth on the premaxilla and the dentary, or teeth multicuspid). Leporinus oliveirai is distinguished from H. megalepis , L. bahiensis , L. melanopleura , L. moralesi , L. octofasciatus , L. paranensis , L. striatus , L. taeniatus , L. taeniofasciatus and L. tigrinus by having 12 circumpeduncular scale series (vs. 16). Leporinus oliveirai differs from L. amae , L. bistriatus , L. sexstriatus , and M. garmani by having dark blotches on the trunk (vs. dark longitudinal stripes in L. amae , L. bistriatus , L. sexstriatus , and only one dark caudal blotch in M. garmani ). Leporinus oliveirai differs from L. reticulatus by large round dark blotches over the body (vs. dark blotches formed by the reticulation of oblique dark bars). Leporinus oliveirai is distinguished from L. guttatus , L. marcgravii , L. microphthalmus , and L. octomaculatus by its pattern of dark blotches on the body in adults including one large midlateral blotch below posterior dorsal-fin base that is isolated from neighboring midlateral blotches by a wide gap (vs. midlateral blotches more regularly sized and spaced) and one or two large blotches in region ventral to the lateral line between the pectoral and pelvic fins (vs. 2 to 3 small blotches in same region).

Description. Morphometric data of the holotype and paratypes are presented in Tab. 2. Lateral view of holotype and lateral view of live specimen in Fig. 1 . Small-sized species for genus Leporinus , largest examined specimen 137.1 mm SL. Body elongated and compressed. Dorsal profile gently convex from snout (posterior to upper lip) to dorsal-fin origin, straight to slightly convex in dorsal-fin base, generally straight from posterior insertion of dorsal fin to adipose-fin origin, and distinctly concave from adipose-fin origin to origin of upper lobe of caudal-fin. Ventral profile broadly convex from lower jaw to the posterior insertion of anal-fin rays and gently concave from this point to the origin of lower lobe of caudal fin. Greatest body depth at dorsal-fin origin. Head somewhat compressed; mouth subinferior, anterior opening of mouth positioned at longitudinal through lower border of orbit.

Dorsal fin ii,10*(40), origin slightly in front of vertical through pelvic-fin origin; base extending through six scales, distal margin rounded. Pectoral fin i,13(4), 14(19), 15*(9), or 16(8), base located posterior to gill opening, lobe extending through five to six scales from fin base, distal margin rounded. Pelvic fin i,8*(40), lobe extending through two or three scales, distal margin rounded. Anal fin ii,8*(40), anal-fin origin at vertical through the fifth scale anterior to adipose-fin origin, when adpressed, anal fin not reaching base of lower caudal-fin rays, distal margin straight or slightly rounded. Caudal-fin rays i,8,9,i*(40), caudal fin forked, upper lobe slightly more elongated than lower lobe.

Scales with few radii (6–8)*. Lateral line complete with 36*(20), 37(19) or 38(1) perforated scales; transversal series with 4*(40) scales from dorsal-fin origin to lateral line and 3.5(14) or 4*(26) scales from lateral line to pelvic-fin base, 3.5*(40) scales from lateral line to anal-fin base, 10(19) to 11*(21) predorsal scales, 12*(40) horizontal scale rows around caudal peduncle.

Osteology. Infraorbital series composed of six plate-like infraorbitals, nasal, antorbital, and supraorbital ( Fig. 2 ) Antorbital not bearing canal, sickle-shaped, longer than infraorbital 1. Nasal large, with ventral lamina much larger than dorsal one. Supraorbital relatively small, rhomboid, not bearing canal. First infraorbital with straight three-pored canal and posteroventral portion overlapped by infraorbital 2 with dorsal and ventral lamina well-developed, dorsal margins form a rounded 90 o angle. Third infraorbital largest, comprising most of ventral margin of orbit, with ventral lamina much larger than dorsal one. Fourth infraorbital with tripartite canal, posterior pore close to fifth infraorbital and extended to posterior margin. Sixth infraorbital relatively small and bearing a tripartite canal with two pores opened dorsally and one ventral directed toward fifth infraorbital.

Premaxilla bone trapezoidal, with dorsal process bent posteroventrally, and dorsoanterior margin with distinct protuberance ( Fig. 2 ). Three unicuspid incisiform teeth on premaxilla, teeth broad (not compressed), with concave scoop-like lingual fossa boarded by ridge along lateral and median margins, teeth decreasing gradually in size laterally. Maxillary bone arranged vertically and curved with distal tips posterior to median portion, dumbbell-shaped with median portion constricted and dorsal portion wider than ventral: and bearing four unicuspid teeth gently decreasing in size laterally Lower jaw trapezoidal, composed of dentary, anguloarticular, and retroarticular. Mesethmoid triangular, forming anteriormost border of anterior cranium fontanel and bearing a relatively large anteroventral process where contralateral premaxillae articulate ( Fig. 3 ). Lateral ethmoid longer than wide, with distinct lateral process directed posterolaterally. Frontal large, square-shaped, united to contralateral bone via epiphyseal bar crossing large anterior cranium fontanel. Parietals wide (width twice length), contralateral parietals separated by large posterior cranium fontanel. Sphenoitc somewhat triangular with distinct lateral process directed posterolaterally. Pterotic on posterolateral border of neurocranium, with distinct posterolateral process. Supraoccipital small triangular forming posterior border of posterior cranium fontanel. Epiotic forming a threearmed bridge on posterior border of neurocranium. Vomer pentagonal in ventral view, with prominent rounded dorsal projection and paired anterior projections articulated to autopalatine. Parasphenoid long and thin, forming ventral margin of neurocranium, with dorsolateral projection forming border of carotid foramen, and paired posteroventral projections extended ventrally to basioccipital and running close to carotid artery. Orbitosphenoid, pterosphenoid, and prootic dorsal to parasphenoid, ventral to frontal, and forming ventral wall of braincase. Exoccipital forming part of the posteroventral face of neurocranium. Basioccipital ventral to exoccipitals and forming ventral process of lagenar capsule. Baudelot´s ligament located on ventromedial surface of basioccipital. Weberian apparatus includes centra and associated elements of four anteriormost vertebrae. Neutral complex laminar and triangular. Claustrum small and rod-like; scaphium small and shell-shaped; intercalarium also small, articulated to tripus via strong ligament. Tripus roughly triangular at base with long hook-shaped posterior process passing ventral to os suspensorium; latter composed of lateral and medial processes.

Hyoid arch composed of dorsal and ventral hypohyals ( Fig. 4 ), anterior and posterior ceratohyals, urohyal, and four branchiostegals. Branchiostegals spatula-shaped, first three articulated to anterior ceratohyal, and last articulated to posterior ceratohyal. Basihyal elongate rod-like and connected to basibranchial 1 via cartilage. Basibranchials 1, 2, and 3 ossified and rod-like. Posterior copula elongate, cartilaginous. Three pairs of ossified, somewhat square basibranchials bordered posteriorly, laterally, and medially by cartilage. First four ceratobranchials elongate, rod-like, with minute rakers along both anterior and posterior margins. Fifth ceratobranchial with rakers restricted to anterior margin, and bony expansion on posterior margin bearing small conical teeth. Four epibranchials, third and fourth, with uncinate process. Four pharingobrachials, fourth associated with uncinate process of third epibranchial. Pharyngeal tooth plate bearing small conical teeth associated with fourth epibranchial.

Suspensorium L-shaped, with longitudinal axis longer than vertical one. Autopalatine elongate with prominent curved anterior tip. Ectopcterygoid vertically elongated, with convex anterior margin. Entopterygoid relatively small, associated with cartilage on dorsum of quadrate. Quadrate relatively large, with dorsal triangular bony projection and lateral bony projection on lateral plane relative to most suspensorium bones. Metapterygoid large, triangular. Metapterygoid-quadrate window relatively small, especially when compared to most anostomids (see, e.g., Sidlauskas et al., 2020: fig. 9; Sidlauskas, Vari, 2008: figs. 40–42). Symplectic on medial face of suspensorium, rod-like. Hyomandibular relatively large, with two dorsal condyles articulated to sphenotic and pterotic. Preopercle large, overlapped by hyomandibular and overlapping interopercular. Opercular large, somewhat triangular, rounded dorsally, and overlapping subopercle. Pectoral girdle connected to neurocranium via extrascapular and posttemporal, and pterotic ( Fig. 5 ). Supracleithrum large, vertically elongated. Cleithrum large with short triangular posterior process. Coracoid with short acute posterior process. Mesocoracoid columnar, forming strut on posterior face of girdle between scapula and cleithrum. Scapula columnar and located on ventromedial face of girdle. Three postcleithra present, ventralmost one including a long ventral process. Pelvic bone elongated, parallel to its counterpart, with fanned anterior portion and prominent ischiatic process, supporting one unbranched plus eight branched rays. Dorsal fin with 11 pterygiophores, first with enlarged anterior bony expansion and partially cartilaginous stay, supporting two unbranched and ten branched rays. Anal fin with nine pterygiophores united by sutured ventral bony expansions and partially cartilaginous stay, supporting three unbranched and eight or nine-branched rays. Caudal-fin skeleton composed of parahypural and two hypural plates on lower lobe (parahypural and second hypural fused to terminal compound centra), and four hypurals on upper lobe, with hypurals decreasing in size dorsally, third hypural contacting terminal compound centra, last hypurals separate. Uroneural one larger than two and associated with pleurostyle. Three separate epurals dorsal to modified neural process of pleurostyle. Neural and haemal spines adjacent to caudal-fin skeleton with anterior bony projections.

Coloration in alcohol. Overall, ground color tan ( Fig. 1 ). Head and body gently counter-shaded, becoming gradually darker above longitudinal line from mouth, through lower border of orbit to midline of opercle, and body above lateral line. Smaller specimens with eight transversal bars, of which the one below posterior insertion of dorsal fin and the subsequent one are slightly enlarged ( Fig. 6A ). In gradually larger specimens, the bars become interrupted midlaterally (bars 3 and 5, sometimes 7), or enlarged midlaterally, forming tall blotches corresponding to the second, fourth, sixth and eighth bars ( Fig. 6B ). In larger specimens (holotype, 94.4 mm SL), the second midlateral blotch becomes two, one dorsolateral and rounded, the second larger, vertically elongated from midlateral region to area posterior to pectoral-fin base; the third and fifth bars are broken into dorsolateral and ventrolateral blotches, respectively; the fourth bar becomes a large midlateral blotch; the sixth bar is dominated by a midlateral blotch; the seventh bar remains continuous (or nearly so); and the eighth bar is enlarged as a caudal blotch. Ventral surfaces of head and body pale to cream, without chromophores. Adipose fin with dark distal margin. The remaining fins nearly hyaline with few chromophores along margins of rays.

Sexual dimorphism. In one of the two c&s specimens, a mature male, the first and second ribs are hypertrophied and posteriorly concave in a “shovel-like” shape ( Fig. 7 ). Observations during induced breeding failed to verify any occurrence of sound production in breeding males.

Geographical distribution. Leporinus oliveirai is only known from the upper rio Braço Norte (also known as rio Cachimbo, see comments in Birindelli et al., 2009), at Serra do Cachimbo, in Pará State. Rio Braço Norte is a tributary of rio Teles Pires, a large tributary of upper rio Tapajós ( Fig. 8 ). The absence of L. oliveirai from inventories in the lower portion of rio Braço Norte indicates that the new species likely is restricted to the upper portion of the river. The series of waterfalls along the course of the river may be responsible for the geographic isolation of L. oliveirai in the upper portion of the river.

Ecological notes. Most specimens were caught in fast flowing clear and black water streams in high altitude tributaries (460 m asl) of rio Braço Norte on Serra do Cachimbo ( Fig. 9 ).

Etymology. Named in honor of Ivan Oliveira Nogueira da Silva, for his intensive work on introducing fishes bred and raised in captivity into the International Aquarium trade. Ivan is a fishing engineer who has been working since 2005 on the creation and reproduction of ornamental fish, as part of the Psicultura Tanganyika team. He was primarily responsible for introducing the new species to the International Aquarium trade. A patronym.

Conservation status. Due to anthropogenic alterations along the rio Braço Norte basin in recent years, especially the construction of a series of dams for small hydroelectric power plants (see Discussion), it is probable that the species’ abundance and distribution have recently experienced a significant reduction. However, there is no data to support this hypothesis, and the species’ population size, distribution, and habitat preferences remain unknown. On the other hand, the species distribution encompasses the Nascentes da Serra do Cachimbo Biological Reserve and the Brazilian Air-Force military base (FAB), which are protected areas. Therefore, according to the International Union for Conservation of Nature (IUCN) categories and criteria (IUCN Standards and Petitions Committee, 2022) Leporinus oliveirai can be classified as Least Concern (LC). Given its restricted geographical distribution and recent impacts to rivers within its range, additional collection effort is needed to better understand the species’ population size and ecology for future conservation status assessment.

Comparative analyses. Morphometric analysis. The principal component analysis showed no overlap between specimens confidently identified as either L. octomaculatus and L. oliveirai ( Fig. 10 ). Specimens exhibiting coloration intermediate between the two species (i.e., putative hybrids) plotted between L. octomaculatus and L. oliveirai and overlapped with both. The morphometric variables that showed the most differences when comparing the two species were caudal peduncle length, preadipose distance, eye diameter, caudal peduncle depth, interorbital bone distance, and body depth at the origin of the dorsal fin.

Genetic distance. The genetic distance ( Tab. 3) between Leporinus oliveirai and the closest described congener L. octomaculatus was 3.9% for the DNA Barcode (COI gene). The distance is greater than the limit used for delimitation of many species, which is 2% (Pereira et al., 2013). Leporinus oliveirai also has a relatively high distance from its other congeners ( L. cylindriformis Borodin, 1929 , L. multimaculatus Birindelli, Teixeira & Britski, 2016, L. reticulatus , L. tristriatus Birindelli & Britski, 2013 , L. bistriatus , L. unitaenitatus Garavello & Santos, 2009, L. vanzoi Britski & Garavello, 2005 , and L. sidlauskasi Britski & Birindelli, 2019 ), with all values being higher than 7%. These values are relatively high for congeners, compared to species in other genera (Ramirez, Galetti, 2015; Burns et al., 2017; Ramirez et al., 2020). On the other hand, intraspecific distances were low in all species samples, ranging from 0 to 0.60%.

Species delimitation analyses. Methods for species delimitation based on COI gene sequences generated different results ( Fig. 11 ). The PTP analysis recovered 10 MOTUs (Molecular Operational Taxonomic Units) and ASAP found ten partitions, with the partition with the lowest asap-score (2.0) recovering 9 MOTUs. In both analyses, Leporinus oliveirai and L. octomaculatus were delimited as different species. A difference between the analyses was that, according to ASAP, L. vanzoi and L. sidlauskasi were considered in the same MOTU.

Figures

FIGURE 1 | Leporinus oliveirai, A. MNRJ 34085, holotype, 94.4 mm SL. B. MZUSP 96836, paratype, Brazil, Pará, rio Braço Norte, a tributary of the Peixoto de Azevedo (photo by Mark H. Sabaj).

FIGURE 2 | Infraorbital series, medial (left) and lateral (right) views of left jaws Leporinus oliveirai, MZUSP 119371, paratype, 103.6 mm SL.

FIGURE 3 | Neurocranium in dorsal, ventral and lateral view, respectively, from top to bottom left to right of Leporinus oliveirai, MZUSP 119371, paratype, 103.6 mm SL.

FIGURE 4 | Suspensory and opercular series in medial view (below) and lateral view (above); hyoid arch in ventral view, and branchial arches in dorsal view (except for the dorsal elements on the left side, in ventral view) of Leporinus oliveirai, MZUSP 119371, paratype, 103.6 mm SL.

FIGURE 5 | Left pectoral girdle in lateral view, pelvic girdle in dorsal view, and caudal skeleton, dorsal fin, and anal fin in lateral view of Leporinus oliveirai, MZUSP 119371, paratype, 103.6 mm SL.

FIGURE 6 | Leporinus oliveirai, MZUEL 20844. A. Larva, 17.4 mm SL, and B. Juvenile, 32.7 mm SL.

FIGURE 7 | Leporinus oliveirai in lateral view of the body skeleton, with the first modified rib highlighted, MZUSP 119371, paratype, 103.6 mm SL.

FIGURE 8 | Geographic distribution of Leporinus oliveirai. The black dot represents the type-locality, and the red bars indicate the dams.

FIGURE 9 | Salto do Cachimbo, at the Brazilian Air Force base, rio Braço Norte, a tributary of rio Teles Pires, upper rio Tapajós basin, Pará State.

FIGURE 10 | Projection of individual scores of the second and third principal components of the samples of Leporinus octomaculatus, L. oliveirai and the putative hybrid specimens. In dark blue, L. octomaculatus; in red, L. oliveirai; in purple, individuals collected that show an intermediate pigmentation between L. octomaculatus and L. oliveirai.

FIGURE 11 | Cladogram of phylogenetic relationships among Leporinus oliveirai and congeners based on DNA Barcode sequence and a Maximum-likelihood analysis.