Rineloricaria buckupi, Mejia & Ferraro & Souto-Santos, 2025

Mejia, Eduardo, Ferraro, Gustavo A. & Souto-Santos, Igor C. A., 2025, A new species of whiptail catfish Rineloricaria (Siluriformes: Loricariidae) from Macaé and São João river basins, southeastern Brazil, Neotropical Ichthyology (e 240087) 23 (2) : -

Rineloricaria buckupi , new species urn:lsid:zoobank.org:act:

( Figs. 1–3; Tab. 1)

Holotype. MNRJ 51116, 111.2 mm SL, Brazil, Rio de Janeiro, Macaé, Macaé River , bridge on RJ-168 highway, 22°19’39”S 41°58’55”W, 11 Nov 2017, P. A. Buckup, V. de Brito, E. Malanski & R. M. Dias.

Paratypes. All from Brazil, Rio de Janeiro State: Macaé River basin: MCP 55326, 1 alc, 105.0 mm SL, 1 tis, Macaé, Ouro River, Forested section on Bicuda road, 22°17’15”S 42°00’36”W, 25 Nov 2011, P. A. Buckup, C. Quijada & J. C. Pascoli. MCP 55327, 1 alc, 104.8 mm SL, 1 tis, Rio Bonito, Rio Bacaxá River, near the bridge on BR-101 highway, 22°41’36”S 42°33’13”W, 14 Aug 2023, P. A. Buckup, I. C. A. Souto-Santos & J. E. Mejia de Loayza. MNRJ 51002, 4 alc, 46.3–107.5 mm SL ( 1, 107.5 mm SL), 2 tis, Conceição de Macabu, Aduelas Creek (Macaé drainage), under the bridge, near a sign written “Projeto Caminhos de Darwin”, 22°11’57”S 41°50’24”W, 17 Aug 2017, P. A. Buckup, D. F. Moraes Jr. & E. Malanski. MNRJ 55875, 1 alc, 155.9 mm SL, Casimiro de Abreu, bridge over the Macaé River near RJ-142 highway, 22°25’49”S 42°11’59”W, 20 Sep 2004, M. F. G. Brito. MNRJ 55876, 3 alc, 146.2–172.6 mm SL, Casimiro de Abreu, bridge over the Macaé River near RJ-142 highway, 22°25’49”S 42°11’59”W, 9 Jan 2005, M. F. G. Brito. MNRJ 55878, 4 alc, 132.6–141.1 mm SL, Casimiro de Abreu, bridge over the Macaé River near RJ-142 highway, 22°25’49”S 42°11’59”W, 9 Jan 2005, M. F. G. Brito. São João River basin: MNRJ 37445, 2 alc, 17.5–34.7 mm SL, Casimiro de Abreu, Aldeia Velha River, at bridge of BR-101 highway, 22°29’54”S 42°16’02”W, 21 Jul 2010, M. R. Britto, L. Villa-Verde & R. Bartolette. MNRJ 37475, 3 alc, 27.1–122.7 mm SL ( 1, 122.7 mm SL), 3 tis, Silva Jardim, Aldeia Velha River, under bridge on Aldeia Velha road, surroundings the RPPN Fazenda Bom Retiro, 22°28’03”S 42°17’51”W, 17 Jul 2010, M. R. Britto & F. Pupo. MNRJ 42777, 1 alc, 72.4 mm SL,1 tis, Silva Jardim, Imbau River, 2 km upstream from BR-101 highway, 22°37’10”S 42°28’02”W, 26 Feb 2014, P. A. Buckup, G. Beltrao & G. A. Ferraro. MNRJ 43012, 1 alc, 48.6 mm SL, 1 tis, Casimiro de Abreu, Lontras River, along BR-101 highway, 22°28’45”S 42°09’03”W, 27 Feb 2014, P. A. Buckup, G. Beltrão & G. A. Ferraro. MNRJ 52425, 1 alc, 46.3 mm SL, 1 tis, Silva Jardim, Maratuã River (tributary left bank of São João River ) bridge on road between BR-101 highway and Bananeiras, 22°30’07”S 42°21’40”W, 2 Sep 2019, P. A. Buckup, I. C. A. Souto-Santos & G. A. Ferraro. MNRJ 54658, 6 alc, 55.3–101.8 mm SL ( 1, 101.8 mm SL), 2 tis, Rio Bonito, Bacaxá River, near bridge on BR-101 highway, 22°41’36”S 42°33’13”W, 14 Aug 2023, P. A. Buckup, I. C. A. Souto-Santos & J. E. Mejia de Loayza. MNRJ 54674, 10 alc, 37.2–99.3 mm SL (1, 99.3 mm SL), 3 tis, Casimiro de Abreu, Lontras River, on secondary road between Casimiro de Abreu and Professor Souza, 22°29’42”S 42°09’01”W, 14 Aug 2023, P. A. Buckup, I. C. A. Souto-Santos & J. E. Mejia de Loayza.

Diagnosis. Rineloricaria buckupi can be distinguished from most congeners except for R. aequalicuspis Reis & Cardoso, 2001 , R. altipinnis , R. anhaguapitan Ghazzi, 2008 , R. anitae Ghazzi, 2008 , R. baliola Rodriguez & Reis, 2008 , R. cacerensis (Miranda Ribeiro, 1912) , R. cachivera , R. caracasensis , R. capitonia Ghazzi, 2008 , R. daraha , R. eigenmanni , R. fallax (Steindachner, 1915) , R. formosa Isbrücker & Nijssen, 1979 , R. hasemani Isbrücker & Nijssen, 1979 , R. heteroptera , R. isaaci Rodriguez & Miquelarena, 2008 , R. jaraguensis (Steindachner, 1909) , R. jubata , R. konopickyi , R. latirostris (Boulenger, 1900) , R. maacki Ingenito, Ghazzi, Duboc & Abilhoa, 2008 , R. malabarbai Rodriguez & Reis, 2008 , R. maquinensis Reis & Cardoso, 2001 , R. melini , R. microlepidogaster (Regan, 1904) , R. morrowi Fowler, 1940 , R. nudipectoris , R. osvaldoi Fichberg & Chamon, 2008 , R. pentamaculata Langeani & de Araujo, 1994 , R. phoxocephala (Eigenmann & Eigenmann, 1889) , R. platyura (Müller & Troschel, 1849) , R. quilombola , R. reisi Ghazzi, 2008 , R. rodriquezae Costa-Silva, Oliveira & Silva, 2021 , R. rupestris (Schultz, 1944) , R. steindachneri , R. stewarti (Eigenmann, 1909) , R. teffeana , R. tropeira Ghazzi, 2008 , R. zaina Ghazzi, 2008 and R. zawadzkii by having five lateral series of plates below the dorsal fin ( vs. four lateral series of plates below the dorsal fin), and mid-dorsal series extending below and posterior to dorsal fin ( vs. mid-dorsal series not extending beyond the origin of dorsal fin). Rineloricaria buckupi differs from R. aequalicuspis , R. anhaguapitan , R. baliola , R. capitonia , R. latirostris , R. maacki , R. malabarbai , R. maquinensis , R. microlepidogaster , R. nudipectoris , R. reisi , and R. tropeira by the extensive ventral covering of the pectoral girdle by plates ( vs. absence of plates on most of the ventral surface of the pectoral girdle). It differs from R. cacerensis , R. fallax , R. formosa , R. hasemani , R. jubata , R. melini , R. morrowi , R. quilombola , R. teffeana , and R. zaina by the mid-dorsal series consisting of four or five keeled plates ( vs. mid-dorsal series consisting of six to twelve keeled plates extending beyond the origin of the dorsal-fin base). It differs from R. isaaci , R. jaraguensis , R. pentamaculata , R. rupestris , R. stewarti , and R. zawadzkii by the mid-ventral and lateral abdominal plates series in contact with each other ( vs. series of mid-ventral and lateral abdominal plates separated by an area of skin). It differs from R. altipinnis , R. caracasensis , R. eigenmanni , R. heteroptera , R. konopickyi , R. osvaldoi , R. phoxocephala , and R. platyura by breeding males lacking hypertrophied odontodes on the dorsum of the head and predorsal region ( vs. hypertrophied odontodes present on the dorsum of the head and predorsal region in breeding males). It differs from R. anitae and R. daraha by having three longitudinal series of plates in the median complex of abdominal plates ( vs. several irregularly organized abdominal plates on the median complex in R. daraha ; or five to six longitudinal series of abdominal plates on the median complex in R. anitae ). It is distinguished from R. cachivera and R. rodriquezae , by its narrow head width 63.8– 70.5% HL ( vs. 73.5–93.5% HL in R. cachivera and 71.6–81.2% HL in R. rodriquezae ). It is distinguished from R. steindachneri by wider cleithrum 15.9–18.1% SL and pelvic-fin margin reaching or surpassing anal-fin origin ( vs. narrow cleithral width 13.4–15.8% SLand pelvic-fin margin never reaching the anal-fin origin).

Description. Morphometric data of holotype and paratypes in Tab. 1. Body strongly depressed at caudal peduncle, tapering posteriorly from pectoral fin. In lateral view, dorsal profile slightly convex from tip of the snout to origin of dorsal fin and relatively concave at dorsal base; straight from base of dorsal fin to caudal peduncle. Head length larger than cleithral width. In dorsal view, head elongated with triangular anterior profile. Snout tip with small naked area, not reaching the anteriormost pore of infraorbital ramus of sensory canal. Eye elliptical, with large, deep postorbital notch; iris operculum present. Lower lip covered by irregularly sized papillae randomly distributed around mouth. Short maxillary barbel; teeth bicuspid; dentary teeth larger than those of premaxilla; 6(5), 7*(10) teeth on premaxilla and dentary teeth 6(2), 7*(13) on dentary.

Two predorsal plates between parieto-supraoccipital and nuchal plate with two low, inconspicuous ridges. Five (dorsal, mid-dorsal, median, mid-ventral, ventral) lateral plate series below dorsal fin. Dorsal series 20*(2), 21(5), 22(8) plates. Mid-dorsal series weakly keeled 4*(5), 5(10) plates. Median series 27*(3), 28(10), 29(2) plates. Lateral line complete. Mid-ventral plate series 15*(6), 16(6), 17(3) plates. Median and mid-ventral series with weak lateral ridge; these keels coalesce in last 11th(5), 12th*(8), 13th(2) plate of median series. Ventral series with 22*(5), 23(10). Lateral abdominal series with 7(11), 8*(4) plates between pectoral and pelvic-fin origin; number of plates on opposite sides of body sometimes different. Adjacent lateral and medial abdominal plates series in contact with each other. Abdomen entirely covered by plates, from opercular region to urogenital papilla. Posterior abdominal plate complex with large well-developed preanal plate anteriorly bordered by three polygonal plates, bordered by five plates. Middle abdominal plate complex, between lateral abdominal plates, with two or three longitudinal series posteriorly and four to six series anteriorly. Anterior complex of abdominal plates irregular and smaller anteriorly; anterior margin of complex with minute polygonal plates.

Dorsal-fin spinelet present. Unbranched dorsal-fin ray (dorsal spine) length shorter than head length ( Tab. 1). Dorsal-fin origin slightly posterior to pelvic-fin origin; dorsal-fin rays i,7*(15); tip of dorsal fin when adpressed surpassing anal-fin origin, reaching eighth plate posterior to fin origin. Pectoral-fin rays i,6*(15); distal pectoral-fin margin slightly convex, when adpressed, surpassing pelvic-fin origin. Pelvic-fin rays i,5*(15); pelvic-fin margin reaching anal-fin origin; distal pelvic-fin margin convex; third branched ray slightly longer than unbranched pelvic-fin ray. Anal-fin rays i,5*(15); posterior anal-fin margin rounded; second branched ray longest. Caudal fin emarginated with i,10,i*(15) rays. Upper unbranched ray slightly longer than lower one, extended as short filament.

Coloration in alcohol. Background color of dorsal surface of head and body light brown. Ventral surface pale yellow. Sensory system pores on head and lateral medial plates notably darker. Five dark brown transverse bars on dorsal surface; first at dorsal-fin origin, second at tip of reclined dorsal fin, following bars located on caudal peduncle; third and fourth bars sometimes fused, forming four bars in some specimens ( Fig. 2). Dorsal fin with dark brown terminal band not reaching border; terminal band with chromatophores concentrated on three unbranched rays on superior edge, becoming inconspicuous with dark dots aligned across inferior fin rays. Pectoral, pelvic, and anal fin covered with dark dots aligned across fin rays forming bands. Caudal fin with two vertical dark bands: broader solid one basally, one at distal margin, with variegated white spots. All fin membrane hyaline ( Figs. 2–3).

Sexual dimorphism. Mature males with abundant hypertrophied odontodes on the lateral margins of the head. Dorsal region of pectoral-fin rays covered almost entirely with thin, long odontodes with curved tips. Unbranched pectoral-fin ray thick, strongly curved, with short, densely arranged odontodes ( Fig. 4).

Geographical distribution. Rineloricaria buckupi is so far known from five tributaries of São João River (Aldeia Velha River, Bacaxá River, Capivari River, Lontra River,

and Maratuã River) and two tributaries of the lower Macaé River (Ouro River and Aduelas Creek). São João and Macaé are coastal rivers flowing directly to the Atlantic Ocean, State of Rio de Janeiro, southeastern Brazil ( Fig. 5). Specimens were collected from shallow streams ( ca. 1–2 m deep) with variable current speeds and associated with sandy or muddy bottom with marginal submerged vegetation. Rineloricaria buckupi was recorded in syntopy with R. zawadzkii in the São João and Macaé basins. However, the new species appears to be restricted to the middle and lower Macaé River basin, with its farthest record at 22°25’49.20”S 42°11’59.58”W ( 64 km from its delta in the Atlantic Ocean), and does not extend to the upper region, where R. nudipectoris and R. zawadzkii are frequently recorded.

Etymology. The specific name buckupi (noun, masculine, singular genitive), is a patronym for Paulo A. Buckup, in recognition of his valuable teachings as an advisor to numerous students, including the authors of this paper. Paulo has done outstanding work and made numerous contributions to Neotropical ichthyology, including advances in the systematics of Rineloricaria over the past 25 years.

Conservation status. Rineloricaria buckupi is endemic to the São João and Macaé river basins in Rio de Janeiro State. Populations of this species are distributed across seven rivers tributaries of two unconnected basins ( São João and Macaé , Fig. 5). Currently, no imminent threats to the species have been identified. Therefore, Rineloricaria buckupi is provisionally categorized as Least Concern (LC) according to the IUCN categories and criteria (IUCN Standards and Petitions Committee, 2024).

Molecular analysis. DNA barcodes based on the partial sequence of mt-co1 mitochondrial gene were generated for 16 specimens of Rineloricaria buckupi . Each river basin hosts a unique haplotype for the mt-co1 gene, with all specimens within the same basin sharing this specific haplotype; these haplotypes differ from each other by six mutations. The algorithm RESL (Refined Single Linkage) available in Barcode of Life Data Systems corroborated the separation of R. buckupi from the other geographically closest species included in this study. Rineloricaria buckupi received the Barcode Index Number BOLD:ADA2018.

The average genetic distance for the DNA barcode (mt-co1) between Rineloricaria buckupi and the closest described species R. zawadzkii was 4.0%. The new species also has a relatively high genetic distance from its other geographically closest congeners: R. nigricauda , R. nudipectoris , R. paraibensis , and R. steindachneri , with all values higher than 6.4% ( Tab. 2). On the other hand, pairwise intraspecific distances in the new species were 0.0% within specimens from the same population and 0.9% between specimens from different populations ( Tab. S2).