Pareiorhaphis pumila, Pereira & Reis, 2022

Pereira, Edson H. L. & Reis, Roberto E., 2022, A new dwarf armored catfish Pareiorhaphis (Loricariidae: Hypoptopomatinae) from the Uruguai River basin, Southern Brazil, Neotropical Ichthyology (e 220049) 20 (3), pp. 1-14 : 3-12

Pareiorhaphis pumila , new species urn:lsid:zoobank.org:act:34B30074-B394-4DE3-9FFB-32776CDD30FC

( Fig. 1 ; Tab. 1)

Holotype. MCP 54782 , 48.2 mm SL, male, Brazil, Rio Grande do Sul, rio Ijuí below dam of Passo de São José hydropower reservoir, Cerro Largo , 28°10’38”S 54°48’56”W, 3–9 Nov 2010, J. F. Pezzi da Silva.

Paratypes. All lots from rio Ijuí basin, Rio Grande do Sul State, Brazil. MCP

45899, 212 alc, 3 tis, 24.1–51.1 mm SL (30 measured, 35.8–47.4 mm SL), MZUSP

126817, 5 alc, 30.5–41.6 mm SL, NUP 23488 , 5 alc, 31.0– 42.1 mm SL, UFRGS 29100 , 5 alc, 32.7–40.7 mm SL, and ZUEC 17448 , 5 alc, 32.5–42.2 mm SL, collected with holotype. MCP 16762 , 1 alc, 40.7 mm SL, arroio Lageado do Moinho , tributary to rio Ijuizinho , 7 km SW of Entre-Ijuís, Entre-Ijuís , approx. 28°27’S 54°22’W, 14 Dec 1993, J. F. Pezzi da Silva , R. E. Reis & M. P. Barros. MCP 26903 , 3 alc, 37.5–41.6 mm SL, rio Palmeira , Panambi , approx. 28°17’S 53°30’W, 5 Jan 1999, W. Bruschi & A. Cunha. MCP 41699 , 20 alc, 20.2–43.7 mm SL, rio Potiribu downstream from Andorinhas Reservoir , tributary to rio Ijuí , Doutor Bozano , approx. 28°24’S 53°48’W, 6 Jun 2006, A. R. Cardoso & V. A. Bertaco. MCP 41705 , 11 alc, 24.8–44.0 mm SL, rio Potiribu downstream from Andorinhas Reservoir , tributary to rio Ijuí , Doutor Bozano , approx. 28°24’S 53°48’W, 14 Feb 2007, A. R. Cardoso & V. A. Bertaco. MCP 47202 , 2 alc, 41.8–44.6 mm SL, rio Ijuí ca. 800 m upstream from road RS-155 between Ijuí and Ajuricaba, Ijuí, 28°18’14”S 53°53’45”W, 9 Jul 2012, J. F. Pezzi da Silva & R. Angrizani. MCP 48497 , 4 alc, 19.2–24.1 mm SL, rio Ijuí near Passo São João hydroelectric plant, Roque Gonzales, 28°08’20”S 55°02’57”W, 7 May 2006, A. R. Cardoso & V. A. Bertaco. MCP 54662 , 2 alc, 42.9–45.7 mm SL, rio Ijuizinho dowstream Igrejinha Resevoir, Boa Vista do Cadeado , 28°47’45”S 53°58’17”W, J. F. Pezzi da Silva , L. Fries & R. Angrizani. MCP 49202 , 1 alc, 1 tis, 40.5 mm SL, rio Alegre , dowstream from Rio Alegre Reservoir , Condor, 28°12’10”S 53°26’39”W, 6 Oct 2015, J. F. Pezzi da Silva & R. Angrizani. MCP 53278 , 5 alc, 1 tis, 33.4–44.3 mm SL, rio Palmeira on secondary road from Panambi to Condor, Palmeira Reservoir, Palmeira, 28°14’37”S 53°33’12”W, 9 Jan 2018, E. H. L. Pereira, R. E. Reis & P. C. Fagundes .

Non-types. All lots from rio Ijuí basin, Rio Grande do Sul State, Brazil. MCP 31720 , 1 alc, 45.8 mm SL, rio Palmeira upstream from Rio Palmeira reservoir, Panambi , 28°14’35”S 53°33’12”W, 2 Nov 2002, J. F. Pezzi da Silva & J. Anza. MCP 41712 , 6 alc, 34.8–43.8 mm SL, rio Potiribu downstream from Andorinhas Reservoir , tributary to rio Ijuí , Doutor Bozano , approx. 28°24’S 53°48’W, 1 Aug 2007, A. R. Cardoso & V. A. Bertaco. MCP 44991 , 3 alc, 28.7–37.8 mm SL, rio Potiribu , tributary to rio Ijuí , Ijuí , 28°22’11”S 53°52’46”W, 8 Apr 2010, J. F. Pezzi da Silva. MCP 48643 , 2 alc, 34.2– 36.0 mm SL, rio Palmeira upstream from Rio Palmeira reservoir, Panambi , 28°14’35”S 53°33’12”W, 24 Mar 2015, J. F. Pezzi da Silva. MCP 49203 , 7 alc, 7 tis, 35.8–49.8 mm SL, rio Palmeira upstream Rio Palmeira Reservoir , Panambi , 28°14’35”S 53°33’12”W, 6 Oct 2015, J. F. Pezzi da Silva & R. Angrizani. MCP 50935 , 4 alc, 2 tis, 34.3–42.8 mm SL, rio Potiribu downstream waterfall near ELEGE factory, Ijuí , 28°22’10.4”S 53°52’43.1”W, 12 Oct 2016, T. Carvalho , R. Angrizani & J. Chuctaya. MCP 53267 , 2 alc, 17.4–35.2 mm SL, creek tributary to rio Palmeira ca. 50 m W of Condor , on road from Condor to Ajuricaba, Condor, 28°12’31S 53°30’07”W, 9 Jan 2018, E. H. L. Pereira, R. E. Reis & P. C. Fagundes .

Diagnosis. Pareiorhaphis pumila is promptly distinguished from most species of Pareiorhaphis by the reduced number of anal-fin branched rays two or three (rarely four) (vs. five anal fin-branched rays in most species of Pareiorhaphis , except in P. hypselurus ( Pereira & Reis, 2002) , P. nudula (Pereira & Reis, 1999) , and P. stomias ( Pereira & Reis, 2002) with four anal-fin branched rays). The new species is readily distinguished from P. hypselurus , P. nudula , and P. stomias by having a well-developed first dorsal-fin spinelet (vs. first dorsal-fin spinelet absent), and by having the pectoral-fin spine of adult males slightly curved and covered with minute odontodes (vs. pectoral fin-spine distinctly straight and covered with short and thick hypertrophied odontodes in adult males). It is also distinguished from most congeners (except P. bahiana (Gosline, 1947) , P. togoroi Oliveira & Oyakawa, 2019 , and P. vetula ) by having a deep notch between the hypurals 1–2 and hypurals 3–5 in the caudal-fin skeleton, reaching or almost reaching to the middle of the hypural plate ( Fig. 2 ; vs. notch shallow, not reaching close to middle hypural plate). Pareioraphis pumila is distinguished from P. bahianus , P. togoroi , and P. vetula by having cheek hyperthrophied odontodes of males shorter than one eye diameter (vs. cheek hyperthrophied odontodes of males equal to or longer than one eye diameter). Furthermore, the new species can be distinguished from all remaining congeners except P. splendens (Bizerril, 1995) , P. eurycephalus ( Pereira & Reis, 2002) , P. hypselurus , and P. stomias by having a wider cleithral width (37.1–41.1 vs. 24.2–36.4% SL). From those species but P. stomias , the new species can be distinguished by having fewer median lateral plates 21–24 vs. 24–29, and larger orbital diameter (14.9–17.7 vs. 10.0–14.8% HL). From P. stomias the new species is further distinguished by having fewer teeth in each dentary (42–57 vs. 94–120) and a shorter pelvic fin, whose posterior margin falls short of the anal-fin origin when adpressed (vs. posterior margin surpassing the origin or even reaching half-length of the anal-fin when adpressed in adult males).

Description. Counts and proportional measurements in Tab. 1. Overall view of body in Fig. 1 . Small-sized loricariid with standard length of measured specimens 35.8–48.2 mm SL. Body short, moderately depressed. Greatest body width at posterior portion of cheek, progressively tapering to end of caudal peduncle. Dorsal profile of body convex from snout tip to dorsal-fin origin, straight to slightly concave from that point to origin of adipose fin, and slightly concave from adipose-fin spine to caudal fin. Greatest body depth at posterior limit of parieto-supraoccipital bone or predorsal plates. Least body depth at shallowest portion of caudal peduncle. Trunk and caudal peduncle mostly oval in cross-section, flattened ventrally and more compressed caudally. Lateral-line canal in median series uninterrupted, with pored tubes visible from compound pterotic to one plate before caudal-fin base. Ventral profile of body almost straight from snout tip to pelvic girdle, slightly elevating posteriorly along anal-fin base, and almost straight along caudal peduncle. Dorsolateral surface of body covered by dermal plates except for small naked area overlaying opening of swim bladder capsule, posteroventrally to compound pterotic. Predorsal plates arranged in two or three irregular transverse rows. Five rows of lateral dermal plates covering body, not forming keels. Mid-dorsal and mid-ventral series of lateral plates incomplete, ending 4–5 plates before caudal fin base. Lower surface of head and abdomen entirely devoid of plates. Anterior portion of first anal-fin pterygiophore covered by skin, not exposed. Anus positioned between pelvic fins and anal-fin origin, closer to insertion of anal fin than pelvic-fin insertion. Arrector fossae of pectoral girdle completely opened, extending almost from midline symphysis of cleithra and coracoids laterally to arrector bridge.

Head broad and moderately depressed. Outline of head round in dorsal view; widened in adult males. Interorbital space flat to slightly concave. Three weakly elevated ridges between orbits and snout tip formed by underlying bones, without emerging hyperthrophied odontodes. Central ridge on snout more prominent. Snout gently convex in lateral profile; snout tip with small ovoid area of naked skin, devoid of odontodes. Rostral plate absent, anterior postrostral plates granular and irregular; two or three large postrostral plates anterior to preoperculum. Canal cheek plate articulated to preopercle dorsally with unbranched sensory canal. Adult males with very low soft fleshy lobe on cheeks. Soft fleshy area with minute, delicate hypertrophied odontodes, approximately perpendicular to body axis. Margins of head covered by minute odontodes in females and immature males. Preoperculum exposed; ornamented with delicate hypertrophied odontodes in adult males. Canal-bearing cheek plate with unbranched canal. Opercle and lateral process of cleithrum with few small or without hypertrophied odontodes. Eye small, dorsolaterally placed; orbital diameter 14.9–17.7% of HL. Iris operculum small or unnoticeable in some specimens, pupil circular. Nares ovoid, slightly longer than wide, positioned much closer to anterior margin of orbit than to snout tip.

Oral disk roughly circular and comparatively small. Lips occupying approximately two-thirds of ventral surface of head. Upper lip narrow, covered with small rounded papillae. Lower lip short, not reaching pectoral girdle. Ventral surface of lower lip densely covered with small rounded papillae, with smooth band devoid of papillae preceding lip margin. Posterior edge of lower lip very finely fringed. Maxillary barbel short, mostly adnate to lower lip, with vestigial small free portion present in some specimens. Tooth series in both premaxilla and dentary with mesial ends slightly curved inwards. Teeth slender, asymmetrically bifid. Medial cusp long and pointed, slightly curved inwards. Lateral cusp small and pointed, almost reaching, or reaching to middle of medial cusp in unworn teeth.

Dorsal-fin origin along vertical passing through origin of pelvic-fin ray. Dorsal fin short, falling short or contacting preadipose azygous plates when adpressed. Posterior margin straight or slightly convex. Nuchal plate and dorsal-fin spinelet exposed, not covered by skin. Dorsal-fin spinelet oval shaped, slightly wider than base of dorsal-fin spine. Dorsal-fin locking mechanism non-functional. Moderately flexible dorsal-fin spine, followed by seven branched rays. Adipose fin with large and well-ossified, straight spine, laterally compressed and covered with short hypertrophied odontodes. Adipose-fin spine connected to caudal peduncle via fleshy membrane; membrane well developed, extended beyond adipose-fin spine. One or two median unpaired preadipose azygous plates preceding adipose fin spine. Pectoral-fin origin situated slightly dorsal to pelvic-fin origin. Pectoral fin small, with spine slightly curved and dorsoventrally flattened, covered by minute odontodes in females, immature males, and juveniles. Adult male with pectoral-fin spine slightly broadened and bearing straight to slightly curved, small hypertrophied odontodes on entire outer face. Pectoral fin with six branched rays, first and second slightly longer than spine. Subsequent branched rays decrease gradually in size, last ray length two thirds of first ray. Distal margin of pectoral fin somewhat rounded. Tip of adpressed pectoral-fin reaching to mid-length of pelvic-fin unbranched ray. Pelvic fin with one unbranched and five branched rays, not reaching or just reaching to origin of anal fin when adpressed. Pelvic-fin unbranched ray depressed, covered by minute odontodes ventrally and laterally. Well-developed dermal flap on dorsal surface of unbranched pelvic-fin ray of adult males; flap distinctly higher near fin base and extending to ray tip; flap absent or poorly developed in females. Anal fin very small with one unbranched and one (4), two (25), three (182) or four (10) branched rays; three anal-fin pterygiophores. Anal-fin origin at vertical passing between end of dorsal-fin base and tip of last dorsal-fin ray. Caudal fin truncate to slightly concave; lower lobe slightly longer than upper; 14 branched rays. Upper and lower caudal-fin lobe with three plate-like procurrent rays, posteriormost elongate. Odontodes on principal and procurrent rays small and irregularly arranged. Total vertebral centra 26 (3); hypural plate asymmetrical with upper lobe slightly shorter than lower and with large open notch between hypurals 1–2 and hypurals 3–5 reaching to or almost to middle of hypural plate.

Dentary teeth

Plates in median lateral series left/ right

Plates at dorsal-fin base

44/47

22/22

5

31

31

31 42–57

21–24

5–7

48.2

22.2

6.1 3.87

0.78

0.54

Color in alcohol. Overall background color of dorsal and lateral surface of head and trunk light brown to grayish brown. Head usually darker than remaining of body. Predorsal area and area around dorsal fin sometimes lighter. Caudal peduncle yellowish brown with three to four irregular, very distinctive transverse dark brown bars; first at end of dorsal-fin base, second at preadipose plates, third and fourth variably below adipose fin and between adipose and caudal fins. Those bars sometimes broken and forming irregular blotches on much lighter background. Ventral surface of head and abdomen yellowish or whitish pale, mostly unpigmented; dark lateral bars of caudal peduncle appearing on lateral portions of ventral surface, sometimes meeting at ventral midline. Dorsal fin with 2–3 irregular dark brown bands on spine and branched rays. Pectoral fin with 3–4 and pelvic fin with 2–3 irregular dark brown bands on spine and branched rays; anal fin with 1–2 inconspicuous dark bands. Caudal fin with one wide band at base and 2–3 additional, slightly slanted dark bands. Posterior bands sometimes coalesced to form one wide band. Interradial membrane mostly hyaline in all fins.

Color in life. Same color pattern as in alcohol but contrast between caudal peduncle dark bars very conspicuous.

Sexual dimorphism. Males of Pareiorhaphis pumila share secondary sexually dimorphic attributes with other members of the genus. The low cheek fleshy lobe that is ornamented with minute, delicate hypertrophied odontodes are present in males, both of which are absent in females. Males also have a thickened pectoral-fin spine, slightly intumescent along its entire length with dorsal, lateral, and ventral surfaces ornamented with short hypertrophied odontodes, and a well-developed skin fold on the dorsal surface of the unbranched pelvic-fin ray that extends to the ray tip, which are absent in females. Finally, females possess an enlarged, swollen urogenital opening, while males have small and pointed urogenital papillae.

Geographical distribution. Rio Ijuí and its tributaries in northwestern Rio Grande do Sul State, Brazil ( Fig. 3 ). The rio Ijuí is itself a tributary to the middle portion of the rio Uruguai.

Ecological notes. Pareiorhaphis pumila occurs in small to medium headwater creeks with fast-flowing, well oxygenated water, and bottom formed by boulders, pebbles, and coarse gravel. It was also found in the middle course of larger tributaries and in the rio Ijuí itself, where it was collected in the main river bed during a low water condition caused by the filling of a hydroelectric reservoir ( Fig. 4 ). Pareiorhaphis hystrix is found in syntopy with the new species, along with several other loricariids across its distribution: Ancistrus taunayi Miranda Ribeiro, 1918 , Eurycheilichthys pantherinus (Reis & Schaefer, 1992) , Hemiancistrus fuliginosus Cardoso & Malabarba, 1999 , H. punctulatus Cardoso & Malabarba, 1999 , Hisonotus charrua Almirón, Azpelicueta, Casciotta & Litz, 2006 , Hypostomus roseopunctatus Reis, Weber & Malabarba, 1990 , H. spiniger (Hensel, 1870) , Loricariichthys melanocheilus Reis & Pereira, 2000 , Rineloricaria capitonia Ghazzi, 2008 , and R. stellata Ghazzi, 2008 .

Etymology. The species name Pareiorhaphis pumila is from the Latin pumilus, meaning dwarfish, little, in reference to the small size which is distinctive of this species. An adjective.

Conservation status. Pareiorhaphis pumila is distributed in the rio Ijuí basin, a tributary to the rio Uruguai, in Rio Grande do Sul State, Brazil ( Fig. 3 ). Its Extent of Occurrence (EOO) was estimated at approximately 14,529 km 2 by the Minimum Convex Polygon drawn around the micro-basins with species records, using Hydrosheds 8 level. A series of small dams exist or are planned for the rio Ijuí basin and the region is severely impacted by agriculture and deforestation of river banks, with subsequent river siltation. Pareiorhaphis pumila was tentatively assessed as Near Threatened (NT) by approaching the criteria B1b(iii), according to IUCN criteria (IUCN Standards and Petitions Subcommittee, 2022).

Figures

FIGURE 1 | Pareiorhaphis pumila, holotype, MCP 54782, 48.2 mm SL, male, rio Ijuí below dam of Passo de São José hydropower reservoir, Cerro Largo, Rio Grande do Sul, Brazil.

FIGURE 2 | Pareiorhaphis species from the upper rio Uruguai basin, hypural plate, lateral view, left side. A. P. pumila, MCP 45899, paratype. B. P. hystrix, MCP 14348, paratype. C. P. vestigipinnis, MCP 14345, paratype. D. P. eurycephalus, MCP 22341. no = caudal-fin notch; hap = hypurapophysis. Scale bars = 1 mm.

FIGURE 3 | Distribution of Pareiorhaphis pumila in south Brazil. Star = holotype; dots = other specimens. Each symbol may represent more than one lot or locality.

FIGURE 4 | Type-locality of Pareiorhaphis pumila, rio Ijuí below dam of Passo de São José hydropower reservoir, Cerro Largo, Rio Grande do Sul, Brazil.