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| Pareiorhaphis pumila Pereira & Reis, 2022 |
Abstract
A new, very distinctive species of Pareiorhaphis is described from the rio Uruguai basin, in Rio Grande do Sul State, southern Brazil. Pareiorhaphis pumila, new species, is a small bodied hypoptopomatine catfish with a maximum standard length barely reaching 50 mm. The specimens were captured from rock-bottomed habitats in various localities in the rio Ijuí basin. Despite occurring in rock-bottomed fast-flowing headwater stream tributaries as the other species of Pareiorhaphis, this is the first species collected also in the main channel of the middle stretch of a large tributary to the rio Uruguai. The new species is promptly diagnosed from all its congeners by the reduced number of anal-fin branched rays, possession of well-developed dorsal-fin spinelet, comparatively lower number of plates in median lateral series, and low number of teeth in each dentary. In addition, osteological features related to the caudal skeleton are also useful to distinguish the new species from most congeners.
Keywords: Biodiversity, Cascudo, Neotropical, New species, Taxonomy.
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| 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. |
Pareiorhaphis pumila, new species
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).
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.
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.
Edson H. L. Pereira and Roberto E. Reis. 2022. A New Dwarf Armored Catfish Pareiorhaphis (Loricariidae: Hypoptopomatinae) from the Uruguai River basin, Southern Brazil. Neotrop Ichthyol. 20(3); e220049. DOI: 10.1590/1982-0224-2022-0049 www.NI.bio.br/1982-0224-2022-0049
