Published November 10, 2025
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Integrative study of Characidium borellii (Characiformes: Crenuchidae): phylogenetic relationships and geographic distribution
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Méttola, V. Ezequiel, Terán, Guillermo E., Aguilera, Gastón, Montes, Martin M., Shimabukuro, Marina Ibáñez, Alonso, Felipe, Mirande, J. Marcos (2025): Integrative study of Characidium borellii (Characiformes: Crenuchidae): phylogenetic relationships and geographic distribution. Neotropical Ichthyology (e250022) 23 (3): 3773-3803, DOI: 10.1590/1982-0224-2025-0022, URL: https://doi.org/10.1590/1982-0224-2025-0022
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- LSID
- urn:lsid:zoobank.org:pub:278C44A5-CD91-4330-8965-4F985F054501
- LSID
- urn:lsid:plazi.org:pub:CA48FFCEAF06FFB7FFE9FFEEFFEDFFAA
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- http://publication.plazi.org/id/CA48FFCEAF06FFB7FFE9FFEEFFEDFFAA
References
- Historically, limited information has been available regarding the morphology, phylogenetic relationships and distribution of C. borellii, with only a brief redescription by Gery et al. (2001). Several characters described by these authors differ from the findings of this study, including iii,9,i or iii,10,i pectoral-fin rays (vs. iii,9 rays), tricuspid teeth in the dentary and premaxillary (vs. conical teeth), and confirmation of a single row of teeth in the dentary. Additional features with phylogenetic potential, such as hooks on the pelvic and pectoral fins of males (Mirande, 2010; Teixeira, Melo, 2021); swimbladder morphology (Agudelo-Zamora et al., 2020) and pseudotympanum anatomy (Zanata, Camelier, 2014), are also provided.
- Secondary sexual characteristics including bony process on the pelvic, also observed by Mirande (2010), and pectoral fins, and longer pelvic fin in males, are recorded in C. borellii. These dimorphic characters are also found in several other species of Characidium (Teixeira, Melo, 2021): bony processes on paired fins in C. bahiense, C. barbosai, C. bimaculatum, C. clistenesi, C. deludens (only on pelvic-fin rays), C. lagosantense, C. laterale, C. litorale, C. mirim, C. nupelia, C. satoi, C. stigmosum, C. xanthopterum, C. xavante; and longer pelvic fins in males of C. deludens, C. kamakan Zanata & Camelier, 2015, C. rachovii, C. orientale, and C. vestigipinne. The combination of having both characters appears to be unique in C. borellii.
- The genus Characidium is diagnosed by the presence of a black basicaudal spot (Buckup, 1993b), a character also present in C. borellii, despite some reversions within the genus. Buckup (1993b) recovered three major clades within Characidium: C1, C4, and C5. Clade C1 (C2+C3) comprises species (e.g., C. fasciatum and C. gomesi) characterized by an unscaled isthmus, reduced or absent poscleithrum 1, and reduction or absence of the cranial fontanel. Clade C4 includes species (e.g., C. rachovii, C. occidentale, and C. laterale) defined by three synapomorphies (Netto-Ferreira et al., 2013; Mendonca, Netto-Ferreira, 2015): absence of the parietal branch of the supraorbital canal, more than 12 transversal bars, and absence of inner row of dentary teeth. Clade C5 includes species with thin transversal bars. Characidium borellii only shares the absence of inner teeth with species in C4 and does not clearly conform to any of these morphological clades.
- Most recent phylogenetic analyses using mitochondrial markers (COI) recognize different lineages or clades (Oliveira-Silva et al., 2024; Serra et al., 2025) but with distinct relationships among them. According to these clades, we recovered C. borellii in the "Nanognathus" clade (= "C. bimaculatum" clade from Serra et al., 2025 or CI clade from Oliveira-Silva et al., 2024), grouped with C. bahiense, C. bimaculatum, C. cf. zebra (from Parana and Sao Francisco basins), C. deludens, C. lagosantense, C. samurai, and C. varii. Genetic distances are consistent with the close phylogenetic relationships among these species. Combining the morphology data, C. borellii appears most closely related to C. bimaculatum and C. deludens, sharing several features: the presence of hooks on the pelvic fins, a muscular hiatus of the pseudotympanum formed by a single aperture, absence of an inner row of dentary teeth (in C. deludens), and the presence of parietal branch of supraorbital canal (in C. deludens). A combined phylogenetic analysis integrating both morphological and molecular data with a broader range of species is needed to confirm these relationships.
- Specimens previously identified as Characidium cf. zebra or C. fasciatum from Sali, Bermejo and Juramento-Salado basins (Liotta, 2005; Mirande, Aguilera, 2009; Cancino, Aguilera, 2016; Teran et al., 2016; Alonso et al., 2025) were misidentified and correspond to C. borellii. The molecular and morphological data showed no significant differences among these populations, with high morphological variation attributed to sexual dimorphism or allometry. Therefore, Characidium borellii represents a valid species within the genus Characidium, with a distribution restricted to Northwestern Argentina.