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| Porotergus sambaibensis Mendonça, Peixoto, Chamon, Akama & de Santana, 2025 |
Abstract
A new species of ghost electric knifefish, Porotergus sambaibensis sp. nov., is described from the Javaés River, a tributary of the Araguaia River in Brazil. The new species was assigned to the genus Porotergus as the closest relative to Porotergus gimbeli through maximum likelihood reconstruction of a concatenated multilocus dataset. Additionally, the origin of adductor mandibulae, pars stegalis in P. sambaibensis sp. nov. provided further evidence to support the molecular hypothesis. External and internal anatomical characters diagnosed the new species. DNA barcode data were used to test species monophyly and its genetic divergence from other species in the clade. Porotergus sambaibensis sp. nov. is distinguished from its closely related species by the colour pattern of the trunk, dark brown; the lower count of total anal-fin rays, 146–160; the higher number of teeth rows on the dentary, two; the presence of premaxilla teeth; two prominent foramina on dorsal portion of hyomandibula and its distribution pattern; and the second basibranchial, unossified. The genetic divergence between the new species and its relatives ranged from 3.7% in P. gimbeli to 10.3% in Porotergus duende. The species was categorised as deficient data (DD) based on the International Union for Conservation of Nature (IUCN) criteria.
Keywords: DNA barcode, electric fish, ichthyofauna, Neotropics, taxonomy
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| Porotergus sambaibensis, holotype, MPEG 39639, 110.02 mm total length (TL). (a) Full body; (b) head. Scale bar = 5 mm. |
Porotergus sambaibensis, new species
Diagnosis: P. sambaibensis can be distinguished from P. duende by the colour pattern of the trunk, dark brown (vs. light brown to pale straw pigmentation). The new species can be distinguished from ‘A’. apurensis and P. gimbeli by the lower count of total anal-fin rays, 146–160 (vs. 171–198). P. sambaibensis can be further distinguished from ‘A’. bonapartii by the premaxilla dentition pattern, five teeth arranged in two irregular rows (vs. three tooth rows, each with 2–4 teeth); by the lateral ethmoid position, straight (Figure 4; vs. the lateral ethmoid obliquely positioned, extending ventrally from the frontal at an angle towards the dorsal surface of the parasphenoid; Hilton & Cox Fernandes, 2017: Figure 4; Peixoto & de Pinna, 2022: fig. 25); by the presence of two foramina on the dorsal portion of hyomandibula (Figure 6 vs. one; Hilton & Cox Fernandes, 2017: Figure 4). The new species can be distinguished from P. gimbeli by the unelaborated chin (vs. prominent swelling on the chin, e.g., de Santana & Crampton, 2010: Figure 4). It can be further differentiated from P. duende by the higher number of teeth rows on dentary, two (vs. one); by the presence of premaxilla teeth (vs. absent); and by the second basibranchial, unossified (vs. ossified). P. sambaibensis is differentiated from P. gymnotus by the number of premaxillary teeth, five (vs. two). The new species can be distinguished from ‘A’. ellisi by the anal-fin rays, 146–160 (vs. 170–190).
Etymology: The specific epithet is in reference to the type locality, Sambaíba, a rocky bank in the Javaés River.
Marina B. Mendonça, Luiz A. W. Peixoto, Carine C. Chamon, A. Akama and C. David de Santana. 2025. Molecular Phylogeny reveals A New Species of Ghost Electric Knifefish Porotergus Ellis 1912 (Gymnotiformes: Apteronotidae), from the Amazon basin. Journal of Fish Biology. DOI: doi.org/10.1111/jfb.70085 [14 July 2025]
