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| Xenurolebias tupinikin Gomes, Sarmento-Soares, Martins-Pinheiro & Leite, 2025 Xenurolebias izecksohni, X. cricarensis |
Abstract
The Atlantic Forest coastal tablelands is home to a wide diversity of small-sized freshwater fish sharing a biogeographically congruent distributional pattern. The annual killifish Xenurolebias are among these remarkable inhabitants in the riparian wetlands with four species in the area. Xenurolebias pataxo are located between the Jucuruçu and Mucuri rivers, geographically replaced by Xenurolebias myersi at the Riacho Doce and the Rio Itaúnas, and, further south, Xenurolebias cricarensis are in the floodplains of the Rio São Mateus and Xenurolebias izecksohni, living in temporary environments of the Rio Barra Seca, north of the Rio Doce. Due to their restricted habitat in the lowlands, these annual killifish could all be designated as a target species, providing benefits in the conservation of riparian wetlands. However, less is known about their habits and real distribution. Otherwise, the accelerated habitat loss is worrisome. Two of these species are threatened with extinction on Red Lists; one is Near-Threatened; and one is Data-Deficient. After ten years since the last species description, our investigations revealed a fifth species, the first recorded south of Rio Doce. The present contribution aims to characterize the occupied habitat by each species within the temporary environments and present an updated distributional data on these fish. Additionally, a new Xenurolebias is described, the first one recorded south of Rio Doce.
Keywords: Atlantic Forest; Rio Riacho; swamp; cloud fish; endemism
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Diagnostic features for Xenurolebias tupinikin. Dark blotch overlapping the median portion of the last stripe on the caudal peduncle (arrows). Xenurolebias tupinikin: MNRJ 56004, male, holotype, 23.4 mm SL; MNRJ 56005, female, paratype, 35.4 mm SL. Pool at flooded area on Sertão do Riacho stream, Aracruz, Espírito Santo, Brazil. |
Xenurolebias tupinikin sp. nov.
Diagnosis. Xenurolebias tupinikin is distinguished from remaining congeners by adult males presenting in life a dark blotch overlapping the median portion of the last stripe on the caudal peduncle (Figure 2). It further differs from congeners, except X. myersi, by presenting the dorsal and anal fin borders with a black outline. Additionally, it is distinct from X. myersi by a body depth of 25.9–27.9 in SL (vs. 29.0–31.4 in SL).
It differs from X. izecksohni and X. cricarensis by the caudal fin in males with 5–6 bars (vs. 7–14 bars) and by male head depth 64.5–76.9% of HL (vs. 81.2–85.6% of head length in males). It further differs from X. pataxo and X. myersi due to no yellow spots on the distal half of the dorsal fin in males (vs. yellow spots present).
Etymology. The specific name is a reference to the Tupiniquim Indigenous people, inhabitants of lowlands in the central north of Espírito Santo. On the left margin of the Rio Comboios is the Indigenous land Comboios (Figure 4, green stripes near coast), which corresponds to the nearest human occupation relative to the environments inhabited by these fish.
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| Xenurolebias izecksohni: (A) MBML 14205, male, 54.2 mm SL; (B) MBML 14208, female, 29.6 mm SL. Isolated pool in flooded area in Barra Seca, Linhares, Espírito Santo, Brazil. Images: Bruno Pinheiro. |
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| Couple of Xenurolebias cricarensis in field aquarium. Female in front, male behind. Image: Bruno Pinheiro. |
Bruno Pinheiro Gomes, Luisa Maria Sarmento-Soares, Ronaldo Fernando Martins-Pinheiro and Gustavo Rocha Leite. 2025. Habitat and Conservation Assessment of Annual Killifishes of the Genus Xenurolebias (Rivulidae: Cynolebiinae) from Coastal Floodplains, Including the First Record South of the Rio Doce, Southeastern Brazil. Diversity. 17(9), 644. DOI: doi.org/10.3390/d17090644 [12 September 2025]
(This article belongs to the Special Issue Evolution, Systematic and Conservation of Freshwater Fishes)
