 |
| Monotocheirodon duda Carvalho, Thomaz, Urbano-Bonilla & Prada-Pedreros, 2024 DOI: 10.1111/jfb.15738 |
Abstract
A new species of characid with remarkable sexual characteristics is described from the upper Guayabero River drainage from the Orinoco basin in Colombia. The new species is included in the genus Monotocheirodon by sharing most of the previously proposed diagnostic features of this genus. It differs from all Stevardiinae by the combination, in adult males, of an enlarged urogenital papilla in contact with the first anal-fin unbranched ray and a highly modified anal fin with enlarged and distally elongated first and second branched anal-fin rays, forming a gonopodium-like structure. In addition, it differs from congeners by the presence of an adipose fin, an incomplete lateral line, an ascending process of the premaxilla dorsally oriented, and a long snout. The new species was discovered from a poorly sampled region in Colombia and is an unexpected new record given its disjunct geographic distribution from other species of the genus. Monotocheirodon species were previously known from piedmont drainages in Bolivia and Peru. The conservation status of the new species is herein categorized following IUCN criteria.
Keywords: endemism, insemination, Monotocheirodon, sexual characters, South America, species diversity
 |
| Lateral view of live specimens of Monotocheirodon duda showing live colouration. Above a male and below a female specimen. Specimens not cataloged. |
Monotocheirodon duda, new species
Diagnosis: The new species differs from all Stevardiinae species by the combined presence in adult males of an enlarged urogenital papilla (length about one-third to half of the first unbranched ray), which is in contact with the first anal-fin unbranched ray and a highly modified anal fin, with enlarged (anteroposteriorly) and distally elongated first and second branched anal-fin rays, forming a gonopodium-like structure (Figure 2). The new species differs from all other species of Monotocheirodon by the presence of an adipose fin (Figure 1, vs. absent); lateral line incomplete, pored scales not reaching the caudal fin (vs. lateral line complete); ascending process of the premaxilla dorsally directed (Figure 3, vs. strongly bent posteroventrally); and a longer snout that occupies about a fourth of the head length (HL), between 23.1% and 30.0% of HL (vs. short snout, <20% of the HL).
Etymology: Monotocheiron duda is named after the river where the new species was captured, mostly tributaries to the Duda River or captured in the Duda River itself (type locality). In Spanish, the epithet specific “duda” means doubt, which also refers to its presumed placement into the genus Monotocheirodon, an assumption that needs further evaluation.
Tiago P. Carvalho, Andréa Tonolli Thomaz, Alexander Urbano-Bonilla and Saúl Prada-Pedreros. 2024. A New characid Species with remarkable sexual dimorphism (Characiformes: Characidae: Stevardiinae) from the upper Guayabero River, Orinoco basin, Colombia. Journal of Fish Biology. DOI: 10.1111/jfb.15738
