Researchers have described a vividly coloured new killifish from small forest pools in the Brazilian Amazon, adding another species to the region's remarkable freshwater biodiversity.
Waldir Miron Berbel-Filho with Laimosemion laranja.
At less than 3cm long, it would be easy to overlook. Its colours, however, are considerably harder to miss.
Researchers working in the Brazilian state of Amapá have described a new species of killifish whose males carry striking orange-red markings across their bodies and fins. The fish has been named Laimosemion laranja—with laranja meaning both the colour orange and the fruit in Portuguese. The name also honours Laranjal do Jari, the municipality where the species was found.
The description, published in Zoosystematics and Evolution, is based on both physical characteristics and genetic evidence. DNA analysis found a genetic divergence of 5.3% from its closest relatives included in the study, while differences in scales, fins and skeletal features further distinguished it as a separate species. Eschmeyer's Catalog of Fishes now lists L. laranja as a valid species.
A very small world
So far, L. laranja is known from only three locations in the lower Cajari River drainage. The fish inhabits shallow freshwater pools and streams associated with forested areas, giving this colourful little species a remarkably restricted known range.
Some members of the killifish family Rivulidae have evolved an unusual response to seasonally disappearing habitats. Their embryos can suspend development in damp substrate, effectively waiting for water to return. The genus Laimosemion forms part of this fascinating evolutionary story, although the new study did not experimentally investigate this behaviour in L. laranja.
Its discovery comes with a less cheerful footnote. The three known sites show signs of disturbance from deforestation, mining, urban development, and plastic pollution. With an estimated extent of occurrence of only 25 sq km, the researchers propose that the species meets IUCN criteria for classification as Endangered. It has not, however, yet received a formal IUCN Red List assessment.
