Campellolebias intermedius

Campellolebias intermedius is a small annual killifish belonging to the family Rivulidae, native to temporary freshwater pools in the lowland wetlands of Uruguay. Like other annual killifish, it has evolved a remarkable life-history strategy adapted to ephemeral water bodies: eggs are laid in soft substrate and can enter diapause, surviving the dry season buried in mud until rains refill the pools and trigger hatching. Adults are short-lived, typically completing their entire life cycle within the brief window that seasonal pools hold water, and males often display the vivid coloration typical of the genus, used in courtship within these isolated aquatic habitats.

This species is classified as Critically Endangered (CR) by the IUCN, reflecting a severely restricted range and ongoing population decline. Its survival depends entirely on the persistence of specific temporary pool habitats, which are highly vulnerable to drainage, agricultural conversion, and alteration of local hydrology. Because Campellolebias intermedius occupies such a narrow and fragmented set of microhabitats, even localized disturbance can eliminate entire breeding populations.

Conservation attention for annual killifish in Uruguay has grown in recent years, with regional researchers and aquarist conservation networks working to document remaining populations and maintain ex situ breeding lines as a safeguard against extinction. These captive assurance populations, maintained by specialist hobbyist and scientific communities, represent a genuine point of hope, preserving genetic diversity that could support future reintroduction efforts if wild habitat can be protected or restored. Continued survey work in Uruguay's wetland basins remains essential to understanding the species' current distribution and guiding site-specific protection measures.

This killifish inhabits temporary seasonal pools and shallow wetlands in Brazil's Atlantic Forest region that fill during rainy seasons and dry completely during drought periods. The species has adapted to these ephemeral aquatic environments, completing its entire life cycle within the brief periods when water is present.