Hypsolebias janaubensis

Hypsolebias janaubensis is a small annual killifish belonging to the family Rivulidae, part of a remarkable group of fishes adapted to survive in ephemeral wetland pools across South America. This species is restricted to a very narrow range within the seasonally flooded savanna wetlands of northeastern Brazil, where it completes its entire life cycle within the brief window that temporary pools hold water. Like other annual killifish, it likely displays the characteristic biology of the group: eggs that enter diapause and remain dormant in the substrate through the dry season, hatching rapidly when seasonal rains refill the pools, followed by fast growth, breeding, and death before the habitat dries again.

Males of this genus typically show vivid coloration used in courtship displays, though detailed morphological descriptions for this particular species remain limited in the scientific literature. The species is classified as Critically Endangered (CR) by the IUCN, with a decreasing population trend. Its survival is jeopardized by the extreme restriction of its range to a small number of temporary pools, making it acutely vulnerable to any disruption of the local hydrology or landscape.

Conservation attention for Brazilian annual killifish has grown in recent years, with regional researchers documenting new populations and advocating for protection of remaining wetland habitats in the Cerrado and adjacent biomes, offering a genuine, if fragile, opportunity to secure the species' future through targeted habitat safeguards and continued field surveys. Public and scientific interest in annual killifish conservation has also encouraged ex situ breeding programs among specialist aquarists, which serve as an important safety net for critically endangered species like this one should wild populations continue to decline.

This critically endangered killifish inhabits temporary pools, seasonal wetlands, and shallow water bodies in the Brazilian Cerrado savanna. The species depends on ephemeral aquatic habitats that fill during rainy seasons and may dry completely during drought periods.