What new fish species, Nothobranchius sylvaticus, the first known killifish to live in a forest habitat, was discovered in Kenya's Gongoni Forest in December 2025?

The fish species Nothobranchius sylvaticus, recently described from Kenya's ancient Gongoni Forest, is a type of killifish. Killifish are a diverse group of small, egg-laying fish found in various freshwater and brackish habitats across the Americas, Africa, Asia, and southern Europe. Many killifish species are known for their ability to inhabit ephemeral environments, such as seasonal pools in savannas, where their eggs can survive dry periods in the substrate, hatching when the rains return.

What makes Nothobranchius sylvaticus particularly noteworthy is that it is the first known killifish species to be found persisting in a forest habitat. This discovery, stemming from fieldwork conducted in 2017 and 2018 and formally described in a study published in 2025, sheds light on the adaptability of killifish and provides valuable insights into the evolutionary history of both the fish and the ancient Gongoni Forest itself. The forest, a part of the East African Mosaic, is estimated to be over seven million years old, with the killifish lineage diverging from its closest relatives around that same time.

The iridescent blue scales and vibrant fins of Nothobranchius sylvaticus distinguish it from other species within its genus. However, despite its recent scientific description, this unique fish is already considered critically endangered due to its severely restricted habitat within the Gongoni Forest. Conservation efforts are crucial to protect this small yet significant species and its ancient forest home, which continues to reveal secrets about East Africa's geological and biological evolution.