Kryptolebias

Kryptolebias is a genus of small, freshwater fish belonging to the family Rivulidae. These fish are commonly known as South American killifish or annual killifish. They are native to South America, primarily found in the Amazon Basin, Uruguay, and southern Brazil. Kryptolebias species are characterized by their small size, often reaching only a few centimeters in length. They typically exhibit vibrant coloration, with males often displaying more elaborate patterns and hues than females.

The life cycle of many Kryptolebias species is particularly noteworthy. They are often referred to as "annual" killifish because their lifespan is closely tied to seasonal flood and drought cycles. Eggs are laid in the substrate, and during dry periods, the eggs can enter a state of dormancy called diapause. When the rains return and flood the habitat, the eggs hatch, and the fish complete their life cycle before the next dry season. This remarkable adaptation allows them to survive in environments that experience extreme fluctuations.

Kryptolebias species inhabit a variety of freshwater habitats, including ephemeral ponds, swamps, and slow-moving streams. They are generally omnivorous, feeding on small invertebrates, algae, and detritus. Due to their small size and attractive appearance, some Kryptolebias species are popular in the aquarium hobby. However, their specific needs regarding water parameters and life cycle require dedicated care from aquarists. Conservation status varies among species, with some facing threats from habitat degradation and pollution.