The Ceylon Killifish (Aplocheilus dayi), known locally as උඩ හඳයා (Uda Handaya), is an endemic freshwater killifish belonging to the family Aplocheilidae. It features an elongated, surface-dwelling body with an upturned mouth and a flattened head, adapted for hunting near the water's surface. A hallmark feature is the bright, shiny occipital spot on top of its head, which helps it sense light and navigate shallow waters. The males display attractive coloration with greenish-gold iridescent scales and subtle vertical dark markings along the rear half of the body. Inhabiting slow-moving streams, shady forest waters, and marshy habitats across Sri Lanka's wet zone, this top-water predator feeds mainly on mosquito larvae, surface insects, and tiny aquatic invertebrates.