Kressida

Kressida is a small, recently described genus of freshwater perciform fishes belonging to the family Cyprinidae. The genus was established in 2018 by ichthyologists Zhang and Rivera following a revision of the subfamily Rhabdiinae based on molecular phylogenetic data. Currently, two species are recognized within Kressida: Kressida pulchella and Kressida floresi, both endemic to tributaries of the upper Río Amazonas basin in southern Peru.

Morphologically, members of Kressida are characterized by a slender, fusiform body and a transparent to pale golden coloration. The dorsal fin has an extra soft ray compared to closely related taxa, and the caudal fin is truncate. The genus displays a distinctive pattern of black pigmentation along the lateral line, a feature that likely serves in intraspecific recognition. Kressida pulchella attains a maximum length of 10.2 centimetres, whereas Kressida floresi grows up to 9.8 centimetres.

Ecologically, Kressida species inhabit clear, fast-flowing streams with moderate current and a substrate of gravel or coarse sand. They feed primarily on aquatic insects and small crustaceans, foraging in the mid-water column during daylight hours. Spawning occurs in the rainy season, with a spawning site selection linked to substrate type and flow rate. Eggs are demersal and adhesive, hatching within 48 hours.

Conservation assessments by the IUCN (2024) have listed both species as Least Concern, although localized threats such as habitat modification from small-scale hydroelectric projects and deforestation could affect their populations. Ongoing monitoring and habitat protection measures are recommended to ensure long-term viability.