piscicola

Piscicola is a genus of leeches in the family Piscicolidae, comprising species that parasitize fish. Members of this genus are obligate ectoparasites that feed on the blood of their hosts, typically attaching to the body, fins, or gills.

Physiology and appearance are generally those of small, flattened leeches. Individual specimens are commonly a few millimeters to several centimeters long, with coloration ranging from pale to dark brown. They use anterior and posterior suckers to cling to hosts and to move between meals, often remaining attached for a period of feeding that can last from minutes to several hours.

Ecology and life cycle involve aquatic environments where fish hosts are available. Piscicola species are typically found in freshwater and, in some cases, brackish waters. Most are hermaphroditic, with eggs laid in cocoons deposited in vegetation or debris. Juveniles hatch and begin seeking fish hosts. The life cycle is closely tied to the presence of suitable fish hosts, and parasites may be found on a wide range of freshwater fish species.

Host interactions and impact include wound formation at attachment sites, potential bleeding, stress, and, in heavy infestations, anemia or reduced growth. While generally a natural part of freshwater ecosystems, Piscicola species can be a concern in aquaculture and ornamental fish systems due to their feeding activity and potential to transmit pathogens.

Distribution is worldwide in suitable aquatic habitats, with many species occurring in temperate regions and in various freshwater systems. The best-known member of the genus is Piscicola geometra, frequently cited in studies of fish leeches. The name derives from Latin piscis (fish) and cola (dweller).