Caligidae

Caligidae is a family of parasitic copepods in the order Siphonostomatoida, commonly known as sea lice. They are external parasites of marine fishes and comprise several genera, most notably Caligus and Lepeophtheirus, with numerous described species worldwide.

Members of Caligidae are small crustaceans with a compact cephalothorax and a tapered abdomen. They attach to the host’s skin, fins, or gills using specialized appendages and secretions. Their feeding typically includes epidermal tissue, mucus, and sometimes blood, causing lesions, irritation, and stress to the host.

The life cycle of caligids is multi-stage. It begins with two free-swimming naupliar stages, followed by a copepodid stage that is the infective form. After attaching to a host, they pass through chalimus stages during which the parasite remains tethered by a frontal filament, then progress to preadult and adult stages. Reproduction occurs on the host, with females bearing eggs in sacs or strings that hatch into new free-swimming larvae.

Ecology and economic importance: Caligids infect a wide range of marine fishes and are particularly significant in aquaculture, where they can reduce growth, increase susceptibility to disease, and cause mortality. Management typically involves monitoring, physical removal, and delousing treatments within an integrated approach, though chemical resistance and environmental concerns pose ongoing challenges.

Taxonomy and distribution: Caligidae is cosmopolitan, occurring in temperate and tropical seas. The family includes dozens to hundreds of described species, predominantly in the genera Caligus and Lepeophtheirus.