Fish louse

Argulus foliaceus

ORDER

Arguloida

FAMILY

Argulidae

TAXONOMY

Argulus foliaceus Linnaeus, 1758, Europe.

OTHER COMMON NAMES

German: Karpfenläuse.

PHYSICAL CHARACTERISTICS

Abdominal lobes broadly rounded at tip; anal cleft less than half the length of abdomen. First to third legs, with darkly pigmented patches near base. Male with triangular process on posterior surface of leg two, directed towards base. Body length to 0.39 in (10 mm) for female and 0.35 in (9 mm) for male.

DISTRIBUTION

Europe, through to central Asia and Siberia.

HABITAT

Ectoparasitic; attaching to wide variety of freshwater fishes.

BEHAVIOR

On hatching, the larvae swim actively in the water column for about 2–3 days, after which their infectivity decreases.

FEEDING ECOLOGY AND DIET

Feeding externally on host, will take host epidermis and blood.

REPRODUCTIVE BIOLOGY

Eggs are laid in strings, of between two and six rows, containing up to 400 eggs; hatch after 25 days (at 59°F [15°C]), and development time is very dependent on temperature. Eggs within a string tend to hatch within 4–6 days. First larval stage lasts about six days, and molts occur at intervals of about 4–6 days until maturity.

CONSERVATION STATUS

Not listed by the IUCN.

SIGNIFICANCE TO HUMANS

May occur as epizootic infestation in fish hatcheries and other facilities. Can cause severe mortality in cultured fish stocks and can transmit viral diseases such as spring viraemia between fishes.