Fish-lice (NB: Some Isopoda also are known as fish lice, and some Copepoda parasitise fish)

Code OK019999

The class or subclass Branchiura comprises a single family, Argulidae. These are small to medium-sized (to approx. 10 mm), strongly dorso-ventrally flattened, oval-shaped crustaceans with a strongly reduced abdomen and few thoracic appendages. Both the antennules and antennae are small to minute. The first pair of mouthpart appendages (maxillules) are developed into a pair of suction disks with central hooks. The trunk bears four pairs of short appendages, the last three pairs having feathery margins.

Argulidae are intermittently ectoparasitic on marine or freshwater fish where they feed on blood and mucus. The freshwater species retain mobility and can swim or crawl free from their host.

In Australia, species of the genus Argulus are reported from aquaria, from golden carp (perhaps an introduced species), from a native trout gudgeon in eastern Australia and from an unknown host in WA.

A second genus, Dolops, was reported as an ectoparasite on a galaxiid in the late, lamented Lake Pedder, Tasmania.

Reference:

Williams, W.D. (1980) Australian Freshwater Life: The Invertebrates of Australian Inland Waters. The Macmillan Company of Australia, Melbourne.