Common name: Fish lice
Agent / classification: Branchiura, Argulus
Host: variety of fishes
General: 150 spp., mainly parasitic on freshwater fishes, but over 30 marine forms
5-10 mm long, highly flattened, broad carapace, 1st maxillae modified as a large sucker, suckers unusual in crustaceans (usually hooks). Some have a stylet that can inject a toxin. Rapid movements over body surface. Feed by secreting digestive enzymes that break down tissues, can result in localized lesions.
Direct, leaves host, deposit eggs on substrate. Copepodite-like stage hatches, molts and attacks fish.
Pathology: Infected fish exhibit erratic swimming and darting behavior, irritation from stylet penetration. Toxins can kill fish in heavy infections. (summer flounder).
Transmission: direct life cycle
Diagnosis / Identification:
Treatment: 0.15-0.25 mg/l trichlorfon. Dylox also very effective.
Control: Quarantine where possible. Disinfect tanks with 2% chlorox bleach and allow to dry (kills egg masses).