The parasitic copepod Lernaea species infects the goldfish Carassius auratus and induces lernaeosis in commercial aquaria in Egypt. The early stages of Lernaea parasites appeared macroscopically as whitish spots. At about 15-24°C,
the infected fish with primitive stages were reared for reaching adult females. The former stages gradually change into brownish color and well adapted to attach to body surface of the host fish, causing at least 5 mm inflamed bloody
ulcers in the skin, fins, and muscles. Various postmetamorphic adult females of Lernaea parasites were differentiated, sketched, measured, and compared with previous related species. The majority of the present females were synchronized
on one fish specimen. The adult females were different according to the shape and size of holdfast organ. For the present females, the distinguishable taxonomical character was the wide variability in shape of anchors and their
processes (sub-horns). In addition, the variation in general morphology for each form was discernible. Moreover, Lernaea was found as economically important parasites. The massive infection reached about 29 parasites/ infected fish during
winter. The infected fish became nervous, loosing scales with severe damage particularly at the bases of fins. They also appeared stressed, exhausted and stopped feeding. Lernaea parasites also induced disruption, haemorrhage,
proliferation or necrosis and edema along the path of penetration in the host
tissue. Approximately two months later, white spots appeared on the naturally
infected fish and after nearly two weeks, most of them extruded without further
modifications.