Lepeophtheirus pectoralis copepodid stage, during which the copepod attaches itself to the fish. Stages IV, V, VI and VII are the chalimus stages, and are followed by the pre-adult and adult stages, when differentiation of males and females is possible. Lepeophtheirus pectoralis Lepeophtheirus pectoralis is a species of parasitic copepod. It is a parasite of flatfish, the most frequent hosts being the European flounder ("Platichthys flesus"), the plaice ("Pleuronectes platessa"), and the dab ("Limanda limanda"). It feeds on the mucus, skin and blood of the fish, with oviferous females being found in the pectoral and pelvic fins of the host, while immature
Hypselodoris kanga white. The inner edge of each gill is reddish orange in the upper quarter, deep blue in the mid region and white in the basal quarter. The smooth outer side of each gill is orange-red in the upper quarter and the rest has a background colour of light blue with a row of large yellow spots. The two outer corners of each gill are bordered with red at the tip becoming dark blue at the base. This species can reach a total length of at least 70 mm and has been observed feeding on yellow sponges from the genus "Dysidea".