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
Flatfish be a valid species in its own right. Flatfishes are found in oceans worldwide, ranging from the Arctic, through the tropics, to Antarctica. Most species are found in depths between 0 and , but a few have been recorded from depths in excess of . None have been confirmed from the abyssal or hadal zones. An observation of a flatfish from the Bathyscaphe Trieste at the bottom of the Mariana Trench at a depth of almost has been questioned by fish experts, and recent authorities do not recognize it as valid. Among the deepwater species, "Symphurus thermophilus" lives in congregating