Developmental stages of Caligus epidemicus Hewitt,a copepod parasite of tilapia cultured in brackish water

The larval development of Caligus epidemicus comprises ten stages: two nauplii, one copepodid, six chalimus, and one preadult (young adult) stages. The morphology of each of these ten instars is described based on material reared from eggs in the laboratory. Addition of fifth and sixth chalimus stages in the ontogeny of C. epidemicus is discussed in the light of the developmental changes in the leg armature. Some peculiarities about the structure of the frontal filament in various chalimus stages are also discussed.