Poecilostomatoid copepods

According to Huys & Boxshall (1991), the origin of the Poecilostomatoidea is linked with a shift in their mate-grasping behaviour. During copulation the male holds the female with the maxillipeds not with the antennules, and this has resulted in marked sexual dimorphism in the maxillipeds in all known members of the group. Virtually all poecilostomatoids have parasitic or other associations with animals and most of them are marine. Many are associated with invertebrate hosts, but about ten families are parasites of fishes. Huys & Boxshall (1991) regard the group as probably the most diverse order of copepods in terms of gross body morphology. This diversity is apparent even among the subset of poecilostomatoids parasitising British fishes. These range from the ergasilids (including the only freshwater parasitic poecilostomatoids), bomolochids and taeniacanthids, still readily recognisable as copepods, through the bizarre chondracanthids to the virtually endoparasitic Philichthys xiphiae.