Adaptations and Types of Crustacean Symbiotic Associations

Abstract

Crustacean symbionts occur in all the oceans and in all the river systems and wetlands of the world. In the ocean, they are associated with almost all the invertebrate phyla and the vertebrate classes of fish, reptiles, birds and marine mammals. In freshwater, the crustacean associations are mainly with fish and some amphibian tadpoles. In almost every order of the Crustacea, there are species in some kind of association with other species. Associations range from facultative to highly specialised parasitism where the parasite undergoes total morphological adaptation, becoming metabolically completely reliant on the host for its survival. The crustacean associations are grouped into six categories: epibiosis, inquilinism, commensalism, mutualism, parasitism and eusociality. The most diverse category, parasitism, is subdivided into ectoparasites, mesoparasites, endoparasites, parasitic castrators, parasitoidism and sponge hotels, the latter to accommodate the complex crustacean association with sponges. In the category eusociality, the social behaviour of snapping shrimps is examined. The concluding sections discuss some interesting observations and deductions on parasitic crustacean parasite adaptations and associations using the subclass Branchiura, of which all the species are parasites of fish and amphibian tadpoles, as a case study due to the available information and expertise of the authors on this group.