adult pomphorhynchus in bluefish
general patterns
acanthocephalans have complex life cycles, involving number of hosts, both developmental , resting stages. complete life cycles have been worked out 25 species.
having been expelled female, acanthocephalan egg released along feces of host. development occur, egg, containing acanthor, needs ingested arthropod, crustacean (there 1 known life cycle uses mollusc first intermediate host). inside intermediate host, acanthor released egg , develops acanthella. penetrates gut wall, moves body cavity, encysts, , begins transformation infective cystacanth stage. form has organs of adult save reproductive ones.
the parasite released when first intermediate host ingested. can suitable final host, in case cystacanth develops mature adult, or paratenic host, in parasite again forms cyst. when consumed suitable final host, cycstacant excysts, everts proboscis , pierces gut wall. feeds, grows , develops sexual organs. adult worms mate. male uses excretions of cement glands plug vagina of female, preventing subsequent matings occurring. embryos develop inside female, , life cycle repeats.
an example – polymorphus spp.
a diagram of life cycle of polymorphus spp.
polymorphus spp. parasites of seabirds, particularly eider duck (somateria mollissima). heavy infections of 750 parasites per bird common, causing ulceration gut, disease , seasonal mortality. recent research has suggested there no evidence of pathogenicity of polymorphus spp. intermediate crab hosts. cystacanth stage long lived , remains infective throughout life of crab.
the life cycle of polymorphus spp. occurs between sea ducks (e.g. eiders , scoters) , small crabs. infections found in commercial-sized lobsters in canada acquired crabs form important dietary item of lobsters. cystacanths occurring in lobsters can cause economic loss fishermen. there no known methods of prevention or control.
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