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Home , Acanthocephala, Proboscis

with rows of recurved hooks is used (spiny-headed ) to pierce the gut wall of the final for attachment

1150 the size and arrangement of these hooks and spines are used to identify species all are parasites in intestines of fish, birds & proboscis can be retracted into a specialized pouch body wormlike, somewhat flattened show eutely (constant number of cells/species most are less than a couple inches long; up to 1 M long Body Wall especially common in the intestines of freshwater syncytial epidermis fishes secretes thin cuticle on outer surface are intermediate hosts covered in crypts 4-6 microns deep one of the most completely parasitic organisms in the lacunar system of fluid filled canals in body wall

bands of circular and longitudinal muscle fibers à the digestive tract is completely lost

à only the reproductive system is well developed body wall muscles tube-like and filled with fluids

Body Form body cavity a large pseudocoelom long, unsegmented, wormlike body with eversible proboscis at front end no digestive system in or adult look like roundworms but with retractable proboscis exchange of gasses, nutrients and wastes across body

Animals: Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 1 : Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 2

wall by diffusion gonads contained within thin walled sacs Respiration males with pair of testes and no respiratory system also contain a conspicuous cement gland absorbs oxygen through secretes ‘cement’ into the after mating Circulation which hardens into a plug which prevents other males from copulating with her no heart or circulatory system sperm ejected into vagina and end up in à but muscle contractions pump fluids through pseudocoel canals and within body cavity female has no well defined , instead the Excretion fragments as she matures forming numerous “ovarian balls” that float freely in if present, excretory system consists of 2 the fluid filled ovarian sac protonephridia fertilized egg develops in pseudocoel of female Nervous System mature eggs enter the nervous system with central ganglion near saclike proboscis receptacle shelled is released in host’s but overall greatly reduced up to 100,000’s/day

eggs hatch when ingested by intermediate host Reproduction Cycle dioecious; females larger than males requires two hosts to complete its life cycle: intertnal fertilization Animals: Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 3 Animals: Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 4 filled body cavity where it completes Adult development

endoparasite in : especially fish, birds life cycle may include several “transport hosts” to and mammals complete its life cycle

also in and reptiles eg. crustaceanà snailà fish

only occasional, rare reports of infections in juvenile can modify the behavior to make (children) it more likely to be eaten by final host

can be several 1000 in a single host eg. adult in birds (ducks); larva in amphipods

Amphipods (fw ) typically hide in dark attach to intestine by spiny proboscis vegetation during the day to avoid predation

a host may contain 1000’s of worms when infected with acanthocephalan , amphipod becomes highly photophilic and conspicuous near water’s surface Juvenile

the juvenile cannot complete development and Evolution infect a without first going through an intermediate host recent molecular evidence indicates that acanthocephala are highly derived and in arthropods (crustaceans & insects) should be placed in that phylum

usually an for a terrestrial host

usually a for an aqutic host

arthropods eat feces with eggs to get infected

in intermediate host the juvenile hatches and bores through the intestine and into the fluid

Animals: Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 5 Animals: Phylum Acanthocephala; Ziser Lecture Notes, 2015.10 6