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Home > Fishing > Fish Health Laboratory > Fish Health Issues > Volume 4, Issue 9 -Protozoal Parasite:Leptorhynchoides thecatus
Acanthocephalan: Leptorhynchoides thecatus
Volume 4, Issue 9
Figure 1. Leptorhynchoides thecatus from the gi tract of a largemouth bass.
The acanthocephalan life cycle involves the eggs being first shed by the adult worm in the fish intestine and then eaten by a small freshwater crustacean (ostracod, copepod, amphipod, or isopod).
Figure 2. Encysted immature hookworm in the smooth muscle layers of a white sucker’s gi tract. This structure is called a cystacanth.
If hookworms are numerous, their hooked proboscides may inflict serious damage to the intestine; in some cases, this damage may be exacerbated by the worms’ retracting the spined proboscis and reinserting it in another place.
Hookworms have no mouth or digestive tract. They absorb nutrients directly through their body surface. Normally, adult hookworms live in the lumen of the digestive tract only, but occasionally adult worms bore through the wall of the digestive tract and come to lie in the body cavity.
Leptorhynchoides thecatus can infect many species of Maine fishes including: suckers, whitefish, salmonids, cusk, minnows, pike and pickerel, bass and sunfish , perch, smelt, and bullheads.
Special points of interest:
Hookworms are parasitic animals.
Hookworms can harm fish by damaging the fish with their spines.
For more information read: Hoffman 1999 Parasites of North American Freshwater Fishes.
Images in this document were made possible in part by a grant from the Maine Outdoor Heritage Fund.
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