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Acanthocephalan: Pomphorhynchus bulbocilli

Volume 4, Issue 7
July 2002

Pomphorhynchus bulbocilli

Figure 1. Hundreds of yellow bodied Pomphorhynchus bulbocilli were found attached to the intestine of white suckers C. commersoni.

Phylum: Acanthocephala

Class: Palaeacanthocephala

Order: Echinorhynchida

Family: Pomphorhynchidae

Genus: Pomphorhynchus

Thorny-headed worms or hookworms (Acanthocephalins) are easy to recognize attached to the inside of the intestine of some fishes because of their proboscis (spiny attachment organ). The worm uses the proboscis to secure itself to the fishes intestinal wall, and many species can be identified by the number and pattern of chitin hooks on the proboscis.

The lifecycle of the hookworm P. bulbocilli begins when an adult sheds eggs into the intestine of the host. Thorny-headed worms are both male and female, each individual has both ovaries and testes. The fertilized eggs are shed into the water with the fish’s feces. Eggs are eaten by a variety of aquatic crustaceans (copepods, ostracods, amphipods, or isopods). The eggs hatch and the tiny “acanthor” migrates through the intestinal wall of the crustacean into it’s body cavity. Once within the crustacean’s body cavity, the acanthor metamorphoses into a second stage larva called an “acanthella.” Typically once the second stage larva has formed (about 30 days), it rests in the crustacean waiting to be eaten by a fish.

Pomphorhynchus bulbocilli

Figure 2. Proboscis of Pomphorhynchus bulbocilli 4x microscopy. The literal Latin translation of their species name means: “bulb neck.”

If the crustacean is eaten by a suitable host fish, the “acanthella” emerges into the fish’s intestinal tract and attaches. Here it matures into an adult and begins shedding eggs for the next generation. If the acanthor is eaten by a fish unsuitable to be an adult host or before it can become an acanthella, it may finish becoming an acanthella in the fish and wait hoping the unsuitable host is eaten by a suitable host.

Hookworms can cause considerable damage to the host, reduce their fitness, rob them of energy resources, and may even spread other diseases.

The Pomphorhynchus bulbocilli proboscis pictured in Figure 2 has a large bulb near the tip of it’s long proboscis and it has 12-20 rows of 10-14 hooks. It has been reported to infest a variety of fish species including: temperate basses, Atlantic salmon, rainbow trout, minnows, white suckers, pike and pickerel, smelt, perch, and even snakes.

Special points of interest:


Hookworms found in fish cannot infest people.

Hookworms can harm the host by sucking blood, or other nutrients from the host.

Hookworms infect many species of fish.

For more information read: G. Hoffman 1999. Parasites of North American Freshwater Fishes.

Images were made possible by a grant from the Maine Outdoor Heritage Fund.