Life Cycle of Tapeworms in Sharks

All sharks are plagued by tapeworms.

The tapeworm, a parasitic flatworm, spends its adult life within the gut of its host vertebrate. All known species of sharks carry tapeworms. The sharks aren't sick. For them, tapeworms are just a fact of life.

No Digestive Tract

Unlike free-living flatworms, tapeworms lack digestive tracts. They absorb food through their skin.

Birth of a Tapeworm

Tapeworms hatch from eggs. They then develop into cysts, which contain little, round creatures that use tiny hooks to crawl around inside their host.

Proglottids

Tapeworms are composed of segments called proglottids, which often have eggs and organs that form sperm.

Growing a Scolex

At maturity, the tapeworm grows something resembling a head. This head-like organ is called a scolex. The scolex is used like a clamp, to keep the tapeworm in place inside the host's gut.

Studying Blue Sharks

In a study off Long Island, Stephen Curran and J.N. Caira of the University of Connecticut examined the innards of 24 blue sharks. They found one to four different species of tapeworms in every shark.

An Abundance of Tapeworms

In Curran and Caira's study, each shark hosted up to 2,382 individual tapeworms.

References

• The Free Library: What's Eating Our Sharks and Rays?
• Discover Magazine: Tapeworm Mystery
• JSTOR: Attachment Site Specificity and the Tapeworm Assemblage in the Spiral Intestine of the Blue Shark