THE ANIMAL FILES

Pork tapeworm

Taenia solium

A ribbon-shaped animal with a journey between hosts.

Adult pork tapeworms attach inside the human intestine and absorb nutrients through their surface. Larval cysts develop in intermediate hosts such as pigs, so the worm’s structure and host change across its life cycle.[1]

Follow the evidence ↓
Pork tapeworm
Image: Roberto J. Galindo · Commons · CC BY-SA 3.0
Adult attachment
A scolex with suckers and hooks[1]
Body surface
An absorptive tegument[1]
Typical intermediate host
Pigs and wild boars[1]

An anchor rather than a familiar head

The small scolex fastens the adult worm to the host’s intestinal wall using suckers and hooks. Behind it, a short neck produces the chain of reproductive segments. New growth near the neck means the segments farther back are older; the body is not a row of identical independent animals.[1]

A surface built for absorption

The adult’s covering is a specialised tegument bearing minute projections called microtriches. This is an absorptive interface with the surroundings inside its host.[1]

One species, different stages

In the usual cycle, pigs ingest eggs and the developing larvae migrate into tissues, where cysticerci form. Adult worms occur in the definitive host, humans. These contrasting locations belong to different developmental stages. When tissue containing a cysticercus is ingested by the definitive host, the inverted scolex turns outward in the small intestine and attaches with its suckers and hooks. New segments then form behind the neck as the adult body lengthens.[1]

A COMMON MIX-UP

Is a tapeworm segment a separate little worm?

No. The proglottids form part of one segmented adult body. Their position reflects growth and reproductive maturity, with younger segments near the neck and egg-filled segments toward the rear.[1]

TRY A LITTLE REASONING

Why would a picture of a cyst not resemble the adult?

Reveal the explanation

The cysticercus is a larval stage in an intermediate host. A different shape is expected because it occupies a different place in the life cycle, rather than representing a different species.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Pork tapeworm (fixed revision; adapted and translated)
  2. NCBI Taxonomy — Taenia solium (identity and classification)

Last fact check:

One discovery leads to another

Common liver flukeA leaf-shaped body with an active outer coat.Fasciola hepatica ↗Common earthwormA fallen leaf can travel down an earthworm’s burrow.Lumbricus terrestris ↗European medicinal leechTwo suckers, three jaws, and a meal that must stay liquid.Hirudo medicinalis ↗