Range: Cosmopolitan Habitat: Inside host organisms Size: About 1 inch - more than 13 feet (2.54cm-4m) long Diet: Nutrients from host organism Threats: Host death Life span: Up to thirty years

Transcript:

Today on Animal Fact Files we’re talking about tapeworms. There are thousands of tapeworm species and only a handful are found in humans. Tapeworms are endoparasites and are thus found inside the body of a host. They’re most well known in their adult form, but these animals go through life stages, which we’ll be explaining shortly. And while the most well known type of tapeworm is the most common type there are actually three types of tapeworms found throughout the world.

The most well known tapeworms are called “true” tapeworms. Adults of these tapeworms have a head with hooks or other tools for holding onto tissues and a neck from which body segments originate. These segments make up the rest of the adult tapeworm’s body. The segments closest to the neck are the least mature while those closer to the rear end bear eggs.

Not all tapeworms are segmented, though. Other tapeworms have leaf-like bodies without segments. There are few known species of these leaf-like tapeworms. Adults of these tapeworms are often found in the body cavity of the host, like the spaces between the stomach and the outer body wall. This trait is common in larvae of “true” tapeworms. There’s speculation that these leaf-like tapeworms are the larvae of prehistoric tapeworms whose original hosts have become extinct, and they have developed to have reproductive capabilities without the need of the original hosts.

There are also tapeworms with a rosette structure at their rear ends used for holding onto their hosts. These tapeworms may not require an intermediate host or they may use jellyfish as intermediate hosts. These tapeworms are commonly found in pairs, so it’s believed they may require cross fertilization in order to produce viable offspring.

Tapeworms are hermaphroditic and are generally able to self fertilize, but they can also cross fertilize with another member of their species if found within the same body. We’ll explain the tapeworm life cycle in brief here, but remember there are thousands of species, so of course variation exists.

A tapeworm begins life as an egg. The egg may be retained in the adult and then hatch, the egg may be released within those body segments we talked about previously, or the segment may dissolve to release the egg, or, really eggs. Typically, the eggs get out of the host’s body through the host’s feces. In many cases, the larvae end up in water and swim until consumed by their first intermediate host.

This host is often a copepod or other small crustacean. This animal is eaten and the larvae develop in the next animal. Tapeworms have at least one intermediate host and often have multiple intermediate hosts. When the tapeworm reaches its final host, it develops into an adult. Adult tapeworms are often found in the intestines and remain there for however long they can survive. For example, one tapeworm species may live in the human body for thirty years!

Tapeworms don’t eat: they don’t even have mouths; a tapeworm obtains nutrients from its host through the tapeworm’s body wall. Often, a definitive host won’t even be aware of the tapeworm’s presence. More problems arise when larvae or eggs get into a final host before they should be there. The larvae will spread throughout body tissues, sometimes to the brain, creating cysts which can lead to headaches, seizures, and more. This can happen in humans when feces is accidentally consumed, which is why washing our hands is so important - among... other… reasons…

Tapeworms may be as small as an inch (2.54 centimeters) or longer than 13 feet (4 meters), and they’re found in mammals like bears and whales, reptiles like turtles, fish including sharks, and more!

For more facts on tapeworms check out the links in the description. Give a thumbs up if you learned something new today, and thank you for watching Animal Fact Files.