Identifying Endoparasites in Animals

The question asks us to identify an organism from the given options that lives inside the body of another animal. Organisms that live inside their host's body are called endoparasites.

Let's examine each option provided:

• Ctenoplana: This belongs to the phylum Ctenophora, commonly known as comb jellies. Ctenophores are typically free-living marine animals, not endoparasites.
• Pleurobrachia: This is also a genus of comb jellies (Ctenophora). Like Ctenoplana, Pleurobrachia are free-living predators found in marine environments and are not endoparasites in animals.
• Flatworms: Flatworms belong to the phylum Platyhelminthes. This phylum includes a wide variety of organisms, and many of them are known to be parasitic, living either on the surface (ectoparasites) or inside the body (endoparasites) of other animals. Examples of parasitic flatworms that are endoparasites include tapeworms (Cestoda) which live in the digestive tracts of vertebrates, and flukes (Trematoda) which can inhabit various organs like the liver, lungs, or blood vessels of animals. Therefore, flatworms are indeed found as endoparasites in animals.
• Adamsia: This is a genus of sea anemones, belonging to the phylum Cnidaria. Sea anemones are marine invertebrates, typically sessile (attached) or free-swimming. While some cnidarians can form symbiotic relationships, Adamsia itself is generally a free-living or commensal organism (often living on shells inhabited by hermit crabs), and it is not known to be an endoparasite in animals.

Based on the nature of these organisms, flatworms are the group that commonly includes species functioning as endoparasites in animals.

Why Flatworms are Endoparasites

Many members of the phylum Platyhelminthes, or flatworms, have adapted to a parasitic lifestyle. This adaptation involves living inside the body of a host animal, obtaining nutrients from the host, and often causing harm. These internal parasites are specifically called endoparasites.

Common examples found inside animals include:

• Tapeworms: These segmented flatworms live in the intestines of vertebrates, absorbing digested food directly through their body surface.
• Flukes: These leaf-shaped flatworms have suckers to attach to host tissues and feed on blood, mucus, or tissue cells. They can live in various internal organs.

This makes 'Flatworms' the correct identification for an endoparasite found in animals among the given options.

Revision Table: Comparing Options Regarding Parasitism

Additional Information on Animal Parasites

Parasitism is a type of symbiotic relationship where one organism, the parasite, lives on or inside another organism, the host, and harms it. Parasites can be broadly classified based on where they live on the host:

• Endoparasites: These live inside the host's body. Examples include tapeworms in the gut, malaria parasites in blood cells, and liver flukes.
• Ectoparasites: These live on the external surface of the host. Examples include ticks, fleas, lice, and leeches.

Flatworms like tapeworms and flukes are classic examples of endoparasites that have evolved complex life cycles, often involving multiple hosts, to facilitate their transmission and survival within different animal bodies.