Helminthes

In earlier times, the term Worm was loosely used to describe any small animal having a long slender body without appendages. It was used to include not only worms but caterpillars and other insect larvae, and even creatures as unrelated as rotifers and centipedes, all lumped together in the now obsolete category Vermes.

In modern classifications, worms are still recognized as a highly diverse group, and there are a number of systems in use for classifying them. Depending on the particular system, there are around ten worm phyla. Most worms are marine, and many live their lives in tubes which they construct in the sand of the ocean floor. Others live as internal parasites of marine animals including whales and fish, molluscs and octopus.

Many of the parasitic worms of terrestrial animals have larval stages in fresh water, and these can be encountered in water samples collected from lakes and ponds. The three worm phyla of most interest to freshwater biologists are presented below. Additionally, the category "Parasitic" is included, which acknowledges the immense impact of worm parasites upon human and other animal communities.

Helminthes is One of the grand divisions or branches of the animal kingdom. It is a large group including a vast number of species, most of which are parasitic. Called also Enthelminthes, Enthelmintha.