Copepods may be small, and with typical lengths of 1 or 2 millimetres (0.04-0.08 in) they certainly are that, but it doesn't stop them from being one of the most successful and important creatures on Earth. They are crustaceans that can be found inhabiting almost any patch of water: ponds, rivers, 10,000 metres down in the deep sea, 5,000 metres up in Himalayan lakes, freezing polar seas, boiling hot springs, swamps, bogs, damp moss, leaf litter, underground water systems and more. So far so
Water Bear, but many of the estimated 14,000 species of copepod are parasitic, sucking blood, eating skin or absorbing nutrients. Their unwanted attentions are lavished not only on fish and mammals, but molluscs, corals, sponges and others as well.