Light micrograph (darkfield microscopy) of a marine copepod (Tigriopus sp.). Copepods are the most abundant metazoan in the earth waters and are found in marine and fresh water, from lakes and streams to ocean trenches. They range in size from 0.1 to 10 mm and are a crucial link in the aquatic food web for fish and other planktivores. Magnification: x30 when printed at 10 centimetres wide at its longest edge.