River otters primarily eat fish. They are also known to eat whatever is easiest to find, like crustaceans, mollusks, insects, birds, oysters, shellfish, crabs, crayfish, frogs, rodents, turtles and aquatic invertebrates.
1667: Robert Hooke 's famous Micrographia is published, which outlines Hooke's various studies using the microscope. 1675: Enter Anton van Leeuwenhoek, who used a microscope with one lens to observe insects and other specimen. Leeuwenhoek was the first to observe bacteria. 18th century: As technology improved, microscopy became more popular among scientists. Part of this was due to the discovery that combining two types of glass reduced the chromatic effect.
Answer   Microscope was invented by ZACCHARIAS JANSSEN a DUTCHMAN in 1590. From 1632-1723 ANTON VAN LEUWENHOEK was getting better results with a powerful single lens, whiâ¦ch he made himself. He was a dry goods dealer who made lenses as a hobby. Leuwenhoek kept his method of lens making a secret.