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.
The compound microscope was invented 40 years before Anton van Leeuwenhoek was born. He used a simple one lens microscope. More: Anton van Leeuwenhoek, (October 24, 1632 -- August 26, 1723) is known as the Father of Microbiology. He was from Delft, Netherlands. He was not trained in science, but was originally a tradesman.