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.
Charles Spencer demonstrated that light affected how images were seen. It took over one hundred years to develop a microscope that worked without light. The first electron microscope was developed in the 1930âs by Max Knoll and Ernst Ruska.harles Spencer demonstrated that light affected how images were seen. It took over one hundred years to develop a microscope that worked without light. The first electron microscope was developed in the 1930âs by Max Knoll and Ernst Ruska.