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 first light microscope dates back to 1595, when Zacharias Jansen created a compound microscope that used collapsing tubes and produced magnifications up to 9X. Microscopes have come a long way since thenâtoday's strongest compound microscopes have magnifying powers of 1,000 to 2,000X.he first light microscope dates back to 1595, when Zacharias Jansen created a compound microscope that used collapsing tubes and produced magnifications up to 9X. Microscopes have come a long way since thenâtoday's strongest compound microscopes have magnifying powers of 1,000 to 2,000X.