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.
There is a lot of controversy regarding the inventor of compound microscope. Though, there are three contenders-Hans Lippershey, Zacharias Jansen-Hans Janssen and Giovanni Faber who coined the name 'Microscope' for Galileo Galilei's compound microscope in 1625. Galileo used to call it the 'Occhiolino' or 'Little eye'. However, Zacharias Jansen and Hans Janssen are widely regarded as the inventors of compound microscope. Zacharias Jansen was a Dutch spectacle-maker from Middelburg. He is also known as Zacharias Janssen and Sacharias Jansen. During 1590-1595, zaccharias janssen and his son hans, while experimenting with several lenses in a tube, discovered that nearby objects appeared greatly enlarged.