Scientists are studied by psychologists, sociologists and other social scientists. They are also studied by scientists in virtually all fields of science. For instance, it is common for physicists to take an interest in other physicists.
The name of a scientist that studies sports is called a sports scientist.
An arachnologist
A scientist who studies crystals is known as a Crystallographer.
A scientist who studies animals is called a zoologist.
A scientist who studies animal life is a zoologist. There is no particular name for a scientist that specialises in platypuses.
The name for this type of scientist is a teuthologist
This answer is a entomologistA scientist who only studies fish is called an ichthyologist.
Parasitologist
geologist
physicist
environmentalist
ecologist