While the tadpoles of competing species may complete metamorphosis in as little as just a few short months, Bullfrog tadpoles can remain in the same state for as long as one to two years before they actually become adult frogs.
Two types of white blood cells called lymphocytes are vital to the specific immune response. Lymphocytes are produced in the bone marrow, and mature into one of several subtypes. The two most common are T cells and B cells. An antigen is a foreign material that triggers a response from T and B cells.
After activation by T H cells, B cells release proteins called antibodies. Antibodies travel through the body's fluids and attach to antigens, targeting them for destruction by nonspecific defenses. This type of immune response is called antibody-mediated immunity (or humoral immunity).