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.
Once mature, B-Cells and T-Cells move to Secondary Lymphoid Organs such as the lymph node and spleen. This is where these cells come into contact with foreign pathogens. If the pathogen the cell can interact with is present the cell will be activated. After activation the cells proliferate making clones of themselves that are all capable of recognizing and fighting against the same antigen. However, not all T & B Cells will be activated.