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.
B-cells and T-cells are lymphocytes found in lymph nodes and lymph tissues. When B-cell lymphocytes become activated due to the presence of a particular antigen, they create antibodies that are specific to that specific antigen. The antigen is tagged as an intruder and labeled for destruction by other immune cells.