Blood collection in amphibians is often difficult because of low body weight and poor access to vessels. Unfortunately, it may be necessary to euthanize animals in order to maximize sample volume. Acceptable blood withdrawal methods are toe web clipping, cardiac puncture, and venous cutdowns of ventral abdominal veins. Toe clipping can be done with a sharp fingernail clipper to obtain a few drops to 0.5 ml of blood. The blood flow usually stops spontaneously, but silver nitrate sticks may be needed to cauterize the wound.
Amphibian blood contains nucleated erythrocytes, leukocytes and thrombocytes.
Amphibian erythrocytes are biconvex, oval and the largest of all vertebrate erythrocytes. Accurate RBC counts are obtained by means of hemocytometer and standard counting procedures. The use of automated white cell counters is contraindicated. Anesthesia Delicate aquatic species such as Xenopus should be handled with soft nets for unanesthetized procedures. Chemical restraint is required for prolonged or invasive procedures.