Zebrafish (Danio Rareo), a fresh water tropical
fish (8) offers an excellent model system because
near saturation mutagenesis is possible and embryos
are transparent, thus, all stages of development
are accessible for study. The zebrafish is
small (3 cm) and can be accommodated in small
aquaria and, thus, is suitable for breeding and
developmental studies. Previous studies using a
technique called thrombelastography, revealed that
blood coagulation in fresh water fish is similar to
that of humans (9). Similar to disseminated intravascular
coagulation in humans, bubble induced
diffuse intravascular coagulation occurs in fish. In
rainbow trout and salmon, factor X, another factor
in the coagulation pathway, shows similar features
to that found in man (10). Metals such as copper
caused hemophilia in fish (11) and chromium
causes internal bleeding (12). Cloning of cDNAs
for prothrombin (13,14) and fibrinogen (alpha,
beta and gamma forms) from various fishes (Gen-
Bank) indicates a high degree of conservation of
these proteins through 400 million years of evolution.
Thus, teleosts appear to have a conserved
blood clotting mechanism. However, at present
there are no assays to measure the clotting function
in zebrafish and its larvae.