Unit 1 - Fish Blood Constituents
Thrombocytes - Occurrence

Back to Thrombocytes

In mammals, thrombocytes are the precursors of cells called platelets, which circulate in the blood and are responsible for clotting.  Mammalian thrombocytes are seldom found in the circulation. In fish however, unlike mammals, thrombocytes circulate in the blood.

 There is disagreement over the numbers of thrombocytes present in the peripheral blood of fish, which could arise because of the ease with which they can be  mistaken for lymphocytes.

Notes
DISAGREEMENT: In juvenile Rainbow Trout, Oncorhynchus mykiss, thrombocytes account for 1-6% of total leucocytes.

The ratio of lymphocytes to thrombocytes in Rainbow Trout has been measured as 25:1, however for the same species a ratio of 2:1 has also been measured.  Conversely a ratio of lymphocytes to thrombocytes in Plaice (Pleuronectes platessa)  of 1:3 has been reported.

For the percentage of leucocytes comprised of thrombocytes in the Carp (Carassius auratus),  a figure of 70% has been obtained by some researchers, while others have given a figure of just 3-13%.