Circulatory System in Finfish and Shellfish

Cells and Thrombocytes are 
present in plasma 
RBC 
(erythrocytes) 
are 
nucleated, oval and contain 
haemoglobin 
The WBCs may be grannular 
or agranular. They are called 
basophils, 
acidophils, 
neutrophils, monocytes and 
lymphocytes
 
Thrombocytes (responsible 
for blood coagulation) 

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Details of Blood Clot Formation 
 

 Blood clotting is initiated when platelets and 
damaged tissue secrete clotting factor called 
prothrombin
 activator 

 Prothrombin 
activator 
and 
calcium 
ions 
catalyze the conversion of 
prothrombin to 
thrombin
 which then catalyzes the conversion of 
fibrinogen to fibrin threads
. 

 Fibrin threads are sticky and trap more 
platelets, further sealing the leak. 

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Respiratory Pigment in Fishes: 
Hemoglobin 

Tetrameric hemoglobin has two 
α and two β chain 

O
2
bind in reversible and cooperative fashion to four heme group while
H+ and CO
2
bind to specific amino acid residues in the globin chains 

But in fishes, due to acetylation of 
α amino group only β chain available 
in bind to CO
2

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Blood vessels 
The blood vessels 
are of two types, 
arteries and veins. 
The