Physiology of Finfish and Shellfish (2+1)

2.2.22. Function of plasma

1. Transport of products of digestion from small intestine to various tissues.
2. Transport of excretory products from tissues to excretory organs
3. Transport of hormones from endocrine glands to target organs
4. Maintenance of temperature by distribution of heat all over the body
5. Provides factors for clotting of blood (fibrinogen)
6. Retention of fluids in the body (through plasma proteins)
7. Provides body immunity through antibodies (immunoglobulins) which are made by 1 kind of WBC and then released into the plasma.

Unlike the hemoglobin in red blood cells found in vertebrates , hemocyanins are not bound to blood cells but are instead suspended directly in the hemolymph or but floats free in the blood. Unlike hemoglobin, hemocyanin is not stored in a cell but flows freely in the blood. The copper -containing pigment hemocyanin, second in breadth of distribution after hemoglobin, occurs in the blood of various molluscs and arthropods.^{2, 3} Unlike human blood, which is bright red when oxygenated in the arteries and dark red when deoxygenated in the veins, hemocyanin blood is a beautiful blue in the arteries and as clear and colorless as water in the veins. Hemocyanin is always found roaming free in blood plasma, instead of confined within corpuscles as are the relatively smaller molecules of Hb. This copper-based, proteinous, non-porphyrin blood pigment is only about one-quarter as efficient as hemoglobin at carrying oxygen.

• Dorsal heart - single-chambered sac of striated muscle.
• Valves in the arteries prevent backflow of hemolymph.