Yes, seems have blood. They have what is called haemolymph, a fluid which serves as their blood. Further, the fluid contains a copper-based protein called haemocyanin turns blue when oxygenated.
The blood of shrimp – or hemolymph – has a cellular component, which is the hemocytes, and a liquid component constituted of plasma that contains different humoral factors (macromolecules of the circulatory system). The immune-cellular and humoral responses act in an integrated manner creating defense mechanisms such as the coagulation of hemolymph; melanization by the prophenoloxidase (ProPO) system – a major, innate defense system in invertebrates; use of lectins for the recognition of foreign agents; and antibacterial, antifungal and antiviral peptide systems that act with interference RNA and a pattern of recognition proteins. We can also add the production of reactive forms of oxygen, phagocytosis and encapsulation, the latter two mainly performed by hemocytes.
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