Arthropods like spiders do not have blood like animals, rather they have a fluid called hemolymph in their circulatory system. Hemolymph is found in the circulatory system of arachnids, crustaceans and insects. Molluscs too have a circulatory fluid akin to this type.
In insects, exchange of oxygen and carbon dioxide occurs in a tracheal system which means they respire directly through their body surfaces. So the circulatory system transports nutrients but only a small portion of oxygen.
In both insects and other arthropods as well as molluscs, hemolymph contains hemocyanin, a copper based oxygen transport molecule.