Hemolymph, or haemolymph, is a fluid in the circulatory system of some arthropods (including spiders, crustaceans such as crabs and shrimp, and even some insects such as stoneflies) and is analogous to the fluids and cells making up both blood and interstitial fluid (including water, proteins, fats, sugars, hormones, etc.) in vertebrates such as birds and mammals. In addition, some non-arthropods such as molluscs possess a hemolymphatic circulatory system.