Page "Heart" Paragraph 4

In invertebrates that possess a circulatory system, the heart is typically a tube or small sac and pumps fluid that contains water and nutrients such as proteins, fats, and sugars.

In insects, the " heart " is often called the dorsal tube and insect " blood " is almost always not oxygenated since they usually respirate ( breathe ) directly from their body surfaces ( internal and external ) to air.

However, the hearts of some other arthropods ( including spiders and crustaceans such as crabs and shrimp ) and some other animals pump hemolymph, which contains the copper-based protein hemocyanin as an oxygen transporter similar to the iron-based hemoglobin in red blood cells found in vertebrates.