Alaskan King Crabs have an open circulatory system with a dorsal, ostiate heart. An open circulatory system has circulating fluid which somewhat passes freely among the tissues before being collected and recirculated. The heart lies in a pericardial chamber, and blood passes through this chamber into the lumen of the heart through two pairs of osti Seven arteries conduct blood from the heart to various somatic regions. Each region branches extensively, and smaller arteries ultimately end in the hemocoel.