Internal Transport

The circulatory system of crustaceans are advanced compared to many invertebrate taxa. It consists of a well developed hemal system, including a heart, capillaries and veins, and blood containing hemocytes and hemocyanin. The heart is more derived than primitive forms, and is located in the dorsal, posterior area of the thorax under the carapace. Three arteries extend anteriorly from the heart, one in the middle and two either side, laterally along the thorax. The middle artery meets a frontal heart, an enlarged area of the blood vessel. This artery continues over the dorsal side of the foregut, divides into two and joins the supraesophageal ganglion, or the main brain. The other lateral arteries supply blood to the foregut and muscles of the foregut. Two arteries extend posteriorly from the heart; the sternal artery and the posterior aorta. The sternal artery divides into two branches which supply blood to the chelipeds, mouth parts, renal gland, foregut, and the third, fourth and fifth pereiopods. The posterior aorta extends into the pleon under the ventral nerve chord, supplying blood to the gonads, (see Figure 18.) Deoxygenated blood then leaves the capillaries and collects in sinuses which lead to the gills. From the gills the freshly oxygenated blood then travels back to the heart. The distribution of blood around the body is regulated with muscular sphincters in the arteries, (Ruppert, Fox & Barnes, 2004; Tudge, Asakura & Ahyong, 2004.)

Figure 18- The hemal system of the Blue striped hermit crab (Source: Diagram modified from Tudge, Asakura & Ahyong, 2004, by Author, 2014)