Comparative morphology of the hemolymph vascular system in scorpions–A survey using corrosion casting, MicroCT, and 3D‐reconstruction

Although scorpions are one of the better known groups of Arthropoda, detailed knowledge of their anatomy remains superficial. This contribution presents the first comprehensive investigation of the gross morphology of the scorpion vascular system, based on a survey of species representing all major lineages of the order, using classical and modern non-destructive techniques in combination with three-dimensional reconstruction. The investigation reveals that the hemolymph vascular system (HVS) of Scorpiones comprises a central pumping heart which extends the entire length of the mesosoma and is enclosed in a pericardium. Several arteries branch off the heart to supply different organs and body regions. Two different anterior aorta major branching patterns are identified among the species investigated. Arteries that branch off the anterior aorta system supply the appendages (chelicerae, pedipalps, and walking legs) and the central nerve mass with a complex arterial network. This study of the HVS of scorpions provides further evidence that the vascular systems of euarthropods can be highly complex. Use of the term "open circulatory system" within arthropods is re-emphasized, as it refers to the general organization of the body cavity (i.e. mixocoely) rather than to the complexity of the circulatory system.