Sydraulic actuation in spider legs - software and tables

Hemolymph channels (lacunae) in the legs of spiders are part of their open circulatory system. They are defined as hemolymph-filled spaces between tissues within the leg tubes which are otherwise largely filled with muscles. In two of the major leg joints the leg segments are connected via hinge joints that are located at their dorsal rims.The lacunae are used to channel hemolymph to the extensor-less joints during leg extension. However, during flexion drag in the lacunae may hamper movement and force generation. Dynamic flexions of the tibia-metatarsus joint considering anatomical and physiological properties identified for the hunting spider <i>Cupiennius salei</i> were used to investigate the trade-off between muscular force and hemolymph-drainage with the result that the diameters of the hemolymph channels are only weakly optimal but not critical for quick flexions. With small loads of 0.1 g, which is a common prey size, this configuration seems to enable the fastest flexions.