The controversial echinoid heart and hemal system—function effectiveness in respiratory exchanges

Abstract

1. 1. The axial complex (including the “heart”) and the hemal system do not serve, to any significant extent, the general transport of respiratory gases and cannot be considered a functional circulatory system in the adult regular echinoid. 2. 2. The coelomic fluid is the medium for the transport of respiratory gases and nutrients. 3. 3. A marginal long-term transport function for the translocation of elaborated moleculaes may be assigned to the hemal system. A decontaminating function may be assigned to the axial organ.