ABSTRACT
Mutable collagenous tissues, which are also known as catch connective tissues, are characterised by their capacity to undergo rapid, nervously mediated changes in mechanical properties. This chapter illustrates the current level of knowledge and understanding of mutable collagenous tissues (MCTs) by referring principally to work published over the past seven years. A wide range of echinoderm structures has been conjectured or assumed to consist of MCT, sometimes on the basis of insubstantial evidence (or no evidence at all). MCTs are found in two anatomical contexts: at locations where they traverse potential autotomy planes; and at locations remote from autotomy planes. Non-autotomy-associated MCTs show reversible changes in tensile properties, i.e. they can switch between compliant and stiffened states. In their stiffened state, such MCTs fix posture, either the posture of the whole animal or a major part of it, in the case of body wall MCTs (i.e. dermis), or the posture of individual appendages, in the case of mutable ligaments.
