CONNECTIVE TISSUE CATCH IN ECHINODERMS

(1) Catch connective tissue is defined as the collagenous connective tissue whose mechanical properties can be changed rapidly (in seconds or minutes) under nervous control.
(2) Catch connective tissues are found in all five classes of Echinodermata. They function in tone control of the tissues and in autotomy.
(3) The change in mechanical properties occurs in viscosity.
(4) Muscle cells are not responsible for the viscosity change.
(5) The viscosity change is controlled by nervous activities. Neurosecretory-like cells with large electron-dense granules are found in all the catch connective tissues so far studied.
(6) The viscosity change is quite likely caused by the change in the ionic environment in the connective tissues, which alters the weak (non-covalent) interactions between extracellular macromolecules in the tissue.