Mechanical investigations of the mutable collagenous tissues of the echinoderms, Eucidaris tribuloides, Cucumaria frondosa, and Parastichopus parvimensis

Mechanical properties of the collagenous spine ligaments of the sea urchin Eucidaris tribuloides were investigated in vitro. The tensile strength and stiffness of ligaments were relatively high when in artificial sea water (ASW) containing Ca{dollar}sp{lcub}2+{rcub}{dollar}, and low when Ca{dollar}sp{lcub}2+{rcub}{dollar} was chelated via EGTA. This Ca{dollar}sp{lcub}2+{rcub}{dollar} chelation effect was fully reversed by re-addition of Ca{dollar}sp{lcub}2+{rcub}{dollar} to the tissue. Treatment of ligaments with the non-ionic detergent, Triton X-100, irreversibly induced a stiff state even after washing in Ca{dollar}sp{lcub}2+{rcub}{dollar} chelated ASW. This suggests that viable cells are necessary to release the catch state, that they do not release catch by secreting a chelator, and that calcium is nor even needed to induce catch.; The dermis of the holothurian, Cucumaria frondosa, yielded two different extract solutions which were applied to intact pieces of dermis from the same animal to invoke a stiff or compliant mechanical state. The extracts were effective on tissues incubated in ASW or Ca{dollar}sp{lcub}2+{rcub}{dollar} chelated ASW, whether the tissues were fresh of had undergone cell lysis via freeze-thawing. Oscillatory shear tests revealed the shear stiffness (G*) and the relative damping (tan{dollar}delta{dollar}) of the tissue which were interpreted within the framework of a theoretical viscoelastic model. It is concluded that primarily elastic changes take place within the tissue as it stiffens, possibly due to bonds forming between elastic elements in the tissue.; Dissected pieces of dermis from the sea cucumber Parastichopus parvimensis adhered to each other after only two hours of contact, whether the cells in the tissues were intact or had been lysed. Lapshear tests showed that breaking stresses of adherent tissues reached approximately 0.5 kPa after 24 hours of contact. Furthermore, dermal allografts were incorporated into the live recipient individuals without any external pressures, sutures, or artificial gels to keep them in place. Dislodging the grafts after 24 hours of contact required shear stresses of approximately 14 kPa.