Polarised light micrograph of the skin of the sea cucumber, Synapta, (Echinodermata, Holothuroidea), showing paired spicules referred to as plates and anchors'. The sharp spikes of the anchors may act as a deterrent to potential predators. This theory is born out by the fact that the anchors' in the edible sea cucumber have a similar appearance to the plates' and do not have sharp points. Magnification: x136 at 10cm wide.