The growth of new tissues or organs to replace those lost or damaged by injury. Many plants can regenerate a complete plant from a shoot segment or a single leaf, this being the basis of many horticultural propagation methods (see cutting). The capacity for regeneration in animals is less marked, although some cnidarians and annelids reproduce asexually by fragmentation followed by regeneration. Some planarians and sponges can regenerate whole organisms from small pieces, and crustaceans (e.g. crabs), echinoderms (e.g. brittlestars), and some reptiles and amphibians can grow new limbs or tails (see autotomy), but in mammals regeneration is largely restricted to wound healing and, in certain cases, regrowth of damaged nerve fibres.