Injury in animals
Injury in animals is damage to the body caused by wounding, change in pressure, heat or cold, chemical substances, venoms and biotoxins. Injury prompts an inflammatory response in many taxa of animals; this prompts wound healing, which may be rapid, as in the Cnidaria.
Causes
to animals including humans can be caused by wounding, change in pressure, heat or cold, chemical substances, venoms and biotoxins. Such damage may result from attempted predation, territorial fights, falls, and abiotic factors.Human activities such as trawling can cause wound injury to a high proportion of seabed invertebrates; a study of a Nephrops lobster fishery found that all the discarded Ophiura ophiura brittlestars were injured, along with 57% of the Munida rugosa squat lobsters and 56% of the Astropecten irregularis starfish. Species with stronger shells such as scallops were less often injured. A study of beam trawling in contrast found survival rates over 75% for bottom-living invertebrates.
Effects
Injury causes multiple effects at different biological levels from molecular and cellular to physiological, organismal, behavioural, and ecological. These include such harmful effects as direct damage to cells and tissues; loss of energy reserves; stress responses and changes to immune function; defensive behaviour; and reduced ability to move, feed, reproduce, and compete. In addition, injury sets off a chain of responses that tend to restore structure and function.Immune responses
The tissues of many animals respond to injury with inflammation, resulting in repair of the wound. Inflammation occurs in many taxa, but the nature of the response varies widely. In Hydra, a cnidarian, damage to the area around the mouth is fully healed within 20 minutes.Animals in several phyla, including annelids, arthropods, cnidaria, molluscs, nematodes, and vertebrates are able to produce antimicrobial peptides to fight off infection following an injury.
Wound occlusion
Many animals are able to block off the area around an injury rapidly, by coagulating their blood or body fluid. Invertebrates with hydrostatic skeletons are unable to move without internal fluid under pressure, while those with an open circulation quickly die from loss of body fluid. In addition, open wounds allow bacteria to enter the body. The invertebrate coagulation system is comparable with the innate immune system of vertebrates.Wound healing
In arthropods such as insects, wound healing following injury and coagulation of body fluid involves a process of melanisation of the scab, migration of cells to the scab area, and a degree of repair of the cuticle, in locusts restoring it to 2/3 of its original strength.Several vertebrates including lizards and salamanders shed their tails (autotomy) when attacked by a predator, especially if the tail is grasped, giving the animal a chance to escape. The tail is at least partially regrown over a period of weeks or months.