Pretending to be dead is an effective self-defense strategy adopted by young fire ant workers under attack from neighboring colonies. This tactic makes them four times more likely to survive aggression than older workers who fight back. As a result, these young workers are able to contribute to brood care and colony growth to ensure the survival and fitness of their queen. These findings were made by Dr. Deby Cassill from the Biology Department at USF Petersburg in Florida and her team from USF Tampa in Florida. Feigning death is a method of self-defense used by a wide range of species - mammals, birds, amphibians, lizards, dragonflies, and beetles - in response to threats by predators. Cassill and colleagues studied the death feigning behavior of the highly territorial fire ant, Solenopsis invicta, during attacks by ants from neighboring colonies in the laboratory. They showed that the age of the victims was a significant predictor of their response to their aggressors. Days-old workers responded to the attacks by pretending to be dead. Weeks-old workers responded by fleeing and months-old workers fought back. By feigning death, young workers were four times more likely to survive the attack than were the older workers who ran away or fought back. The researchers also found that sustained movement from the victims was necessary to trigger a physical attack – known as a kinetic cue. The authors offer two possible explanations for the death feigning behavior of the young fire ants. The external skeleton of days-old workers is relatively soft. Not only are these young workers prone to injury, they are ineffective in battle as their mandibles and stingers are not sufficiently hardened to penetrate the external skeleton of their aggressors. It may be that young workers pretend to be dead to avoid physical aggression at a time when they are vulnerable to injury and certain to fail. Another explanation is that by feigning death, young valuable workers are spared, allowing them to increase colony growth, which is essential to the survival and fitness of the colony queen. via springer.com
Mechanical pumps to give failing hearts a boost were originally developed as temporary measures for patients awaiting a heart transplant. But as the technology has improved, these ventricular assist devices commonly operate in patients for years, including in former vice-president Dick Cheney, whose implant this month celebrates its one-year anniversary. Prolonged use, however, has its own problems. The power cord that protrudes through the patient's belly is cumbersome and prone to infection over time. Infections occur in close to 40 percent of patients, are the leading cause of rehospitalization, and can be fatal. Researchers at the University of Washington and the University of Pittsburgh Medical Center have tested a wireless power system for ventricular assist devices. They recently presented the work in Washington, D.C. at the American Society for Artificial Internal Organs annual meeting, where it received the Willem Kolff/Donald B. Olsen Award for most promising research in
Comments