If a starfish loses an arm, you know it's too hot. This peculiar behavior is part of a surprising survival strategy, allowing the animal to endure in warmer environments than previously thought.

Ecologists initially believed that cold-blooded animals, known as thermostats, could only adapt to the temperature of their environment since they were unable to change their body temperature. However, Sylvain Pincebourde from the Institute of Insect Biology in Tours, France, and Eric Sanford from the University of California, Davis, USA, suspected that there might be more to it.

To unravel the truth, they collected 70 ochraceous starfish (Pisaster ochraceous) from the California coast and placed them in 10 tanks with temperatures ranging from 26 to 42 degrees Celsius. They used infrared cameras to monitor the starfish's body temperatures.

Their study confirmed that the starfish's body temperatures were not uniform but varied. The central disk's temperature was lower than that of the arms, with a difference of approximately 3 to 5 degrees Celsius. Sanford explained that if the central disk exceeded 35 degrees Celsius, the starfish would die since its vital organs would become unstable and cease to function properly.

However, the starfish's arms could tolerate these high temperatures for several days. Nevertheless, one arm would usually become soft and eventually detach.

The researchers are uncertain about how the starfish regulates the temperature of different body parts. One possibility is that the animals actively transfer heat to their arms, effectively dissipating it into the water due to the arms' larger surface area and smaller internal volume.

This mechanism may also explain why starfish exposed to higher temperatures for prolonged periods tend to lose one or both of their arms. By utilizing the arms as a heat sink, the starfish may damage them to an extent that cannot be repaired.

While starfish are known to regrow lost arms, this study is the first to suggest a link between arm loss and temperature regulation. Starfish play a crucial role as predators along the California coast, influencing the population of mussels and other similar organisms.

Consequently, any changes in the starfish population due to climate change could trigger a ripple effect throughout the food chain. Understanding how these animals respond to temperature fluctuations will aid ecologists in comprehending the impact of climate change on coastal ecosystems.

Mark Denny, a scientist from Stanford University, conducted research on the starfish's prey, mussels. He highlighted that these mussels prefer fewer starfish in their vicinity. The starfish's ability to survive in warm waters by losing their arms poses a threat to the mussels.

Gaining insights into how marine organisms adapt to warmer waters is of utmost importance, particularly as global temperatures continue to rise. This study may inspire further research on other key species using similar approaches, facilitating collaboration between physiologists and ecologists to better understand the effects of temperature changes on animal populations and community sizes.

The starfish's survival strategy of losing arms in response to excessive heat provides valuable insights into their ability to cope with warmer environments.

These findings have significant implications for understanding the impact of climate change on coastal ecosystems and highlight the complex interconnections between different species in these habitats. Continued research into the responses of marine organisms to temperature changes is crucial for developing effective conservation and management strategies in the face of ongoing global warming.