Dollar larvae are cloned to deceive the enemy

In nature there are many creatures trying to make their bodies become as big as possible to threaten their enemies. But sand dollar larvae have a different strategy to avoid being eaten by enemies like changing a dollar into many small coins.

Biologists from Washington University have discovered that 4-day-old sand dollar larvae have produced clones for themselves within 24 hours of exposure to fish mucus - a sign of enemies. is approaching. The cloning process creates new larvae smaller, while the original larvae also become smaller than the original.

According to Dawn Vaughn, a biology student who is pursuing a doctorate at the Friday Harbor laboratory at the University of Washington - the phenomenon is that the larvae react to the threat of enemies in general, not necessarily. Reaction to the immediate attack of predators. This process causes the initial larvae to shrink from about 300 microns (about 1/100 of an inch) to half that size (150 micrometers). The newly created larvae are even smaller.

Vaughn, the lead author of the paper, explaining in the March 14 issue of Science, said: ' We think that by reducing the size, the larvae can reduce their ability to be exposed in the eyes of the enemy. ' .

The sand dollar larvae are cloned.
(Photo: Dawn Vaugh)

The larvae phenomenon has previously appeared in echinoderms, including 7000 species of sea creatures including starfish, sea urchins and sand dollars. However, this is the first time that larval cloning has been seen as a means of survival in order to evade enemies.

The larvae of the sand dollar Dendraster excentricus float along the plankton in different water levels, collecting food to grow gradually. After 6 weeks, the larvae reach 3/100 inch size and settle down on the continental shelf to complete the mature growth process.

But when floating in the ocean, the larvae are not agile, the mortality rate is very high, they are also very easy to bait fish. Vaughn exposed 4-day-old larvae to fish's mucus to see how they responded to the enemy's threat.

"We do not know how they will react, or even if they react," she said.

Within 24 hours, the larvae produced clones then gradually separated to form new larvae much smaller than the original larvae. The original larvae were basically reduced in size, about half of their original size. The larvae not exposed to the mucus of fish are not cloned.

Vaughn argues that cloning can be an adaptive response that helps an organism survive in some form if an enemy threatens . This trick will succeed if only 1 or two larvae created from clones can survive.

She added: 'So, if both the original larva and the cloned larvae survive, it would be great. As a result, there will be 2 identical copies'.

Vaughn also stressed that reducing the size during a cloning process could affect the later survival of the sand dollar. In many species, large size reduces the ability to hunt. The sand dollars when undergoing a cloning process will be smaller than the non-clones when they settle on the ocean floor. Scientists are still unclear whether it makes them weaker than the enemy. Vaughn also plans to study this issue in her next topics.

She said: 'With this point, we think it is a compromise. If they don't avoid the enemy at first, they can't get down to the ocean floor. ' The co-author of the study is Richard Strathmann, a University of Washington biology professor and Vaugh's advisor. The research was funded by the National Science Foundation and Friday Harbor laboratory.

Vaughn believes that the response of sand dollar larvae does not seem to depend on the fish that secrete mucus. Instead, these larvae react to the breakdown of mucus due to the action of bacteria and treat it as an enemy. She added: "The sand dollar species can also react to a fish that has no intention of eating them."