jellyfish - Daniel Bar-On - 07112011
A jellyfish on Gordon beach in Tel Aviv this past summer. Photo by Daniel Bar-On
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Sea creatures that attack their prey by means of poison may at times use two mechanisms to do so, according to new research conducted by Tel Aviv University.

According to the research, led by Dr. Yehu Moran of TAU's Department of Plant Sciences, some sea anemones do not merely sting their prey and inject them with a toxic substance, but use a gland next to the stinging cells, called the ectodermal gland, to increase the intensity of the attack by also excreting venom into the water.

This discovery could explain why many bathers on Israel's beaches suffer irritation from jellyfish even when they haven't actually been stung - the toxins remain in the water because they've been excreted into the water directly.

Results of the research have just been published in the British journal, Proceedings of the Royal Society. Scientists from the University of Vienna and Germany's Heidelberg University were parties to the study.

According to Moran, sea anemones are part of the phylum known as Cnidaria, which includes jellyfish and coral. These marine creatures are carnivores that use venom to paralyze their prey. Some are known as particularly versatile and successful, including the jellyfish found off Israel's shores that have been reproducing at a rapid rate in recent years.

For over 100 years, scientists assumed that the toxins making up the Cnidarians' venom were manufactured within the special stinging cells called nematocytes, which acted like small hypodermic needles that introduce the poison into the body of the prey.

"Our research proved that the theory of venom injection that appears in all the zoology books is not accurate," Moran said. "We used a type of sea anemone known as the starfish, which is a North American species that can be grown in the lab and genetically engineered, and whose toxins can be identified by antibodies."

The researchers used the antibodies to locate exactly where on the starfish's body the toxins were being produced; and they were surprised to discover that they were being manufactured in glands situated near the stinging cells.

"During the hunt, the gland excretes the toxins into the water. This proved to be true for other sea anemones and could also be true for other Cnidarians as well," Moran noted.

The venom is then pushed into the prey's body via the stinging cells.

There are some sea anemones, including the snakelocks anemone, which is common to Israel, that produces toxins both in its stinging cells and in the adjacent glands, making its attack especially lethal.