Reading aloud Like a pair of rabbit ears, two strange pharyngeal tentacles stand off their heads - this has earned the representatives of the so-called Breitfußschnecken the German name Seehasen. The bizarre marine animals can come up with yet another curious properties. When threatened, they emit warfare agents: a red substance to confuse enemies, much like cuttlefish, and a whitish secretion called Opalin. The effect of the colorful ink was already clear, but what about the whitish secretion was unknown. However, US researchers suspected that this substance interferes with the perception of attackers - they could now prove this by experiments. Charles Derby of Georgia State University and his colleagues performed their experiments with lobsters. These crustaceans are known to occasionally try to nibble on sea hares. For their experiments, the researchers took a few opalin from the sea snails and tested the reactions of lobsters to this substance. They stroked the experimental animals directly to the antennas. The crustaceans have sensory organs that can detect dissolved substances in the water - the antennas, so to speak, represent the noses of lobsters.

If it no longer smells delicious lobster from the prey

In order to investigate the reactions of the experimental animals, the researchers did not rely on visible behavior, but the stimuli were detected at an earlier stage: They implanted the lobes of electrodes in the nervous system to be able to document directly via its signals, if the animals took weather had. The attractant was an extract of shrimp. When lobsters perceive this "fragrance", they usually react very intensively - they are almost mouth-watering. The nerve reactions that the researchers were able to detect via the electrodes were correspondingly clear.

However, if they applied the opaline to the lobsters on the antennas, the appetite response to the shrimp extract did not materialize. Analysis of the composition of opaline and further experiments suggested that this effect is not due to anesthesia, but to a mechanical blockage by the sticky consistency of this substance. She sits down on the sensory organs and makes them inaccessible to underwater scents. Thus, a hungry lobster can no longer perceive a sea hares as a source of food and loses his interest in the prey animal, the scientists conclude. This gives enough time for the sluggish water snails to wander off and thus move out of the danger zone. display

Charles Derby (Georgia State University) et al .: J. Exp. Biol. 216, 1364-1372 © - Martin Vieweg


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