The researchers blindfolded the animals, causing them to react with an escape reflex. If the scientists repeated the darkening, the animals learned over time that the procedure is safe. Her escape reflex went out. The researchers observed that the crabs learned much faster when they were in salty water for a few days. Bernhard Crespi from the Simon Fraser University in Burnaby, Canada, can imagine that most of the crabs living on the beach benefit from this surge of intelligence, especially when they are looking for food or a partner in the sea.
Maldonaldo found elevated levels of angiotensin in crab brains. This protein regulates the water content of the body at different salinities. The researchers not only discovered angiotensin in the visual area of the brain, but also where the animal processes odors. The salt water may therefore have a far-reaching effect on the brain power of the crabs via angiotensin production.
Other researchers, however, see no connection here. Steve Morris of the University of South Australia at Adelaide notes that Chasmagnathus granultus lives in the tidal shores of the coasts, where salt levels fluctuate daily. The long "bathing times" of crabs in salt water in Maldonaldo's experiment are therefore exceedingly unrealistic. James McGaugh of the University of Irvine, California, points out that any pharmacological review of the theory is lacking. Only in this way, however, could it be shown that the elevated angiotensin concentrations are actually the result of the saltwater bath. (The Journal of Experimental Biology 203, 3369-3379, 2000)Joachim Schüring