Jellyfish with ‘grenades’
If you’re scared of jellyfish, you’ll definitely want to avoid Cassiopea xamachana, a species found in the Caribbean, the Gulf of Mexico, and the warmer parts of the Western Atlantic. Scientists have discovered that these so-called upside-down jellyfish emit tiny balls of mucus-surrounded cells that swim around stinging anything in their path. Lead author Cheryl Ames, from Tohoku University in Japan, says these “self-propelled microscopic grenades” are designed to stun and kill small fish and other prey; once the target is neutralized, the jellyfish sucks it in by pulsating. “It’s a real evolutionary novelty,” Ames tells New Scientist. She and her team put brine shrimp into a tank with the jellyfish. The jellies released their stinging proxies, named cassiosomes, which killed the brine shrimp in under a minute. Cassiosomes can survive outside their hosts for up to 10 days in the lab, likely because the algae within them generates energy through photosynthesis. The discovery explains why divers have reported feeling “stinging water” in the vicinity of upside-down jellyfish.
Science Source, Edwin Cadena/University of Zurich, Minden Pictures ■