Creature of the Month: Pelagia noctiluca
By: Anna Coffaro, UHM MOP Student

The month of March heralds a new creature feature, and we are excited to be spotlighting the purple-striped jelly! Otherwise known as “the mauve stinger” or Pelagia noctiluca, this species is considered to be a true jellyfish, or part of the class Scyphozoa, because of its exclusivity to marine environments, and similarly to other cnidarians, its radial symmetry. P. noctiluca typically inhabits the tropical and temperate waters of the Mediterranean and Red Seas, as well as the Atlantic Ocean, but has also more rarely been sighted in warm waters of the Pacific Ocean, including off the coasts of Hawaiʻi!

This incredible invertebrate can be distinguished by its pink and purple coloration, and is adorned with stripes of magenta and sanguine spots which contain stinging cells called nematocysts. They are truly stunning to look at, resembling gestural, dangling Fuschia flowers, and are somehow even more remarkable when they illuminate. Yes, these purple jellies can really glow in the dark! In fact, their name in German colloquially translates to “night light” for a scientific reason.

Looking more closely at the Latin origins of P. noctiluca, its nomenclature indicates that it is an open ocean (“pelagia”) and night-dwelling (“noct”) light-producer (“luc”), meaning that these jellies have the ability to bioluminesce, or produce light, naturally. While their bioluminescence is known as a response to motion disturbance, the chemistry of the jellies’ phosphorescence continues to be researched by scientists in the biomedical field, as their fluorescent proteins could possibly be useful in genetic studies pertaining to human protein movement or gene expression.

P. noctiluca, though academically valuable in the controlled settings of a lab, is unfortunately notorious for scaring away tourists from beaches, especially in the Mediterranean region where it is known to form large blooms. As planktonic creatures that float adrift in the water column, they often form swimming aggregations, or shoals, that can extend up to 45 kilometers in length and involve thousands of jellyfish the closer they drift inshore! Drifting is easy for purple striped jellies, because their pulsating movements are restrained to a mostly vertical range of motion. Vertical migration patterns can thus be attributed to these pulsations, as well as changes in currents and search for food.

Mauve stingers are carnivorous and typically consume zooplankton, other jellyfish, small fish, crustaceans, and eggs of other marine animals. For creatures without any organs, including a brain, one might wonder how catching these prey is possible! But P. noctiluca is adapted smartly! The umbrella-like mass of this species is bell-shaped and frilly-edged, strung with eight flexible, stinging tentacles and four “oral arms,” or lobes hanging down from the mouth. These tentacles wield the previously mentioned “nematocysts,” which contain immobilizing toxins and barbed filaments for trapping prey. This is the same machinery that can cause venomous, painful stings to humans! Most cases of these stings will normally result in a whip-like scar across the body, but in some rare allergic reactions, life-threatening conditions, such as anaphylaxis, can occur. But humans shouldn’t worry too much, because thankfully, the dense swarms and colorful beauty of P. noctiluca make them highly visible, and therefore allow people to clear the area upon sighting. Beauty is pain, as they say!