Range: Marine waters worldwide

Habitat: Shallow waters to depths beyond 3.5 miles (5,600m)

Size: Average 2 inches (5cm) across, up to 5 inches (13cm)

Diet: Krill, copepods, siphonophores, and other planktonic organisms

Threats: Sea turtles, sea slugs, anemones, and more

Lifespan: A year to decades depending on the life stage

Transcript:

Today on Animal Fact Files we’re discussing crown jellyfish. Crown jellyfish get their common name because the medusae, or adult stage, have a groove in their bell with frilly edges and curly tentacles giving their body a royal appearance. There are a few different families in this order. Some are called helmet jellyfish and others are known as thimble jellyfish. The thimble jellyfish, for example, coexists with symbiotic algae that give them nutrients as well as a greenish yellow hue. And purply helmet jellyfish can't handle light or else they'll burn to a crisp in an unfortunate bout of sunburn. Others are red in color which helps them fade away into the depths of the ocean. They can also light up! These jellyfish are bioluminescent.

Crown jellyfish let out blue-green colors on contact. It's believed this helps deter predators who might find a mouthful of the jellyfish's stinging tentacles distasteful. Still, some animals eat them and these include fish, sea turtles, sea anemones, crustaceans like shrimp, sea spiders, as well as sea slugs who may steal the stinging cells of the crown jellyfish to use as their own! If their light isn’t enough to deter an attack, the jellyfish may also leave behind bits of their body to get away. Crowned jellyfish also use their bioluminescence to lure prey in. In fact, simulations of the crowned jellyfish’s light was used by scientists to help capture footage of a giant squid! Of course, it was the distress flashing that drew the giant squid in. Crowned jellyfish eat copepods, krill, siphonophores, and other planktonic organisms. These are caught on their tentacles and drawn to the mouth for consumption.

Crowned jellyfish are relatively small. Most are less than two inches (5cm) across their bell, though the largest species can reach about five inches (13cm) across. They could easily fit in the palm of a person's hand, though this wouldn't be advised as they do sting. In fact, in large numbers as larvae they're known to cause sun bather's eruption, a skin rash caused by their sting!

Crown jellyfish life in oceans around the world and ride on oceanic currents. Some species dwell in the midnight zone of the ocean while others stick to shallow water. Some species alternate between the two habitats. They can reach depths beyond three and a half miles (5600m) and are known from warm tropical waters to icy fjords.

Little is known about the life cycle of these jellyfish, though in laboratory settings they developed quickly - from just a few millimeters to about the size of a dime in just a few weeks time. They begin life as an egg. Eggs may be fertilized internally or externally, though it's not always known for each species. The male may hold the female and deliver sperm to her through their mouths, or they may release their gametes at the same time where they meet in the water column. They may follow the pattern of other stinging jellyfish as shown here where the larvae hatch from eggs and settle as a polyp that reproduces asexually, or they may develop directly skipping a sessile polyp stage and reaching the adult stage after just three months time. Crown jellyfish species that have a polyp stage form a citonous tube in which the polyp lives and may remain this way for years, possibly decades. So even their lifespan is dependent on which part of their lifecycle they're living and what species they are! It can be a few short months to many, many years!

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