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AnimalsNatureOceansScience

Rare Jellyfish — Black Jellyfish Species Swarming In Southern California

A rare jellyfish species — Chrysaora achlyos, also known as the black stinging jellyfish — recently made an appearance at a popular Southern California beach. The rare black jellyfish was seen in very large numbers and apparently left quite a few people with stings — not surprisingly when you consider that the tentacles of the species can grow to be up to 30 feet long.

Image Credit: Screen Capture
Image Credit: Screen Capture

Jellyfish numbers — and also the frequency of large blooms — have been climbing in recent years, making occurrences such as this more and more likely in the coming years. Previously rare species of jellyfish have been becoming common, overall numbers have been growing, and enormous blooms covering huge tracts of ocean, have all been becoming more and more common during the last 30 or so years — largely as a result of the overfishing of ecologically important species. With further overfishing jellyfish are expected to become more and more common.

The rare black jellyfish species that recently made its appearance at Laguna Beach may not be so rare within only a couple of years — it’s an “interesting” species though, so large blooms may be quite a nuisance.


Chrysaora achlyos — also known as the Black Sea nettle, the black jellyfish, or the Sarlacc jellyfish — is a species of rare jellyfish that is found throughout portions of the Pacific Ocean. The species current range is estimated to be from somewhere around Monterey Bay in the north, to Baja California and Mexico in the south. They have spotted as far north as British Columbia though.

They can grow to be quite enormous — with a bell diameter that is over a meter long, oral arms more than 5 or 6 meters long, and tentacles over 9 meters long. The species — as its name implies — is of course a very distinctive opaque dark purplish or black color.

Image Credit: Black Sea Nettle via Flickr CC
Image Credit: Black Sea Nettle via Flickr CC

The jellyfish is also of course a stinging one — in humans the toxins injected are nonlethal, but should cause a painful stinging sensation for somewhere around 40 minutes or so.

Wikipedia provides a bit of background on the species:

Each nettle tentacle is coated with thousands of microscopic nematocysts; in turn, every individual nematocyst has a “trigger” (cnidocil) paired with a capsule containing a coiled stinging filament. Upon contact, the cnidocil will immediately initiate a process which ejects the venom-coated filament from its capsule and into the target. This will inject toxins capable of killing smaller prey or stunning perceived predators. In addition, the black sea nettles stomach is lined with a fibrous network of vessels that attach themselves to a swallowed victim and darkmaws for quick digestion or breaking apart large prey, though the maws will close when exposed to bright lights, hence their name. Marginal sense organs are spaced around the bell margin after every set of 3 tentacles, for a total of 8.

Black sea nettles are carnivorous. They generally feed on zooplankton and other jellyfish. Nettles immobilize and obtain their prey using their stinging tentacles.

The species was actually only very recently scientifically described, or “discovered” — it’s actually the largest invertebrate to have been “discovered” in all of the20th century. While they have typically only been rarely seen, large blooms of the species have been seen several times — in 1989, 1999, and 2010. Somewhat interestingly, the blooms seem to coincide with large blooms of red tides.




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