Shore Scene: Marine Menace


By Mia Davidson and Jan Sattler


The Purple-Striped Jelly
The Purple-Striped Jelly

Before dinosaurs roamed the earth, sea jellies drifted in the oceans. As a member of one of the oldest phylum of animals found on earth today (over 600 million years old), unlike other creatures that have evolved or become extinct, jellies haven’t needed to change. The purple-striped jelly (Chrysaora colorata) is a species of jelly with a limited range off the coast of California. In Laguna, they tend to be found in the summer months when the water temperature warms up. A gelatinous invertebrate (animal without a backbone), the radially symmetrical purple-striped jelly lacks a brain and has a very simple nervous system that only responds to light, odor and other limited stimuli.

It is up to three feet in diameter with a milky-white transparent umbrella-shaped body called a bell with 16 dark purple stripes radiating out from a purple ring at the center of the bell.  Although the bells are buoyant and pulse to propel the jelly vertically in the ocean, they travel long distances passively riding ocean currents. Along the margins and trailing from the bell is a fringe of eight long tentacles that are used for feeding and defense and four frilly oral arms extending from the center of the bell. The oral arms are dark in color and several meters long when they are young. As the jellies mature, the tentacles and oral arms tend to become pale, thicker and shorter.  We tend to see more mature jellies in Laguna Beach.

Purple-striped jellies are carnivorous (meat eaters), feeding on zooplankton, copepods (tiny crustaceans), small fish, salps and other marine organisms. Their mouth is located in the center of the underside of the bell. When feeding, prey come in contact with the venomous tentacles, covered with millions of harpoon-like stinging cells called nematocysts that stun, paralyze and sometimes kill the victims. Prey is then brought by the oral arms up to the mouth where it is consumed. Predators that feed on the jelly include Mola mola (ocean sunfish), turtles, and other fish that seem to be immune to the toxic venom. In addition, the juvenile slender crab (Cancer gracilis) can often be found symbiotically living on and in the jelly until dropping off to live independently on the bottom of the ocean.

Population studies are currently underway because in recent decades there has been an increase in abundance and territory, and a shift in distribution of jellies. As summer arrives, we will be seeing more of them in the waters off Laguna.

Jelly sting symptoms include stinging, pain, itching, rash and welts. If you are stung by a jelly, contact the lifeguard.

A general guide is get out of the water, remove the tentacles and wash with seawater to deactivate the stinging cells. Do not wash with fresh water because it can cause reactivation. If an allergic reaction such as nausea, dizziness or difficulty breathing starts, call 911. Rinsing with acetic acid (vinegar) for 15 to 30 minutes will stop further release of the toxins. Popular myth suggests urinating on the sting relieves pain. Unfortunately, urine is either acidic or alkaline depending on what has been recently consumed and may ultimately not be the best treatment.


Residents Mia Davidson and Jan Sattler are year-round ocean swimmers and board members of Laguna Ocean Foundation, which encourages ocean protection.

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