This five-inch-long sea creature looks like it belongs in a “Star Wars” movie as it wiggles through the dark night sea as if it was in deep space. The feeling of doing a night dive in Hanalei Bay on a full moon with hundreds of these crazy-looking creatures wiggling all around you is hard to explain. It is like laying in a bathtub full of centipedes that are crawling quickly in every direction with the moon making them look like they glow in the dark!
The fireworm breeding event only happens a few times a year in the summer on a full moon when the sea is super calm. These colorful marine polychaete worms are made up of many segments that have toxic stinging bristles that can break off in human skin causing itching and burning that can last for hours. Their Hawaiian name is ‘aha huluhulu, which means “hairy cord.” They are called fireworms because if you touch one it feels like you just stuck your hand into a fire.
It is good that swimmers and divers almost never see these sea creatures as they may not ever want to go back into the water if they knew how many of them live right below on the coral reef. Fireworms are very common but they usually live under rocks or deep in the cracks in the reef and only rarely do they come out into the open to breed. Within one hour in the middle of Hanalei Bay at night I shot video of hundreds of these worms free swimming in every direction glowing red and gold in the moonlight. They had no interest in harming me as they were just busy making baby fireworms.
The fireworms are predators and often are found crawling on the backs of the large crown-of-thorns starfish where they will enter the sea star through an open wound to eat the star from the inside out. The big fireworms in Hanalei Bay were up to six inches long but most of the fireworms are quite tiny and they seem to vary in color and shape on each of the Hawaiian Islands. Not much is known about this elusive creature but last summer in our Coral Reef Kids Camp for our non-profit Reef Guardians Hawaii we looked at some sea stars under the microscope and they were just covered with tiny fireworms!
You can see ‘aha huluhulu in action up on my underwater educational web page at www.underwater2web.com in my movie “The World’s Guide to Hawaiian Reef Creatures,” and also follow my marine life Instagram post at terry.lilley.
Terry Lilley is a marine biologist living in Hanalei and co-founder of Reef Guardians Hawai‘i, a nonprofit on a mission to provide education and resources to protect the coral reef. To donate to Reef Guardians Hawai‘i go to www.reefguardianshawaii.org.