Tag Archives: urchin

Snorklers see red with slate pencil sea urchins

Published July 8, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

A slate pencil sea urchin is tucked into a tight place for a daytime nap. This type of urchin can be found in the Indian and Pacific oceans. ©2017 Susan Scott

Last week when I arrived at one of my favorite snorkeling spots, I found fishermen lined up near the waterline. To avoid their hooks and lines, I had to enter the water far down the beach and swim in an area different from my usual.

It caused me to see red. Not red as in anger, but red as in scarlet.

The outer reef in this North Shore area takes a beating from the surf every winter, and is therefore riddled with cracks and crevices. Wedged tightly into one of the smaller holes, in about 3 feet of water, was a large, red slate pencil sea urchin.

Slate pencil urchins are found throughout the Indian and Pacific oceans, but they are only abundant in Hawaii’s clear shallow waters. Lucky us. In some island areas these sea urchins decorate the reef like glorious gaping flowers. To see some of Hawaii’s exquisite red sea urchin gardens, click here.

Slate pencil urchins have blunt, paddlelike spines that reminded someone of the chalk sticks people once used to write on slates. Unlike their cousins, the long-spined black sea urchins, or wana, the slate pencil’s blunt spines can’t pierce human skin.

Even so, for the sake of the animal, you don’t want to touch these red beauties. Covering each of the creature’s “pencils” is a thin layer of tissue that inhibits the growth of algae and other marine organisms. Handling these animals, even gently, can damage their natural protection.

At night the slate pencil sea urchin uses its suction-cup tube feet to walk around the reef, scraping up algae with its underside mouth. During the day the creature tucks into reef holes for rest and protection.

Really tucks in. Often the animal looks so crammed into the space with its paddlelike spines pointing every which way, it’s hard to imagine how the urchin got in there and, come dusk, how it will get out.

These creatures are more flexible than they look. The sea urchin can’t bend its spines, but can move them in most any direction because each is attached to the body with a movable ball-and-socket joint.

Red isn’t a common color on the reef. Because the sun’s red wavelength doesn’t penetrate water very far down, red looks red only in shallow water. At about 30 feet deep, red looks brown. Continue to 60 feet and below, and red turns black.

Most slate pencil sea urchins hang out on the top and sides of shallow reefs, displaying their stunning paddles for all to see.

I admit that I get grumpy about fishermen casting into shallow reef areas, because when their lines get stuck, the anglers cut them, leaving yards of monofilament to wrap around coral heads and strangle turtle flippers. This time, though, the shoreline anglers gave me a gift: a new place to see red.

Collector urchins munch up fast-growing invasive algae

Published November 24, 2014 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2014 Susan Scott

A collector urchin is dotted with items it has picked up. ©2014 Susan Scott

Who knew that a poky marine animal the size of a snow globe could do such a stellar job of fighting aliens?

The plodding heroes are collector urchins, a native species the state has been raising by the thousands and releasing in Kane­ohe Bay. There the sea urchins work like slow-motion Pac-Men, gobbling up weeds, the weeds in this case being three seaweed species gone to the dark side.

But we can’t blame the seaweeds. Industrial researchers brought the edible red algae, native to the Philippines and Malaysia, to Coconut Island in 1974 to raise for its rich carra­geenan content.

A nearly endless number of foods and household products contain carrageenan, a thickener. On the long list are toothpaste, ice cream, beer, shampoo, diet soda, pet food, milk, jam and medicines.

Red algae aquaculture failed as a business, but the hardy seaweeds escaped and went wild. One species can double in size in 15 to 30 days, growing to 6 feet tall with a 1-inch-diameter base and sprawling, finger-thick branches. The dense stalks shield the bay’s native corals from the sunlight they need to live.

To keep the seaweeds from destroying Kane­ohe Bay’s reefs, workers remove bulk weeds with a machine called the Super Sucker. Because bits of broken-off seaweed tips can quickly grow into mats, tens of thousands of algae-eating collector urchins are being released in the bay.

As vacuum cleaners of the reef, the urchins use hundreds of suction-cup feet to amble around, day and night, eating seaweed with a circle of five teeth at the center of their undersides. Following a Super Sucker session, the black whiskery creatures hoover their little hearts out.

Collector urchins are not the needle-sharp, long-spined sea urchins we call wana. Collectors, called hawae maoli in Hawaiian, are endearing little creatures with a touchable surface similar to a stiff hairbrush.

I have dozens of pictures of collector urchins because they wear silly hats, piling everything from rocks to plastic spoons to skeletons of their own babies on top of their round shells. Biologists think the animals’ hodgepodge collections act as shields from bright sun and might also disguise an urchin from fish and octopus predators. Whatever the reason, the results are adorable.

Our spheroid storm troopers might not have light sabers to battle plant aliens, but they’re making impressive progress with teeth and tube feet. May the Force be with them.


Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2014 Susan Scott

Wana spines offer refuge for tiny domino damselfish

Published October 14, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

Baby damselfish sheltering among the spines of each of these wana are black with white spots. ©2013 Susan Scott

Interesting, yes, because I have never seen a fish that looked like a pipefish or a trumpet fish hiding among wana spines. I have, however, seen lots of baby damselfish sheltering among those needlelike spines.

While snorkeling in about four feet of water, I spotted several long-spined sea urchins (wana in Hawaiian) with iridescent blue patterns so dazzling in the morning sun that I stopped to take their picture. Only after I downloaded the photos to my computer did I realize that a couple of “spines” had spots on them. Without realizing it, I had photographed two tiny domino damselfish.

The disklike, black-and-white-spotted damselfish that showed up in my picture are common in the South Pacific. Their common name is three-spot or domino damselfish.

Hawaii has its own similar species, called the Hawaiian domino damselfish or Hawaiian dascyllus (pronounced da-SILL-us). (Dascyllus is the scientific name of this damselfish group.)

Domino damselfish swim in small schools on the reefs of Hawaii, the South Pacific and Indian Ocean like perky poker chips, hovering in the water column as they eat passing plankton. The largest are about 4 inches in diameter; the smallest are thumbnail-size.

Juvenile domino damselfish are fun to play with. At the approach of a snorkeler, the entire school rushes into the folds of a branching coral head. First there are dozens of cute little fish in front of you; then there are none.

Looking into the coral’s arms, all you see are pairs of dark eyes peeking out. Hold still a moment and the curious fish venture out. Any fast movement, though, will again send them into hiding.

Domino damselfish will also take cover among crown-of-thorns starfish spines, bury themselves in sea anemone tentacles and seek protection between wana spines.

I don’t know which creature Gordy meant when he wrote that his fish looked like a sea urchin spine, but I think he might have seen a long, narrow shrimp commonly found on wana.

I’ve never spotted these shrimp or anything that looks like a pipefish among wana spines, but you can bet I’ll be looking more carefully in the future. Thanks, Gordy, for the heads-up.

Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2013 Susan Scott