Tag Archives: crab

Clinger crabs are members of wind drift community

Published February 3, 2018 in the
“Ocean Watch” column, Honolulu Star-Advertiser ©2018 Susan Scott

A pregnant clinger crab fits in the palm of a hand. ©2018 Susan Scott

When the wind is howling and the surf is busy salting everything in my house, I hit the beach. Those aren’t the best conditions for soaking up sun or playing in the water, but for us avid walkers it’s prime time for finding marine treasures.

Because I make mosaics from litter I find in albatross nests at Midway and on beaches in the Pacific, my gems are usually bits and pieces of colored plastic. Last week, though, my prize was alive. When I got home and dumped my junk in a colander for rinsing, there on a barnacle- and algae-encrusted toy truck clung an offshore crab.

This species of crab is a member of the wind drift community, a diverse bunch of animals that float on the surface eating anything they run into, including each other. They’re called wind drifters because they are indeed adrift, their direction and speed controlled entirely by current, wind and waves.

Common jelly-type critters floating offshore are Portuguese men-of-war (Physalia), by-the-wind sailors (Velella) and blue buttons (Porpita).

You might not expect snails to be members of this community, but two species are common: violet snails (Janthina) and snails-without-shells called nudibranchs (Glaucus).

Another unlikely offshore mariner is a little crab I call the clinger crab because it doesn’t have its own float system, as the others do, nor does it swim. Rather, the clinger crab spends its life hanging onto a piece of wood or debris. (I can’t find a common or scientific name for this little crab. If you have one, please write.)

Clinger crabs are about the size of a quarter and come in shades of blue or brown, depending on which object they’ve chosen to call home. This clinger was brown, a perfect match to the brown seaweed that grew on its floating toy.

You can tell a male crab from a female by the flap on the center of its underside. Narrow is male; females have wide flaps that hold their eggs.

When I examined my crab’s belly, I discovered, with some excitement, that I had a female with eggs. Hoping to raise some baby clingers, I rushed back to the ocean for a bucket of water, half filled my rescue tank and gave my pregnant crab her tiny truck, a pile of rocks to reach it and some frozen brine shrimp for energy.

A pregnant clinger crab fits in the palm of a hand. The eggs are the yellow mass under the flap. ©2018 Susan Scott

Alas, a tank being the utter opposite of her natural habitat, she did not survive. Even so, I was happy to have had a wind drift pet, even if just for a day.

During my beach walks I sometimes forget to bring a bag, and have to go trash-can diving for containers. Failing at both those things last week, I called Craig to come get me in the car, because I couldn’t walk home. After stuffing my pockets full of flotsam, I then filled my Crocs.

I have lived in Hawaii long enough that I sometimes think it’s too cold to go snorkeling. Never, ever, though, is it too cold for beachcombing.

Naming sea creatures sometimes had odd results

Published March 7, 2016 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2016 Susan Scott
 A ghost crab has a turtle hatchling caught in its pincers. The tiny turtles must pass the crabs to make it to the ocean. ©2016 Susan Scott

A ghost crab has a turtle hatchling caught in its pincers. The tiny turtles must pass the crabs to make it to the ocean. ©2016 Susan Scott

In my Feb. 22 column, I wondered about the origin of the odd fish name “Moorish idol.” About that, Honolulu reader Ned Conklin emailed an excerpt from a 2007 book, “When Languages Die,” by K. David Harrison (Oxford University Press).

The author writes that early European explorers and naturalists disregarded native names for plants and animals, and instead gave them English names relating to something the species reminded them of back home. For instance, on Capt. James Cook’s third voyage, 1776-80, the naturalist aboard named a damselfish with stripes a sergeant, because a British sergeant’s uniform had stripes.

Scientists later learned that the sergeant fish was actually three species. Fish namers stuck with the historic term “sergeant” but added other words to tell the species apart. Hawaii’s endemic sergeant became the Hawaiian sergeant. The damselfish with wider and longer stripes and a wide range is the Indo-Pacific sergeant. And the fish with stripes that lighten and darken, and that has a black spot on its rear, was named the blackspot sergeant.

As to the Moorish idol, Harrison writes, “A fish with a dark-colored face spotted by Capt. Cook’s crew off Hawaii received the exotic name ‘Moorish idol.’”

Another reader, Utah biologist Robert Schmidt, emailed about my Feb. 8 column on ghost crabs. Robert thought he read that ghost crabs blinded or maimed turtle hatchlings before pulling them into their burrows, thereby preventing the hatchlings from escaping. He can’t find a reference to these behaviors and asked, “Do you know anything about this?”

Only what I saw. On Tern Island I watched turtle hatchlings run the ghost crab gauntlet in their race to the ocean. If the crab got hold of only one flipper, the turtle usually got away. But when the crab got a flipper in each of its two pincers the turtle couldn’t escape.

I rescued several hatchlings before they got dragged down a crab hole, and they ran away seemingly uninjured. But I got there too late for some. Lifting one turtle from a crab hole entrance, I found its head missing and the entire body hollowed out. Efficient, those crabs.

Besides being occasional crab food, turtle hatchlings are pupu for seabirds from above and fish from below. Only about 1 hatched turtle in 1,000 makes it to adulthood.

On the bright side, healthy adult turtles are common in Oahu waters, as are ghost crabs performing their daily beach cleanups and sand aeration.

Ned and Robert, thanks for the interesting emails. But I still don’t understand why a naturalist linked the term “Moorish” with “idol.” An exotic name indeed.

7-11 crab gets its name from its array of spots

Published September 15, 2014 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2014 Susan Scott

This 7-11 crab was found in a Waia­lua tide pool. The crab is named for its spots — 11 total, with seven in front and on top, and four in back. ©2014 Susan Scott

I recently received an email with the subject “Crab on V-land beach.” (V-land, or Velzyland, is a North Shore surf spot.) Reader Bill Quinlan wrote, “I have attached two photos of a dead crab we found this afternoon. A lady we showed the crab to said she was from Kauai and they call that type of crab a 7-11 crab. She did not explain why.”

Oahu people call them 7-11 crabs, too. The striking species ranges throughout the Indian and Pacific Oceans on reefs from tide pools to 50 or so feet deep. Other names are spotted reef crab and dark finger coral crab. In Hawaii, though, and for many people around the world, it’s a 7-11 crab.

A common story about the unusual name is that it’s a reference to the crab’s maroon spots. Although some individuals have more, most crabs have seven spots across the shell’s front and top, and four across the lower back, totaling 11.

This logic would make it a 7-4 crab, but the words “seven-11” have more of a ring. A convenience store chain called Tot’m liked the rhyming words, as well.

In 1946 the name was changed to 7-Eleven to reflect its long (for the ’40s) operating hours, 7 a.m. to 11 p.m.

Two days after Bill’s email, I received another 7-11 crab email from my friend Mary. “This morning I found the remnants of a huge 7-11 crab on the reef at Ala Moana. His shell was about 8 inches across. First one I ever saw, living or dead. I understand from other locals there that about two years ago a lot of juveniles washed ashore. What an interesting world!”

It sure is. For unknown reasons, in July 2012 thousands of blueberry-size creatures washed ashore on Oahu. Being in their larval stage, the creatures didn’t look much like adult 7-11 crabs, but that was an expert’s conclusion. Check out the baby crabs at bit.ly/1CKYqFA.

I also found a 7-11 crab, but it was alive and well in a Waia­lua tide pool. After I took this picture, I put the little crab back in its pool to grow up and make more crabs. In Singapore the species is considered threatened due to pollution and over-collecting.

Seven-11 crabs grow to about 6 inches across, so the crab Mary found was as big as they get. She took it home to let the ants clean it outdoors before giving it a place of honor in the house.

Bill considered his crab a gem, too. “My wife, Rita, and I have been dive buddies for almost 40 years and have dived in numerous countries,” he wrote. “We both feel this is the most special crab we have ever seen. A graphic designer couldn’t come up with a design anywhere close to as good.”

I agree. A certain convenience store would do well to make this crab its logo.


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

©2014 Susan Scott