Monthly Archives: July 2013

Beyond serpentine shape, eels and snakes not related

Published July 29, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

The snowflake moray eel morphs from female to male is it ages. ©2013 Susan Scott

Last week I received an email from a reader who went for an early morning swim in Kaneohe Bay. “I looked down and saw what looked like a dozen or so snakes on the floor, maybe 15 feet deep,” the unsigned note said. “Was I seeing things? Sorry, no pics. I just beat it back to the house that I am house-sitting this week.”

With no photo I can’t be sure of the identity of my reader’s “snakes.” but as Hawaii hosts no reef-dwelling sea snakes, my bet is it was a bunch of eels still out from a night of hunting.

Because eels are well adapted to hiding in cracks and holes in the reef, and usually search for fish and invertebrates at night, it’s hard to appreciate their numbers and diversity in Hawaii.

Island waters host 42 species of moray eels, second in number only to the wrasses (44). And there are more: snake eels, conger eels, garden eels, worm eels and spaghetti eels. To further muddy the identification waters, some morays are called snake morays, and a few form a family called false moray eels.

But don’t let the shape, names, spots or stripes fool you. All Hawaii’s eels, as well as all eels in the world, are fish. No relation to snakes. It’s just that the serpentine form works well in the ocean.

Because of their snaky appearance, fears and myths about eels abound. But eels are so amazing on their own, we don’t need to make stuff up. Here are some of my favorite eel facts:

» Moray eels usually swallow fish or crabs whole, but when a captured prey is too big, morays tie themselves in knots. The eel forms two loops around its body with its tail and jerks its head through the tightened knot. The motion either tears or flattens the prey into swallowing size.

» The snowflake moray has blunt cone-shaped teeth for crushing its favorite food, crabs and shrimp. This beautiful eel could be the poster child for the transgender community: It begins life female and later changes to male.

» The sharply pointed tails of snake eels are digging tools so efficient that the eels can cruise around tail-first beneath sand and sediment.

» Because some of Hawaii’s eel species bear stripes and spots, people often mistake them for sea snakes. They’re just, however, great pretenders. “Back off,” those colors warn. “I might be a snake.” For my house-sitting emailer, the mimicry worked.

I once witnessed an eel convention while swimming at dusk. After finding myself in the company of eight eels of several species, I too beat it back to my house. My rush, though, was to fetch my camera.

eels

Small Snowflake Eel – Hanauma Bay. ©2013 Scott R. Davis


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

©2013 Susan Scott

Dazzling iridescence earns this seaweed its nickname

Published July 22, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

Martensia fragilis glows blue and green. ©2013 Susan Scott

While snorkeling on the North Shore last week, I found myself surrounded by an organism flashing so much bling I felt I was swimming through Tiffany’s.

The ocean was flat, calm and clear as drinking water, and when the sun emerged from a cloud, the reef lit up like a thousand opals. Iridescent blues and greens glowed in the early morning rays, their hues dazzling in the gentle surge.

I pulled out my camera to record the spectacle, but there was no need for stealth or haste. The entity couldn’t swim away if it wanted to because it was rooted to rocks. The organism was a seaweed.

Back home, I downloaded my photos and opened a guide book called “Hawaiian Reef Plants,” a University of Hawaii Sea Grant publication, to learn the name of this extraordinary plant. That turned out to be easier said than done.

Although the book is nicely color-coded with the four main seaweed categories — blue-green, red, green and brown — my lustrous blue-and-green jewel was neither a blue-green nor a green seaweed. It’s a red.

Blame the confusion on evolution.

The most primitive marine plants are the blue-green algae, appearing on Earth 3.5 billion years ago. It seems logical that the other three evolved from there, but no. A primitive animal ate the blue-green plant and, rather than digest it, took advantage of its ability to make carbs from sunlight. This animal, then, is the ancestor of the green and red seaweeds.

The browns are unrelated to the other three, having evolved separately. You can see how different brown seaweeds are by the size of some species, such as kelps that form entire forests.

Color categories don’t always match seaweed colors in real life. A marine plant’s appearance depends on its reproductive state, pigment-masking cells, local conditions and other variables.

Seaweeds might look simple, but when it comes to studying them, nothing is simple. Take the Latin name of my glorious, glowing seaweed, Martensia fragilis. That’s all it’s called. This plant has no common English or Hawaiian names.

Up to 2 inches tall, the seaweed is native to Hawaii. It also grows in the warm Indian, Pacific and Western Atlantic oceans from tide pools to waters 150 feet deep. In shallow water and bright sunshine, this light-reflecting seaweed is an astonishing work of nature — so lovely, it made me want to give it a hug.

I can’t hug a seaweed with its species name meaning “fragile,” but I can call it something that reflects its beauty. To me, Martensia fragilis will always be the opal weed. Swimming through that patch of it made me happy to be alive.


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

©2013 Susan Scott

Similar slimy fishing forms mix up worm, snail identity

Published July 15, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

How do you tell a tube worm from a worm snail? Got a few hours?

That’s how long I spent reading last week after I wondered about these different marine invertebrates while sorting my underwater photos. After I read three invertebrate zoology textbooks, checked out a dozen Internet sites and looked through two underwater guides, I finally found a sentence regarding my question: “Vermetid (worm snail) tubes can be distinguished by their shiny white lining from tube worms, which have a dull lining.”

This made me laugh because I cannot see the insides of the tubes either in my pictures or on the reef. But I can see other parts of these unusual creatures, and after all that reading, the differences became clear.

nudi

A worm snail starts out life like most other snails, first as a drifting larva and later as a juvenile inside a tiny spiral shell. After settling down, a young worm snail glues its coiled shell to a rock, coral head or another shell. As the snail grows, the coils of its shell separate and spread out, often in a wavy tube or in spirals like a corkscrew.

Some worm snails settle together in a clump, their shells growing over and under one another in irregular shapes and directions like a mass of hard, hollow noodles. An unfurled shell gives the snail more surface area for attaching to its spot than if it remained in whorls.

The tubes of marine worms, however, nearly always remain hidden.

A worm snail feeds by casting from its opening a sticky mucus net that snares passing plankton. Periodically, the snail hauls in its net, eats the catch and sends out a new net.

It’s this fishing method that had me puzzled because some tube worms that build their tube homes inside coral heads, cracks and reef holes also make mucus nets to trap food.

My other photo is such a worm, casting out its net from its tube inside a living coral head.

nudi

Rather than discourage me, my long search for facts on tube worms and worm snails made me love marine biology more than ever. Where else could mucus be so much fun?


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

©2013 Susan Scott

Spanish dancer’s flare, eggs attract many devoted fans

Published July 8, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott

A rose is a rose is a rose — except when it’s the egg cluster of a Spanish dancer.

My recent column about that nudibranch and its roselike eggs generated some inspired email. About the lovely red or pink “flower,” a reader wrote, “I have seen the same thing and it looked like someone cut chiffon rosettes off an old-fashioned dress and glued them to the reef. I couldn’t figure out what in the heck they were. Now I know! Thank you.”

And thank you, Steph­a­nie, for describing so elegantly one of the world’s prettiest clutches of eggs.

Biologists call these flower look-alikes egg ribbons, and they are fastened with remarkable strength to the reef. The nudibranch might attach the eggs with a special glue, or the adhesive quality might be in the stickiness of the gelatinous egg cases. No one knows.

Also remarkable is the concentration of poison in the eggs, which contain more recycled sponge toxin than the nudibranch that laid them. In one lab experiment, researchers ground up the red eggs and fed them to creatures that eat almost anything.The offering were rejected.

Another Honolulu
reader, physician and photographer Russell Gilbert, wondered how the nudibranch
eggs held together, so he took a close-up picture. You can see the individual
eggs (and Russell’s other excellent underwater photos) here.

“After taking this shot,” he wrote, “I realized how the eggs were structured — embedded in sheets in some kind of gel-like material.”

He’s right. Multiple eggs are enclosed in rigid, protective mucus capsules, which stick to each other to form the spiraled ribbon.

Once hatched, free-swimming larvae drift in the plankton, eating tiny plants. When a baby dancer is ready to settle down, it alights on its food, one of several species of sponges.

Depending on which sponge species they’re eating, Spanish dancers are red, pink or orange, sometimes mixed with yellow or white.

Most nudies only crawl, but Spanish dancers get their common name from their ability to swim in midwater, flexing their bodies energetically, their soft edges flaring like the skirts of a flamenco dancer. Most people who see this flamboyant dance become lifetime fans and protectors of Spanish dancers.

Nudibranchs in general are not long-lived, some for only a month. The life span of dancers is about a year.

Occasionally, they beach. A San Francisco reader wondered by email whether returning a grounded one to the water revives them or if the creatures were trying to die.

I don’t know, but since nudibranchs have no eyes, my guess is that groundings are accidents occurring when the creatures get too near the shore break.

At the shoreline I once found a live Spanish dancer larger than my hand and waded, fully clothed, to place the creature on the ocean floor. I don’t know whether the orange beauty survived, but it was worth getting wet to give it a chance.

Spanish dancers and their eggs inspire most everyone who sees them. Maybe Elton John’s tiny dancer was a nudibranch, and Gertrude Stein’s rose its eggs.


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

Gobies form partnership with shrimp for survival

Published July 1, 2013 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2013 Susan Scott
Shrimp gobies

Two gobies retreat toward a hole dug by their shrimp roomies. ©2013 Susan Scott

While waiting for my car to be serviced last week, I went through a stack of mail I had pulled from the box as I left home, and found a local marine guide I ordered. I put the book on my lap, and it opened to gobies.

“Gobies form by far the largest family of marine fishes,” the author wrote.

This came as a surprise because I see so few. Marine gobies, though, are apparently abundant. It’s just that most are so small and secretive, we snorkelers and divers rarely notice them.

The average goby is about 4 inches long, and even that’s big compared with some. The littlest goby, Trimmatom nanus, is the smallest vertebrate in the world, two-fifths of an inch long when fully grown. The tiny fish lives in the Western Pacific and Indian oceans but is not found in Hawaii.

Gobies are hard to spot because nearly every carnivore on the reef preys on them, and therefore gobies spend much of their lives hiding.

Some species live in burrows they dig themselves, using their large mouths to haul away rocks and sand. Many tuck into cracks in the reef, and others reside on coral surfaces, hovering close to a nearby hideout.

Then there are the gobies that trade labor for guard duty. Known as shrimp gobies, the fish live in pairs with a pair of snapping shrimp, two very different couples sharing a single abode.

The shrimp dig out and maintain the burrow in sand or mud, constructing an arched doorway of coral, rock or shell bits. The shrimp, nearly blind, welcome the fish as lodgers because gobies have excellent vision and serve as sentries, twitching their tails when danger approaches to warn the shrimp to duck inside.

This is symbiosis at its cutest. While snorkeling in the Tua­mo­tus, I watched two alert gobies stand guard, one on each side of the burrow, as their two shrimp roomies shoveled out clumps of sand. When I lowered my camera near the entrance, the fish backed up (pictured) and the shrimp retreated. With the lens even closer, the fish joined their shrimp pals in hiding. Seconds later I saw two bright eyes peek out, checking to see whether the coast was clear.

About 2,000 goby species exist in the world, but because their short-lived larvae don’t often survive long distances, Hawaii hosts only 34. One is a 2.5-inch-long shrimp goby, common in Kaneohe Bay’s shallow flats.

So writes John Hoover, author of the book I was reading, “The Ultimate Guide to Hawaiian Reef Fishes, Sea Turtles, Dolphins, Whales and Seals.” The new book felt like an old friend because I keep giving my copies away as gifts. This was my fifth copy.

Hoover’s book is my favorite marine reference at home and on the boat. And now it’s a favorite for making waiting-room time fly by.


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

©2013 Susan Scott