Tag Archives: blennies

Isles host 20 species of native spider crab

Published December 30, 2017 in the
“Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

 

Hawaii is home to at least 20 species of small spider crabs. Pictured is one such Hawaii spider crab. Courtesy Morris Moribe

Year-end highlights or summaries aren’t my favorite reading material because the articles mostly contain facts about things I already know. Therefore, for this last Ocean Watch of the year, I’ll share some emails sent to me in 2017 that I loved, and answered, but didn’t have room to publish.

In March, reader Greg wrote, “My coworker found an odd crab … and we were wondering if this is an illegal alien that came to Hawaii during the Navy war games. … It’s a small guy … approximately one inch wide.”

Greg put the crab on ice in his freezer in “solidarity confinement.”

No need to worry about an invasion, though. Greg’s photos showed a spider crab native to Hawaii’s waters.

Hawaii hosts at least 20 species of spider crabs, all oddly triangular shaped. The one Greg’s friend found is common near Hawaii’s shorelines where brown seaweeds wash ashore.

But bring a magnifying glass to examine them. The crabs are only a half-inch to 1 inch wide, as well as being remarkably camouflaged.

Also called collector or decorator crabs, spider crabs have hooked hairs on their bodies that snag bits of seaweed, sponges, corals or other tiny animals drifting past. So besides being small, spider crabs can look like anything but a crab.

Claire, a loyal reader in the Seattle area, brought new facts about another marine animal to my attention last spring in a New York Times link (goo.gl/27XbPN) about fang blennies. (Claire is my 94-year-old mother-in-law who keeps me on my toes via her iPhone.)

Fang, or sabertooth, blennies are little Davids to the ocean’s Goliaths. When a predator fish takes a fang blenny in its mouth, the 2- to 4-inch-long blenny uses its two lower front fangs to bite the captor’s mouth. In response to the pain, the predator spits out the rascal unharmed.

Researchers recently learned that some fang blennies go a step further, injecting an opioid-containing venom during a bite. The venom doesn’t get the predator high, but rather drops its blood pressure by 40 percent.

We humans would feel faint and dizzy with such a drastic BP decrease. Although no one knows how it makes the fish feel, it can’t be good. With its head aquiver, the predator spews out the blenny.

Hawaii hosts several fang blennies but none that pack poison.

Ah, once again, I am out of space and have barely scratched the surface of my 2017 emails.

Readers, please know that I appreciate your personal stories, thoughtful questions, links to news items and words of encouragement. When I’m traveling or sailing I can’t always reply, but I read and enjoy all your messages.

Thank you for swimming with me into 2018. Another year, another 52 fish.

Tiny blennies may be cute but they have a mean bite

Published August 24, 2015 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2015 Susan Scott

blennies

Endemic Hawaiian zebra blennies. Credit Willy Asprey.

A friend of a friend of a friend placed a GoPro in a tide pool on Oahu’s North Shore. When he downloaded the footage, he saw eight adorable faces peering at the camera.

“OMG they are so funny,” emailed the middle friend, who wrote “sea monkeys” in the subject line. “Any idea what they are?”

Much as I love the name sea monkeys, the little charmers in the photo are called blennies.

Most blennies are timid reef fish that range from 4 to 7 inches long, depending on species. Some hide in holes, others live in tide pools and several rest in the open on rocks or corals. These bottom blennies eat algae and dead plant and animal tissue.

It’s easy to mistake blennies for gobies, and vice versa, because both have googly eyes, are similar in size and shyness, and hang out near rocky reefs. But here’s a clue: Startled blennies usually dash into holes tail-first; gobies dive in head first. Another sign is that many blennies have either frilly or antennaelike tendrils above their eyes. So if a fish with eyelashes or “My Favorite Martian” antennae is peeking from its hole, it’s a blenny. Gobies lack such tendrils.

Because bottom blennies have no swim bladders to control their buoyancy, the fish sink when they stop swimming. Some blennies make up for this bottom heaviness by performing acrobatics. When startled, they leap from pool to pool. One called the Hawaiian zebra blenny can detect a potential predator up to 50 feet from its tide pool. If the danger approaches, the fish will leap, skip or slide to the next pool, somehow knowing where that is.

Zebra blennies have been seen jumping as high as 2 feet above the water’s surface. Sometimes, the fish behave like frogs, slipping nearly out of the water to bask in the sun.

In addition to bottom blennies, the family has a branch of free swimmers called fang or sabertooth blennies. These fish use a set of curved lower teeth for defense. When caught by a predator, the blenny bites the inside of the captor’s mouth, causing it to spit out its potential meal intact. Unlike their vegetarian cousins, fang blennies are hit-and-run carnivores, nipping the sides of fish to eat mucus and scales.

The Ewa fang blenny mimics the cleaner wrasse, causing unsuspecting victims to swim toward the blenny thinking it’s going to lose some parasites. Instead, it loses some skin. Fang blennies sometimes bite divers, but the tiny nip does no damage.

I bought a GoPro recently and wasn’t quite sure what todowithit. I do now. I’m going hunting for sea monkeys.


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

©2015 Susan Scott