This is one Hawaiian reef creature you more than likely will never see, but they are extremely common! When you snorkel or dive you often will see markings on a flat, smooth coral species that look like ancient Hawaiian petroglyphs. Sometimes when people see these unusual markings they think that someone carved up a piece of live coral with a knife, but these dark-brown channels in the live coral are carved by a pair of tiny shrimp!
This is one Hawaiian reef creature you more than likely will never see, but they are extremely common! When you snorkel or dive you often will see markings on a flat, smooth coral species that look like ancient Hawaiian petroglyphs. Sometimes when people see these unusual markings they think that someone carved up a piece of live coral with a knife, but these dark-brown channels in the live coral are carved by a pair of tiny shrimp!
You may not see the tiny petroglyph shrimp because they are clear and very small. But you will hear them. When you go diving, just shut your eyes and listen to the sound of the sea. On most of our shallow coral reefs you will hear a snapping noise that almost sounds like a buzzing swarm of bees. Sound travels further and faster in the salt water than in the air, and the petroglyph shrimp are snapping shrimp that constantly make noise that is heard all across the coral reef.
These tiny shrimp carve a channel in the live coral, and the female shrimp lives in one channel and the male in a different channel. They line the sides of the channel with stinging hydroids so they are protected from intruders. In their channel they farm algae for food. The coral reacts to the stinging hydroids and pesky shrimp by making a raised coral wall around the dug-out channels. All of this activity makes a normally smooth coral like a rice coral look carved up with all kinds of unusual designs on the surface. No two shrimp-carved channels look alike, so each coral has its unique set of designs on it. The Hawaiian coral reef is just alive with sound. I did an acoustical study with Scripps Institute of Oceanography a few years back at Makua Kaua‘i (Tunnels Reef), where we put down some equipment on the reef for two weeks that monitored the sound all the animals make. In the two-week period the equipment recorded over a billion different reef noises! Basically, on a coral reef, the corals all talk to each other, and they talk to the crabs, shrimp, lobsters, dolphin and fish! Each reef has a different set of sounds that is called their “acoustical footprint.” Once the normal sounds of a coral reef are recorded, then if the reef becomes unhealthy the acoustical footprint will change. Modern scientists nowadays can float sensitive sound equipment above a coral reef and tell if the reef is becoming unhealthy just by the sound changes. This will help us marine biologists know there is a problem out on our coral reefs before the problem gets out of hand. You can see the petroglyph shrimp in action on my underwater educational web page, www.underwater2web.com and also my wide range of underwater and surf movies on my YouTube at underwater2web.
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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.
