I Poop Sand: The Life and Times of a Parrotfish
by Julie Cremer
What eats coral, poops sand and wraps itself in a ball of mucus? The parrotfish, of course! These colorful reef dwellers in fact play a significant role in maintaining populations of coral and algae within the reef they call home. If these fish didn’t eat the algae that they enjoy, coral would not be able receive the proper amount of sunlight they need in order to survive and would be smothered. Different species of coral have a special relationship with zooxanthellae;a type of algae that utilizes photosynthesis to make food. The coral, in turn, provide carbon dioxide and other elements that are essential for photosynthesis.
Since these fish prefer the algal covering found on coral for dinner, they end up munching on the coral itself. Teeth that are shaped like long, thin plates plus a sharp, beak-like mouth allow parrotfish to consume different coral species. After they tear off a chunk, flattened teeth in the back of their throats grinds the coral pieces down into a fine, sandy substance. No stomach is present in the digestive systems of parrotfish. Rather, the coral sand hops on the intestine express, makes a one-way trip out the fish’s rear-end coming to a complete stop on the ocean floor. Due to their strange preference in food, parrotfish eliminate hundreds of tons of coral reef sand throughout their lifetime! Talk about an achievement! However, parrotfish are not the only the only ones who create sand. A few species of wrasse and triggerfish (cousins of the parrotfish in the family Labridae) also create ocean floors and beaches from their poop.
Six years ago, I studied field research and ecotourism in Madagascar on a study abroad program in college. My group went snorkeling for three days in the Indian Ocean off the northern coast of the island. During one snorkeling excursion, I heard a strange crunching and grinding noise underwater right beneath me. Lo and behold! A large species of parrotfish was feasting on brain coral just a few feet away from me! A few minutes later, I witnessed a triggerfish engaged in the same activity.
Parrotfish are diurnal, or daytime, dwellers just like their namesake. What is really cool, but also wonderfully weird, is that a few different kinds of parrotfish produce and spin a hammock of mucus. The fish then roll themselves into the mucus when it is time to hit the hay. Mucus “beds” may serve as a scent shield to keep the parrotfish safe from predators including sharks. I prefer to sleep in my cozy and solid mattress at home thank you very much!
Parrotfish have puzzled and confused scientists for a long time when it comes to identifying different species. Different colors and patterns occur throughout the lifetime of one specific species of parrotfish. At one time, researchers discovered up to 300 different species of parrotfish. But based on the various color patterns at different age stages and gender, that numbered has decreased to just 60!
For example, take a look at the picture below of a Bi-color parrotfish (Cetoscarus bicolor).
Now take a close look at this next photograph of another parrotfish.
Would you believe me if I told you that these are the same species of parrotfish?! The first picture features a male Bicolor parrotfish. The second image is of a female Bicolor parrotfish. Even juvenile parrotfish are colored differently than their parents. These animals would be great candidates for a mystery television show! The detective would have a super hard time discovering who committed the crime. “Detective SCUBEE DIVER cracks mysterious case of missing coral! Polly Parrotfish confesses to be the perpetrator of the crime! Polly sentenced to lifetime of sand excretion.”
The next time you travel the world and head to a pristine white-sand beach, whether it’s in Hawaii or off the coast of Madagascar, thank the parrotfish for this amazing feat of Nature. Our Earth’s coral reefs would not be the same if the parrotfish did not exist to help keep them healthy and clean. Incredible how one small fish can help produce infinite layers of sand. Big things indeed come in little packages.
- Monterey Bay Aquarium. “Parrotfish”. Monterey Bay Aquarium. Web. Accessed 9. February 2015. http://www.montereybayaquarium.org/animal-guide/fishes/parrotfish
- Cook Islands Biodiversity Database. “Bicolor Parrotfish (Cetoscarus bicolor), Cook Islands Biodiversity and Natural Heritage. Web. Accessed 9, February 2015. http://cookislands.bishopmuseum.org/species.asp?id=8358