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It's a Bird! It's a Fish! It's Supermale!

It's the parrotfish, a fish that looks like a bird! But it's no ordinary fish: it's a female, it's a male, it's a supermale! Why there are even supermale Queen and supermale Princess Parrotfish. And not only that, these strange, bird-like, gaudily colorful fish travel in herds and graze on plants. So how can one fish have the beak and colors of a parrot, behave like a cow, and change from female to male and from male to supermale in a single lifetime? For the parrotfish, it's all part of an ordinary day in the coral reefs.

Home on the Reef
Water-bound, scaly, gilled, and finned, parrotfish are all-fish, in spite of the name. They have large, smooth scales and can be brightly, even garishly colored. Their teeth are fused into beak-like structures that make them look a bit like parrots. Very common on coral reefs, parrotfish are herbivores and are therefore restricted to relatively shallow water where sunlight penetrates to allow plant growth. They often travel in groups, and, like terrestrial grazers, they crop from various locations (and thus do not destroy their food source).

Parrotfish use their beaks to nip pieces of large algae and to scrape algae and other encrusting organisms such as sponges from rocky bottoms. In the process they ingest large quantities of rock and coral, which is ground to a fine powder by highly specialized teeth in their throats. They then void the ground-up rock and coral, thus creating sand. A study in Bermuda estimated that parrotfish create a ton of sand per acre of coral reef per year. Those swimmers over coral reefs have discovered that when parrotfish feed, the noise of their teeth scraping rock is easily heard.

Supermale Gets His Female
These striking fishes undergo an unusual sexual development, marked by distinct color phases. In some species, all the young are drably colored females, and some of these then change to males. In others there are two kinds of males -- those that start life as males, and those that complete a female phase before transforming into males. A number of species include juvenile, young adult male and female, older female, and terminal male or supermale phases. The Stoplight Parrotfish is one species with all of these phases. Its young adult/female coloring is so different from that of the supermale, the two were long thought to be different species.

Most adults of a given parrotfish population are ordinary males and females; supermales are pretty rare. So what's so great about being a supermale? Well for one thing you get to be super colorful. And for another, a supermale parrotfish gets to spawn with an individual female or a group of females, while ordinary males spawn in groups with other males. A supermale, therefore, is more likely to pass his genes along to a new generation.

A Little Night Mucus
At the end of a busy day, parrotfish turn in for the night. They burrow into the sand or squeeze into a crevice to sleep. Some species of the genus Scarus, which includes both the Queen and the Princess parrotfish, are then able to secrete a mucous envelope around themselves. It takes a fish about half an hour to fully wrap itself in the slimy secretions, which appear designed to mask the fish's scent from hungry sharks and morays. A bed of slime may not seem like an apt resting place for a Princess, but it sure beats being a shark snack.

Learn more about parrotfish.

 

 

 

 

 

2007 eNature.com