Blue tang

Natural history

The blue tang was first described in 1766 under the name Teuthis hepatus. About a century later, it was moved to its own genus and renamed Paracanthurus hepatus. Today it lives on coral reefs across the Indo-Pacific, from East Africa to the central Pacific, including the Great Barrier Reef.

Reproduction

Blue tang spawn in groups, releasing eggs and sperm into the water at the same time. The fertilized eggs float in the open ocean and hatch within about a day. The tiny larvae drift with the plankton for several weeks before settling onto a reef.

Conservation

Blue tangs depend on healthy coral reefs. When threatened, they wedge themselves into branching coral for shelter. Climate change threatens these reefs in two major ways.

The first is ocean acidification. As the ocean absorbs carbon dioxide from burning fossil fuels, seawater becomes more acidic, which makes it harder for corals to build their skeletons.

The second is rising sea temperatures. When water gets too warm, corals expel the symbiotic algae living in their tissues, a process called coral bleaching. Corals can recover if conditions improve, but prolonged or repeated bleaching often kills them.

Cool facts

• Blue tangs have a sharp, scalpel-like spine on each side of the tail base, which they use for defense.
• They can live alone, in pairs, or in groups.
• Young blue tangs graze on algae. Along with other plant-eating reef fishes, this helps keep algae from overgrowing corals.
• Paracanthurus hepatus goes by many names, including regal tang, palette surgeonfish, royal blue tang, hippo tang, flagtail surgeonfish, Pacific regal blue tang, and blue surgeonfish.
• Larger predatory fishes, like groupers, eat blue tangs.
• The blue tang's color comes from special cells called iridophores, which contain tiny reflective crystals that bounce back blue light.