Doctorfish tang

Acanthurus chirurgus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Actinopterygii
Order:	Perciformes
Family:	Acanthuridae
Genus:	Acanthurus
Species:	A. chirurgus
Binomial name
Acanthurus chirurgus Bloch, 1787
Synonyms
Acanthurus chirurgicus Bloch, 1787 Acanthurus hepatus non Linnaeus, 1766 Acanthurus nigricans non Linnaeus, 1758 Acanthurus phlebotomus Valenciennes, 1835 Chaetodon chirurgus Bloch, 1787 Hepatus hepatus non Linnaeus, 1766 Teuthis hepatus non Linnaeus, 1766

Acanthurus chirurgus, commonly called the Doctor fish and the Doctorfish tang in English or the Barbero rayado and the Cirujano rayado in Spanish, is a tropical marine fish common in the Atlantic Ocean.

Description

Reaching a maximum size of 39 cm and 5.1 kg, Acanthurus chirurgus gets its common name for the structures called "scalpels", which are found on either side of the caudal peduncle. The "scalpel" is used during fights with other Doctor fish and as a defense mechanism against predators. Its coloration generally varies from blue-gray to dark brown. Even with this variety of colors, 10 to 12 vertical bars are always present, no matter how faint. Also regardless of body color, the edges of the caudal, dorsal, and anal fins are blue. There is also a faint blue ring that can be seen encircling the "scalpel" on either side.

Black variety

There exists a black genetic variant of the Doctorfish tang. However, it is neither a subspecies nor a regional mutation. It has only been documented a limited number of times.

Range and habitiat

Typically found among rocky outcrops and coral reefs, Acanthurus chirurgus is found commonly in the Atlantic Ocean from Massachusetts to Brazil – this includes the Gulf of Mexico and the Caribbean. It can also be seen on the tropical west coast of Africa. Acanthurus chirurgus is the most widely ranged fish within its genus of 38 species spaning 3 oceans.

A Doctorfish tang swimming off the coast of the Yucatán peninsula

Feeding

Acanthurus chirurgus spends most daylight hours grazing on algae, or any organic detritus. Its teeth are specially shaped for scraping algae and other plant matter from rocks. Because it swallows its food whole, it has a gizzard-like organ in the intestine, filled with particles of sand, designed to grind food before entering it into the digestive process.

Life history

Doctor fish spawning occurs during evening hours in a group event. Each egg is less than one mm in diameter and contains a small amount of oil for flotation. The translucent, plankton-like larvae hatch within 24 hours of fertilization. The larvae are laterally compressed and diamond-shaped with large eyes and pectoral fins. Other parts of the fish (scales, dorsal, and anal fins) do not develop until the larvae have reached 2–6 mm in length. The "scalpel", however does not appear until about 13 mm in length is attained. While the "scalpel" grows, the anal and dorsal spines that are common in Acanthurus chirurgus larvae shrink. Once the fish reaches around 25 mm in length, it moves to the bottom where it continues to grow, eventually reaching sexual maturity in at least 9 months.

References

• Acanthurus chirurgus, Doctorfish – MarineBio.org. Retrieved Tuesday, September 11, 2007, from http://marinebio.org/species.asp?id=27.
• http://fishbase.org/Summary/speciesSummary.php?genusname=Acanthurus&speciesname=chirurgus
• http://www.cbif.gc.ca/pls/itisca/taxastep?king=every&p_action=containing&taxa=Acanthurus+chirurgus
• REEF FISH Identification FLORIDA CARIBBEAN BAHAMAS; Humann, Paul and Ned Deloach; New World Publications Inc., Jacksonville, Fl; pp. 34–35
• IUCN 2007. 2007 IUCN Red List of Threatened Species. <www.iucnredlist.org>. Downloaded on 28 September 2007.