MASTERS OF THE WATER-BONY FISHES 265 



has no ocellar spot on the forehead, and the pectoral and caudal hns only are 

 edged with vellovv. The young are barred as are the young of the queen angelfish. 



TANGS: Family Acanthuridae 



There are many species of these tropical reef fishes found throughout the 

 world. All are characterized by their silhouette, in which the dorsal and ventral 

 curvatures and fins are verv similar, giving the body an ovoid shape. Tangs are 

 no less velvety than angelfish in appearance. They have a formidable weapon 

 in the scalpellike vertebral spine, which is usually folded forward in a groove 

 in the tail, but which may be erected and used in a slashing manner to inflict 

 deep cuts on an adversary. This weapon has given them the names of "surgeon- 

 fish" or "doctorfish." Among Spanish-speaking peoples they are known as "bar- 

 beros" or "medicos." In early davs, it was the barber who practiced phlebotomy, 

 or blood-letting, and who was the local general practitioner. 



Tangs usually swim in small groups, often with parrot fishes, and often use 

 the pectoral fins in a flapping manner for propulsion, though this kind of pro- 

 pulsion is not as predominant as in parrot fishes. The teeth are different from 

 those of other scaly-fin fishes. A single series of incisorlike teeth is present in 

 each jaw. These are used to scrape away plant arid animal substances from the 

 reefs on which they graze. Dark brown and blue colors predominate. The young 

 are colored very differently from the adults. 



BLUE TANG (blue DOCTORFISH, surgeonfish) : Acatithurus coeruleus— 



Color Plate 7 



Size: Averages 8 inches. Up to 1 foot. 



Weight: Up to 1 pound. 



Distribution: West Indies to Florida. Straggles to New York. 



Identification: The blue color is dark, exceptionally velvety, and very hard 

 to catch on film, requiring more exposure than would appear necessary. This 

 color, however, is variable, becoming very pale over a sandy bottom, so the very 

 deep, almost circular shape and the tail lancets of white are the best marks. 



The young of this fish, formerly described as a separate species, is an exceed- 

 ingly brilliant, jewellike yellow fish up to the time it is about 3 inches or so long 

 (it has been reported to 6 inches). It is common in the company of wrasse about 

 coral heads and has the shape of a butterfly fish, but the tail spine gives it away. 

 It tends to keep close to the protection of the coral. 



Habits: Tangs are found in groups, singly, or swimming with other reef fishes 

 (parrot fishes commonly). They graze, much after the manner of parrot fishes, 

 and show some of the same wary habits, though less pronounced. 



Similar Swedes: The doctorfish, Acanthurus hepatus QColor Plate 7)-, is a 

 West Indian species which also goes as far north as Cape Cod accidentally. It 

 is less deep of body than the blue tang and varies from a dark to light brownish 

 color. The lancet on the tail is dark. This fish reaches 10 inches. 



The ocean tang, Acanthurus bahianus, also has dark and light brown phases 

 but keeps more offshore, and large specimens have the upper lobe of the caudal 

 fin elongated into a filament. Its range is the West Indies, accidentally to Cape 

 Cod, and it commonly reaches 1 foot. 



The barbero negro, Acanthurus crestonis, is found from Mazadan south and 

 is usually very dark in color. 



