Chap. 34 



AMPHIBIANS 



683 



Class Amphibia 



There are some 2500 species of living amphibians; at least 1500 of them are 

 frogs and toads. This smallest of the classes of vertebrates is usually divided 

 into 3 groups: Caudata or Urodela (tailed); Anura (tailless); and Apoda 

 (limbless). 



Order Urodela — Salamanders 



The Urodele's body is long and slender, carried or dragged on puny legs as 

 if it belonged to a pigmy dachshund (Fig. 34.2). All larvae and some adults 

 have gills. Among the gilled adults are the common mud-puppies (Necturus) 

 of the eastern United States and Canada that live in rivers and creeks, crawl- 

 ing over the bottoms, mostly at night. It is easy to see why they are called 

 puppies. The "ears" are the very beautiful gills that swing rhythmically as the 

 puppy breathes (Fig. 34.3). 



The majority of tailed amphibians are without gills in adult life. They include 

 the better-known and generally smaller salamanders. There is no sharp distinc- 

 tion between salamanders and newts or efts except that the latter are smaller 

 and more delicate. Newt, eft, and asker with varied spelling are old names for 

 salamanders, commonly taken for lizards. Like frogs and toads, they are bound 

 up with superstition, often with witchcraft (Fig. 34.26). 



Many salamanders are abundant and some of them such as the spotted sala- 

 mander {Ambystoma maciilatiim) and the newts (Triturus) are subjects of 

 important experimental studies. The tiger salamanders {Ambystoma tigrimim) 

 widely distributed in the United States resemble the spotted salamanders. They 

 start life as typical aquatic larvae, breathing by gills. In most regions, the 



Fig. 34.2. Newt (Triturus) walks on its 4 weak legs at the same time weaving 

 its body like a fish. Drawings from photographs of slow locomotion. (After 

 Evans. Courtesy, Young: The Life of the Vertebrates. Oxford, England, The 

 Clarendon Press, 1950.) 



