442 



VERTEBRATE LIFE AND ORGANIZATION 



Streamlined fishes of the open waters. But there have been many inter- 

 esting departures trom these generahzed types. The 20,000 or more 

 species of teleosts have spread out into all parts of the aquatic environ- 

 ment, and have become adapted to nearly every conceivable ecologic 

 niche. This phenomenon of adaptive radiation is seen in all large 

 groui:)s. Apparently the resources of the environment can be utilized 

 more fully if subgroups become specialized for certain parts of the en- 

 vironment than if all try to compete with each other in the total environ- 

 ment. 



Tlie halibut, soles and flounders have become specialized for a 



Figure 22.13. Adaptive radiation among the teleosts. A, A tarpon, Tarpon, one of 

 the more primitive types of teleosts; B, a halibut, Hippoglossus, one of the flatfish that 

 feeds along the bottom; C, a male sea horse, Hippocampus, with the brood pouch in 

 which the female deposits her eggs, young shown at right; D, the sargassum fish, Histrio, 

 appears very bizarre out of its natural environment, but is well concealed among sea- 

 weed; E, the sharksucker, Remora; F, the moray eel, GymnoUwrax, normally lurks within 

 interstices of coral reefs. {A, C, D, E, F, courtesy of Marine Studios; B, courtesy of the 

 American Museum of Natural History.) 



