MASTERS OF THE WATER-BONY FISHES 179 



carangiform movement is made. Carangiform movement is an adaption for speed. 

 Just how fast fishes can travel is not well known. Some tuna and spearfishes 

 probably can travel over 40 mph. 



The various senses are as highly developed in bony fishes as in sharks and 

 rays, but the emphasis is on the eye rather than on the nose. As in sharks and 

 rays, the lateral line serves to detect water vibrations. Taste is well developed 

 and hearing is somewhat less so. Barbels about the mouth, when present, are 

 delicate taste organs used for detecting food. The nervous system is developed 

 to a fairly complex degree as compared with invertebrates. Groupers can be 

 trained to follow a swimmer who has fed them a few times and, in fact, can 

 be a nuisance. The social behavior of fishes is complex and a huge topic in 

 itself. Some fishes are known to perform extraordinary migrations (many 

 mackerels and eels) and others have complex courtship behavior (demoiselles, 

 wrasse, gobies, blennies, and possibly grunts), but most piscine social behavioral 

 patterns remain unknown. 



Most marine fishes lay large numbers of pelagic or adhesive eggs. Some, such 

 as demoiselles, build nests. Only a few bear living young as do most sharks 

 and rays. 



Bony fishes exhibit a wide range of colors. Many of them are able to change 

 their colors greatly and rapidly. Color change is accomplished by the expansion 

 of pigment-bearing cells in the skin. These cells are called "chromatophores" and 

 are under both nervous and hormonal control (pituitary gland). A spectacular 

 color and pattern control is known for flatfishes, whei'e agreement of color 

 with the surroundings is remarkable. It is even possible for these fishes, if placed 

 on a checkerboard, to assume the checkerboard's pattern. Many fishes exhibit 

 several color phases which confuse identification. 



Color and body form may differ strikingly in young and old fish of the same 

 species. A well-known example is the black angelfish in which the young are 

 striped and the adults are not (Co/or Plate 7). The underwater swimmer, 

 however, is very likely to see, especially about coral reefs, many small, oddly 

 shaped, brilliantly colored fishes that are hard, if not impossible to identify. 

 These are the voung of reef species, and it must be admitted that very little is 

 known of them. 



These several topics— motion, the senses, social behavior, food, color vari- 

 ation, and change of form during growth— merely touched on here, offer 

 almost unlimited opportunities for observation and study. In this age, when man 

 is constantly expanding his numbers and activities, the sea is assuming a vital 

 importance, and bony fishes are, perhaps, the chief reason for this because of 

 their value as food. 



THE PRIMITIVE BONY FISHES: Subclass Chondrostel 



{"cartilage bone") 



Ancient chondrosteians possessed bone, but the modern ones, the sturgeons, 

 have skeletons of cartilage. These huge fishes are possibly the largest of bony 

 fishes. They are toothless, bottom-feeding, sluggish, and reminiscent of sharks 

 both in movements and form. The tail is asymmetrical, with a longer upper lobe 

 (heterocercal), and there are five rows of large bony plates along the body. 



