Odor Perception and Taste 219 



which probably represented fields of higher intensity such as are pro- 

 duced by the crests of interfering waves or by a standing wave. 



Sound Production 



Among freshwater fishes known to produce sounds are the sheepshead 

 or drum, several kinds of minnows ( Cyprinidae ) ,-"•- ^^^ and the catfishes. 

 Others probably produce noises or vibrations of various frequencies. 



Records of sounds produced by freshwater drum were made in Lake 

 Winnebago (Wisconsin) using a Type H-11 hydrophone (U. S. Navy).^"* 

 The sheepshead started "drumming" in early May and continued at a 

 decreased intensity until the end of August. Drumming began about 

 10 A.M. and continued until sunset; highest drumming activity occurred 

 during the afternoon. Sounds were produced by sexually mature males 

 only and appeared to be for communication during the spawning season. 



The drumming sound of the sheepshead is produced by muscular con- 

 ti'actions which actuate a tendonlike structure across the swim bladder. 

 The frequency spectrogram of the sounds produced covered a broad 

 range of frequencies between 150 and 2000 cycles per second with the 

 largest relative amplitudes within the range of 250 to 400 cps. 



In the blacktail shiner and the red shiner only the ripe females pro- 

 duced sounds. These sounds were useful in attracting ripe males of their 

 own species.-^ The satinfin shiner is reported to make a sound similar to 

 the sound made when one strikes wood with his knuckles. These sounds 

 were produced when males fought and when males and females courted. 

 Isolated females also produced fainter, less frequent knocks than males, 

 so diat it was impossible to positively identify the source of the sound 

 when males and females were together. Males also made a purring sound 

 when actively courting females. ^"^ 



Many species of marine fishes are known to produce sounds, and some 

 deep sea forms are believed to use their sound-producing apparatus to 

 engage in echo-sounding.^- 



ODOR PERCEPTION AND TASTE 



Fishes demonstrate an ability to taste and "smell" substances dissolved 

 in water. In fact the sense of "smell" appears to be very highly developed 

 and probably has many functions other than that of food finding. Ter- 

 restrial animals are able to detect an odor when ( according to one theory ) 

 minute particles of a substance are dissolved on membranes associated 

 with sensory cells of olfactory nerves. These minute particles are carried 

 on air currents and are, in some instances, subject to dessication. One 

 modern theory of odor perception suggests that substances having odor 

 interfere with enzyme-catalysed reactions in the receptors. The fact that 



