29 8 BULLETIN OF THE BUREAU OF FISHERIES. 



SENSE ORGANS. 



Simple experiments showed that receptors for the sense of smell are located on 

 the flagellae of the antenna. No specialized organs have been found, unless the setae 

 are the receptors, and it is not possible to locate any definite region where the sense of 

 smell is most acute. Pieces of fish suspended in the water near the antenna will attract 

 the spiny lobster, and the flagellae are moved so that they come into contact with the 

 fish even though the food may be hidden by seaweeds. Experiment showed that in 

 still water the reaction takes place to a piece of fish suspended a meter away from the 

 antennae, but the scent of food under natural conditions is probably carried much farther 

 by currents. 



Different sense organs are located on the legs. Pieces of fish dropped on the legs 

 cause a definite response The legs are moved, causing the piece of fish to be brought 

 under the body. This takes place even though the spiny lobster is eating other food. 

 The response is different when inorganic materials, such as stones, are dropped in place 

 of food. There seem to be similar receptors at the bases of the antennules and about 

 the mouth parts. These two chemical senses differ from each other only in sensi- 

 tivity. Particles of food must be dissolved in the water before they can stimulate either 

 kind of receptor, but since one set of receptors receives stimuli from a distance it is 

 more closely allied to the olfactory sense organs of air-breathing animals, while the 

 other set of receptors receives the stimuli of particles of food directly in contact with it 

 and is similar to the sense organs of taste in other animals. 



Vision does not seem to be acute, for objects thrust near a spiny lobster do not 

 always cause movement, and in diffused light the lobsters are more readily caught 

 with a dip net than in bright sunlight. The antennae are raised when a shadow passes 

 over the spiny lobster, which will turn in different directions as the shadow moves. 

 Vision, therefore, appears to be limited to distinguishing the quality of light rather 

 than the qualities of definite images as in higher animals. It has been observed that 

 food is not located by vision, since pieces of fish suspended in a current below the spiny 

 lobster will not attract it although the distance is very short. 



It is often thought that animals capable of producing sound are able to hear. If 

 this is the case, the spiny lobster should respond to various noises, but experiments do 

 not show that the auditory sense is present. The strident sound produced seems to be 

 made only when an enemy has driven the spiny lobster into close quarters and hearing 

 may not accompany it. This noise may be a means of defense. 



HABITAT AND MIGRATIONS. 



No direct observations have been made to determine the depth and distance from 

 shore at which spiny lobsters may be found, but the following has been inferred from 

 observations of catches brought into the market. 



Traps are often set in deep water by the fishermen while they are fishing for large 

 fish along the reefs 5 miles off Key West. Spiny lobsters are caught frequently on the 

 outside of these reefs in 70 feet of water, and several fishermen claim to have taken a 

 few with hook and line from somewhat deeper water. It is not probable that spiny 

 lobsters in deep water inhabit different kinds of places from those found in shallow 

 water; that is, they are restricted to rocky places or places where the growths of sponges 



