THE STARFISH 

 Phylum Echinodekmata Class Asteroidea 



I. BEHAVIOR AND EXTERNAL FEATURES 



Exercise 1. — General Activities. 



(a) The following directions may be used with Asterias vulgaris 

 or A. forbesi; both species are found along the Atlantic Coast of North 

 America. Asterias vulgaris is distinctly northern, ranging chiefly 

 from Cape Cod to Labrador, although it may be found in colder or 

 deeper waters as far south as Cape Hatteras. A. forbesi ranges from 

 Maine to Florida. Both species vary greatly in color when alive and 

 must be seen in the living condition if their beauty is to be appreci- 

 ated. The most obvious difference between the two species is in the 

 shape of the arms, which taper more rapidly and are more sharply 

 pointed in A. vulgaris than in A. forbesi. Also, in A. vulgaris there is 

 a median row of spines upon the aboral or upper surface of each arm 

 which rarely occurs in A. forbesi. Living animals can be maintained 

 inland in aquaria containing artificial sea water. 



(b) If it is impossible to examine the starfish alive, some under- 

 standing of the animal's activities can be obtained from specimens 

 preserved in various ways. Several dozen specimens, dried with no 

 attempt to preserve them in the form desirable for dissection, will 

 illustrate the diversity of shape that may be assumed in locomotion 

 over irregular surfaces and in crevices among the rocks where the 

 animals abound. Specimens preserved dry after having crawled into 

 bottles, and masses of starfishes dried after they have "felted" to- 

 gether in a pail, may be examined. The consistency of the living 

 animal is not unlike that of specimens preserved in formalin. The 

 activities of various parts will be explained in the directions for study 

 of their structure. 



(c) If living animals are available, watch them as they crawl about 

 in an aquarium. Are there anterior and posterior ends? Are the 

 movements of the tube feet coordinated? Touch a glass rod to the 

 ends of some of the tube feet. Pull the rod away. Do the tube feet 

 exert suction? Frequently the tube feet become so firmly attached 

 that they may be pulled off before releasing their hold. Can the ani- 



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