308 



COLLEGE ZOOLOGY 



Reproduction 



The sexes of starfishes are separate. The 

 reproductive organs are branched structures, 

 two in the base of each arm (Fig. 193). 

 The female has been known to release as 

 many as IVz million eggs in two hours, and 

 200 million eggs may be liberated in a 



season. A male produces many times that 

 number of sperms. The eggs of many star- 

 fishes are fertilized in the water and de- 

 velop into a type of larva called a bipin- 

 naria (Fig. 194) that has bilateral sym- 

 metry before it attains the radial symmetry 

 of an adult. 



OJI 



/ Young starfish 



Metamorphosis 



Fertilization 

 of egg 



Brachioloria 



Bipinnaria 



Gastrula 



Blastula 



Figure 194. The life cycle of the common starfish. Note that in the later larval stages the 

 starfish has bilateral symmetry before it attains radial symmetry. 



Regeneration 



The starfish has remarkable powers of 

 regeneration. A single arm with part of the 

 disk will regenerate an entire body. In all 



species tested, arms cut off at any level are 

 regenerated, although at a slow rate. If an 

 arm is injured, it is usually cast off near the 

 base at the fourth or fifth ambulacral 

 ossicle. This is autotomy. 



