136 



By the 7th — 8th day of development the bipinnaria is about 350 |i,m long 

 (Figure 93). The brachiolaria stage of A. amurensis has not been satisfactorily 

 described. However, Kume and Dan (1968) present photographs of the late 



Figure 93: Asterias amurensis. 

 Late bipinnaria. 



bipinnaria and brachiolaria of this sea star. Judging from these photographs, 

 in A. amurensis the planktotrophic brachiolaria has three brachiolar arms, 

 typical for the genus Asterias, long pigmented larval processes, and skeletal 

 elements of the juvenile sea star in the posterior end of the body (Figure 94). 

 Information on the duration of larval development is lacking. The larval 

 stage of a closely related species, A. rubens, extends for 8 - 9 weeks (Gemmill, 

 1914). One may tentatively estimate the duration of the pelagic stage of ^. 

 amurensis as 1.5-2.0 months; however, this requires verification. 



Ecology 



Larvae of A. amurensis are found in the plankton of Peter the Great Bay 

 from the end of April to November (spawning twice a year; April - June and 

 August - September at surface water temperatures of 12- 16°C) Kasyanov et 

 al., 1976; Novikova, 1978). 



Besides Peter the Great Bay, the spawning period of A. amurensis is 

 known for some regions in Honshu: Tonkin Bay — January to June at 6- 



