134 



collar, extending ventrally to the midline of the stomach. The left and right 

 somatocoels lie lateral to the stomach. The first plates of the definitive 

 skeleton (Figure 89) begin to form in the middle and late bipinnaria. The 

 early bipinnaria is formed by the 2nd -3rd day of development and the 

 completely formed late bipinnaria by 13th- 15th day at 14-16°C. 



Brachiolaria 



As in other asterinids, the brachiolaria of Patiria bears two lateral brachiolar 

 arms with termini papillae. The brachiolar arms are smaller in size than in 

 the asteriid brachiolaria. The medioventral process performing the function of 

 a third brachiolar arm is relatively larger than the lateral brachiolar arm, 

 bearing two rows of small papillae (3 — 7 in each row) and one large papilla 

 at the tip of the process. The other processes remain almost unaltered (Figure 

 90). The brachiolaria is about 700 )a,m long. 



Ecology 



Larvae of Patina pectinifera are found in the plankton of Vostok Bay 

 from the second half of July to September. Patina spawns in Vostok Bay 

 from the second half of July to early September (Kasyanov et ai, 1976, 

 1980). According to Novikova (1978), a second spawning is possible in 

 November. In Sagami Bay (Pacific Coast of Japan), Patina spawn from April 

 to May (Kume and Dan, 1968). 



ASTERIAS AMURENSIS LUTKEN 



(Asteriidae) 



Asterias amurensis belongs to the order Forcipulaida. The development of 

 most species of this order proceeds from a pelagic planktotrophic larva stage 

 through subsequent metamorphosis. Most species of this order exhibit devel- 

 opment with the pelagic larva stage followed by metamorphosis. 



Egg 



The eggs of ^. amurensis are about 100 |a.m in diameter and colorless. 

 Cleavage is radial, with some signs of bilaterality, and somewhat asynchro- 

 nous. Division by cleavage results in a smooth blastula stage 14—16 hr after 

 fertilization (at 19°C). 



In the blastula stage, the embryo exists from the fertilization membrane 

 and begins active swimming by means of cilia that uniformly cover the body 

 surface. 



Gastrulation occurs through invagination. During gastrulation the larva is 

 stretched slightly along the animal-vegetal axis. At the end of gastrulation, 

 rudiments of the left and right coelom form. The gastrula is 100 |im x 150 



