250 



Prepentactula II 



This stage is characterized by the anal ambulacral podium which can 

 extrude by means of it the larva is capable of attachment to the substrate. All 

 the five ciliary rings persist and continue to perform a locomotory function 

 (Figure 195). 



Figure 194: Stichopus japonicus. 

 Prepentactula. Large cavities have 



disappeared. 



Primary tentacles are distinctly visible in 



the vestibular cavity. 



Figure 195: Stichopus japonicus. 



Prepentactula. Anal ambulacral podium has 



emerged outside the body. One of the 



primary tentacles protrudes from the 



vestibular cavity. 



Pentactula 



At this stage, the primary tentacles of the larva are not retracted into the 

 vestibular cavity, which now remains wide open. The larva is capable of 

 moving by means of its tentacles and podia. At this stage, it is possible to 

 distinguish skeletal rods of different shapes scattered throughout the body 

 under the integument. The length of the larva is about 500 jim (Figure 196). 

 In the trepang as well as in Thyone briareus (Ohshima, 1925) and Cucumaria 

 elongata (Chia and Buchanan, 1969), the first tentacles begin to appear only 

 in the juvenile. 



Ecology 



Larvae of the trepang begin to appear in Vostok Bay in July when the 

 water temperature is 18°C. Spawning is observed until August. According to 

 Mokretsova (1975), in Posjet Bay the average duration of development from 



