222 



Figure 171: Ophiura sarsi. 



A — Pluteus I stage; general view of the larval skeleton; B — Pluteus II stage; beginning of 



formation of the posterodorsal rods. 



Legend same as in Figure 162. 



are interconnected. At this stage, it is possible to distinguish spicules in the 

 larvae, which give rise to the first plates of the definitive skeleton (see Figure 

 182). 



Ecology 



Brittle stars of this species are ready for spawning in Vostok Bay in late 

 April when the water temperature is 4.9°C. Larvae of this species were found 

 in the plankton only one month later, in May, when the water temperature 

 was 11°C. Larvae completing metamorphosis were found in early July when 

 the water temperature was 15°C. 



Mortensen (1898, 193 1 ) described the larva of ''Ophiopluteus compressus" 

 with characteristic perforated rods and purplish-black granules of the postero- 

 lateral and posterodorsal arms and proposed that it might belong to Ophiura 

 sarsi on the basis that the adult animals of this species are fairly numerous 

 in Danish waters and their reproduction period coincides with the appearance 

 of the larvae in the plankton. Thorson (1946), based on Mortensen's data, also 

 proposed that Ophiopluteus compressus might possibly be the larva of O. 

 sarsi. These larvae are found in Oresund Strait (The Sound) in April at a 

 water temperature of 5.8°C. However, Thorson does not describe the larvae 

 obtained by him while rearing O. sarsi. 



