OPHIUROIDEA 



159 



arms all the spines are short, hook-shaped ; this also holds good 

 of the younger specimens, where all the arms are still equal in 

 size. No spines at the first pair of pores ; no tentacle scales. 

 Mouth shields very small or even lacking in larger specimens ; 

 only the madreporite fairly well developed. Colour a faint 

 reddish. Reaches a very considerable size, up to ca. 35 mm. 

 diameter of disk. The stronger arms up to ten times as long as 

 diameter of disk. 



Development unknown ; from 

 the rather large size of the eggs 

 it is, however, fairly evident that 

 the development must be direct, 

 without a pelagic larval stage. 

 In very young specimens the disk 

 is covered by large primary plates, 

 forming a beautiful rosette ; these 

 plates, however, gradually dis- 

 appear, being totally dissolved. 

 In specimens of a size of ca. 2 mm. 

 diameter of disk and an arm 

 length of ca. 10-15 mm. the ter- 

 minal plate is large, basket-shaped; 

 it then gradually assumes a 

 simple, cylindrical shape. 



It is generally found cUnging 

 high above the ground to slender 

 Pennatulids, like Funiculina quad- 

 rangularis, more rarely to Gor- 

 gonids. It has two or three of 

 the arms wound around the Pen- 

 natulid, the other arms waving free 

 in the water, catching the small 

 pelagic animals (mainly Copepods) 

 on which it feeds. It appears 

 that it also to some degree feeds on the polyps of the Pennatulid 

 to which it clings. The young specimens are detritus-eaters, until 

 at a size of ca. 5-6 mm. diameter of disk they crawl up and attach 

 themselves to the Pennatulid, then becoming plankton- eaters. 



The remarkable transformed Copepod, Chord eumium obesu7n 

 (Jungersen), is rather commonly found parasitic in its gonads, 

 which are destroyed by the parasite ; the other gonads, however, 

 go on functioning normally, the Ophiuroid thus not being castrated 

 by the parasite. 



Fig. 90. — Asteronyx Loveni, cling- 

 ing to a Funiculina. Seen 

 from the dorsal side. Nat. 

 size. (From Danmark's 

 Fauna. ) 



