131 



1 (4). Preoral part of larva shorter than, or almost equal in length to 



postoral part. 



2 (3). Preoral part of larva shorter than postoral part. Processes short, less 



movable. Pigment absent on tips of processes 



Asterinidae, Figures 70 and 74. 



3 (2). Preoral part of larva shorter than, or almost equal in length to, 



postoral part. Processes long, movable, especially posterolateral and 

 posterodorsal. Tips of processes orange. . . Asteriidae, Figures 76. 



4 (1). Preoral part of larva longer than postoral part 



Luidiidae, Figures 71 and 72. 



Key to Planktotrophic Larvae Based on Brachiolaria Stage 



In addition to the characters listed in the key above, new diagnostic characters 

 are found in the brachiolaria stage. 



1 (4). Brachiolaria stage present. 



2 (3). Lateral brachiolar arms relatively short, less movable. Crown of 



papillae absent on middle brachiolar arms; papillae arranged in two 

 rows on ventral surface Asterinidae, Figure 80. 



3 (2). Lateral brachiolar arms relatively longer, movable. Middle brachiolar 



arm with crown of papillae Asteriidae, Figure 87. 



4 (1). Brachiolaria stage absent Luidiidae, Figure 71. 



CHARACTERS OF LARVAE ACCORDING TO FAMILIES 



Luidiidae 



In some species the bipinnaria is giant in size — 15—30 mm in length. The 

 preoral part of the larva is very long, and curved. Larval locomotion is 

 powered in some species by beating of the cilia bordering long arms, in other 

 species by contraction of the muscles in the preoral part. Branching of the 

 paired arms may be observed. The bipinnaria stage with characteristic attach- 

 ment organs is absent. Metamorphosis occurs in the planktonic period of life. 

 The larval body is resorbed or discarded. In the latter case, it may exist 

 independently in the plankton for over a month. 



Luidia quinaha bispinosa Djakonov is found in Peter the Great Bay. The 

 larva of Luidia quinaria von Martens has been described (Komatsu et al., 

 1982). 



