127 



Forcipulatida; however, such development generally occurs in species inhab- 

 iting polar and adjacent waters, for example, species of the genus Leptasterias 

 (D'yakonov, 1950) (also see Table 4 and Kasyanov, 1987). 



IDENTIFICATION OF PELAGIC LARVAE OF SEA STARS 

 (Terminology and Diagnostic Characters) 



In the bipinnaria of a sea star (Figure 86) the dorsal and ventral, right and 

 left sides, and anterior and posterior ends are well defined. On the ventral side 

 lie the mouth and anal openings; on the left dorsal side, the hydropore leading 

 into the coelomic cavity; usually, there is no hydropore on the right dorsal 

 side. In the anterior part of the larva, in front of the 

 mouth, lies the preoral lobe, which is delimited from 

 the rest of the body by an independent preoral cili- 

 ated band. The anterior part of the preoral lobe 

 forms the medioventral process (arm), below which 

 the right and left preoral processes are located lat- 

 erally. The lower part of the preoral band borders 

 the preoral depression, which is hemmed by the 

 peristomial ciliated ring girdling the mouth. The 

 preoral depression is posteriorly bordered by the 

 transverse area of the main postoral ciliated band, 

 which hems the rest of the body of the bipinnaria. 

 This ciliated band ventrally passes over the left and 

 right postoral processes and the posterolateral pro- 

 cesses situated in the posterior part of the larva. 

 Dorsally, the cilited band borders (extending 

 posteroanteriorly) the left and right posterodorsal 

 and anterodorsal processes and finally the unpaired mediodorsal process. 



In the later larva — brachiolaria — of the sea star (Figure 87), additional 

 projections appear on the preoral lobe, namely, the left and right brachiolar 

 arms, which are equipped with a crown of attachment papillae. The 

 medioventral process is also transformed into a brachiolar arm, with papillae 

 located on its tip and/or in two rows along the ventral surface. The large 

 attachment disk lies between the brachiolar arms. 



The following parameters and characters are important in the identifica- 

 tion of larvae of sea stars: 



Figure 86: Bipinnaria of 



Patiria miniata (from 



Strathmann, 1971). 



1. Length of larva from tip of mediodorsal process to posteriormost point 

 of body (between posterolateral processes), measured in a larva in an 

 extended condition. 



