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LECITHOTROPHIC LARVAE 



Species of sea cucumbers with lecithotrophic larvae have large eggs rich in 

 yolk. Their early development differs little from various species with 

 planktotrophic larvae. Differences are observed only from the gastrula stage. 

 A larva entirely covered with cilia and having a coelom and gut divided into 

 sections develops later (Kowalewsky, 1867; Ohshima, 1921; Inaba, 1930). 

 The anal end becomes slightly flattened and the oral opening forms from the 

 ventral side. The ciliary cover changes. Cilia persist at the preoral end and 

 near the anus; between these fields two- five ciliated bands form (Figure 187). 

 Thus, the doliolaria is formed, avoiding the stages of dipleurula and auricularia. 

 Oil drops are present in the preoral part of the doliolaria, which enable the 

 larva to maintain a vertical position in water. The doliolaria swims by rotating 

 around the animal-vegetal axis. In lecithotrophic larvae the digestive system 

 is not fiilly formed and the principal formative processes are associated with 

 the development of the coelom (Figure 188). 



Figure 187: Caudina chilensis (Inaba, 



1930). 

 Doliolaria of lecithotrophic type of 

 development. Ciliary cover is retained on 

 the preoral lobe, oo — oral opening. 



Figure 188: Chiridota rotifera (Clark, 1910). 



Differentiation of coelom into sections, 

 arch — archenteron; bl — blastopore; 

 cb — ciliated band; he — hydrocoel; 

 hp — hydropore; is — left somatocoel; 

 rs — right somatocoel. 



The structure of the pentactula in sea cucumbers with planktotrophic 

 larvae shows no substantial difference. The ciliated bands are retained and the 

 larva can swim as well as creep. In apodous pentaculae the ambulacral podia 

 do not develop, while in cucumariids one or two podia appear at this stage 

 (Figure 189). Their development, as in the species with planktotrophic larvae, 

 is associated with the medioventral ambulacral canal. 



It is necessary to note that in some species development with lecithotrophic 



