Sea Cucumbers, Sea Stars and Brittle Stars

This chart shows the early developmental stages of three classes of Echinoderm.  Holothuroidea are the class of sea cucumbers, Asteroidea the sea stars and Ophiuroidea the brittle stars.  Note the change in classification of brittle stars from within the Echinoidea (sea urchins) to an independent class within the same Subphylum which differentiates feather stars from all other Echinoderms.  Progressive development of an auricularian larva (from a sea cucumber) is shown (fig. 1-9) with it’s bands of cilia in place and adult tentacles forming (fig. 9).  Different stages of the bipinnaria larva of a sea star can be seen developing structures from gastrodermal and meso dermal tissue (fig. 10, 17 & 19). An ophiopluteus larva of a brittle star is shown forming it’s arms (fig. 11).