Name: early juvenile stage
ECAO ID: 0000550
Definition: "The early juvenile is morphologically similar to both the late rudiment and a miniature sea urchin adult. Like the rudiment, it harbors five primary podia (or tube feet), five quartet of definitive spines, five pairs of immature spines located at the basis of the primary podia, 5 to 7 immature spines supported by the genital plates as well as 1 to 4 pedicellariae. Like the adult, it displays a pentarial symmetry and is settled on the substrate. An early juvenile is about 300 µm in diameter. On its aboral side, it still exhibits some remaining larval rods and tissues, although these will soon disappear. In addition, the plates forming its endoskeleton are still rather light and porous making it looking relatively clear, although it bears lots of red-pigmented cells. However, the postlarva is still deprived of a mouth and an anus, hence of a functional digestive tract. The early juvenile is thus endotrophic, meaning that its growth and development solely relies on energy derived from internal sources. Furthermore, the early juvenile is sexually immature."
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