Name: metamorphic larva stage
ECAO ID: 0000520
Definition: "The metamorphic larva stage consists essentially of the evagination of the echinoid rudiment. It is characterized by the execution of conspicuous and relatively abrupt physical changes that take place quite quickly, in about one hour, and during which the planktonic larva is transformed into a benthic juvenile. At that stage, the larva is settled on the substrate and is firmly attached to it by the primary podia of the rudiment. The ectodermal epithelium of its arms has started to collapse, making the spicules supporting the larval arms piercing through the epidermis. The larval mouth and anus have further closed, while in parallel, within the larva, the rudiment spines have lifted up thereby distending the vestibular wall and wide opening the vestibular pore. Following these movements, the rudiment has farther down accomplished and finalized its complete eversion, encapsulating the digestive tract and reaching the right side of the larval body. During this process, the genital plates and the associated pedicellariae and immature spines present on the right side of the larva have further completed the production of the aboral part of the adult body. At the end of metamorphosis, hence at the end of the metamorphic larva stage, the individual has thus become benthic, it is settled in the substrate, and it looks like an adult pentaradial sea urchin although it is smaller in size, deprived of a functional digestive system and sexually immature."
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