| Figure 9. Major stages of C. intestinalis metamorphosis from larva to juvenile. At the moment of larval settlement (A) metamorphosis is triggered. Tail resorption can be completed in a very short time (B); the outer tunic layer is usually cut off shortly after the completion of tail resorption. (C, D) Rapid morphogenetic movements, involving physiological changes lead to the opening of two lateral siphons and of the first pair of functional stigmata (E, first ascidian stage or FAS). Ascidians continue metamorphosis: the number of stigmata on each side of the branchial basket increases (F), until the fusion of the two peribranchial siphons into the single atrial siphon is complete (G, second ascidian stage or SAS). Scale, 200 µm.
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