Fig. 2

(A) Post-metamorphic juvenile approx. 2 mm in HD. The red granules are red pigment cells that accumulate in areas of rapid growth, usually around the sutures, the apical plate and genital pores. There is a higher concentration of these cells around the sutures of the ambulacral plates; all primary spines have a purple band roughly midway down the spine. All post-metamorphic juveniles look very similar irrespective of adult color phenotype. (B) Later stage juvenile that will become a purple urchin. The purple along the spines accumulates and will eventually cover the entire spine and the test will become progressively darker. (C) Later stage juvenile that will become a white urchin. The purple band along the spine becomes fainter until it disappears altogether. The test may become light as it in this individual or may become darker. (D) Later stage bicolored juvenile that displays both spine and test patterning. The spatial differentiation of green and purple on the spines is clearly visible as is the difference in color between the ambulacral and interambulacral sectors.