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Table 1 Soft tissue stages in rudiment

From: A detailed staging scheme for late larval development in Strongylocentrotus purpuratus focused on readily-visible juvenile structures within the rudiment

Stage Shorthand Days Drawings Smith et al. 2008 [[37]] Chino et al. 1994 [[38]] Description
- pre invagination < 13 I-II a-c 6-8 arm larva, no invagination forming on the left side yet.
i invagination 14 III c-d Rudiment invaginating on left side, not yet contacting hydrocoel; this can be further subdivided as “% invagination” (i.e., the depth of the invagination measured from the ectoderm through the axis of the invagination to the hydrocoel).
ii contact 15 IV e-f Rudiment has contacted the hydrocoel, but has not flattened alongside it yet.
iii contact flattened 16 IV f-g Invaginated rudiment has now flattened alongside the hydrocoel, but there is as yet no 5-fold symmetry apparent in the mesoderm or the invaginated ectoderm.
iv 5-fold mesoderm 17 V h Hydrocoel showing first visible signs of 5-fold symmetry (5 bumps), but the ectoderm (invaginated rudiment) not yet showing any sign of 5-fold symmetry.
v 5-fold ectoderm 18-19 V i Ectoderm now also showing 5-fold symmetry as the primordia of the 5 podia begin to push through the floor of the vestibular ectoderm. At this point, the interior of the 5 incipient podia are spherical in shape or shorter than wide.
vi primary podia (pp) 19-21 V i-j Interior of 5 primary podia are now taller than wide, but the podia are not yet folding in towards one another.
vii pp-folded 21-23 VI? k The 5 podia are now folding towards one another (i.e. towards the center of the oral field of the forming juvenile), but the tips of adjacent podia are not yet touching one another. This soft tissue stage usually coincides with skeletogenic Stage 1 or 2 (see Table 2).
viii pp-touching 23 VI k-l The tips of at least 2 of the 5 tube feet are now touching. This soft tissue stage usually coincides with skeletogenic Stage 2+ (see Table 2).
  1. Description and illustration of stages presented in the new staging scheme as well as approximate timing in days after fertilization at 14°C. Note that roman numerals in the column “Smith et al. [37]” and the letters in the column “Chino et al. [38]” are the stages proposed in those studies (see Figure eleven in [37], and Figure two in [38]) as they relate approximately to the stages used in our new soft tissue staging scheme here. Question marks indicate ambiguities in the comparisons between staging schemes.