Table 1 Crepidula fornicata staging system

Cleavage

Formation of the four micromere quartets

0-48hr

Zygote to 25-cell stages

0-27hr

Fig. 1a, e, i

Formation of the first three micromere quartets and 4d

Compaction, Round stage

40-47hr

Figs. 1n, 10a, 11a

Fourth Quartet formation

47-48hr

not shown

Formation of 4a-4c

Epiboly

Coverage of macromeres by the animal cap micromeres (% Epiboly)

48-140hr

50-55 % Epiboly, Round Stage

60hr

Figs. 1c, g, k-w, 7a, 10b, 11b

65 % Epiboly

91hr

Figs. 1d, h, 2a, 3a, 6b-e, 7b-d, 8b-e, 9j, 10c-d, 11c-d

Flattened Round stage

Compressed along the AV axis

Convergent-Extension occurring and 2d progeny have been excluded from the blastopore

97-140hr

Figs. 2b-c, g-h, 6f-o, 11e-i, 12a-aa

Ectomesoderm enters the blastopore

110-130hr

Figs. 7g, 9p-u

Ectomesoderm begins to disperse

130hr

Figs. 7h, 8g, 9v

Elongation

Embryo undergoes elongation along the anterior-posterior axis

117-169hr

Square or Rectangular stage

117hr

Figs. 2h, 3b-e, 7e-f

Short or early ovoid stage

120 hr

Figs. 2i, 3f-h, 4b-l, 5a-f, 6k-o, 7g-h, 9v-z, 10e-h

Blastopore still central

Invaginated shell gland is present

137hr

Figs. 3i, 4p-q, 5j-l, 12kk-mm

Long or late ovoid stage

140hr

Figs. 3j, 5j-l, 6q-s, 7j-k, 10i-n

Mouth displaced anteriorly

Organogenesis

Appearance of external morphological rudiments, including: velar lobes, foot, shell

170-227hr

Early Organogenesis

170hr

Figs. 4r-w, 6t-w, 11n-o

Flattened shell plate

Late Organogenesis

196hr

Figs. 3k-o, 4x-y, 5m-t, 6x-dd, 7n-o, 8n-o, 10o-t, 11p-s, 13a-g, k-n

Embryo, shell have a pronounced convex dorsal curvature

Larval Development

Pre-hatching veliger larvae have prominant ciliated velar lobes, a foot, operculum, pigmented ocelli, curved external shell enclosing the visceral mass, protruding absorptive cells, and beating heart

228hr-4 weeks+

Young Veliger Larva

228hr

Figs. 11t-y, 13j, o-s

Anus opens

12 days

Figs. 13h-i