Fig. 6

Cirrate egg capsules with prematurely hatched embryos. a Specimen P: naturally ruptured egg capsule with partially embedded octocoral host. b Specimen P: embryo with 12 mm ML pictured directly after leaving the egg capsule, ventral view—note small external yolk sac within arm crown. c Specimen P: virtual horizontal section through 3D MRI data set showing large internal yolk sac, shell, white body, buccal mass, as well as other internal organs. (d, e) Specimen P: surface-rendered 3D model of selected internal organs shown with semi-transparent virtual MRI section, dorsal (d) and right lateral view (e). f Specimen P: surface-rendered 3D model of selected internal organs, oblique fronto-dorsal view. g Specimen Q: naturally ruptured egg capsule with partially embedded octocoral host. h Specimen Q: embryo with 13 mm ML shown directly after leaving the egg capsule, dorsal view. i Specimen Q: arm crown of fixed embryo showing small external yolk sac, funnel, funnel organ, and shallow primary web, ventral view. j Specimen Q: close-up view of arms showing suckers, cirri, and primary web. k Specimen Q: virtual horizontal section through 3D MRI data set showing large internal yolk sac, shell, white body, buccal mass, as well as other internal organs. (l, m) Specimen Q: surface-rendered 3D model of selected internal organs shown with semi-transparent virtual MRI section, dorsal (l) and right lateral view (m). n Specimen Q: surface-rendered 3D model of selected internal organs, oblique fronto-dorsal view. Images (a, g, i, j) courtesy Elizabeth K. Shea, images (b, h) courtesy Timothy M. Shank. Dark green = branchial glands, dark blue = digestive tract, orange = eyes, pink = fin cartilages, light green = gills, yellow = nervous system, red = shell, purple = statocysts, white = white bodies, grey = yolk sac; ar = arm, bm = buccal mass, ch = chorion, ci = cirrus, ec = egg capsule, es = external yolk sac, ey = eye, fc = fin cartilage, fi = fin, fo = funnel organ, fu = funnel, oh = octocoral host, pw = primary web, sh = shell, su = sucker, wb = white body. Scale bars = 1 mm