BeschrijvingParacentrotus lividus adult rudiment development.jpg |
FIGURE 12. Paracentrotus lividus adult rudiment development under light microscopy. (A) Schematics of an 8-arm pluteus stage larva in anterior and left views. The vestibule (of ectodermal origin) is in blue and the larval coelomic pouch derivatives (of mesodermal origin) are in dark grey. Of note, although for simplicity we only represented an 8-arm pluteus larva, adult rudiment development actually takes place between the end of the 4-arm pluteus stage and the end of the 8-arm pluteus stage. In (B–S), developmental stages are as follows: (B–D) vestibule contact stage (VesCon); (EA) vestibule flattened stage (VesFlat); (FA–FD) vestibule waving stage (VesWav); (GA–GD’) 5-fold mesoderm stage (5foldMe); (HA–HD) 5-fold ectoderm stage (5foldEc); (IA–ID+) primary podia stage (PPodia); (JD–JD+) primary podia touching stage (PTouch); (KD) primary podia twisting stage (PTwist); (LD–ND+) primary podia papilla stage (PPap); (O,P) juvenile spine stage (JuvS); (QA–S) mature rudiment stage (MRud). In (B–S), images were acquired using bright-field light microscopy and correspond to close-ups of the developing or developed adult rudiment. (B–D) Close-ups of the regions highlighted by brown boxes in (A). (EA–LD,QA,ND+) Close-ups following the development of the regions outlined by yellow boxes in (B–D), with panels with superscript letters A corresponding to regions XA, with panels with superscript letters S corresponding to regions XS, and with panels with superscript letters D, D' or D+ corresponding to regions XD. (M) Close-up of the region marked by the yellow box in (LD), but at a different focal plane. (P) Close-up of the region highlighted by the yellow box in (O). (S) Close-up of the region outlined by the yellow box in (R). In (EA–LD,QA,ND+), superscript letters refer to the position of the larva in order to observe the developing rudiment as presented, hence A (EA,FA,GA,HA,IA,QA) refers to larva in anterior view (such as is (B)), S (FS,GS) refers to larva in left view, with a focal plane set at the surface of the vestibular floor (such as is (C)), and D (FD,GD,GD',HD,ID,ID+,JD,JD+, KD,LD,ND+) refers to larva in left view, but with a focal plane positioned at a deeper level than the vestibular floor (such as is (D)). (GD') is the same as (GD) but zoomed out and ((GD') inset) is a close-up of the stone canal. (ID+) and (JD+) correspond to views even deeper than (ID) and (JD), and (ND+) is at the same depth as (JD+). In (O,R), the larva is in a tilted view and in (QA) a zoom of the larval apex is presented, with the larva in anterior view. In (B,C), the cyan dotted line outlines the vestibule. In (B,D), the white dotted line delineates the left hydrocoel. In (FD,GD,GD',HD,ID–JD+,ND+), the letters Ⓐ-Ⓔ identify the developing primary podia according to Carpenter’s nomenclature (1884). In ((GD,GD',GD') inset), blue dotted lines outline the position of the developing water vascular system. In (GD'), green dotted lines highlight the left axocoel, and in ((GD') inset) red dotted lines mark the stone canal. In (HA), red arrowheads mark the folded vestibule epidermis. In (HD), blue dotted lines mark the ring canal and radial canals of the water vascular system. In (IA), the yellow arrow marks one left somatocoel bud. In (KD,LD,M,P,S), green asterisks indicate the definitive spines, and red asterisks mark a primary podia papilla. In (M), the white dotted line delineates a primary podia papilla. In (P,S), magenta asterisks and white dotted lines mark the juvenile spines. In (QA), the magenta dotted line outlines the developed adult rudiment, and the white dotted line delineates the larval stomach. Scale bar: (B–EA,KD–M,O–S) 50 μm; (FA–JD+,ND+) 30 μm; ((GD') inset) 20 µm. Coel: coelomocyte; Epi: larval epidermis; HC: hydroporic canal; Hyp: hydropore; JS: juvenile spine; LA: left axocoel; LH: left hydrocoel; LS: left somatocoel; Mo: mouth; Pap: papilla; PP: primary podium; RaC: radial canal; RiC: ring canal; Rud: adult rudiment; SC: stone canal; St: stomach: Ves: vestibule; VesC: vestibular cavity; VesF: vestibular floor; VesL: vestibular lip; VesP: vestibular pore; VesR: vestibular roof; VesW: vestibular wall. |