DOI: 10.5061/dryad.d5p60
title: Data from: Normal table of embryonic development in the four-toed salamander, Hemidactylium scutatum

description: We present a complete staging table of normal development for the lungless
 salamander, Hemidactylium scutatum (Caudata: Plethodontidae). Terrestrial
 egg clutches from naturally ovipositing females were collected and
 maintained at 15 °C in the laboratory. Observations, photographs, and
 time-lapse movies of embryos were taken throughout the 45-day embryonic
 period. The complete normal table of development for H. scutatum is
 divided into 28 stages and extends previous analyses of H. scutatum
 embryonic development (Bishop, 1920; Humphrey, 1928). Early embryonic
 stage classifications through neurulation reflect criteria described for
 Xenopus laevis, Ambystoma maculatum and other salamanders. Later embryonic
 stage assignments are based on unique features of H. scutatum embryos.
 Additionally, we provide morphological analysis of gastrulation and
 neurulation, as well as details on external aspects of eye, gill, limb,
 pigmentation, and tail development to support future research related to
 phylogeny, comparative embryology, and molecular mechanisms of
 development.
description: Representative Stage
 ImagesThese folders contain
 representative images for each stage of the embryonic table. Each image is
 numbered with two identifiers. The first number represents the individual
 identifier and the second number is the image identifier. Please contact
 the author for more details or to gain access to more
 images.StageImageFolders.zipMovie 1Shows cleavage from a dorsal view of four embryos still in their jelly coats, from 4 cell through gastrula stages. Epiboly is evident beginning at around 30 hours elapsed time (frame 180). Embryos increase in diameter throughout cleavage and gastrulation. Mesendoderm migration during gastrulation is faintly visible through the blastocoel roof during gastrulation, starting about 50 hours (frame 300), and appears less coherent than that of Xenopus. 10 minutes elapsed time per frame. Playback at 15 frames per second (fps). Scale bar is 1 mm.Movie1.aviMovie 2Shows dorsal view of cleavage through blastula stages. Roughly 11 minutes per frame. 15 fps. Scale bar is 1 mm.Movie2.aviMovie 3Shows vegetal view of cleavage from just before 4 cell stage through blastula stages. Contraction of the vegetal region is apparent by about 20 hours elapsed time (frame 120). 10.5 minutes per fame, 15 fps. Scale bar is 1 mm.Movie3.aviMovie 4Shows vegetal cleavage and the large amount of contraction that occurs in the vegetal endoderm leading up to blastopore formation. Contraction begins at about 3.3 hours elapsed time (frame 20). Blastopore formation begins at 16.5 hours elapsed time (frame 94) and is complete by the end of the movie (23 hours elapsed). There is an abnormally large cell just vegetal of the blastopore. 10.5 minutes per frame, 15 fps. Scale bar is 1 mm.Movie4.aviMovie 5A later view showing blastopore formation at stage 10 and the large amount of contraction that occurs in the vegetal endoderm. Blastopore formation starts about 4 hours elapsed time (frame 25) and continues to the end of the movie (about 13.7 hours). Both here and in movie 4, vegetal endoderm contraction appears to end as blastopore formation is complete. 10 minutes per frame, 15 fps. Scale bar is 1 mm.Movie5.aviMovie 6Shows gastrulation from approx. stage 11 to 13 (45 hours elapsed time), showing the inversion of the blastopore. This movie is comprised of time-lapse sequences of two different embryos, spliced together (between frame 61 and 62) to give a more complete view of gastrulation. 10 minutes per frame, 15 fps. Scale bar is 1 mm.Movie6.aviMovie 7Shows gastrulation from late stage 11 through neurulation from a posterior view (74 hours elapsed time). Shows inversion of the blastopore and it’s enclosure at the posterior end of the neural folds. 10 minutes per frame, 15 fps. Scale bar is 1 mm.Movie7.aviMovie 8Shows an anterior view of gastrulation from stage 13 through stage 20. 48.4 hours elapsed time. Spinning due to ciliary flow begins near end of movie. 8 minutes per frame, 15 fps. Scale bar is 1 mm.Movie8.aviMovie 9Shows posterior view from stage 12 to stage 18. 30.5 hours elapsed time. Shows posterior neural tube closure, and the enclosure of the blastopore within it. 8 min per frame, 15 frames per second. Scale bar is 1 mm.Movie9.aviConfocal Stack 1An overview of the region around the dorsal blastopore lip and vegetal pole, dorsal at the top left, ventral at the bottom. Stack progresses from mid-sagittally fractured face to lateral. Shows that most of the larger vegetal endodermal cells have already involuted (in addition to one abnormally large cell), and that the tissues involuting around the dorsal lip are interdigitated, with no discrete epithelial layer. Confocal slices are 17 μm apart.ConfocalStack1.aviConfocal Stack 2The lateral blastopore lip, from the parasagittally fractured face to lateral. Animal to the upper right, vegetal to the lower left. Shows that the tissue involuting around the lip is 2-3 cell layers thick, interdigitated, with no discrete epithelial layer. Confocal slices are 7 μm apart.ConfocalStack2.aviConfocal Stack 3Same embryo as in Confocal 2, centered more vegetally, and progressing further laterally. Shows that the entire vegetal endoderm is now internal, with the “vegetal” surface of the embryo being covered by cells that are much smaller than the initial vegetal endoderm cells, which can be seen inside the embryo. Confocal slices are 7 μm apart.ConfocalStack3.avi