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.
Representative Stage Images
These 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.zip
Movie 1
Shows 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.avi
Movie 2
Shows dorsal view of cleavage through blastula stages. Roughly 11 minutes per frame. 15 fps. Scale bar is 1 mm.
Movie2.avi
Movie 3
Shows 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.avi
Movie 4
Shows 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.avi
Movie 5
A 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.avi
Movie 6
Shows 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.avi
Movie 7
Shows 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.avi
Movie 8
Shows 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.avi
Movie 9
Shows 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.avi
Confocal Stack 1
An 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.avi
Confocal Stack 2
The 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.avi
Confocal Stack 3
Same 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