2006 Hemidactylium scutatum movies
These are some of the best examples from this years movies. I can fool with these movies some more to enhance their contrast and focus, combine them to show animal and vegetal views side-by-side and in-synch, etc., if there's something in particular you want to look at, or just want a better show movie.
Cleavage and Gast onset
At least a couple of these have obvious "dead spots" in the animal region. Remarkably, they still develop pretty well.
The one remarkable thing I thought I saw in these movies was the formation of small cells in the vegetal region. The claim that these embryos were not good, and the observation that they tended to have dead spots in the animal cap, make me think that these small cells are probably artifactual (or actually just extruded yolk), perhaps again representing dead or damaged spots. I often see vegetal dead spots in Ambystoma that have gotten too cold. In any event, might suggest that at least in these embryos, the furrow was incomplete internally.
The other potentially intersting thing was the funny wiggles the cleavage furrows made as new ones were conecting. I'll see if I can find a good example of this.
They show a fair amount of vegetal contraction toward the end of the movies; this seems much more pronounced than in Xenopus; morphometrics could nail this down. In combination with the dramatic vegetal contraction associated with blastopore formation (which begins a few hours later), this seems like it could be an important mechanism in this species.
0327 Embryo 2 above.mov
0327 Embryo 2 below.mov
above: dead spot in AC (suggests a sick embryo); dead region gets sucked under; surrounding cells strangely larger, with clear nuclei spots (white dots)
below: small blastomere cleaved off bottom of right of 4 blastomeres, apparently by a furrow that comesthrough the top blastomere of 4 (other examples as well?). Vegetal contraction starts about 18:00; cells appear to start sinking into vegetal pole region about 00:00; not clear whether they are actually ingressing -- seems unlikely. Dorsal blastopore lip (DBPL) begins to form (about 4:30), but then later re-expands -- suggests a sick embryo.
Both: Animal contraction corresponds to initial formation of DBPL;
0329 embryo 2 above.mov
0329 embryo 2 below.mov
above: looks like minor damage in dejellying, but recoveres & is pretty healthy
below: looks good; definite vegetal contraction action at end, pretty good DBPL formation
both: looks like animal contraction begins after DBPL is formed in this case
0401 Embryo 1 above.mov
0401 embryo 1 below.mov
Seems to show fairly uniform neural closure?
0403 Embryo 1 above.mov
0403 Embryo 1 below.mov
above view is an hour behind because of daylight savings switch problem (one computer did automatically, the other didn't). Shows a clear delay in posterior closure.
0403 Embryo 2 above.mov
0403 Embryo 2 below.mov
again, above is one hour behind below. Best movie showing a delay:
- hind brain touches in above movie at 23:45; below view shows posterior neural plate wide open at 0:49
- posteior ward zipping of fold touching starts in above view at about 0:13; little change in posterior at 01:13
-most of hind brain region more-or-less touching by 02:03 above; posterior is in the process of closing, but is not touching at 03:05
- most posterior visible point in above view looks more-or-less touched at 03:27; posterior neural plate still closing, but not touched anywhere at 04:25.
- anterior neuropore closed by 05:47 in above view
- posterior neural tube finishes closing at 07:45 (3 hours later) in below view (most posterior part of tube actually touches first about an hour before)
-actual fold fussion is a different matter; looks like it's started anterior and posterior by 15:50/16:50; maybe somewhat advanced in anterior, resolution not as good.
- you can see head neural crest migration begin at about 13:15 in the above view
060330.2 H.sc. giant.mov
made about 10+ (early dorsal lip, little invag.; maybe 3.5 days?); lasts about 37 hours, so to about 5 days, or late gastrula stage (st 12; horizontal BP). No clear indication of subduction movements, though maybe some in BP region flanking notochord, starting around 18:00 (about 4.5 days); apparent subduction movements at very end look more like folding upward than real subduction. This is much different than other urodeles I've looked at.
There are however very strong convergence and extension movements, with extension beginning at about 9 hours, or roughly "Mid gastrulation". I'll have to think about how this corresponds to the onset of extension in Ambystoma, but I think Ambystoma is much earlier.