Furthermore, the accumulation of hypertonic fluid within the blastocoel
is in part due the action of the Na+/K+ ATPase pump (20).
At 51 h PF, mesenchymal cells can be seen inside the blastocoel
, near the base of the archenteron (Fig.
During embryonic genome activation, mitochondria progressively undergo functional and structural changes, and also generate higher levels of ATP to supply the increasing energy demands of the embryo that result from RNA and protein synthesis and blastocoel
formation (Khurana and Niemann, 2000).
At this stage a space was formed between yolk and blastoderm which is called blastocoel
Ca2+), a feature that may be of importance for maintaining junctional integrity and thus of importance for compaction and blastocoel
Developmental Stage Time(h or days) Oviposition 0 h First division 6 [+ or -] 1 h of cleavage Four-cell stage 8 h Eight-cell stage 11 h Morula 16 h Blastula, appearance of blastocoel
2 days Gastrula 2 days Motion of larvae by velar rudiment 3 days Early veliger stage, velum visible, viscera 4 days differentiated in stomach, left and right digestive diverticulum, shell color changed to purple Hatched 6 days No.
Either these embryos are primitive and don't have a clear blastocoel
, or a blastocoel
existed but didn't survive the preservation process," notes the report.
However, there was no sign of a blastocoel
, a fluid-filled hole in the centre which is a common feature of modern animal embryos.
Although cleavage divisions were affected only at very high DMAE concentrations, embryos treated with lower concentrations at the two-cell stage subsequently developed malformations (Figure 3): overabundance of mesenchyme-like cells that accumulated first in the vegetal half of the blastocoel
, and later occupied all of the blastocoel
, blocking or inhibiting gastrulation; absence of a second pair of arms in mid-pluteus, or sometimes shortening or absence of one arm of the first pair (Figure 3H).
Some features of early embryos (the blastocoel
, the archenteron of the gastrula) could be seen in specimens pressed gently between a glass slide and coverslip.
At the blastocyst stage, however, sodium pumping on the part of the trophoblast results, through osmosis, in the drawing of water into the blastocoel
, enlarging the blastocyst within the zone pellucida.
Ciliated, swimming blastulae with a small blastocoel
were formed about 16 h after fertilization (Fig.