Stephanie Freeman
Developmental Biology Lab Video

A dozen eggs, time-lapse microscopy of cell development
Society of developmental biology

The Video reviewed early development, and migration in different species of animals and plants. Early development was discussed in the video, with narration to the time-lapse microscopy. 1st cleavage involves nuclear envelope breakdown, spindle formation, nuclear division formation, and cytokines. Cleavage is synchronous occurring approximately every 30 minutes. Then there is blastocoel formation, and the blastomeres move to the periphery. Also basal blebbing of the cells can be seen. Primary mesenchyme cells migrate from inner cell mass, and the vegetal plate invaginates. Archencheron cell formation, primitive gut tube elongates, and contact the blastoceal roof. Spicule grows from primary mesenchyme, and the sea urchin embryo advances. Individual amoebas migrate on an agar plate. In a chemo tactic response to migration individual amoeba migrate to form large aggregates. They form moving streams, which flows into what appears to be one clump of amoeba. Migration of pseudoplasmodium, or crawling slug, leaves a visible slime trail. A large pseudoplasmodium splits, to form two pseudoplasmodia. When the pseudoplasmodium ceases migration it differentiates into a fruiting body, the posterior portion forms a stalk and the anterior form spore cells. When cut into pieces each differentiates and rearranges into a complete fruiting bodies. Snail polar lobe formation, transient exclusions of the vegetal cytoplasm, called polar lobes. White polar bodies mark the animal pole. Formation of the large vegetal polar lobe, attached by the cytoplasmic stalk, and exchange of cytoplasm through stalk can be seen. 1st cleavage is complete giving a large and small blastomere. There is 2nd polar lobe formation, cleavage to the 4-cell stage. Meitoin blebbing in flat worms. Fertilization is the trigger for completion of meiosis, the surface blebs, and the 1st polar body appears, and the cell surface is quiescent. And second period of active blebbing occurs at the time of second polar body formation. 1st cleavage forms the two-cell stage, Nematode development, pronuclear migration and fusion, Female pronuclease begins migration, fusion occurs, zygote pronuclease migrates to center of the cell. 1st cleavage occurs, with mitosis and cytokineses. Cleavage involves asymmetric cell division, with circular division and cleavage patterns. Gastrulation begins when progenitors synch to the anterior embryo and others follow. Gut differentiation is visible in anterior of embryo, there is tail formation, and the first muscular movements occur. Fruit fly development. Early cleavage is marked by cytoplasmic contractions as the nuclei divide. At the posterior end of the embryo the pole cells will form. The nuclei migrate to the cell periphery. The wave of cellularization is visible, and ventral caudal formation marks the beginning of gastrulation. During the time of Germ band extension, major organ systems are established. There is germ band retraction, and the anterior and posterior midgut fuse. Somatic contractions are the first contractions of the gut. The trachea fills with air, by this point in development, all major organ systems are established and in their permanent positions. In the next day the first larva will hatch from the chorion. Ascidian development, after fertilization undergoes rearrangement to reveal yellow crescent. Small cells between the zygote and chorion are the inner follicle cells. 1st Gastrulation, then neural plate formation, and early tail bud pigment is restricted to the tail. The tadpole is visible approximately 12 hours after fertilization.
Frog gastrulation begins at the gastro pore pigment line, consisting of epithelial cells, which will form endoderm. Involution convergence and extension narrows and lengthens the embryo. The yolk plug is covered. Neural plate formation, neural fold fuse to form neural tube, brain is anterior, spinal chord is posterior. Zebra fish development, cleave involves only the animal cytoplasm, the vegetal yolk mass does not divide. Cleavage forms the blastula stage. Involution, conversion and extension, forms the axis along the left hand side. Epiboly is complete. The head is forming, and the tail is curving around to form. Somites can be seen. The large eye forms. Killifish cell migration, by blebbing locomotion, and deep cell migration. The population as a whole shows no directionality. Deep cells migrate toward sites of wound closure.
Chick development. Hensen’s node regresses posteriorly, neural groove folds to form neural tube. Anterior posterior portal can be clearly seen. Somites are visible. Large optic lobe can be seen at anterior, and heart is beginning to form. Development progresses anterior to posterior. Mouse development, cleavage is asynchronous. At 8 cell stage compaction begins, cells become polarized and cell junctions form. Blastoceal formation can be seen as a large fluid fill space displaces cells and forms a central cavity. Outer trophoblast forms the embryonic contribution to the placenta. Inner cells form the embryo proper. The embryo hatches from the zona pellucida as a blastocyst. The video was very informative about the early development of different species, and the time-lapse microscopy was especially educational and interesting. Please show more videos like these in class.