Your friends, the echinoderms
Sea urchins and other echinoderms are favorite animals for studying fertilization and early development, especially when many eggs and embryos are needed. On the left is a female Strongylocentrotus purpuratus spawning 10 million eggs. On the right is a male spawning sperm.
Mixing the two yield large numbers of embryos that develop easily in cultivating flasks stored at 16ºC.
Embryos develop rapidly, initially inside the fertilization envelope, forming in the egg on the left.
Inside the sea urchin are guts and gonads. A is the top (dorsal) surface of a female adult that is spawning eggs. B is the animal opened form the bottom (ventral) surface, revealing the five large orange gonads, because echinoderms are pentamericaly symmetrical.
Upon fertilization, the contents of the cortical granules are released into the extracellular matrix to form the fertilization envelope. Pictured are transmission electron micrographs of the cortical granules from L. varigatas (left) and S. purpuratus (right).
The fertilization envelope raises and after several hours, begins to divide. The following is a model of the progression of envelope formation. The entire sequence takes less than 1 minute in real life.
We would also like to give a shout out to the people at Creature Cast, a fantastic blog of scientists describing the work of other scientists.
Members of PRIMO have been closely involved with synthetic biology and iGEM at Brown.
BioBattery image from: Nature 441, 277-279