ABSTRACT

Pattern formation during development refers to the processes by which the structure of the organism is spatially and temporally organised. All teleosts show a discoidal meroblastic cleavage pattern, where the large yolk volume restricts cell division to a small area at the animal pole. The process of gastrulation in teleosts is associated with a cell movement called epiboly, where the blastoderm spreads over the yolk from the animal pole, eventually enveloping the entire mass. The ectodermal layer which, following gastrulation is the outermost tissue layer of the embryo, gives rise to the neural tissues, sensory organs, pigment cells, placodal tissues and the epidermis. Neural crest cells are unusual in that they delaminate from the neuroepithelium during neurulation, and undergo long-range migrations throughout the embryo to form a variety of cell types, such as most of the peripheral nervous system, all epidermal pigment cells and much of the head skeleton.