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	...	The Effects of NiCl2on Spicule Formation Jessica Ann Billet, Franklin and Marshall, Class of 2000 Background and Objective Sea urchins exhibit radial holoblastic cleavage, eventually forming a blastula. Shortly after the blastula hatches from the fertilization membrance, the embryo begins gastrulation. Gastrulation begins when the vegetal side of the blastula begins to thicken and flatten. This flat sheet of cells is called the vegetal plate. In the center of the vegetal plate a small group of cells begins to change. These cells extend and contract long, thin filopodia. These cells then break off from the epithelium and migrate into the blastocoel. These migrating cells are known as the primary mesenchyme cells (PMCS). Eventually the migrating cells localize within the ventrolateral region of the blastocoel. It is in this area that the PMCs fuse together to form syncytial cables. Syncytial cables will eventually form the axis of the calcium carbonate spiculesof the larval skeleton. The purpose of this lab is to explore the development of spicules in a sea urchin's larval skeleton. NiCl2interferes with spicule and skeletal formation, by introducing half of the embryos into a solution of NiCl2, we hope to observe the effects of blocking skeleton formation. We will stain all of the embryos with an Ig8 immunoflourescent antibody. Ig8 will stain or 'tag' the primary mesenchyme cells of the developing embryo.