THE EFFECT OF CYTOCHALASIN B UPON TAIL RESORPTION AND METAMORPHOSIS IN TEN SPECIES OF

¹ Department of Anatomy, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19174; Department of Zoology, University of Washington, Seattle, Washington 98195; Marine Biological Laboratory, Woods Hole, Massachusetts 02543; and Friday Harbor Laboratory, Friday Harbor, Washington, 98250

Cytochalasin B reversibly inhibits tail resorption and disrupts the organization of arrays of cytoplasmic filaments in the contractile cells. The effects of cytochalasin B on tail resorption and metamorphosis has been examined in ten species of ascidians, including representatives of 8 different families and 3 suborders. There is a considerable variation in the effective concentration of the drug when it is used with different groups of ascidians, and within a single species, discrete morphogenetic events characteristic of metamorphosis are differentially affected. The effective range of concentration of cytochalasin B which prevents tail resorption exhibited a striking phylogenetic correlation.