Fertilization of frog body cavity eggs enhanced by treatments affecting the vitelline coat

Abstract

AbstractAmphibian eggs which have not been coated with jelly in the oviduct (body cavity eggs) are not fertilized when placed with sperm. When body cavity eggs of the frog Rana pipiens were briefly treated with trypsin and then inseminated in a water‐extract of the jelly (egg‐water), however, high frequencies of fertilization were obtained. A low frequency of fertilization of trypsin treated eggs but not of untreated eggs was obtained even in the absence of egg‐water. Similar results were obtained when eggs were pretreated with cyanide. Both trypsin and cyanide produced a visible weakening of the vitelline coat, the extracellular coat surrounding a body cavity egg. When a rip was made in the vitelline coat and the eggs were inseminated in egg‐water, fertilization occurred. The success of these three pretreatments in producing fertilization of frog body cavity eggs strongly suggests that the vitelline coat is a block to fertilization of these eggs.The fertilized body cavity eggs exhibited considerable difficulty in completing gastrulation. Those that began neurulation often had abnormalities of the pos terior end. However, tadpoles that appeared to be normal could be raised from fertilized body cavity eggs.