LOCAL CHANGE OF AN EXOGASTRULA-INDUCING PEPTIDE (EGIP) IN THE PLUTEUSLARVA OF THE SEA-URCHIN ANTHOCIDARIS-CRASSISPINA

Immunofluorescence staining of cryosections of pluteus larvae of the s ea urchin Anthocidaris crassispina was performed with an antiserum rai sed in rabbit against exogastrula-inducing peptide D (EGIP-D). The api cal side of the ectoderm and gut of pluteus larvae that had been cultu red for 36 hr was stained. However, the gut of pluteus larvae that had been cultured for 38 hr was only partially stained and the gut of lar vae that had been culltured for 40 hr was not stained at all. By contr ast, the ectoderm of the 38-hr and 40-hr pluteus larvae remained stain able. These results suggest that EGIP-D is present in the gut of plute us larvae 36 hr after fertilization, but it begins to disappear from t he gut at 38 hr and is lost at all from the gut at 40 hr. The signific ance of the disappearance of EGIP-D from the gut of the pluteus larva is discussed in relation to the differentiation of the gut.