EGG JELLY LAYERS OF XENOPUS-LAEVIS ARE UNIQUE IN ULTRASTRUCTURE AND SUGAR DISTRIBUTION

Jelly coats surrounding the eggs of the South African clawed toad, Xen opus laevis, consist of three transparent, gelatinous layers: the inne rmost layer (J1), the middle layer (J2), and the outer layer (J3). The distribution of N-acetylglucosamine within these jelly coats, as prob ed with FITC-conjugated wheat germ agglutinin (WGA-FITC), and the matr ix ultrastructure of each layer, as visualized in platinum replicas pr oduced by the quick-freeze, deep-etch, and rotary-shadowing technique, suggests that each layer has a unique fiber and glycoprotein composit ion. J1 extends nearly 200 mu m from the egg surface and exhibits no W GA-FITC staining. Stereo images of platinum replicas indicates that J1 consists of a tightly knit network of 5-10 nm fibers decorated with 1 0-20 nm particulate components. In contrast, J2 is a relatively thin l ayer, extending only 25-40 mu m from the outer aspect of J1. When visu alized by confocal microscopy, J2 displays a multilayered WGA-FITC sta ining pattern. The ultrastructure of J2 consists of sheets of fine fib ers that run parallel to one another and that can be identified by the ir ability to bind WGA-colloidal gold. The fibers of each sheet run at an oblique angle to fibers in neighboring layers. J3 extends 100 mu m or more from J2. The WGA-FITC staining pattern shows high intensity i n its outer region and less intensity in regions closer to J2. Like J1 , the J3 ultrastructure consists of a network of 5-10 nm fibers, decor ated with 10-20 nm particulate components. The results of these studie s add to a growing body of information that suggests the jelly coats s urrounding the eggs of many animals consist of a fibrous glycoprotein superstructure that acts as a scaffold to which globular glycoproteins are bound. (C) 1996 Wiley-Liss, Inc.