Structure and Macromolecular Composition of the Egg and Embryo Jelly Coats of the Anuran Lepidobatrachus laevis

Abstract

Eggs and cleavage‐stage embryos of the frog Lepidobatrachus laevis are encased by 3 μm thick vitelline/fertilization envelope and two jelly layers, termed J1 (innermost) and J2 (outermost). Based on light and transmission electron microscopy, J1 had a dense reticular appearance whereas J2 had a laminar structure. Direct dissolution of the jelly coats was accomplished by reduction of disulfide bonds with 0.08 M 2‐mercaptoethanol at pH 10. Soluble jelly preparations were uncontaminated with nucleic acid (A280/A260=1.44) and yielded an average of 150 μg protein/egg or embryo (n=5). The biochemical composition of the jelly coats in unfertilized eggs was different from that in embryos. When examined via gel permeation chromatography, soluble jelly from unfertilized eggs contained macromolecules which were markedly larger and more heterogeneous (earlier eluting and broader peaks) than jelly from embryos. Differences in the components of jelly from unfertilized eggs and embryos were also observed by electrophoresis, however, a 29,700 molecular weight glycoprotein chain was common to both jelly preparations. The electrophoretic pattern of jelly obtained from parthenogenetically activated eggs was identical to that of unfertilized eggs, therefore the fertilization‐associated changes are not due to the exclusive action of cortical granule products.

Morphological Diversity and Evolution of Egg and Clutch Structure in Amphibians

“…Clear jelly layers certainly are not as structurally uniform (e.g., Carroll et al, 1991) throughout their thickness as they appear. The egg of Rana pipiens, for example, has two, clear layers of jelly (Wright and Wright, 1949:35).…”

Effects of environmentally relevant concentrations of endosulfan, azinphosmethyl, and diazinon on Great Basin spadefoot (Spea intermontana) and Pacific treefrog (Pseudacris regilla)

“…At environmentally relevant concentrations (%60 ng/L for endosulfan; %50 ng/L for azinphosmethyl; and %350 ng/L for diazinon; [16]), mean mortality was 8% for endosulfan, 23.5% 29,2010for azinphosmethyl, and 9% for diazinon. Using an additive model of total pesticide exposure at these concentrations, this represents potential mortality of 40.5% for S. intermontana tadpoles.…”

The Primary Egg Envelope of the Anuran Lepidobatrachus laevis: Physicochemical and Macromolecular Alterations During Development

“…The developmental and reproductive biology of the Paraguan anuran Lepidobatrachus laevis is being studied in our laboratory (4,27). Lepidobatrachus has only two jelly layers with a relatively simple molecular composition and one component has been purified (3,4).…”

“…Lepidobatrachus has only two jelly layers with a relatively simple molecular composition and one component has been purified (3,4). In the present work, the structural, chemical and macromolecular composition of the Lepidobatrachus primary egg envelopes are characterized, and mechanisms for these envelope conversions are examined.…”