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Modifications of the fertilized egg surface following the cortical reaction in Limulus polyphemus L. as viewed with the scanning electron microscope
Author(s) -
Barnum Susan R.,
Clapper David L.,
Brown George G.
Publication year - 1985
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1051830207
Subject(s) - limulus , biology , ultrastructure , human fertilization , horseshoe crab , anatomy , blastoderm , biophysics , electron microscope , scanning electron microscope , embryogenesis , cleavage (geology) , granule (geology) , embryo , microbiology and biotechnology , materials science , optics , evolutionary biology , composite material , physics , paleontology , fracture (geology)
In the development of the horseshoe crab, Limulus polyphemus , the fertilized egg undergoes a complicated cleavage (Stages 1–3) resulting in blastoderm formation (Stage 4). Stage 1 involves intralecithal cleavage and consists of nine discrete surface modifications (events) which have been briefly described with light microscopy by Brown and Barnum ('83). Since in Stage 1 the cortical reaction (events 1–4) has already been examined with ultrastructural methods, the objectives of the present study were to examine with scanning electron microscopy: (1) the first two of three intermittent granulations (events 5 and 7), and (2) the associated events characterized by smooth surfaces (events 4, 6, and 8). The first granulation occurs 2 1/2 to 3 hours after fertilization (22°C) and lasts approximately 1 1/2 hours. The second granulation appears approximately 5 hours after fertilization and lasts about 3 hours. The dynamic changes that occur during the two granulations involve the transformation of a smooth appearing embryonic surface, liberally coated with microvilli, into a granule‐dominated surface on which microvilli are greatly reduced in number. Also of considerable interest are the numerous projections which begin to appear on the surface near the end of the second granulation (event 7) and dominate the surface of the following smooth step stage (event 8). Hypotheses on the significance of these dynamic changes and surface modifications involve relationships to the cell cycle, possible mechanisms for membrane storage, and secretory function.