Cytological aspects of fertilization in the lamellibranch,Mytilus edulis I. Polar body formation and development of the female pronucleus

1. The somatic cells in both sexes of Phytophaga destructor Say contain four pairs of V-shaped chromosomes, the sex-group being indistinguishable in size or form. 2. The germ-cells in both sexes contain eight pairs of chromosomes. 3. The maturation of the egg follows the normal course of development, eight bivalents being formed. After polar body formation the female pronucleus has eight chromosomes. The polar bodies are never extruded from the egg. 4. Spermatogenesis is a complicated process, the details of which have not been satisfactorily determined. The growth stage appears to take place before the last spermatogonial division. No pairing of chromosome has been observed, and apparently no metaphase plate is formed at meiosis. Eeduction is effected by the expulsion of two buds each containing four chromosomes. Thus only one sperm is produced from each spermatocyte. 5. One or more sperms may enter the egg at fertilization. 6. The germ-line is differentiated from the soma at the eightcell stage. 7. At the fifth cleavage the somatic nuclei eliminate half their number of chromosomes, and are left with eight chromosomes. 8. Migration of the germ nuclei takes place at the sixteencell stage. 9. The relation of the chromosome numbers in the somatic and germ lines is discussed.

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An ultrastructural analysis of fertilization in the surf clam, Spisula solidissima. I. Polar body formation and development of the female pronucleus

Journal of Ultrastructure Research ◽

10.1016/s0022-5320(70)90177-2 ◽

1970 ◽

Vol 33 (5-6) ◽

pp. 495-514 ◽

Cited By ~ 60

Author(s):

Frank J. Longo ◽

Everett Anderson

Keyword(s):

Polar Body ◽

Ultrastructural Analysis ◽

Spisula Solidissima ◽

Surf Clam ◽

Body Formation ◽

Female Pronucleus ◽

Polar Body Formation

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Polar Body Formation in Tubifex Eggs

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.1990.tb21685.x ◽

1990 ◽

Vol 582 (1 Cytokinesis) ◽

pp. 260-272 ◽

Cited By ~ 18

Author(s):

TAKASHI SHIMIZU

Keyword(s):

Polar Body ◽

Body Formation ◽

Polar Body Formation

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Preimplantation development of gynogenetic diploid mouse embryos

Development ◽

10.1242/dev.69.1.215 ◽

1982 ◽

Vol 69 (1) ◽

pp. 215-222

Author(s):

Ewa Borsuk

Keyword(s):

Cytochalasin B ◽

Polar Body ◽

Mouse Embryos ◽

Fertilization In Vitro ◽

Body Formation ◽

Male Pronucleus ◽

Step Procedure ◽

Gynogenetic Diploid ◽

Polar Body Formation

Diploid gynogenetic mouse embryos were produced in a three-step procedure: fertilization in vitro, suppression of the 2nd polar body formation by Cytochalasin B, and microsurgical removal of the male pronucleus. The operated eggs were transplanted to the oviduct of recipient females for 72 or 96 h. The overall recovery rate was 73%, but compacted morulae and blastocysts constituted only 28·6% of transplanted eggs. After 72 h blastocysts were rare (3·5%) but 24 h later their incidence increased to 21·2%. In eggs homozygous for T6 chromosome it was possible to prove karyologically that the male pronucleus was effectively removed and that the diploid genome was of purely maternal origin.

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