Sôbre a meiose de Dysdercus mendesi bloete (1937) - Hemiptera, pyrrhocoridæ

Sôbre a meiose de Dysdercus mendesi bloete (1937) - Hemiptera, pyrrhocoridæ

Luiz O. T. Mendes

SUMMARY

1 — The spermatogonia of Dysdercus mendesi Bloete have 16 chromosomes : 7 pairs of autosomes and 2 sex-chromosomes.

2 — After the last spermatogonia! division, the chromatin of the autosomes diffuses and the nucleoplasm assumes an uniform granulai- aspect ; each sex-chromosome is involved by a vesicle and stands well colored.

3 — While the chromatin of the autosomes starts to condense again, to form the long threads (that finnally are seen in a paired condition) the cycle of the sex-chromosomes is as follows :

a) yet contained in the vesicles, they grow in size and become long rods ;

b) the vesicles disappear, the sex-chromosomes move inside the nucleoplasm and come to be disposed longitudinally, close together.

c) they touch each other, become fissured, and a tetradlike chromatic element is formed, which contracts itself, remaining always well colored.

4 — The hetero-pycnosis of the sex-chromosomes is observed through the whole grow phase of the spermatocyte I.

5 — The separation of the sex-chromosome tetrad, originating two independent sex-chromosomes, is observed in the early grow phase of the spermatocyte as well as during any other period of this phase. The latest separation is observed during the diffuse stage of the nucleus.

6 — When the autosomes are in diakinesis, the sex-chromosomes assume the aspect of chromosomes in pachytene.

7 — In metaphase I the autosomic tetrads are in a more condensed and colored condition than the sex-chromosomes. The sex-chromosomes move to the center of the autosome-forming circle, but there is no contact between them.

8 — In anaphase I it is observed 2 interzonal connections between each autosomic dyad ; some exceptions are observed. Only one interzonal connection is observed between the separating sex-chromosomes. Moving to the poles the sex-chromosomes also approximate one to the other.

9 — In telophase I the sex-chromosome touch each other, and fuse side-by-side, forming only one chromatic element. The line of fusion is well visible through the subsequent stages of meiosis.

10 — In metaphase II the autosomes are disposed at the equator. The sex-chromosome, dyad is also disposed at the equator, as well as at any other position.

11 — In anaphase II the separation of the auto.somes is normal, and it is seen only one interzonal connection between its halves. The sex-chromosome dyad do not separate and moves to one pole, always in precession.

12 — There are two classes of spermatids : a) with 7 autosomes ; b) with 7 autosomes plus the sex-chromosome dyad.

13 — During the first phases of the spermatogeneses the 7-autosomc containing nucleus presents a reticulated aspect ; the sex-chromosome-dyad containing nucleus shows this chromatic element well colored inside the reticulated nucleoplasm.

14 — The male of Dysdercus mendesi Bloete has 7 AA + XX chromosomes.

NOTE — A discussion on the movements of the sex-chromosome and its cycle. as well as on some aspects of the pairing of the autosomes, is being prepared. It will be published in the near future. The female of Dysdercus mendesi Bloete has 2n = 14A+4X.

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AGRADECIMENTOS

O autor deixa aqui consignados seus melhores agradecimentos ao sr. A. J. Teixeira Mendes, Chefe da Secção de Citologia do Instituto Agronômico, pelos auxílios prestados durante esta investigação, bem como pelas sugestões apresentadas.

LITERATURA CITADA

• 1.  Mendes, Luiz O. T. Os "Manchadores do Algodão" (Dysdercus spp.), Inst. Agr. Bol. Tecn. 23 (II) : 1-23, 2 est.. Campinas, 1936.
• 2.  Mendes, Luiz O. T. Sôbre algumas espécies de Dysdercus do Brasil e do Peru, Rev. Ent. VIII (1-2): 204-205, Rio de Janeiro. 1938.
• 3.  Mendes, Luiz O. T. Genetics of Dysdercus. I. Behaviour of a melanic form (mm) of Dysdercus mendesi Bloete. Jour. Herod. XXIX (10) : 387-391. X. York. 1938.
• 4.  Mendes, Luiz O. T. Genetics of Dysdercus. II. Behaviour of a yellow striped form of Dysdercus mendesi Bloete. Journ. Hered. XXX (11) : 498. X. York, 1939.
• 5.  Piza, S. de Toledo, Jr., Cromossômios de Dysdercus (Hemiptera-Phyrrhocoridae). Ann. Esc. Sup. Agr. "Luiz de Queiroz'''. 4 (65) : 209-210. 14 fig., Piracicaba. 1947.

Datas de Publicação

• Publicação nesta coleção
  08 Jun 2010
• Data do Fascículo
  1947