Orientation and segregation of Robertsonian trivalents in Dichroplus pratensis (Acrididae)

C BIDAU; P. MIROL

GENOME

Año: 1988 vol. 30 p. 947 - 955

0831-2796

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman";} @page Section1 {size:595.3pt 841.9pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> Pairing behavior, metaphase I orientation, and anaphase I segregation of centric fusion trivalents were studied in 26 single, 15 double and 2 triple male fusion heterozygotes of the polymorphic South American melanopline grasshopper Dichroplus pratensis. They represent the seven different fusions and their combinations already described n different populations of the species. Our analysis showed the following: 1. pairing behavior is very regular in all trivalents. 2. frequencies of linear orientation was very low irrespective of the trivalent involved, 3. reorientation seems to occur frequently since frequencies of abnormal segregation and aneuploid second division cells were invariably lower than those of nonconvergent orientation, 4. aneuploidy and abnormal sperm production increase with increasing number of fusions, 5. chiasma frequency and localisation is relevant to trivalent orientation since trivalents with non convergent orientations showed proximal and interstitial chiasmata more frequently than convergently oriented ones. The results are in agreement with the hypothesis that these polymorphisms are old and stable.