Cytological studies of the two-spotted spider mite Tetranychus urticae Koch (tetranychidae, trombidiformes) II. Meiosis in growing oocytes

✍ Scribed by C. C. M. Feiertag-Koppen

• Publisher: Springer Netherlands
• Year: 1980
• Tongue: English
• Weight: 632 KB
• Volume: 54
• Category: Article
• ISSN: 0016-6707
• DOI: 10.1007/bf00055988

✦ Synopsis

The morphology and behaviour of the holokinetic chromosomes of Tetranychus urticae Koch were studied in maturing oocytes from diplotene up to and including metaphase. Each of the three diplotene bivalents contains 2-3 chiasmata.

During congression the dyads of the axially orientated bivalents make turning movements in opposite directions till they have reached an equatorial orientation which leads to an equational first meiotic division.

It was argued that chiasmata terminalise towards both ends of the dyads and that each dyad contains two sister chromatids.

It has been supposed that the inverted meiosis of organisms with holokinetic chromosomes can be brought about by the way in which chiasmata ter-minalJse and the kinetochores are assembled subsequently on each chromatid.

During congression vesicular strands form a Feulgen-negative zone round the bright plasm in which the bivalents are embedded. The question was raised whether these strands originate from the dense plasm surrounding each of the diplotene bivalents and bear some relation to the elimination chromatin present during the meiotic telophases.