Banding techniques on tardigrade chromosomes: the karyotype of Macrobiotus richtersi (Eutardigrada, Macrobiotidae) |
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Authors: | Lorena Rebecchi Tiziana Altiero Roberto Bertolani |
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Institution: | (1) Department of Animal Biology, University of Modena and Reggio Emilia, Via Campi 213/d, 41100 Modena, Italy |
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Abstract: | This work represents the first attempt to define tardigrade chromosomes using banding techniques. Macrobiotus richtersi, a eutardigrade morphospecies with amphimictic diploid and thelytokous triploid cytotypes, was used as a model. Prime consideration
was given to oocyte chromosomes because they are larger than those of spermatocytes and of mitotic chromosomes. With Giemsa
staining, the chromatids of the 6 bivalents of the diploid cytotypes and those of the 17–18 univalents of the triploid cytotypes
were very similar to each other and appeared rod- or flame-shaped. In the amphimictic strain, a chiasma was generally present
in each bivalent at diplotene, whereas there were no chiasmata in the oocyte prophase chromosomes of the triploid strain.
Both in diploid and triploid cytotypes, C-banding and fluorescence showed a heterochromatic centromeric band on the telomere
of each chromosome oriented towards the spindle pole, indicating that all of them were acrocentric. Silver staining showed
the presence of a NOR in only a pair of chromosomes, close to the centromeric C-banded site. NOR was particularly evident
in the oocyte prophases. Other silver positive regions, corresponding to the kinetochore, were located on all other chromosomes
on the telomeres towards the spindle pole.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | C-banding Macrobiotus richtersi NOR oocyte chromosomes tardigrades |
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