In samples of Macrobiotus hufelandi found near Andalo (Trento) the sex-ratio changes in different places of the same rock (from 1:1 to 1:4). The caryological examination of the spanandric population (sex-ratio = 1:4) shows that many animals have 12 chromosomes in the mitoses and 6 bivalents in the meiotic prophase, as in the appenninic populations, but most of the females have 18 chromosomes in the mitoses and the same number of univalents in the ovarian eggs. Therefore in some sites of the rock two sympatric populations are present, one being bisexual and diploid and the other thelytokous and triploid. These results explain previous data of spanandric populations and of populations without males in M. hufelandi. The presence in the same species of both biotypes, one amphigonic and the other having ameiotic parthenogenesis is a frequent event among the Tardigrades.
Referenze Bibliografiche
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Con il contributo del Ministero per i Beni e le Attività Culturali