Protistology 4 (4) 347-352 (2006/7)
The effect of cultivation temperature on differentiation for mating type in exconjugant clones of the ciliate
Dileptus anser
Alexander L. Yudin and Zoya I. Uspenskaya
Institute of Cytology, Russian Academy of Sciences, St. Petersburg, Russia
Summary
The effect of cultivation temperature on differentiation of exconjugant clones for their mating types was studied
in the ciliate Dileptus anser. Crosses of the clone # 7C (mating type I, MT I) with the clone # 155 (MT III)
yielded 26 exconjugant F1 clones, one clone from each conjugant pair. Each young exconjugant clone was divided into
two subclones. One of the subclones was further cultivated at 17 °С, the other one, at 25 °С. The clones
were tested once a week with three test-clones for their mating ability, and their sexual immaturity vs. maturity,
what permitted to determine their MTs. Of 26 clones cultivated at 17 °С, two clones remained immature throughout
the experiment (23 to 25 weeks after crossing), at 17 °С as well as at 25 °С. 24 subclones cultivated at
17 °С appeared to be mature by the 20th to 23rd week after crossing. Eight of them had MT I, six - MT II, and
ten - MT III. Of 24 subclones cultivated at 25 °С, five changed their MTs early in their maturity state, and
three others did so even twice. In other words, these subclones showed unstable differentiation for their MT (cf.
Yudin and Uspenskaya, 2006). Later, 23 to 25 weeks after crossing, 17 subclones had MT I, 2 - MT II, and 5 - MT III.
The distributions for MTs at 17 °С and 25 °С differed significantly (c2 at 1 = 0.05), MT I prevailing at
25 °С and MT III, at 17 °С.
Key words: ciliates, Dileptus anser, mating types, temperature of cultivation, epigenetic
inheritance
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