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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 3398

Kosaka Toshikazu; Features of Exconjugant Clones Derived from Intraconjugation and Crosses of Selfer by Non-selfer or Selfer in Marine Euplotes woodruffi (Ciliophora). J.Sci.Hiroshima Univ.,Ser.B,Div.1 30:83-99, 1982

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Intramating or selfing is observed in 4 selfer stocks of marine Euplotes woodruffi. Of these, stocks NK-11(S). IW-11(S) and HT-2(S) are derived from the wild, and 4a(S) from a cross. Using the selfers and a non-selfer stock NK-28 (mating type II), the exconjugants and the progeny clones from selfing were compared with those from intermatings in viability, duration of clonal life, monster formation, fission rate and fission rate mode. Viability of the exconjugant clones from selfing is 0% in NK-11(S), 37% in IW-11(S), 28% in 4a(S) and 74% in HT-2(S), while the progeny clones from intermating are viable in 60% in IW-11(S) by NK-11(S), 78% in NK-11(S) by NK-28(II) and 71% in IW-11(S) by NK-28(II). Six to 50% of the exconjugant clones which are destined to die within 15 days after the initiation yield monsters, and the death of these clones occurs immediately after monsters are formed in the cultures. The exconjugant clones from selfing that survive over 15 days also form monsters in 56% in IW-11(S), 21% in 4a(S) and 8% in HT-2(S), while the comparable clones from intermating occur in 20% in IW-11(S) by NK-11(S), 5% in NK-11(S) by NK-28(II) and 6% in IW-11(S) by NK-28(II). The viable clones from both the matings produce repeatedly monsters without perishing: for example, clone 19b has produced monsters at the 38th, 48th, 65th and 68th divisions after the initiation. The exconjugant clones that produce homo- or heteropolar twins also form monsters with abnormal cells in shape. The typical double animals are produced in two exconjugant clones from IW-11(S). In comparing the isolation lines from the exconjugant clones in their fission rates for a month, four fission rate modes A to D are separated from one another as follows: mode A with the fission rates of 1.5 to 2.5; B with 1.0 to 2.0; C varies from 0 to 1.5; D does from 0 to 2.5. In the exconjugant clones from selfing, the modes of the highest frequency are B and D each with 34% in IW-11(S), D of 50% in 4a(S) and D of 73% in HT-2(S). When these clones are classified into 7 ranges of fission rates, the range of the highest proportion is 1.26-1.50 with 38% in IW-11(S), the same range with 50% in 4a(S) and 1.76-2.00 with 38% in HT-2(S). Among the exconjugant clones from intermating, the mode of the highest proportion is A with 62-92% in 3 crosses, and the clones that are grouped into the fission rate range of 1.76-2.00 are in the highest proportion: 37% in IW-11(S) by NK-11(S), 64% in NK-11(S) by NK-28(II) and 35% in IW-11(S) by NK-28(II). Thus, the progeny clones from selfing are inferior to those of intermating in viability, vigor and fission rates, although selfing in HT-2(S) is similar to intermating in various points. In E. woodruffi which is an inbreeder in fresh water and an outbreeder in salt water, the significance of selfing in the outbreeder is reviewed in the discussion section.