Ref ID : 3399
Kosaka Toshikazu; Inbreeding Depression in Marine Euplotes woodruffi (Ciliophora). J.Sci.Hiroshima Univ.,Ser.B,Div.1 30:101-110, 1982
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A selfer stock of marine Euplotes woodruffi, HT-2, can yield progenies with full vigor in the first selfing after the stock has been established. Exconjugants from this selfing are isolated to grow clones in F1 inbred generation. By this way, clones from F2 to F6 inbred generations were examined on viability, fission rate, fission rate modes, and monster production. The clones can undergo selfing in each generation. To compare the effect of selfing with that of outcrossing on their progeny, 3 inbred clones were crossed with a non-selfer stock NK-28(II). Exconjugant viability is 74% in F1 inbred generation, 0-28% in F2 to F5, 0-1% in F6. F7 generation was not obtained. The exconjugants from 3 outcrosses are viable in 82% in F2-24a by NK-28, 84% in F4-C-9b by NK-28, and 78% in F4-D-8b by NK-28. Thus, successive inbred generations lower progeny viability, but one outcross can nullify the inbred depression. Fatal exconjugants without cell division are 0% in F1 inbred generation, 32-100% in F2 to F5, 94-100% in F6, and 2-7% in outcrosses. In contrast, exconjugants that can divide over 26 times in a month are 74% in F1, 0-26% in F2 to F5, only 1% in F6, and 52-82% in outcrosses. Thus, clones from F1 and outcrosses have higher vigor than those of F2 to F6. Among four modes of the fission rate, the highest frequency are fission rate of 0-3.0 (mode D) in F1 to F6 and Cr-B clones (40-100%), 1.5-3.0 (mode A) in Cr-A (83%) and Cr-C (51%). Clones of F2 to F6 do not show a mean fission rate of 1.76 or more, but 46% of F1 and 15-49% of outcrossing clones bear this rate. Of the clones which can survive over a month, 8% of F1 and 38-100% of F2 to F6 clones, and 16-27% of outcrosses produce monsters. Although monsters produced in F1 and outcrosses can divide to recover to normal cells, almost all of those yielded in F2 to F6 do not divide and then die. The result obtained shows that only the first selfing in the selfer stock of the outbreeder is very effective for maintaining life, but selfings in successive inbred generations bring about inbreeding depression on the progeny.