New-born males produced by mictic females induced dnd cultured with emulsified dl-a-tocopherol-5-methyl-H3 were extracted with acetone. A thin-layer chromatogram of the extracted residue was divided into 20 1-cm fractions which were analyzed for radioactivity i n a liquid scintillation spectrometer; 100% of the tritium-labeled lipid co-migrated with authentic atocopherol. Since known a-tocopherol metabolites have migration characteristics different from a-tocopherol in the chromatography system used, i t was concluded that only undegraded a-tocopherol was present i n the males.
The efficiency of extraction of tritium label from 42 males was 89%, and 132 DPM were recovered from the thin-layer chromatogram. Therefore, each male contained about 5 X 10-16 moles, 0.2 pg, or 107 molecules of a-tocopherol.
The distribution of tritium-labeled a-tocopherol in embryonic and new-born males produced by mictic females induced and cultured with emulsified dl-atocopherol-5-methyl-H3 was analyzed by autoradiography. Background-corrected mean grain density values showed that, for two different new-born males, the amount of label i n the testis was 3.7 and 6.7 times that in the rudimentary gut. Grains over the testis appeared to be randomly distributed while those over the rudimentary gut were primarily over the periphery.
A semi-quantitative analysis of mictic females with male embryos in different stages of development showed that only in well differentiated males were grain densities over the testis noticeably greater than those over the rudimentary gut. In younger embryos grains appeared to be randomly distributed over the entire embryo. Grain densities over the rudimentary gut in males about to be born were much lower than those over embryos in earlier stages of development. These results, together with electron micrographs of the testis and rudimentary gut of new-born male Asplunchnu and information available on the subcellular distribution of a-tocopherol i n vertebrates and plants, suggest that during late development of the male embryo a-tocopherol-rich organelles such as mitochondria are lost from the degenerating tissue from which the rudimentary gut of the new-born male is derived.
The results obtained are consistent with the hypothesis that a-tocopherol is essential for spermatogenesis or male fertility in A. sieboldi and that for this reason the species has evolved its requirement of a-tocopherol for mictic female production
In the viviparous rotifers Asplunchnu sieboldi and A. brightwelli dietary a-tocopherol (vitamin E) triggers sexuality by inducing amictic females to produce some mictic female offspring (Gilbert and Thompson, '68). Amictic females, formed exclusively in the absence of dietary a-tocopherol, produce eggs which have one mitotic maturation division, are diploid, and always develop parthenogenetically