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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Ref ID : 2946

Lawrence A. Riggs and John J. Gilbert; The Labile Period for alpha-Tocopherol-induced Mictic Female and Body Wall Outgrowth Responses in Embryos of the Rotifer Asplanchna sieboldi. Int.Revue ges.Hydrobiol. 57(5):675-683, 1972

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Developmental stages of the oldest, first parity embryos of amictic females of the rotifer Asplanchna sieboldi were accurately determined. These amictic females were placed in 10E-6 emulsified d-alpha-tocopherol immediately after staging the embryos. The ability of the staged embryos to respond to the alpha-tocopherol ingested by their mothers and to develop into mictic females and females with body wall outgrowths was determined. In two of the four experiments the end of the embryonic labile period, for mictic female induction occurred between stages 18 and 19. Stage 18 embryos are highly differentiated and have coronal cilia with a strong metachronal beat. Stage 19 embryos are almost completely differentiated, being only one stage from hatching, and exhibit internal muscle contractions. In the other two experiments the end of the labile period occurred somewhat earlier - between stage 17 and 18 and between stages 16 and 17. The end of the labile period for body wall outgrowth induction was slightly later than that for mictic female induction. In three experiments it occurred between stages 19 and 20 (hatched individuals); in one experiment it occurred between stages 18 and 19. The extremely long labile period in A. sieboldi embryos for both mictic female and body wall outgrowth induction is to date unique in rotifers and is contrary to what has been found in brachionid rotifers. In these forms the end of the labile period occurs by the time the probably uncleaved eggs have been extruded from the maternal body cavity. This interesting difference in labile period duration between brachionids and Asplanchna is discussed.