Absence of a Lansing Effect in Drosophila subobscura

Abstract

LANSING¹ has conducted experiments to show the effect of maternal age on the length of life of the parthenogenetic rotifer Philodina citrina. The median length of life of the ‘wild’ strain of this species was 21–24 days, and maximum length and the adult rate of egg production were reached on the sixth day of life. A strain was bred from this wild strain consisting of rotifers hatched in each generation from eggs laid on the fourth day of parental life. Other strains were established, with parental ages in each generation of eleven and of sixteen days. In the fourth-day strain, the mean expectation of life increased over several generations, and the age of attaining the adult rate of egg production was delayed. In the eleventh- and sixteenth-day strains, there was a rapid decrease in the mean expectation of life, the strains reaching extinction in five and three generations respectively. According to Lansing, longevity progressively declines in any strain which is maintained in each generation from eggs laid on or after the sixth day of life. Results similar to those given by Philodina were also obtained by Lansing with Euchlanis triquetra.