Conditional Changes in Brood Size and Speed of Development After Long-term Laboratory Culturing of C. elegans Wild-type Strains.

Prolonged culturing of laboratory animals allows for genetic changes to occur in a population, potentially leading to phenotypic variation in designated wild-type strains. We discovered that two of our laboratory's C. elegans wild-type strains have undergone significant alterations in brood size and speed of development. One wild-type-derived strain displays a conditional increase in brood size, while a second strain exhibits a conditional decrease in brood size. The decrease in brood size in one strain is accounted for by a similar decrease in spermatogenesis. We also found that our two derived laboratory strains differ in speed of development. The strain with increased brood size displayed a faster progression during larval development, while the strain with decreased brood size displayed a slower progression of development. Therefore, both adaptive and non-adaptive changes in wild-type strains may occur after prolonged culturing.