. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EVENTS IN THE LIFE SPAN OF DAPHNIA MAGNA 263 The differences between any two groups either in terms of hours or instars are not statistically significant. However, it is interesting to note that the average number of adult instars is the same for each group and the differences in longevity correspond to the differences in the accumulated time at the end of the pre-adult instar 400 600 800 1000 1200 FIG. 1. Survival curves for female Daphnia magna primiparous during the fifth, sixth, and seventh instars as indicated
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. EVENTS IN THE LIFE SPAN OF DAPHNIA MAGNA 263 The differences between any two groups either in terms of hours or instars are not statistically significant. However, it is interesting to note that the average number of adult instars is the same for each group and the differences in longevity correspond to the differences in the accumulated time at the end of the pre-adult instar 400 600 800 1000 1200 FIG. 1. Survival curves for female Daphnia magna primiparous during the fifth, sixth, and seventh instars as indicated by the numerals. MacArthur and Baillie (1929a) in their experiments on the effect of temperature on longevity found that female Daphnia magna lived ± days ( ± hours) at 28° C. and ± days ( ± hours) at 18° C. Our animals lived longer than would be expected from their results. In all probability our culture conditions were more favorable since, as will be brought out later, the number of young produced was greater. DURATION OF THE JNSTARS The duration of each instar for each pre-adult instar group is given in Table I. This is also shown graphically in Figures 2, 3, and 4. In general the duration of the instars increases with age. This agrees with the results secured by Ingle, Wood, and Banta (1937) for Daphnia longispina. The duration of any one pre-adult instar for animals primiparous during either the fifth or sixth instars is significantly different from that of any other pre-adult instar. This does not hold true for the animals primiparous in the seventh instar. The first adult instar, the instar during which the females are primiparous is distinctly longer than the longest pre-adult instar. While the duration of adult instars varied considerably the differences are not often sig- nificant. In a few cases, notably in the eleventh and twelfth instars of the group primiparous in the fifth instar, the twelfth and thirteenth. Please
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
