EFFECTS OF SEMI-STARVATION ON GROWTH AND MORPHOGENESIS DURING THE LARVAL STAGES OF A COMMON MILLIPED, NARCEUS ANNULARIS (RAF.)

¹ Division of Biological Sciences, Langmuir Laboratory, Cornell University, Ithaca, New York 14850

1. Growth, as measured by length and width, is substantially affected by diet. The length and width measurements were significantly lower for larvae in the semi-starved group.

2. The total number of body segments was statistically lower in the semi-starved larvae in instars 5 through 11. The difference was manifest at molts 5 and 6, remained constant at molts 7 and 9, and decreased slightly at molts 8 and 10.

3. Even though the mean number of segments was lower for adults of the semi-starved group, the range of adult segment number of the semi-starved animals was the same as the well-fed group and the same as the range given for the species.

4. Starvation caused the addition of fewer than normal (as compared to the well-fed group) segments in the early instars and a greater than normal number of segments in the later instars. Similarly, a significant number of semi-starved animals passed through either one or two extra segment-building instars.

5. The time spent in instars 4 through 11 was so variable that it was impossible to establish an index of development in time. Similarly, growth in time was most variable.

6. Diet did not have a significant effect on the number of ocelli added in each instar, or on the maturation of the male copulatory organs. These two characteristics are suitable characteristics for determining the instar of larvae, though the gonopods are difficult to examine in living specimens.