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First published online December 14, 2007
Journal of Experimental Biology 211, 79-85 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.009530

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A cumulative feeding threshold required for vitellogenesis can be obviated with juvenile hormone treatment in lubber grasshoppers

R. B. Fronstin and J. D. Hatle^*

University of North Florida, Department of Biology, 1 UNF Drive, Jacksonville, FL 32224, USA

View larger version (12K): [in this window] [in a new window]   Fig. 1. (A) Time to oviposition in response to feeding rate since adulthood and (B) time to oviposition since 4.0 g dry mass of lettuce was consumed in response to feeding rate. Cumulative diet quantity strongly affects age at oviposition in female lubber grasshoppers, but this plasticity is manifested only early in adulthood. Data from (Juliano et al., 2004).

View larger version (17K): [in this window] [in a new window]   Fig. 2. Body mass profiles of lubber grasshoppers in response to diets (low or high) and timing of gonadotropin treatments (early or late initiation of juvenile hormone analog; JHAi). The body mass profiles imply enhanced weight gain with higher feeding and after hormone treatment.

View larger version (6K): [in this window] [in a new window]   Fig. 3. Mean (± s.e.m.) times from gonadotropin treatments (initiation of juvenile hormone analog; JHAi) to oviposition in response to diets (low or high) and timing of JHAi. Regardless of whether the feeding threshold for vitellogenesis has been attained, early JHAi increases the time remaining until oviposition in lubber grasshoppers (P=0.013).

View larger version (6K): [in this window] [in a new window]   Fig. 4. Mean (± s.e.m.) number of eggs laid in response to diets (low or high) and timing of gonadotropin treatments (early or late initiation of juvenile hormone analog; JHAi). The number of eggs laid by lubber grasshoppers was significantly decreased by early JHAi (P=0.027) but was not affected by diet.

View larger version (11K): [in this window] [in a new window]   Fig. 5. Mean (± s.e.m.) length (A) and number (B) of secondary oocytes in response to diets (low or high) and timing of gonadotropin treatments (early or late initiation of juvenile hormone analog; JHAi). The number of secondary oocytes was significantly greater on high diet than on low diet in lubber grasshoppers (P=0.001) but was not affected by the timing of JHAi. By contrast, the length of secondary oocytes was greater in grasshoppers subjected to early JHAi than late JHAi (P<0.001) but was not affected by diet. Three groups have no error bars for secondary oocyte length because there was no variance in these data sets.

View larger version (11K): [in this window] [in a new window]   Fig. 6. Characteristics of vitellogenin profiles in response to timing of gonadotropin treatments (early or late initiation of juvenile hormone analog; JHAi). (A) Female lubber grasshoppers subjected to late JHAi had vitellogenin profiles consistent with favoring current reproduction at the expense of future reproduction, relative to females on early JHAi (P=0.001) (B). Values (mean ± s.e.m.) on the graphs show, from left to right, time from JHAi to vitellogenin onset, time from JHAi to vitellogenin maximum, maximum level of vitellogenin, and time from vitellogenin maximum to oviposition.

View larger version (12K): [in this window] [in a new window]   Fig. 7. Mean (± s.e.m.) storage protein maxima (A) and storage protein before initiation of gonadotropin treatment (initiation of juvenile hormone analog; JHAi) (B), in response to diets (low or high) and timing of JHAi. Hemolymph storage protein parameters were not affected by diet (P=0.841) or timing (P=0.334) of JHAi in female lubber grasshoppers.