Meeting Abstract

P3.138  Jan. 6  Juvenile hormone controls the timing of oviposition independent of the storage threshold in lubber grasshoppers FRONSTIN, RB; HATLE, JD*; Univ. of North Florida; Univ. of North Florida jhatle@unf.edu

Storage thresholds have been theorized to be important for major life history transitions. These theories hold that sufficient nutrients must be stored to fuel the commitment to develop into the next life history stage. Little is known about the physiological responses to attaining thresholds. Lubber grasshoppers have an adult feeding threshold to initiate vitellogenesis, ultimately leading to oviposition. By testing several mathematical models of development, this threshold has been shown to be 4.0 dry g cumulative feeding on Romaine lettuce. The relationship of this threshold and juvenile hormone (JH, the primary grasshopper gonadotropin) is unknown. Here, we determine whether this threshold and JH release are both needed to proceed toward oviposition, or whether JH only is sufficient. In other words, we test whether JH is solely responsible for the commitment to development to oviposition, or if the nutritional threshold must be met first. We surgically removed the source of JH from all females, then created 4 groups based on feeding rate and age at induction of the JH analog methoprene: High-Early, Low-Early, High-Late, and Low-Late. The Low-Early group was manipulated so that the cumulative feeding was clearly below the threshold at the initiation of JH analog (JHAi). In contrast, the cumulative feeding of the other 3 groups was above the threshold at JHAi. Neither diet nor age at JHAi affected the number of eggs laid (2-way MANOVA, P=0.354). Diet level had no effect on the age at oviposition (P=0.7242). In contrast, the age at JHAi had a strong effect on the age at oviposition (P<0.0001). This suggests that JH is sufficient to control the timing of oviposition, independent of nutrition.