Survival of Empoasca labae (Harris) (Cicadellidae, Homoptera) on Synthetic Media

Nymphs of the potato leafhopper were caged in small clear plastic snap boxes for individual survival studies. All experiments were conducted at 85°F in a darkened incubator, minimizing responses to light and varying temperature. The leafhopper nymphs were sustained on an agar gel matrix containing sugars and amino acids. Relative nutritional adequacy was evaluated by the time required to reach 50% survival. The lowest mortality rate occurred on a 7% sucrose-2% agar medium. Preferential utilization of the glucose fraction of sucrose was indicated. A medium composed of agar, sucrose, and the 10 amino acids essential for human and rat nutrition tripled the 50% survival time compared with agar controls

Symbiosis constraints : Strong mycobiont control limits nutrient response in lichens

Symbioses such as lichens are potentially threatened by drastic environmental changes. We used the lichen Peltigera aphthosaa symbiosis between a fungus (mycobiont), a green alga (Coccomyxa sp.), and N-2-fixing cyanobacteria (Nostoc sp.)as a model organism to assess the effects of environmental perturbations in nitrogen (N) or phosphorus (P). Growth, carbon (C) and N stable isotopes, CNP concentrations, and specific markers were analyzed in whole thalli and the partners after 4months of daily nutrient additions in the field. Thallus N was 40% higher in N-fertilized thalli, amino acid concentrations were twice as high, while fungal chitin but not ergosterol was lower. Nitrogen also resulted in a thicker algal layer and density, and a higher C-13 abundance in all three partners. Photosynthesis was not affected by either N or P. Thallus growth increased with light dose independent of fertilization regime. We conclude that faster algal growth compared to fungal lead to increased competition for light and CO2 among the Coccomyxa cells, and for C between alga and fungus, resulting in neither photosynthesis nor thallus growth responded to N fertilization. This suggests that the symbiotic lifestyle of lichens may prevent them from utilizing nutrient abundance to increase C assimilation and growth.Bio4Energ