Data from: Metabolic plasticity of Mormon cricket Anabrus simplex eggs in three developmental stages

<p dir="ltr">Many organisms have evolved means of dealing with dry periods, including surviving as seeds or eggs beneath the soil. Suppression of metabolism during developmental arrest is one means by which insects reduce maintenance costs and await more favorable conditions. Mormon crickets have a complex lifecycle that can endure more than 10 years with three potential stages for arrested development: prior to initiation of embryogenesis, when the embryo is half grown, and an obligate arrest when the embryo fills the egg. Using an experimental design of two incubating temperature treatments and two moisture levels, I examined whether Mormon crickets reduce their metabolic rate in response to drought to conserve water in these three stages of arrested development.</p><p dir="ltr">Eggs from individual females were kept separate, and sixteen eggs per female were separated evenly into two incubating temperature programs: one averaging 24°C at which embryonic development typically proceeds to the ultimate diapause stage (stage 23), and one averaging 28°C at which embryonic development typically arrests at the penultimate diapause stage (stage 19). The eight eggs in each temperature treatment were separated evenly into two humidity treatments (dry and saturated air). In preliminary results, these two moisture treatments resulted in a broad range of changes in egg mass: those housed in a desiccation chamber lost 10% of initial mass, on average, whereas those housed in saturated air gained 15% of initial mass, on average.</p><p dir="ltr">After 11 weeks of incubation, the eggs were removed from their respective treatments, brushed to remove any sand, weighed, examined under a dissecting scope for development, and placed in a closed metabolic chamber. The metabolic chamber comprised a 5 ml syringe with a three-way stopcock that was flushed with dry, CO<sub>2</sub>-free air for 5 min at 500 ml per min prior to closing to 4 ml volume. After approximately 24 h at room temperature (23.5±0.5°C), 3 ml of air from the chamber was plunged steadily into a Tygon hose with dry, CO<sub>2</sub>-free air flowing at 100 ml per min, which passed through a syringe of magnesium perchlorite to dry the air sample, and then into a FoxBox Respirometry System (Sable Systems, Las Vegas, Nevada) connected to a laptop computer, which recorded the total CO<sub>2</sub> respired by the egg during the time the chamber was closed. An empty chamber treated the same way served as a control. Total CO<sub>2</sub> was adjusted by time the chamber was closed and CO<sub>2</sub> that leaked into the control chamber during the same time period was subtracted. Respiration (in ml CO<sub>2</sub>/h) was divided by egg mass on the day metabolic measurement was initiated to yield ml CO<sub>2</sub>/h/g. Egg development was checked again after 18 weeks incubation (7 weeks later) and any changes in development stage were noted.</p><p dir="ltr">Data are divided into separate text files based on the egg stage at which respirometry was measured. Developmental stages 18, 19, 20, 21, and 23 were observed with a standard dissecting scope. No visible development refers to those eggs that were assumed to be in stage 4 (the stage for egg diapause), which was verified with lack of visible development 7 weeks later. See the readme file for an explanation of column headings.</p>

Tags: drought, egg-stages, energetics, katydids, multiannual-life-cycle, ontogeny, prolonged-diapause, water-conservation, western-u-s
Organization: Department of Agriculture