Effects of temperature on the rates of oxygen consumption during morphogenesis and diapause in the egg stage of Letopterna dolobrata (Heteroptera, Miridae).

Abstract

Oxygen consumption at 25°C was measured continously throughout the egg stage of Leptopterna dolobrata (more than 9 months).The rate of O2-uptake (μl O2/100 eggs · 1 h) is low in freshly laid eggs. Maintaining the eggs at a constant temperature of 16°C, respiration rises abruptly from the first day after oviposition and continues rising steadily for 3 days, reaching an average value of 1.4 μl. Oxygen consumption persists at or near this high level during the developmental phase of prediapause, which lasts about 15 days. After some days of oscillating high and low values, respiration decreases, and from the 24th day a low level (0.3-0.4 μl) is reached. If the eggs are incubated at 16°C continuously, this low diapause-level is maintained until the end of the experiments (42 weeks) and diapause is terminated in a few eggs only.A significant increase in the success of hatching is obtained by exposing the eggs to a sufficient period of chilling.24 groups of diapausing eggs were chilled at 5°C for certain periods (10, 18, 22, 26, 31, and 34 weeks) and afterwards transferred to 16°C and re-incubated. The changes of their O2-uptake at 25°C were traced throughout their chilling and successive re-incubating periods.Oxygen consumption is greatly accelerated during the cold treatment of the eggs. The low values of the diapause-level are raised progressively during the first 6 weeks of chilling. After this primary rapid increase, respiration remains at a level 5-times as high as the diapause values over a period up to the 25th week at 5°C. This is almost exactly the duration of mesodiapause (6 months).The rates of O2-uptake during the subsequent re-incubation at 16°C depend on the extent of chilling. The ability of diapause-breaking is correlated to the rates of O2-uptake, measured after setting of re-incubation. If respiration never decreases by the onset of re-incubation, diapause is terminated in most of the eggs, and the rates of O2-uptake increase as re-incubation goes on towards the emergence of the larvae (postdiapause period).A preliminary interpretation of the cold-stimulated O2-uptake in diapausing Leptopterna-eggs is given.