Decoupling development and energy flow during embryonic diapause in the cricket,Allonemobius socius

Abstract

SUMMARYRespiration rate increases 6.3-fold during 15 days of post-oviposition development in embryos of the Southern ground cricket, Allonemobius socius. This ontogenetic increase in metabolism of non-diapause insects is blocked during diapause, such that metabolic rate is only 36% of the rate measured for 15 days developing embryos. Surprisingly, however, there is not an acute metabolic depression during diapause entry at the point when developmental ceases (4–5 days post-oviposition), as measured by blockage of morphological change and DNA proliferation. The results indicate a decoupling of developmental arrest from metabolism. Both non-diapause and diapause embryos have unusually high [AMP]:[ATP] ratios and low [ATP]:[ADP]ratios during early embryogenesis, which suggests embryos may have experienced hypoxia as a result of an insect chorion that limits water loss but may restrict oxygen diffusion. The similar adenylate profiles for these two developmental states indicate the atypical energy status is not a specific feature of diapause. In addition embryos at day 3 have high levels of lactate that decrease as development proceeds up to day 7. Calorimetric-respirometric(CR) ratios of –353 (day 3) to –333 (day 7) kJ mol–1 O2 are consistent with embryos that are aerobically recovering from hypoxia, but are inconsistent with an ongoing anaerobic contribution to metabolism. Superfusing 3-day embryos with O2 enriched air (40% O2) forces these metabolic indicators toward a more aerobic poise, but only partially. Taken together these biochemical data indicate the metabolic poise of A. socius is only partly explained by hypoxia in early development, and that the atypical set points are also intrinsic features of this ontogenetic period in the life cycle.