Impacts of Paleo-Oxygen Levels on the Size, Development, Reproduction, and Tracheal Systems of Blatella germanica

Abstract

Atmospheric oxygen has varied substantially over the Phanerozoic (the last 500 million years) with periods of both hyperoxia and hypoxia relative to today. Unlike some insect groups, cockroaches have not been reported to exhibit gigantism during the late Paleozoic period of hyperoxia. Studies with modern insects have shown a diversity of developmental responses to oxygen, suggesting that evaluation of historical hypotheses should focus on groups most closely related to those present in the Paleozoic. Here we investigated the impacts of Paleozoic oxygen levels (12-31%) on the development of Blatella germanica cockroaches. Body size decreased strongly in hypoxia, but was only mildly affected by hyperoxia. Development time, growth rate and fecundity were negatively impacted by both hypoxia and hyperoxia. Tracheal volumes were inversely proportional to rearing oxygen, suggesting developmental responses aimed at regulating internal oxygen level. The results of these experiments on a modern species are consistent with the fossil record and suggest that changes in atmospheric oxygen would be challenging for many insects, despite plastic compensatory responses in the tracheal system.

Caterpillars selected for large body size and short development time are more susceptible to oxygen‐related stress

“…Hypoxia generally decreased survival and growth rate in M. sexta , effects that have been observed in a variety of insects now, including mealworms (Loudon ), cockroaches (VandenBrooks et al. ), fruit flies (Klok et al. ), and grasshoppers (Harrison et al.…”

“…; VandenBrooks et al. ). The mechanisms for the negative effects of hypoxia on growth rate and size remain unclear and may vary with life stage and species.…”

“…In the cockroach, Blatella germanica , growth rate, development time, and survival are negatively affected by both hypoxia and hyperoxia; body size is reduced by hypoxia and weakly or not affected by hyperoxia (VandenBrooks et al. ). It has previously been shown that in M. sexta , hyperoxia ( Po 2 40 kPa) does not affect the maximal larval mass (Callier and Nijhout ).…”

“…Caterpillar pupae may also experience hypoxia during flooding as they are buried in the ground. Studies with a variety of insects have shown that hypoxia generally reduces insect body size and growth rates (Peck and Maddrell 2005;Harrison et al 2009Harrison et al , 2010Harrison and Haddad 2011;Heinrich et al 2011;VandenBrooks et al 2012). The mechanisms for the negative effects of hypoxia on growth rate and size remain unclear and may vary with life stage and species.…”

Parental hypoxic exposure influences performance of offspring in Callosobruchus maculatus

“…Hypoxia exposure could also impair reproduction by reducing the fecundity of treated insects and the hatch rate of these eggs . In our experimental setting, this effect was only apparent in cowpea bruchids when hypoxia exposure occurred in the fourth instar larval stage or later (Fig.…”