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Alanine; anaerobiosis; anoxia; free sugar; glycogen; inundation; lactate
Abstract:
The tiger beetle, Phaeoxantha klugii Chaudoir, survives the annual
inundation period in Central Amazonian floodplains as a third-instar larvae
submerged in the soil at approximately 29 C for up to 3.5 months. Previous
studies showed an exceptional anoxia resistance in these larvae and this study
investigates whether they perform anaerobiosis. Larvae collected in the field were
exposed to a pure nitrogen atmosphere for 0–9 days in the laboratory. The content
of lactate, alanine, free sugars and glycogen is analysed in surviving larvae.
Lactate and alanine contents rise during anoxia from around 1.5 and 7 to 6–14
and 15–22 mmol g 1 fresh mass, respectively, providing evidence for anaerobic
metabolism. Both compounds show a steep increase during the first 12 h and a
tendency to rise further with increasing duration of anoxic conditions, indicating a
significant metabolic depression within the first day. Content of free sugars and
glycogen varies greatly between individuals and ranges from 0.08–2.5 and 0.05–
2.9 mg g 1 fresh mass, respectively. Whether glycogen is used as metabolic substrate
for anaerobiosis could not be verified. The findings for free sugars indicate
that larvae apparently maintain the ability to regulate the level of glucose and/or
trehalose even after 9 days of anoxia.
