Exceptional anoxia resistance in larval tiger beetle, Phaeoxantha klugii (Coleoptera: Cicindelidae)

Abstract

The tiger beetle Phaeoxantha klugii inhabits Central Amazonian floodplains, where it survives the annual inundation period in the third-instar larval stage submerged in the soil at approximately 29 C for up to 3.5 months. Because flooded soils quickly become anoxic, these larvae should be highly resistant to anoxia. The survival of adult and larval P. klugii was therefore tested during exposure to a pure nitrogen atmosphere in the laboratory at 29 C. Adult beetles were not resistant (< 6 h). Survival of larvae decreased over time, maximum survival was 15 days, whereas time to 50% mortality was 5.7 days (95% confidence interval 3.8-7.9). Anoxia resistance was additionally tested in third-instar larvae submerged within sediment for 40 days before anoxia exposure in the laboratory. Anoxia resistance was greatly enhanced in these larvae, showing a survival rate of 50% after 26 days of anoxia exposure. It appears that the gradual flooding process and/or the submersion phase induced a physiological alteration, most probably a strong depression in metabolic rate, which requires some days for induction. The degree of anoxia resistance in larval P. klugii is remarkable among terrestrial arthropods worldwide, even more so considering the high ambient temperatures. The species is well-suited to serve as a model organism for studying the physiological mechanisms of anoxia and submersion resistance in terrestrial arthropods inhabiting tropical floodplains.

Functionality of the plastron in adults of Neochetina eichhorniae Warner (Coleoptera, Curculionidae): aspects of the integument coating and submersion laboratory experiments

“…Insects respond to the condition of hypoxia through various strategies such as reduction of metabolic and respiratory rates, and the reduction of the production of ATP. This process causes a decrease in locomotor movements of insects (Hoback et al 2000;Zerm & Adis 2003), as observed during this experiment. It is likely therefore that the condition of hypoxia influenced the respiratory rate, affecting the production of ATP, decreasing the motor activity of N. eichhorniae individuals submerged for short periods in previously boiled water and for periods longer than eight hours in natural non-aerated water.…”

Hidden burrow plugs and their function in the tiger beetle, Cosmodela batesi (Coleoptera, Cicindelidae)

“…The degree of flooding largely explains which strategy may evolve. For example, species that inhabit places that experience prolonged flooding events are more likely to exhibit physiological tolerance (Zerm and Adis 2003) or relocation (Brust et al 2006), presumably because plugging would not be sufficient over a long time. In locations that experience only short-term flooding caused by periodical rain, plugging in response to high soil moisture would be sufficient for the larvae to protect themselves against asphyxiation.…”

“…To survive flooding, tiger beetles that inhabit floodplains, such as Cicindela togata (Hoback et al 1998) and Phaeoxantha klugii (Zerm and Adis 2003), have evolved physiological tolerance to anoxia, and can survive many days of immersion. Some species show behavioral adaptation; for example Cicindela hirticollis larvae abandon their burrows and relocate in response to flooding (Brust et al 2006).…”

Impact of dams on point bar habitat: a case for the extirpation of the Sacramento Valley Tiger Beetle,C. hirticollis abrupta

“…Tiger beetle larvae are known to survive in water edge habitats that have been fully submerged for periods of 1-2 weeks or more (Hamilton, 1885;Willis, 1967;Wilson, 1974), but recent laboratory drowning studies with C. hirticollis found that most larvae survived less than 4 days and none longer than 8 days (Brust et al, 2005). Laboratory tests of Phaeoxantha klugi, a tiger beetle of the Amazonian floodplain, found that larvae could survive much longer (an average of 26 days) when placed in sediments for several weeks before becoming gradually flooded (Zerm and Adis, 2003). In particular, Zerm and Adis (2003) speculated that the increased survival resulted from metabolic depression caused by the gradual flooding which these beetles experience in their native habitat.…”

“…Laboratory tests of Phaeoxantha klugi, a tiger beetle of the Amazonian floodplain, found that larvae could survive much longer (an average of 26 days) when placed in sediments for several weeks before becoming gradually flooded (Zerm and Adis, 2003). In particular, Zerm and Adis (2003) speculated that the increased survival resulted from metabolic depression caused by the gradual flooding which these beetles experience in their native habitat. A recent study with C. hirticollis, however, found that larvae within their closed burrows in laboratory chambers responded to flooding by readily digging out of their burrows and floating to the water surface (Brust et al, 2006).…”