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1 September 2013 Immersion Tolerance in Dung Beetles (Coleoptera: Scarabaeidae) Differs Among Species but not Behavioral Groups
Sean D. Whipple, Michael C. Cavallaro, W. Wyatt Hoback
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Abstract

Dung beetles (Coleoptera: Scarabaeidae) are exposed to hypoxic conditions throughout their life cycle, including exposure to periods of severe hypoxia and hypercapnia within dung pats and closed burrows as adults. For rollers and tunnelers, underground brood chambers may also be exposed to flooding from seasonal precipitation. Because of their routine exposure to hypoxic conditions, these species may exhibit significant tolerance to immersion. Thus, this study examined the immersion tolerance of five species of adult dung beetles, Aphodius haemorrhoidalis (L.), Canthon pilularius (L.), Melanocanthon nigricornis (Say), Onthophagus hecate (Panzer), and Phanaeus vindex MacLeay, representing three behavioral groups (rollers, tunnelers, dwellers) by submersing them in hypoxic water (dissolved oxygen concentrations below 0.3 ppm). We found no differences in time to 50% mortality (LT50) among behavioral groups. Mean survival times ranged from 7–37 hours, with P. vindex having the shortest LT50 of 7.87 hours and A. haemorrhoidalis the longest at 37.04 hours. Additional tests compared survival of C. pilularius in a nitrogen atmosphere and while submerged in normoxic water. Although survival times increased slightly in normoxic water, results were not significantly different. We then quantified lactate in C. pilularius in response to severe hypoxia, demonstrating that this group, and likely other dung beetles, can conduct anaerobic metabolism during periods of severe hypoxia. These results suggest that immersion tolerance in dung beetles is governed by more than life history, and is likely a consequence of numerous ecological and physiological factors.

Sean D. Whipple, Michael C. Cavallaro, and W. Wyatt Hoback "Immersion Tolerance in Dung Beetles (Coleoptera: Scarabaeidae) Differs Among Species but not Behavioral Groups," The Coleopterists Bulletin 67(3), 257-263, (1 September 2013). https://doi.org/10.1649/0010-065X-67.3.257
Received: 9 January 2012; Accepted: 27 June 2013; Published: 1 September 2013
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KEYWORDS
anaerobic metabolism
anoxia
behavior
LT50
survival time
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