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Adaptations of carabid beetles to dry habitats in East Africa

Published online by Cambridge University Press:  10 July 2009

Johan Andersen
Affiliation:
Institute of Biology and Geology, University ofTromsø, PO Box 3085, Guleng, 9001 Tromsø, Norway
Karl Erik Zachariassen
Affiliation:
Department of Zoology, University of Trondheim, 7055 Dragvoll, Norway Department of Animal Physiology, University of Nairobi, PO box 30197, Nairobi, Kenya
Geoffrey M. O. Maloiy
Affiliation:
Department of Animal Physiology, University of Nairobi, PO box 30197, Nairobi, Kenya
John M. Z. Kamau
Affiliation:
Department of Animal Physiology, University of Nairobi, PO box 30197, Nairobi, Kenya

Abstract

The rates of water loss and humidity preference of carabids from dry tropical habitats have been studied and compared with corresponding data from temperate carabids and tropical tenebrionids. Within each group of beetles the rate of relative water loss decreases with increasing body size. Carabids from dry tropical areas have rates of water loss which are lower than those of temperate species, but considerably higher than the values for tenebrionids from dry tropical habitats. Small temperate carabids can stay in dry air for only a few hours, whereas large tropical tenebrionids may survive for weeks without becoming critically dehydrated. Given the choice between a dry and a humid atmosphere, well hydrated beetles of all groups will initially choose the dry atmosphere. Most temperate carabids will switch to humid atmosphere after a few hours and tropical carabids after 1–3 days, whereas tropical tenebrionids may remain in dry air for almost 3 weeks. The temperate carabids are very sensitive to dehydration and will shift to a humid atmosphere when dehydrated by only 2–5%. Tropical carabids and tenebrionids will shift first when they are dehydrated by 7–20% of their body weight in a hydrated state, implying that these beetles are considerably less sensitive to water loss than temperate carabids.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1986

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