The Direct Physiological Costs of Natal Dispersal of the Desert Isopod (Hemilepistus Reaumuri)
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Authors
Rao, Steven T.
Issue Date
1996
Type
Thesis
Language
en_US
Keywords
Alternative Title
Abstract
Terrestrial isopods, commonly known as woodlice, are one of the very
few land-living groups of the Class Crustacea. Furthermore, the xeric-adapted
isopod Hemilepistus reaumuri (Audouin & Savigny, 1826) in particular, is
considered the most successful herbivore and detritivore of the macrofauna
inhabiting many Old World deserts. The life cycle of this semelparous and
monogamous isopod includes a dispersal phase, during which the young
isopods emerge from their subterranean burrows and may travel up to one
kilometer while dispersing from their natal burrows to the sites where they
will attempt to breed. They potentially benefit from this movement by
locating new habitats, by finding a mate, and by avoiding inbreeding with
conspecifics. However, the direct physiological costs of dispersal have not
been studied as thoroughly as other behavioral and life history traits in
terrestrial isopods, let alone other organisms. In the present study, the costs
of this important dispersal phase of Hemilepistus reaumuri were measured
by comparing those isopods which emerged from their subterranean burrows,
with which actively dispersed. The dispersers are defined as those isopods
which emerged from their burrows, but were then allowed to disperse. The
condition at different distances dispersed and the time spent dispersing was
analyzed, as was the amount of water and energy lost while dispersing. Ash
(minerals and inorganic matter) content of these isopods was determined
utilizing an ashing oven. Furthermore, water content was determined with
the use of a drying oven, while organic matter and caloric content were
determined through bomb calorimetry. In these experiments, it was found
that isopods lose energy and water while dispersing, and are generally in
worse condition the longer they disperse. However, they actually gain
organic material while dispersing. Analysis revealed that the primary
metabolic need of emerging isopods is food (organic material), while that of
the dispersers is water. Since the emergers have just come out of their humid
burrows and did not obtain organic material throughout their growing
process, there is a trade-off between time spent eating and time spent
desiccating throughout this dispersal period. As a result of this study, a more
complete understanding of the physiological costs of this behavioral
phenomenon was reached.
Description
v, 51 p.
Citation
Publisher
Kalamazoo College
License
U.S. copyright laws protect this material. Commercial use or distribution of this material is not permitted without prior written permission of the copyright holder.