Gazelle : The Palestinian Biological Bulletin (ISSN 0178 – 6288) . Number 120, December 2014, pp. 30-53. | Page 8

37

Adaptations for arid conditions
This species presents adaptations to arid conditions which significantly improve
its desiccation tolerance. Some of those adaptations include a thick shell with a
relatively reduced aperture (Machin 1967), a thick epiphragm, and slow body
surface heat conduction. About 90% of its shell surface reflects the visible portion
of the solar spectrum, and much over 90% of the solar spectrum itself.
Sphincterochila boissieri also produces a new epiphragm after every period of
activity (Yom-Tov 1971).
These snails dig themselves into the soil to depths from 1 to 5 cm while they
aestivate during summer in the Negev Desert. In the vicinity of the Dead Sea,
they usually either burrow to depths of up to 10 cm, or aestivate hidden under
stones.
All dormant snails of this species can resist ambient temperatures up to 50 °C,
but temperatures of 55 °C and above are usually lethal. The soft parts of the
animal's body shelter inside the second and the third whorl of its shell, where the
temperature can reach up to 50.3 °C. Temperatures of up to 56.2 °C were
measured and are known to occur inside the shell's body whorl, which is mostly
filled with air during aestivation (Wikipedia).

The Study Area to the north of Umm Dimna (Dimona) in Al-Naqab Desert. Photo by the
Author. https://www.flickr.com/photos/50022881@N00/15564979663/
Gazelle : The Palestinian Biological Bulletin – Number 120 – December 2014