Biology Reference
In-Depth Information
CHAPTER EIGHT
Diapause: Delaying the
Developmental Clock in Response
to a Changing Environment
Connor
†,1
*
Department of Biology, University of Padova, Padova, Italy
†
Luca Schiesari
*
, Michael B. O
'
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota,
USA
1
Corresponding author: e-mail address: moconnor@umn.edu
Contents
1.
Introduction
214
2. Hormonal Control of Embryonic Diapause in Insects: The
“
Hatch-Ready
”
Example
215
3. Hormonal Control of Insect Diapause: The Mid-Embryonic Arrest Example
216
3.1 Production of diapause hormone in pupa determines the developmental
fate of the future egg
217
3.2 Control of DH expression
219
4. Developmental Control of Larval Diapause
219
5. Pupal Diapause
221
6. Diapause Can Modify Larval/Pupal Growth
226
7. Seasonal Polyphenisms Correlate with Diapause
227
7.1 Adaptive advantages of seasonal polyphenisms
231
7.2 Molecular mechanism for polyphenism induction
231
8. The Killifish Diapausing Embryo: A Developmental Analogy in a Vertebrate
233
8.1 Do insulin/IGFs play an evolutionary conserved function in diapause?
235
9. Summary and Perspective
236
Acknowledgments
237
References
237
Abstract
Seasonal changes can induce organisms to modify their developmental growth. Many
holometabolous insects, especially Lepidoptera, trigger diapause, an “actively induced”
dormancy, for overwintering. Diapause is an alternative developmental pathway that
reversibly blocks developmental growth during specific transitions and enhances the
hibernating potential of the organism. Changes in environmental cues, such as light
and temperature, trigger modifications in the levels, or in the timing, of developmental
hormones. These in turn switch the developmental trajectory (diapause or direct devel-
opment), strongly altering larval/pupal growth and inducing the appearance of
diapause-bound seasonal morphs (polyphenism). We also discuss an example of
