2 DIFFERENT COLD RESISTANCE STRATEGIES IN CORN BORING CATERPILLARS OFA SAME BIOTOPE

Citation
N. Gillyboeuf et al., 2 DIFFERENT COLD RESISTANCE STRATEGIES IN CORN BORING CATERPILLARS OFA SAME BIOTOPE, Bulletin de la Societe zoologique de France, 122(1), 1997, pp. 21-31
Citations number
16
Language
FRANCESE
art.tipo
Article
Categorie Soggetti
Zoology
ISSN journal
0037-962X
Volume
122
Issue
1
Year of publication
1997
Pages
21 - 31
Database
ISI
SICI code
0037-962X(1997)122:1<21:2DCRSI>2.0.ZU;2-3
Abstract
In the south-west of France (45N, 0) two species of moth larvae overwi nter on corn stalks after harvesting: the European corn borer (ECB, Os trinia nubilalis Hbn., Pyralidae) and the Pink corn stalk borer (PCSB, Sesamia nonagrioides Lef., Noctuidae). ECB is able to resist to cold temperatures as low as -20 degrees C, but PCSB does not survive temper atures below -6, -8 degrees C. The aim of this study was to understand how PCSB was able to survive even to the slightly lower temperatures frequently encountered in this area of France, We used 2 approaches: i ) a biochemical analysis of cold-hardiness of PCSB using ECB as an exa mple of strong cold resistance, ii) an ecophysiological study of PCSB in its natural environment. Under cold temperatures both larvae are ab le to synthesize cryoprotectors; PCSB and ECB accumulate small amounts of hemolymph trehalose and huge amounts of hemolymph glycerol respect ively. These differences can be explained by the changes in the activi ties of two key enzymes of carbohydrates metabolism: Glycogen Phosphor ylase (GP) and Phospho 6 Fructo 1 kinase(PFK). In ECB, GP is highly an d continuously stimulated by low temperatures, producing large amounts of phosphorylated glucose. This substrate is then used to synthesize glycerol as a result of the stimulation of PFK by diapause and cold (t he mechanism of PFK activation is very similar to that of the mammals) . Conversely, in PCSB, GP is only weakly and transiently activated by cold, producing low amounts of phosphorylated glucose over a short per iod of time. Moreover PFK is inhibited and blocks the glycerol synthes is pathway. The phosphorylated glucose is then used for the synthesis of small amounts of trehalose by a PFK upstream pathway. Unlike ECB, d iapausing larvae of PCSB are not able to resist cold as a result of a biochemical adaptation. However they are able to escape cold by an unu sual <<behavioral strategy>>. At The beginning of the fall, diapausing larvae migrate into the roots of the corn plant, under the ground. Th e microclimate of this particular site protects larvae against air tem peratures as unfrequent as -15 degrees C (which are really seldom in t his area of France). The results of this ecophysiological study have l ead to the design of a non pollutant pest control method; after harves ting and before winter, the corn roots are uprooted and laid on the gr ound, where they are exposed to cold temperatures. For this purpose, a new agricultural tool has been designed.