Physiological interactions and development synchronisations between non-diapausing Ostrinia nubilalis larvae and the tachinid parasitoid Pseudoperichaeta nigrolineata
1987
Ramadhane, A. | Grenier, S. | Plantevin, G.
The physiological relationships between Ostrinia nubilalis Hübner and its tachinid parasitoid Pseudoperichaeta nigrolineata Walker are described under abiotic conditions which induce development of the host without diapause. The parasitoid lowers the larval growth of the host: the maximal weight attained by the parasitized larvae represented only 78% of that of healthy ones. The duration of the last larval host instar increased to 10.4 days in parasitized O. nubilalis compared to 8.0 days in unparasitized ones. The influence of the host on the parasitoid development was studied experimentally after parasitization of O. nubilalis larvae of instars 2 to 5. When the second larval instar of the host is parasitized, the overall duration of parasitoid larval development lasts twice as long as when the fifth instar is parasitized. The best yield of parasitoid pupariae (50%) is obtained when parasitization occurs in instar 3. We show that good synchronisation exists between the larval development of the host and its parasitoid. There are four phases of parasitoid development which would appear to require a ‘signal' from the host: the start of the growth of newly hatched parasitoid larvae and the 3rd to 4th instar ecdysis of the host; the first moulting of the parasitoid and the 4th to 5th instar ecdysis of the host; the growth resumption of the parasitoid instar II (weight about 1 mg) and the small rise of the ecdysteroid level in the middle of host instar 5; and in all probability, the second parasitoid moulting and the larval-pupal apolysis of the host.
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