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When exposed their whole larval life to a 24 h. thermoperiodic cycle in constant darkness, individuals of Pieris brassicae L. give diapausing or non-diapausing pupae according to the length of the cold and warm sequences. The curve of thermoperiodic induction is similar to the photoperiodic curve.
Allatectomised females (whose diapause has been broken by chilling) do not lay though sham-operated or unoperated or unoperated controls do lay: corpora allata are essential for maturation. Ovocyte size is the same for allatectomized females as for diapause females. So it seems that the lack of ovocyte development might be the result of the inactivity or inhibition of corporal allata.
Actias selene has been reared under different conditions of lights, photophases and temperatures. The red light (630-670 nm) corresponding to the maximum of absorption of pterobilin and phorcabilin chromoproteins reduces the average length of development from 29 days to 50 days and totally inhibits the nymphal diapause. The results are discussed.
The diapause hormone (DH) responsible for arrested development of the silkworm Bombix mori consists of two active principles of peptide (A and B). Since both hormones form aggregates in aqueous phases, the molecular weights were determined by gel permeation chromatography of Merckogel OR 6000 using methanol-dichloromethane mixture as the developing agent. Gramicidins and modified peptides soluble in the organic solvents were used as the standard markers for the molecular weight measurements of the hormones. The molecular weights of DH-A and -B are estimated to be 3300 +/- 400 and 2000 +/- 200, respectively.
In the same experimental conditions, injections of ecdysterone induce moulting phenomena appearing after significantly different times according to whether the nymphs of Pisaura have been captured in October or January. The variable sensibility of the spiders towards an equal amount of hormones allows us to confirm the occurrence of winter-diapause in this Arachnid.
Facultative pupal insect diapause is induced by daylight rhythm and temperature furnished for the larval growth. Receptors of these factors are generally considered as larval eyes or brain. This work analyzes the possible role of pterobilin pigment of hemolymph and integument. This pigment seems to act independently and, sometimes with antagonistic actions, on the general physiology.
The content of juvenile hormone in the haemolymph of Anacridium, normal and infected by Metacemyia (Diptera Tachinidae), has been evaluated by the Galleria bioassay. In all the diapausing locusts, the level of juvenile hormone is very low. It is slightly increased in the males and the parasited animals. In all the locusts,, activated by electrostimulations of the pars intercerebralis, the level of juvenile hormone is high. It is the highest in the infected females with an inhibited vitellogenesis. The allata system cannot therefore be implicated in parasitic castration.
N. giardi collected at the end of the summer diapause were amputated at two levels of the posterior part of the body: After amputation of the 100 posterior segments (nearly half the body), the regeneration processes appear quickly. An amputation removing only the 30 posterior segments is followed by a reorganization in the injured area, but the worms are incapable of regeneration.
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