Determination And Analysis Of The Metal Elements In The Fifth-instar Silkworm And The Pesticide Poisoning Silkworm

There are18major nutritive elements in the silkworm, Bombyx mori L, which play animportant role in the silkworm growth and development. Thus, scientists pay more and moreattention to the element contents and their biological function in silkworm, especially theinfluence on the cumulative toxicity of heavy metals. In this study， silkworm variety ofC108was selected as experimental materials. The metal contents in the5thinstar of thesilkworm were determined by ICP-MS with microwave digestion as sample pre-treatmentmethod. The main results are as follows:1. Detection methods of metal elements in the silkworm have been established. Theconditions of pre-treatments were optimized in the amount, time and temperature ofdigestion solution. It has been found that the accuracy of mass spectrometer detectiondepends on the injection rate, the parameters of the instrument and the collision gas rate, andso on. The national standard reference material Astragalus was used as reference, and therecoveries of standard were applied to verify the accuracy of the method. The differentdetection modes were used to reduce the interference of the impurity elements in thesamples and reagents. After optimizing, determination of²³Na,²⁴Mg,³⁹K,⁴⁴Ca,⁵⁵Mn,⁵⁶Fe,⁶⁰Ni,⁶⁵Cu,⁶⁶Zn and⁸⁵Rb contents were accurate, simple and rapid.2. Some relevance between metal content and physiological activities of the5thinstarsilkworm has been found. The contents of K element in the four tissues of5thearly stage ofsilkworm were significantly higher than those of other stages, especially that in the fat body.This is because the development of5th early instar larva of silkworm needs lot of nutrientsand energy. By contrast, the K contents in some tissues decreased to some extent at the endof the fifth instar, which might cause by the low osmotic pressure and the physiologicalfunction damage. Meanwhile, similar trends of the contents of Fe, Ni, Na were also found intissues of5thof silkworm. These results infer that synergistic action among elements Fe, Ni,Na might exist in the processes of material transport, energy transmission, enzyme activityand conformational transition of the protein in5thsilkworm.3. Compared with the control, the elements contents were obviously changed in thepesticide poisoning silkworm.The contents of Ca, K, Ni, Mg, Zn in silk gland, midgut and fat body of theChlorfenapyr-poisoning silkworm were higher in the middle dose group than that in the lowand high dose groups. The results of experiment showed that most of the elements contentsin the blood had no significant difference among the different dose groups. The content of K in blood was high in the low dose group, which was significantly different from that in silkgland, midgut and fat body.The content of Ni in organizations of the Phoxim-poisoning silkworm was generallylower than that in the control, which might cause by the low activity of enzymes inPhoxim-poisoning silkworm. Though Rb content in treatment groups was lower than that inthe control group, it was raised in treatment groups with the phoxim dose increased, this wasbecause of the accumulation of acetylcholine and the increased activity in nerve of thePhoxim-poisoning silkworm.The content of Na in the high dose group of the Cypermethrin-poisoning silkworm wassignificantly higher than that in the low, middle and control groups. Meanwhile, the contentof Fe in the control group was generally higher than that in the pesticide treatment groups.The results showed that the internal environment in silkworm had been significantlychanged and the physiological function of some proteins in hemolymph had been damagedin the Cypermethrin-poisoning silkworm.