Study On The Defensive Organ, Defensive Substance And Their Functions Of Tenebrio Molitor L.

Tenebrio molitor L. is a kind of resource insects with high nutritional value and various health functions, and being endowed with the "treasury of protein feedstuff. The adults formed a special chemical defensive mechanism during long-term struggle for existence. That is to say, they can release a kind of special irritant smell and poisonous secretion through their partially everted defensive glands in abdominal terminal.The study mainly includes the inserted position and the morphology of the defensive glands in abdominal terminal of the adult. Chemical constituents in the defensive secretion of different aged and sexual adults were analyzed qualitatively and quantitatively by the gas chromatography-mass spectrometry (GC/MS), so were the body fluid from the abdominal terminal of larvae and pupae. Then the antimicrobial tests with the defensive secretions of the adults, and with the standard materials of methyl-p-benzoquinone and p-cresol as the main defensive chemicals in the secretion were conducted.The research results show that:1. The defensive organ of the adult is a cystiform configuration, the invagination of the intersegmental membrane between the 7^th and the 8^th sternites. Two reservoirs are tapering toward their blind distal ends and have a common chamber at their basilar part in the coelom. The defensive glands locate at the dorsal root of the reservoirs. The duct of each secretory unit of the defensive glands runs the full distance to the junction with the reservior and the ducts of 30 to 40 cells are collected into bundles. Lots of short shallow cones project out from the location where the bundles merge with the sac wall.2. Dichloromethane is selected from three kind of solvents as the optimal extracting solvent. More than 20 peaks appear when each extraction of defensive secretions of the adults aged 15, 30 and 60 days is analyzed respectively by GC/MS, among them 7 chemicals: methyl-p-benzoquinone,p-cresol, tricosane, tetraconsane, 12-pentacosene, pentacosane and hexacosane are identified. Comparing the amount of the two defensive substances between different aged males and females, the contents of methyl-p-benzoquinone in per gram defensive secretion and in per beetle of 15-day-old females is lower than those of the same aged males. From age 15 to 30 days and 30 to 60 days, the content in females goes up sostenuto. The content in males goes up at first and falls later on in two periods respectively, but the contents are far lower than those in females. The contents of methyl-p-benzoquinone of 60-day-old females and males all arrive at the maximum, the former is about 155.12μg/g and 23.39μg/g respectively, the latter is about 0.90μg/beetle and 0.27μg/beetle respectively. The content of p-cresol in per gram defensive secretion of 15-day-old female is lower than that of the same aged male, the content in female goes up sostenuto in two periods, but the content in male is always lower than those in female. The content of p-cresol in per beetle's defensive secretions of female is lower than that of the same aged male. During the two age periods, the content in female goes up at first and falls later on. Moreover the content in males falls on sostenuto, but the content is gradually lower than that in females. The changing rule of the total amount of the two chemicals in per gram defensive secretions and in per beetle is the same as those of methyl-p-benzoquinone. When aged 60 days the contents of methyl-p-benzoquinone and p-cresol in both sexes all arrive at the maximum, the former is about 176.89μg/g and 34.34μg/g respectively, the latter is about 1.03μg/beetle and 0.37μg/beetle respectively. At the same time, the author finds that the defensive substance in adult is re-generable. The contents of methyl-p-benzoquinone and p-cresol may recover to about 59.39% and 104.43% of the former levels respectively 15 days after the 30-day-old female empties its defensive substance. In this experiment, none methyl-p-benzoquinone or p-cresol is detected in the outflows of pupae and larvae when their abdominal terminals are stabbed.3. The Oxford Cup method is used in detecting the inhibitory intensity of the defensive secretion in 30-day-old adults over 5 species of microbes, the effects of inhibitory intensity are: Penicillium citrinum>Escherichia coli and Staphylococcus aureus> Candida albicans, but the secretion does not affect Aspergillus niger at all. Dichloromethane does not show inhibitory effect against the 5 species of microbes. The dilute-plate method of methyl-p-benzoquinone aqueous solution and p-cresol aqueous solution is used to detect each antimicrobial effect on the 5 species of microbes, their inhibitory intensities go higher with the boosting concentration of the two solutions. The Minimal Inhibitory Concentration (MIC) of methyl-p-benzoquinone solution on Escherichia coli and Staphylococcus aureus is 62.5mg/L, on Candida albicans and Penicillium citrinum is 250mg/L, and on Aspergillus niger is 500 mg/L. The MIC of p-cresol solution on Penicillium citrinum and Aspergillus niger is 500mg/L, on Escherichia coli and Staphylococcus aureus is 1000mg/L. The inhibitory effect of p-cresol solution (1000mg/L) on Staphylococcus aureus is very remarkable. Obviously, both methyl-p-benzoquinone solution and p-cresol solution may inhibit the 5 species of microbes, but the former one is more effective.In conclusion, by studying the defensive substance in the abdominal terminal of the adults, and studying the secretion rule of the substance and the antimicrobial effects of the substance,it may deepen our understanding in the defensive mechanism and defensive function of Tenebrio molitor L. It may provide a theoretic basis for the further research and practical production for Tenebrio molitor L. as a kind of resource insects.