Antimicrobial activity of the pygidial gland secretion of the troglophilic ground beetleLaemostenus(Pristonychus)punctatus(Dejean, 1828) (Insecta: Coleoptera: Carabidae)

The antimicrobial activity of the pygidial gland secretion released by adult individuals of the troglophilic ground beetleLaemostenus(Pristonychus)punctatus(Dejean, 1828), applying microdilution method with the aim to detect minimal inhibitory concentration, minimal bactericidal concentration and minimal fungicidal concentration, has been investigated. In addition, morphology of the pygidial glands is observed. We have tested 16 laboratory and clinical strains of human pathogens – eight bacterial both gram-positive and gram-negative species and eight fungal species. The pygidial secretion samples have showed antimicrobial properties against all strains of treated bacteria and fungi.Micrococcus flavusproved to be more resistant compared with other bacterial strains. More significant antimicrobial properties of the secretion are observed againstEscherichia coli, which proved to be the most sensitive bacteria.Aspergillus fumigatusproved to be the most resistant, whilePenicillium ochrochloronandPenicillium verrucosumvar.cyclopiumthe most sensitive micromycetes. Commercial antibiotics Streptomycin and Ampicillin and antimycotics Ketoconazole and Bifonazole, applied as positive controls, showed higher antibacterial properties for all bacterial and fungal strains, except forP. ochrochloron, which proved to be more resistant on Ketoconazole compared with the pygidial gland secretion ofL.(P.)punctatus. Apart from the role in ecological aspects, the antimicrobial properties of the tested secretion possibly might have medical significance in the future.

Über Arthropodenabwehrstoffe, LXV. Die Chemische Ökologie des Grundschwimmers Laccophilus minutus / On Arthropode Defensive Compounds, LXV. The Chemical Ecology of the Water Beetle Laccophilus minutus

According to a GC-MS analysis of methylated extracts the abdominal tips of the water beetle Laccophilus minutus (Dytiscidae) contain four β-hydroxyalkanoic acids. On the basis of MS and GC data another compound was assigned the structure of 6-octenoic acid.The same β-hydroxyalkanoic acids, and in addition, traces of β-hydroxyheptanoic acids were identified in dissected pygidial defensive glands after trimethylsilylation. Methyl 3,4-dihydroxyphenylacetate was recognized as a further main component in the pygidial gland secretion from the mass spectrum of its TMSi ether.The Laccophilinae occupy unique position among all the dytiscide subfamilies because they are the only water beetles which store β-hydroxyalkanoic acids in their pygidial glands. On the other hand the dytiscides appear to form a monophyletic group which is supported by the occurrence of methyl 3,4-dihydroxyphenylacetate. This class of compound is also commonly encountered in the other dytiscide subfamilies