Chemistry of prothoracic defensive glands of water beetles

Water beetles (Coleoptera: Dytiscidae) are characterized by two complex gland systems. The pygidial glands contain mainly low molecular aromatic compounds. The pygidial secretion, which is spread on the integument, possesses antimicrobial activity and increases the wettability of the cuticle. In their prothoracic defensive glands, many Dytiscids store steroid compounds of the vertebrate hormone type, which show a deterring, anesthetic or toxic effect against predators (fishes, frogs).

In our institute the elucidation of chemical structures and biological effects of Dytiscid defensive compounds (mainly steroids) plays a crucial role. Furthermore, we investigate semiochemicals from pygidial glands of hydradephagous water beetles. A participation of microorganisms in the Dytiscid steroid biosynthesis is explored (isolation of microorganisms, steroid biotransformation experiments). The chemical analyses are performed by thin layer chromatography (TLC), gas chromatography (GC) and mainly gas chromatography-mass spectrometry (GC-MS) of the derivatized compounds (trimethylsilylether, O-methyloxim trimethylsilylether derivatives).