The leaves and young stems of the Giant Stinging Tree are covered by tiny hollow hairs made of silica (a glass-making compound) that contain a poisonous cocktail of substances. When the hairs break off in the skin of animals that may be attempting to eat the plant, these chemicals enter the tiny wound that is created and cause pain and discomfort. If human skin comes in contact with these hairs it can cause an itchy, burning rash.
Brown Beech (Pennantia cunninghamii)
The Brown Beech is a rainforest tree that stores a toxic glucocyanide compound in its leaves to inhibit or prevent them being eaten by caterpillars and other herbivores.
Millipedes
Millipedes are small invertebrates that mostly feed on dead or decaying plant material. They have a tough and firm exoskeleton but have virtually no other defense against larger aggressive carnivores. As a result, many millipedes have adapted sophisticated chemical defenses and are able to produce chemicals such as quinones, cresols, phenols and hydrogen cyanide. In flat-backed millipedes cyanide is produced in double-chambered segmented glands that initially produce a cyanophore (a harmless organic cyanide compound) in one chamber. When needed the cyanophore is secreted into the other chamber which produces an enzyme that breaks the cyanophore into hydrogen cyanide, which escapes through a pore and can kill an attacking insect or sicken a toad or frog. Millipedes survive their own toxins by closing off their breathing pores until the danger passes. If a human handles the millipedes the release of the odourless cyanide can be detected as a result of the simultaneous release of a benzaldehyde, which has a strong smell of crushed almonds.
A European species of millipede, Glomeris marginata produces a powerful sedative belonging to a chemical group called quinazolinones (includes the commercial sedative Quaalude). As a result, attacking wolf spiders simply go to sleep, sometimes for days. An additional component released with it contains powerful anti-feedant chemicals, which initially stop the spider from biting and feeding until the sedative takes effect. To let would-be predators know they are lethal the millipedes exhibit aposematic colouration (bright colours, such as reds and yellows to advertise their toxicity or distastefulness).
Acknowledgments
Shear, W. A. (1999) Millipeds – These ‘thousand-legged’ arthropods are little known by appear to hold many secrets for scientists, American Scientist Volume 87:232-239.