Scorpion venom is known to enhance the excitability of nerve and muscle cells. Some venom appears to act preferentially on muscle cells while others have effects on neurones and neurotransmitter release. Scorpion venoms have been shown to release acetylcholine, noradrenaline and serotonin. The alpha scorpion toxins delay inactivation of sodium channels and thus prolong the action potential. The beta scorpion toxins affect activation in addition to slowing inactivation of sodium channels. The sodium channel opens at a membrane potential level at which the channel would be normally closed.
Box jelly fish (blue bottles found in Australia and South East Asia), man of war (USA) and sea anemones (China)
These animals discharge stinging capsules, nematocytes, which penetrate the skin and inject venom which may cause cardiorespiratory failure. Sea anemone toxin prolongs nerve action potential and causes spontaneous and repetitive activity in axons
Sea snail: cone shells
The genus Conus includes several marine snails with beautifully cone-shaped shells. These snails found in the Pacific and Indian oceans produce an extraordinary variety of neurotoxins (alpha, mu and omega conotoxins) that are deadly to their prey and can cause fatal respiratory paralysis in humans. Alpha conotoxins are potent antagonists at the postsynaptic nicotinic receptor while the other components act on sodium and calcium channels mu Conotoxins differ from tetrodotoxin and saxitoxin as they primarily block sodium channels in skeletal muscle with less effect on action potential conduction in motor nerves. There is no specific remedy. Cardiorespiratory resuscitation and maintenance of vital function can be life saving.