27 July 2010

Antarctic octopuses wield icy venom

Cosmos Online
Antarctic octopuses contain venom that is active in sub-zero climates, at temperatures which would render most other venoms useless, Australian scientists have discovered.
Antarctic octopus

One of the Antarctic octopuses discovered by Bryan Fry and his team on the Australian Antarctic Division's research cruise Credit: Courtesy of Bryan Fry

SYDNEY: Antarctic octopuses contain venom that is active in sub-zero climates, at temperatures which would render most other venoms useless, Australian scientists have discovered.

Enzymes in the octopuses’ venom become more active at 0°C, as opposed to 37°C, which is the optimal temperature for most venom activity. This enables the octopuses’ venom to be effective in their sub-zero surroundings.

This new finding helps to explain how some animals have adapted their venom to be effective in cold climate environments. It’s hoped that a better understanding of the composition of venom may also lead to new drug developments.

New species discovered, venom tested

While on the Australian Antarctic Division’s third International Polar Year research cruise, Bryan Fry from the University of Melbourne, lead author of the research published in Toxicon, and his team collected 203 octopuses, discovering in the process four new species.

Choosing four known Antarctic octopus species, they tested the composition and effectiveness of the venom in relation to the extreme temperatures of their environment.

The effectiveness of all venom is temperature dependent, with most enzyme activity peaking within certain temperatures ranges and ceasing when things become more extreme. If it reaches below 4°C, most venom is virtually inactive.

Octopus venom more effective in the cold

Most venomous animals such as snakes, spiders and jellyfish, have an optimal thermal range between 25°C and 65°C, and the further outside this range the temperature goes (on either side) the less active venom.

However, Fry and his team discovered that the venom of Antarctic octopuses peaks at 0°C.

“Not only do Antarctic octopuses have the most unique venoms out there, but there is a lot more species than we originally thought,” said Fry in a statement.

Venomous octopuses are everywhere

“All octopuses are venomous!” said Fry, of the cold-blooded cephalopods. A fact often overlooked because aside from the deadly blue-ringed octopus ( Hapalochlaena sp.), most octopus venom does not affect humans.

Mainly produced in its salivary glands, an octopuses’ venom is predominantly used for subduing and killing its prey, releasing it through its saliva when it bites.

The octopus use their venom to capture larger or more difficult prey like crabs or molluscs. They ‘drill’ a hole through the prey’s shell or exoskeleton using their tough beak and tongue and insert their venomous saliva into the soft interior. The venom not only kills the prey but it also helps to detach the soft flesh from the exoskeleton or shell.

Venom has possible drug applications

What enables the Antarctic octopuses’ venom to be effective at such low temperatures is still unknown. Fry hopes to continue work with Antarctic octopuses along with temperate and tropical octopuses, hoping to “compare and contrast where they are different”, and to figure out “the biochemical trickery of making the venom active” he said.

Fry’s research may also have other far-reaching applications, “an understanding of the structure and mode of action of venom found in all octopuses may help design drugs for conditions like pain management, allergies and cancer.”

Richard Lewis from the University of Queensland says Fry’s study “opens opportunities to find new bioactives with potential as research tools and possibly even leads to new therapeutics”.


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