The research was conducted on four Antarctic octopus species (Adelieledone polymorpha, Megaleledone setebos, Pareledone aequipapillae, and P. turqueti) collected from the coast off George V's Land, Antarctica. The scientists investigated the biochemical properties of extract from the posterior salivary glands of these four species. These samples were assayed for alkaline phosphatase (ALP), acetylcholinesterase (AChE), proteolytic, secreted phospholipase A(2) (sPLA(2)), and haemolytic activity. ALP is an enzyme that is also found in spider and snake venom and is thought to help immobilize prey. AChE breakes down acetylcholine (a neurotransmitter), disrupting neuromuscular function. Proteolytic enzymes sever peptide bonds, breaking down proteins. sPLA(2) hydrolyzes phospholipids at the sn-2 position to form fatty acid and lysophospholipid products. Haemolytic refers to the break down of blood or disintegration of red blood cells.
So lets break the results down:
ALP activity - all species
AChE activity - little activity in any species (but results were inconsistent)
Proteolytic activity - all species
sPLA2 activity - all species
Haemolytic activity - all species but weak; P. turqueti had weak to none
So the octopuses have a nice venom cocktail at their disposal. One interesting finding though was that some biochemical activity, like ALP, were tested at two different temperatures: 0 degrees Celcius and 37 degrees Celcius. The researchers found that the biochemicals actually worked better at the colder temperatures, suggesting long term evolution of the chemical structure for optimal function at low temperatures.
Alright, so they tested to see if a bunch of stuff was there. What does that matter? These chemicals characterize the venom itself. They also collected the dietary and morphological data on these species from the literature in order to explore the ecological and evolutionary importance of venom. It is important to note that the authors point out that few clear venom-related adapations in diet or anatomy were present in these species. For example, A. polymorpha feeds on amphipods and polychaete worms, so why exactly is venom necessary? But perhaps that is an experiment for another study.
Here's the article:
Undheim EA, et al. (2010) Venom on ice: First insights into Antarctic octopus venoms. Toxicon: published online. (PubMed link)
(image from blogs.nationalgeographic.com via Census of Marine Life)