Advertisement There is a lot of misinformation on these boards and other boards dedicated to tarantulas, with regards to their venom. I don’t particularly blame anyone, as often they’re just regurgitating what they’ve read elsewhere. As many of you have seen, I have had a lot to say on the subject. I’m no toxicologist, but I have spent a lot of time trying to digest information that is presented in papers relating to venomous animals on the whole – ever since I started keeping venomous snakes. There may be some people who haven’t read my previous comments, so I will be including them in this thread (sorry to those of you, whom have read parts of this before), as well as new information/facts relating to tarantula venom and anaphylaxis. Stromatopela calceatum: The most “toxic” Tarantula Often touted as the most dangerous/toxic Tarantula around, but is it? We simply do not know, from reading the many bite reports around on this forum and several others, to me it seems as if systemic effects from Stromatopelma are of no greater medical significance than those symptoms produced by Lampropelma, Poecilotheria, or Haplopelma, etc. I actually cannot find anything to support the notion that this tarantula is the most dangerous. The disposition of the animal has most likely contributed to this inflated perception. I would say it's actually completely incorrect to suggest it's the most dangerous, or "most potent tarantula" without adequate research. Often phrases such as “potent venom”, “highly toxic”, “incredibly dangerous”, “life threatening”, are wrongly used to describe this species. These phrases should be synonymous with animals that pose a serious and immediate risk to one’s life, not an animal with a mildly ‘toxic’ venom. Many of you have read Phillip Charpentier’s entry into Exothermae, regarding S.calceatum, if you have not, you can read it here: http://www.reptileforums.co.uk/forums/6087262-post9.html Part of his post, has potentially contributed to this notion that this is the most dangerous Tarantula around. This part in particular “I am sure that, without the immediate intervention of a primed and ready venom extraction kit, this young fellow might well have died” – categorically incorrect. Further to that his comment “Stromatopelma is the link between the relatively harmless mass of Theraphosids, and the few species that can be life-threatening to man.” – A view that is supported by… no one else or any data. The document linked below, categorically states just how ineffectual extraction kits are, and how they can actually worsen effects of the bite – from a world renowned expert on clinical envenomations. (His view is supported by pretty much any medic or toxicologist worth their mettle). http://www.doctorross.co.za/wp-cont...-suction-devices-suck-emerg-med-clin-n-am.pdf The only means we have of determining how dangerous a venomous animal is, is by the rough approximation, LD.50 and known deaths. From: Venom of an aggressive African Theraphosidae (Scodra griseipes): milking the venom, a study of its toxicity and its characterization The LD.50 is around 8.1 mg/kg for a young female, and 9.5 mg/kg for an adult male. The max average yield from a young female is 18.7 mg - thus it is able to kill a 2.3kg human. The max yield obtained from a young female, was 46.6 mg - able to kill a 5.75kg human. The max average yield from an adult male 13.4 mg - able to kill a 1.4kg human. The max yield obtained from an adult male 49.6 mg - able to kill a 5.22 kg human. LD.50’s While this method is not the most accurate in every single scenario, however when looking at the majority of venomous animals and their LD.50’s – usually the ones with the lower number, have proven to be the most dangerous to humans (providing they have a large enough yield – obviously). You can compare Oxyuranus microlepidotus (inland taipan – 0.025 mg/kg sc) to Crotalus lepidus klauberi (banded rock rattlesnake, 23.95 mg/kg sc), or P. nigriventer (brazilian wandering spider = 0.13 mg/kg iv) to S.calceatum (Feather leg baboon – 8.1 mg/kg iv), and those with the lower LD.50 are considerably more dangerous. However, I said usually for a reason. There are a few exceptions to this, such as Atrax robustus (Sydney funnel web), has a relatively low standard LD.50 value, but its clinical effect on humans is much greater than expected. Also when comparing Tropidechis carinatus (rough scaled snake) which has a low LD.50 in mice, compared to a snake with higher LD.50 in mice, Notechis scutatus (tiger snake). You would assume N.scutatus to be more medically significant, yet they’re almost as dangerous as one another when considering clinical effects in humans. Having said that, it can be shown from the countless envenomations from tarantulas, that humans do not react in an unexpected fashion. So it would be plausible to use LD.50 values as a reasonable approximation, for toxicity towards humans. iv: Intravenous sc: subcutaneous There are many wrong figures on these boards, such as people stating that some species have an LD.50 of 0.7mg/kg. But they must’ve skimmed over the part where they said they isolated a particular toxin. Which is completely different to an actual envenomation, as you’re not just injected with a particular toxin, you’re injected with the full cocktail, as well as the proteins, you have things such as inorganic ions and salts, free acids, glucose, nucleic acids, free amino acids, etc. For example, that 0.7mg/kg of a particular toxin, may ‘reside’ in 30 mg of the other constituents, so the actual LD.50 will be much higher. Yields: It goes without saying, the larger the yield, the more dangerous said animal will be to you – it’s one of the other factors to consider. If a Taipan could inject 2000mg, it would be more dangerous than one that could only inject 0.000001 mg. Tarantulas simply do not have the capability to produce enough venom to be life threatening in the majority of situations. A 6 month old child? Yes. A three year old? Highly unlikely, even 3 year olds are able to survive Latrodectus bites without needing antivenom. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3200105/ Venomous animals will rarely give their full yield in a defensive bite, which is another factor to consider. Venom is a highly precious substance that requires lot of resources for a venomous animal to produce. T’s can also dry bite, even Satan himself - S.calceatum. As an interesting side point. Yields can be affected by state of nutrition (not in the way you’d necessarily think at first), and moulting. Taking into consideration the opisthosoma/prosoma ratio, and time from moulting, some interesting things were found – with Coremiocnemis tropix. For example: “The present results demonstrate that a change in the long-term state of nutrition (as expressed in the o/p ratio) does not significantly affect the venom yield. However, towards very high and low o/p ratios, there seems to be an increase of spiders that do not yield any venom. This might be explained in two ways; badly-nourished spiders (with a very low o/p ratio) do not have sufficient energy resources for venom synthesis, whereas extremely well-nourished spiders (with a very high o/p ratio) have a decreased demand for venom, as they do not need to capture prey for some time.” Taken from this paper: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086189/ Yields from T’s are far too low to cause any real concern, many species haven’t been studied to obtain yields, but it’s fair to say this covers enough to give a rough idea. We aren’t going to have any tarantulas producing 100mg of venom. B.epicureanum 14.7 ± 2.6 mg P.regalis 8.7 ± 1.1 mg C.darlingi 4.0 ± 0.1 mg S.cal (f) 9.7 ± 9 mg (m) 6.7 ± 6.7 mg Pterinochilus sp 4mg Death: To date there have been no deaths recorded for any tarantula species. Others will claim “They have killed, we just don’t know it yet” – which simply doesn’t hold any water. There are enough cases of envenomation, in captivity and in their natural habitat – yet, not a single person has a death to report. I could say the same for Boiga dendrophila, and label it a life-threatening species – incorrectly. In 99.9% of cases it will not kill, thus isn’t ‘worthy’ of the title “life-threatening”. What would we then call highly dangerous spiders or venomous snakes…’Extra life threatening’? It is all too easy to suggest they’ve killed without any supporting evidence. Even when Phillip went to Sierra Leone, no one had a death to speak of – it’s not something people forget. It is also a story people would pass down generation to generation, so the children know to be wary of these animals. 9 people were bitten in his short trip...for these plantation workers, being bitten would seem to be a relatively common occurrence. In Cambodia, for example, children hunt tarantulas to eat – young children would almost certainly have been bitten by OW’s, but still there are no deaths to report. http://www.dailymail.co.uk/news/art...r-olds-munch-tarantulas-Cambodian-jungle.html I recently spoke to Wolfgang Nentwing over a few brief emails, if you’re unaware who he is, he has been at the forefront with regards to spider venom for several decades now. He gave me his permission to share the details. He put it quite succinctly: “There is no lethal risk from tarantula spiders. A few genera among them (Poecilotheria) are more dangerous than others”. “Comparing Latrodectus with tarantulas? Latrodectus has a very potent venom, acting strongly on the membranes of nerve cells. Tarantulas have the “usual” simple spider venom cocktail, moreover, their venom is not so potent. Theraphosid bites are generally rather harmless.” “Latrotoxins (from widow spiders) are very large, the largest toxins among spiders (140 kDa = 1400 amino acids) and they construct pores into membranes. They are only known from Latrodectus and a few other theridiid spiders. All other neurotoxins in spiders are in the range of 5 to 15 kDa (50 – 150 amino acids), thus much smaller. They inhibit ion channels, usually a reversible action. These small toxins are known from mygalomorph spiders (tarantulas) and all other spiders.” This last quote, is more so to do with my points on anaphylaxis which will come later. Obviously, in very acute circumstances a tarantula may well kill someone, but they should not be labelled, potentially deadly, incredibly potent, highly dangerous, or any of these ridiculous phrases that are so often used. Anaphylaxis: Tons of interest in this topic and speculation, some correct to a degree and others not so correct. So far there isn’t an actual case to study with regards to anaphylaxis and tarantula venom. Unlike venomous snakes or Latrodectus which have produced anaphylaxis – but there may well be a good reason for that. In general tarantula venoms consist of much smaller proteins, as outlined by Wolfgang, the neurotoxins are around 5 to 15 kDa (50 – 150 amino acids), compared with that found in Latrodectus which are as large as 140kDa (1400 amino acids), some proteins in venomous snakes can be as large as 350kda (3500 amino acids). A large percentage of T venoms contain proteins below 10 kDa (100 amino acids). Supported by various studies on T venom, there are some larger components, but they’re much less common (a couple of papers, but can link more): http://www.nature.com/ncomms/2014/140506/ncomms4765/full/ncomms4765.html#s1 https://www.researchgate.net/public...m_from_Chinese_tarantulaChilobrachys_jingzhao Anaphylaxis is already a rare event, whether it’s from venomous snakes or true spiders. But there are no cases in people who are bitten by tarantulas – more than once. Important to add here that, you cannot suffer anaphylaxis on your first exposure. When you hear of people suffering anaphylaxis from a Bee sting on their “first exposure”, they often were too young to remember the first time they were stung, or they have been stung by other vespids – which share some of the same common allergens. Why might that be, that we haven’t seen a case of anaphylaxis from Tarantulas, when there are so many keepers of these animals around the world? For a protein to elicit anaphylaxis it must meet several conditions. One of those conditions, is size of the protein. “An allergen must therefore contain at least two IgE binding sites (epitopes), each of which will be a minimum of approximately 15 amino acid residues long, in order that antibody binding can occur. This implies a lower size limit for protein allergens of approximately 30 amino acid residues (M.W. of approximately 3 kD).” Naturally it follows, the larger the amino acid, the more IgE binding sites are present, thus being much more immunogenic. Tarantulas also contain nucleic acid, which is a poor immunogen by itself. Taken from: http://toxsci.oxfordjournals.org/content/55/2/235.full Potent immunogens, are those over 100kDa, and those below 10kDa are said to be weak immunogens (T venom is mostly below 10kDa). (http://megaslides.com/doc/1395182/immunology) – page 52 states this, and you can bring up various papers on the internet that also state the same. Is it possible to suffer anaphylactic shock to tarantula venom? From the information we have, and our understanding of how anaphylaxis works – yes, it is possible. BUT considering that anaphylaxis is rare in venomous snakes or Latrodectus sp, which contain much more potent immunogenic constituents, and that tarantula venom is primarily made up of weak immunogenic constituents, it would be wise to assume that it is unlikely one would suffer anaphylaxis. A view that has been shared by other toxicologists/immunologists previously. End note: These animals deserve respect, because they can cause some systemic effects. But are they deadly? No. Are they highly venomous? No. Are they likely to kill a young child or an adult? No. Could they kill a 6 month old baby or a frail elderly person? Quite possibly. Could they kill a loved pet? Quite possibly. So just like you wouldn't let a Burmese python escape around your pets, or young family, it's wise to be prudent with any animal that is armed with venom.