Would the REAL Brazilian Wandering Spider Please Rear up?

As a follow on from my previous article dispelling a few of the spider scare stories that have been propagated by the press over the last year or so, I now wanted to focus on the story that seems to keep rearing its head. Brazilian Wandering Spiders in Bananas. It seems every time that a spot of mould or an innocuous egg sac is found on a bunch of bananas, the collective public loses its head and that old favourite the Brazilian Wandering Spider or Phoneutria, is brought up, as clearly it is definitely that, besides, increasingly as it ‘looks the same as one found with Google’, so it must be! This recently was the case where the Sun boldly proclaimed ‘WORLDS DEADLIEST SPIDER ON THE LOOSE’ on the front page before just a day later printing a one column retraction on page 11, once an apparently more sensible person indicated that the eggs in question were in fact probably not Phoneutria.

Oddly enough the Sun didn't feel the retraction warranted front page coverage. 

As you may have seen in my previous article where I briefly covered this phenomenon, there are many other arachnid culprits identified in fruit and the actual percentage of verified Phoneutria is actually remarkably low. Not to say that it doesn't happen, but certainly we do not need to be jumping to conclusions that the world’s deadliest spider resides within nearly every bunch of bananas! In fact, I have been privy to a study performed by Rick Vetter who has documented spiders found in Banana Shipments to the US. Firstly, as most bananas from Brazil are consumed domestically, most exports will be from Central America, such as Belize, Honduras, Costa Rica, and Guatemala, plus others from Ecuador 3. In a total of 135 spiders found in cargo entering the USA were studied by Vetter, from 1926 to 2014. The vast majority of specimens dated from 2006 onwards. Of these only ONE was found to be a Phoneutria sp.,of medical significance, specifically P. nigriventer. 6 more were P.bolivenisis (another of the same genus, but with relatively benign venom) and 5 were tarantulas. By far the most common findings were a large bodied huntsman spider, Heteropoda venatoria and another harmless wandering spiders Cupiennius chiapaniensis and salei. Both of these species were often misidentified by authorities as Phoneutria species 4..

Cuppienius salei - The AMERICAN Wandering Spider. Relatively harmless and much more likely to be found in bananas - Photo Credit: Mark Chillybean Chilvers

Phoneutria boliviensis   (photo by Stanislav Macík from Czech Arachnological Society - European Arachnology)

Thankfully in this latest article I have a secret weapon, an erstwhile ally and partner in crime. Dr Stuart Longhorn, who is an academic researcher in the arachnology section of Oxford University Museum of Natural History (a collection I am keen to check out myself seeing as the bulk of specimens has been removed from display in London) Between us, and armed with facts and figures (and not just Google identifications and hearsay) we hope to be able to once and for all provide a conclusive report on Phoneutria and the danger (or lack thereof) to the Public.

So, before we get onto Phoneutria itself, let us quickly discuss the myriad of other similar species that you COULD find inhabiting your curved (or not if the EU has anything to do about it!) yellow fruit. 

Phoneutria keyserlingi -   (photo by Stanislav Macík from Czech Arachnological Society - European Arachnology)

A Ctenus sp Africa 'Red Fang'  - Authors own photo and spider. 

Put simply, the eight or so known species of Phoneutria are but a drop in the ocean when compared to the many thousands of known spider species inhabiting the forests of Central and South America. For example a recent count for Central American spiders revealed just under 2,000 kinds are described for the region, of which only ONE is a Phoneutria sp. (i.e. 0.0005%). However, of these and others, there are a myriad of different Huntsman and Wandering spiders that can be easily misidentified by the journeyman as a Phoneutria species. I’d not depend upon the identification skills of even the most experienced medical doctor or nurses either – who are typically not familiar with even the commonest tropical spiders, and beware the pest control companies who often WANT the animal to be something that needs their specialist service to eradicate!. None of these are likely to be well versed on the different species of arachnids in question. The most recent ‘positive identification was made by the family affected because ‘it looked like one on Google’ (even Google finds an impressive number of wrongly identified images when it comes to search pictures of the definitive article – a problem propagated by each and every ADDITIONAL mistake that comes to light, and when newspapers run yet another scare story with another misidentified image!)

Simply keying in on the Red Chelicerae (what the uninitiated call fangs - although they are merely the housing for the muscles acting on the fangs) is insufficient. There are simply so many other species that possess these characteristics, such as Cupiennius chiapanesnis, but also seen in some C.salei and C.getazi. In fact, I have recently come into possession of some African Ctenidae spiders that have even more striking red Chelicerae. Simply put, just because a spider is large, brown with long legs and red mouthparts, that doesn't automatically make it a Brazilian Wandering Spider! As an aside, the name is a misnomer as (a): many Phoneutria species are found outside Brazil and (b): there are a great deal of other types of ‘wandering’ spiders in Brazil that are not Phoneutria (that said, the inadequacy of Common names in Arachnology is probably best a subject for another time.) There ARE features that will allow you to accurately identify Phoneutria species, such as eye arrangement, dark striation (often a central stripe) on the pedipalps, and a thin line along the dorsal cephalothorax. Indeed the most definitive feature of Phoneutria is the presence of a soft brush of hairs on the inner surface of the first appendages nearest the mouth – aka ‘a dense prolateral scopulae on the pedipalp tibiae and tarsi in males and females’, but this aspect, put bluntly, would be a vital taxonomical feature that is far beyond your average housewife or roach killer. 

So just because you have found a small white patch on a bunch of bananas it doesn't mean you have encountered Phoneutria, in fact this picture, mocked up by Dr Longhorn will ably demonstrate why this is likely not the case:
  

See that? I rather think you would notice if you had the real thing on your bananas. Obviously it is still possible to have the spider itself present (as has happened a few times in the UK (after all our border control has been long proven to be rubbish!), but the chances of you having hundreds of them making it over and having to have your hoover destroyed (REALLY?) are frankly infinitesimal. So feel free to keep buying and eating your bananas, after all we cannot have the UK public suffering from a Potassium deficiency can we?

So onwards to discuss the members of the genus Phoneutria itself, and more specifically to address two main points. The main thing that is spouted time and time again about these spiders is that their bite is fatal and that is causes priapism (uncontrollable and painful erections), but are either of these really the case?

First off, as I have already alluded to, ‘Phoneutria’ is a genus, and contains many different species. Amongst these, the potency of the venom varies WILDLY. Get a fully envenomed hit from P. bolviensis and you will likely shrug it off (albeit not particularly enjoy it), but a bite from P. nigriventer will have markedly different implications. A breakdown follows.6

P. nigriventer: Severe Toxicity
P. fera: Severe Toxicity
P. keyserlingi: Moderate to severe Toxicity
P. boliviensis: Low to moderate Toxicity
P. reidyi: Moderate toxicity but venom is 20x more toxic than P.nigriventer for invertebrates whereas nigriventer venom is more toxic to mammals
P. pertyi: Unknown- no studies
P. bahiensis: Unknown- no studies
P.eickstedtae: Unknown- no studies

The last few species were only relatively recent additions to the Phoneutria genus. Likely any information on them with regards to bite reports would be as the result of various misidentifications.7

So as you can see, the seriousness of the bite can greatly differ with the effects varying from benign to fatal, though not often. In fact most fatalities from Phoneutria bites (and there have only been 10 confirmed through 1926 to 2008) have been in small children. So in fact, it might shock you to find out - have the majority of reported medical cases of priapism also been in small children! For example 422 bites were studied between 1984 and 1996, of which 89.9% presented symptoms of MILD envenomation. Here, just one fatality was recorded (a of three year old child). The remaining moderate envenomations (8.5%) were much predominantly in the very old, 70yr+ victims, but no deaths attributed.1

Phoneutria fera This is the display you will get before you get bitten as a last resort. No one can say this is not fair warning.   (photo by Stanislav Macík from Czech Arachnological Society - European Arachnology)

You see, in the countries where they  are naturally found, people DO get bitten by Phoneutria, and it even happens on a regular basis. Due to their nomadic nature (hence the name ‘wandering spiders’), these animals encounter humans fairly often, and although they do not go out of their way to attack or bite humans, these spiders CAN BE highly defensive (not aggressive, any bite is always as a reaction), especially the mature females guarding egg cases or freshly hatched young. The majority of recorded bites in the respectable medical literature are from P. keyserlingi and P. nigriventer, as those species tend to inhabit heavily populated areas in the South of Brazil. Phoneutria have a striking and dramatic defensive display whereby they raise their front four legs vertically, showing off the vivid under-leg colouration as a warning. They then dance from side to side to ward off predators, biting as a last resort anything that gets too close. But even when a bite occurs the envenomation of the bite can vary widely. Not every bite will result in a full load of venom being delivered, they have the capacity to regulate the amount delivered, and can even give what is called a ‘dry bite’ where no venom is used. Put simply venom is a precious commodity to a spider. It is used to incapacitate prey so that the spider can consume at its leisure – and own safety, it is generally not used against predators as then would largely be wasted. Some species such as Atrax robustus (the Sydney Funnel web spider) lack the ability to regulate their venom delivery, and always deliver a fully envenomed bite. That is why bites from that species are always treated with a very effective antivenin (and no one has died from a spider bite in Australia for nearly 40 years). So what may we ask were the amount of recorded bites (in the above study of 422 patients) from Phoneutria that required medical treatment from Antivenin? Just a staggering 2.33%!1 In the vast majority of cases the experienced medical staff determined that very little direct treatment was required. So, even the most toxic species of this spider is hardly the serious threat to humanity that it is portrayed to be (especially by the fear-mongering British media). 

Believe it or not this is a native UK species: Pisaura mirabilis - The Nursery Web Spider: Photo credit Sarah Wells.

And even looking at the venom itself, it seems not all is as it appears. Phoneutria venom contains the toxin Pn-Tx3, a component which attacks the nervous system and inhibits calcium ion channels, causing paralysis, which in extreme instances can lead to cardiac arrest or suffocation. It also severely imbalances levels of the neurotransmitter serotonin, which can lead to excruciating pain. Much is made of the LD50 level of Phoneutria. This is the Lethal Dose in 50% of subjects in a clinical trial, and here such scores are based on rodents. It is true that in laboratory tests only 0.06mg of Phoneutria venom was required to produce 50% fatalities in laboratory mice compared to 3.0mg of Latrodectus venom. Now the problem with these LD50 scores here, is that it assumes the physiology of a rodent is similar to that of a primate. It isn’t. Indeed tests of Pn-Tx3 on primates have yielded remarkably different results. Of course when you think about this, it makes a lot of sense. As I have already mentioned, a spider’s venom is used primarily to subdue their prey, and certainly a small rodent would constitute a great prey item (Phoneutria are not a small spider). Thus it makes evolutionary sense that their venom would be developed to be rather effective on such potential prey animals8..

And as for the Priapsm? Well that’s PnTx2-6 right there, and again tests on rodents have shown that it certainly can have an effect on boosting erectile function. Indeed the toxin is being actively researched for more mainstream medical applications. However the total amount of Priapism reported in the bite study was well under 10% of males affected,1 and typically only present in the very young. Once again, this is just an aspect of the venom that has been misrepresented and twisted over numerous scaremongering articles, and where the often-touted idea of affecting men ‘for more than 4 hours’ comes from is a mystery!

So the venom although highly optimised, is rather effective to kill rodents like rats and mice, but not humans2. This coupled with the low percentage of envenomed bites means the threat from Phoneutria is actually pretty low. The vast percentage of serious symptoms (i.e 0.5% presented in the above study) were in children below 10 years, and the elderly above 70 age. This can be attributed to the reduced efficiency of their physiology to counteract the venom, which are expected to be compromised in the very young and very old. But, let’s put this in perspective. When you consider the tiny likehood of encountering a large specimen of one of the REAL: Phoneutria species in the UK (not one of the countless others misidentified or an eggsac!), coupled with the very small fatality rate after a confirmed bite in their native country LINKED to the very low percentage of serious envenomations, it becomes clear the public essentially has NOTHING to be concerned about, despite what certain publications would have you think!

So as always, Keep calm and carry on. After all, it’s only a spider.

Sources:

1) A CLINICO-EPIDEMIOLOGICAL STUDY OF BITES BY SPIDERS OF THE GENUS Phoneutria
Fábio BUCARETCHI, Cláudia Regina de DEUS REINALDO, Stephen HYSLOP, Paulo Roberto MADUREIRA, Eduardo Mello DE CAPITANI & Ronan José VIEIRA

2) The effect of PnTx2-6 protein from Phoneutria nigriventer spider toxin on improvement of erectile dysfunction in a rat model of cavernous nerve injury.
Jung AR, Choi YS, Piao S, Park YH, Shrestha KR, Jeon SH, Hong SH, Kim SW Hwang TK, Kim KH Lee JY.

3) Distinguishing Two Often-Misidentified Genera (Cupiennius, Phoneutria) (Araneae: Ctenidae) of Large Spiders Found in Central and South American Cargo Shipments Richard S. Vetter and Stefan Hillebrecht

4) SAMPLING,DISTRIBUTION,DISPERSAL
Spiders (Araneae) Found in Bananas and Other International Cargo Submitted to North American Arachnologists for Identification
RICHARD S. VETTER,1,2,3 RODNEY L. CRAWFORD,4 AND DONALD J. BUCKLE5

5) Lucas, S. M., and J. Meier. 1995. Biology and distribution of spiders of medical importance, pp. 240–258. In J. Meier and J. White [Eds.]. Handbook of clinical toxicology of animal venoms and poisons. CRC Press, Boca Raton, FL.

6) Martins, R., and R. Bertani. 2007. The non-Amazonian species ofthe Brazilian wandering spiders ofthe genus Phoneutria Perty, 1833 (Araneae: Ctenidae), with the description of a new species. Zootaxa 1526: 1–36.

7) Simó, M., and A. D. Brescovit. 2001. Revision and cladistic analysis ofthe Neotropicalspider genusPhoneutria Perty, 1833 (Araneae, Ctenidae) with notes on related Ctenidae. Bull. Brit. Arachnol. Soc.12: 67–82.

8) 7. COSTA, S.K.P.; MORENO, J.R.H.; BRAIN, S.D. et al. - The effect of Phoneutria nigriventer (armed spider) venom on arterial blood pressure of anaesthetised rats. Europ. J. Pharmacol., 298: 113-120,