[Odonata-l] Frog legs and odonates - simplistic answer - Occam

[Joshua Rose]

Occam's Razor actually tends to be wrong in many ecological cases.  
Academic science favors oversimplification; everyone wants to boil  
each effect down to a single cause, that being conducive to winning  
grants, getting published, and receiving tenure. Real life usually  
does not cooperate.

The publications I read concerning that chytrid indicated that it had  
been present in many areas without causing any undue harm to  
amphibians; but that other environmental effects - acidification, UV,  
and so on - degraded the amphibian's immune responses such that the  
formerly innocuous chytrid became a threat. To the extent that  
herpetologists carried the chytrid to isolated populations and helped  
wipe them out, if that did take place, it was A cause but probably not  
THE cause. A number of frog populations disappeared that had been well  
known to herpetologists and under study for many years before the  
chytrid reared its ugly head.

Another study indicated that non-native Bullfrogs were carriers of the  
chytrid, hosting it but not being killed off by it, and had helped  
spread it to at least four continents. African Clawed Frogs are  
carriers as well. One more piece of the complicated puzzle.

Back to the issue relevant to this listserv, the odonate larvae eating  
the legs off of amphibian larvae. The study in question took place in  
three ponds in one county in England. The answer may be simple in this  
one small area. There is a LOT more research to do before odonates can  
be generally accepted as a single worldwide cause of amphibian limb  
shortages....

Josh Rose, Ph.D.
McAllen TX (but soon relocating to Amherst MA)

On Jun 26, 2009, at 8:38 PM, Richard Rowe wrote:

> Occam says 'go with predation' ... it is the simplest solution and  
> seems consistent with the scope and scale of the data. The  
> herpetology crowd have been very well funded on the basis of dire,  
> apocalyptic warnings revolving about 'canaries in coal mines'. The  
> 'vanishing frogs' events weren't because the system was collapsing  
> or UV radiation on mountain tops but due to a pandemic of an  
> invasive chytrid, most likely vectored by herpetologists; the  
> multilegs wasn't due to unspecified trace toxins but to a well- 
> recognised parasite ... By looking for exotic solutions they have  
> actually endangered their study animals. In Australia there was a  
> decade of discovering new and pristine habitats with healthy  
> populations of frogs, only for the frogs to go bust at the next  
> visit while everything else was doing just fine. Making haste slowly  
> could have been well worthwhile and saved a lot of frogs.
>
> I think we should sit with Occam until it is shown that some more  
> exotic solution is necessary.
>
> Lawson, Tamara wrote:

>> This article is misleading as it makes the “answer” sound  
>> simplistic at best.  My husband is a herpetologist (although he  
>> prefers to study snakes) and I’ve occasionally gone to meetings  
>> with him and sat in on some of the presentations.  The overwhelming  
>> thought of most herpetologists that I’ve talked to (and Nova had a  
>> program on amphibians recently as well that stated this idea) is  
>> that THERE IS NO SINGLE CAUSE for the mutations (as well as the  
>> deaths) observed in amphibians.  Research as shown that some  
>> chemicals (this includes man-made ones as well as some secreted by  
>> plants’ roots), some parasites (some worms, some fungi, as well as  
>> single-celled species, etc.), and some environmental factors  
>> (temperature extremes, salinity, predators, etc.) all contribute to  
>> current problem of amphibian deformities.  The cause for the world- 
>> wide problem is just different in different bodies of water with  
>> some research showing multiple cumulative causes and even additive  
>> causes in the same pond.  It all goes back to the old saying (or it  
>> should be a saying) “don’t look for simple answers in a complicated  
>> system”.
>>
>> Tamara Lawson, Science Lab. Manager
>>
>> From: odonata-l-bounces at listhost.ups.edu [mailto:odonata-l-bounces at listhost.ups.edu 
>> ] On Behalf Of Michael Blust
>> Sent: Friday, June 26, 2009 9:10 AM
>> To: odonata-l at listhost.ups.edu
>> Subject: [Odonata-l] Frog legs and odonates - attempt #2
>>
>>
>>
>>
>> Legless Frogs Mystery Solved
>>
>> from BBC News Online
>>
>> Scientists think they have resolved one of the most controversial  
>> environmental issues of the past decade: the curious case of the  
>> missing frogs' legs.
>>
>> Around the world, frogs are found with missing or misshaped limbs,  
>> a striking deformity that many researchers believe is caused by  
>> chemical pollution.
>>
>> However, tests on frogs and toads have revealed a more natural,  
>> benign cause. The deformed frogs are actually victims of the  
>> predatory habits of dragonfly nymphs, which eat the legs of tadpoles.
>>
>> http://snipr.com/kx70t
>>
>> ------------------------------------------------------------
>> Michael Blust
>> Dept. of Natural Science
>> Green Mountain College
>> Poultney, VT   05764
>> 802-287-8331
>> blustm at greenmtn.edu
>>
>>
>
> -- 
> Dr Richard Rowe
> Zoology & Tropical Ecology
> School of Marine & Tropical Biology
> James Cook University
> Townsville 4811
> AUSTRALIA
>
> ph +61 7 47 81 4851
> fax +61 7 47 25 1570
> JCU has CRICOS Provider Code 00117J
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