Frog-mimic spider

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Lou Jost
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Frog-mimic spider

Post by Lou Jost »

Two students of mine, Natalia Espinoza and Dylan Moore, found this spider in our Rio Zunac Reserve in Ecuador. They at first thought it was a small tree frog.

Here is a stack of a few hand-held images:

Image

Here's a stack of 150 pictures taken in less than two minutes with the camera on a tripod. OLy PEN F and Oly 60mm macro lens, in-camera focus bracketing, processed later in Zerene:

Image

ChrisR
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Post by ChrisR »

Ohmy! Is it "known"?
Chris R

Lou Jost
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Post by Lou Jost »

I'm trying to figure that out. I've never heard of such a thing, and it seems like the kind of thing one would hear about. Maybe it is new. I have preserved the specimen. Any arachnologists out there reading this?

Smokedaddy
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Post by Smokedaddy »

I would like to know more about how to stack 150 pictures in less than two minutes. I am still in the manual era. <g> Are we talking about a video frame stacking?

-JW:

Lou Jost
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Post by Lou Jost »

No, not stacking video frames. In-camera focus bracketing, as implemented in the bodies of recent Olympus and Panasonic cameras (and software solutions that provide the same functionality for other cameras), automatically takes up to 1000 photos at full sensor resolution and including RAW files, each focused on a slightly different point, with a settable time delay from 0 to 60s between them to allow for a flash to recharge if desired. The number of photos per minute is limited only by the shutter speed and, eventually, the size of the buffer and the camera's and card's write speed. This can be so fast that the stacks can be made handheld. I've posted some lichen stacks that I took handheld with this technique here (some of these were on a tripod though):

https://ecomingafoundation.wordpress.co ... est-twigs/

houstontx
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Post by houstontx »

Amazing evolution!

Smokedaddy
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Post by Smokedaddy »

Thanks Lou I wasn't aware that it even existed. :oops:

Lou Jost
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Post by Lou Jost »

Smokedaddy, I should note that most of these cameras don't actually process the stack, you still need Zerene and that still takes more than two minutes. of course. A few cameras do manage to process the stack as well, but as you know, no stacker worth his salt would let a machine make all the decisions necessary to produce a decent result.

theNEWT
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Post by theNEWT »

Interesting....I dont think its mimicking a frog though if it's mimicking anything.

Lou Jost
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Post by Lou Jost »

All I can say is that everyone who saw it in life thought it was a frog at first.

Deanimator
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Post by Deanimator »

Lou Jost wrote:All I can say is that everyone who saw it in life thought it was a frog at first.
I have to agree with you. If I weren't paying attention, I'd think it was a frog.

Lou Jost
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Post by Lou Jost »

I also posted this on a biology website (https://whyevolutionistrue.wordpress.co ... mics-frog/). Some commenters on that site thought there would be little evolutionary advantage for a spider to mimic a frog, so they doubted the mimicry. But one commenter noted that this could be an example of misdirection about an escape route. Frogs jump forward, and a predator (even if it ate both frogs and spiders) would therefore expect this to jump in the opposite direction that the spider would jump. Even if that little trick saved only one in a thousand spiders, populations genetics shows that a gene which produced the illusion (and had no important deleterious effect) would soon be fixed in the population.

Selection for misdirection of escape route is very strong in arthropods. The best examples are the fake heads, complete with eyes and moving antennae, on the hindwings of the hairstreak butterflies. Here are some examples of this kind of adaptation:
https://am22.akamaized.net/tms/cnt/uplo ... terfly.jpg
http://cdn.c.photoshelter.com/img-get/I ... 002879.jpg
https://www.whatsthatbug.com/wp-content ... eter_2.jpg

Here is another photo of the spider, from the side:
Image

JohnKoerner
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Post by JohnKoerner »

Interesting!

mtuell
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Post by mtuell »

While not brightly colored as you might expect, another possibility is that it is saying "look, I'm a poisonous frog, don't eat me!".

I too was curious what the evolutionary advantage would be.

Thanks for sharing!
Mike

Lou Jost
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Post by Lou Jost »

We thought about that, but as far as we know, the frogs it might be imitating are not poisonous, and are quite shy and flighty, unlike poison arrow frogs. In fact our Pristimantis frogs, the most likely models, are famous for their dramatic jet-assisted escapes. They expel drops of liquid as they jump when frightened. A memorable escape if a bird has ever seen it.

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