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Ethan Bright

Dolometes - fishing spider

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I came across a vial of some small Dolometes fishing spiders I collected about 8 years ago. I took some very quick photos through my microscope this afternoon. I hope they come out alright. (The first isn't great because I didn't properly compress the image). Enjoy!

 

Habitus

Close-up of eyes

Mouthparts

Spinnerets

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Great photos Ethan! The Dolomedes Fimbriatus is the biggest spider we have here in sweden and an impressive hunter it is! It can run out on the water surface and catch insects on the surface or even dive down under water to catch tadpoles and small fish, but I am sure you knew that already :)

 

I did this realistic fly that were supposed to imiate it about a year ago.

 

Ulf

post-2830-1156481091_thumb.jpg

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Ulf,

 

That is great work! How much time did it take to do it? And did it catch any fish?

 

Like most spiders, most people over-estimate the size of spiders because of the out-streatched appendages. Still, I've seen some really big fishing spiders (ca. 3-4 cm body length), and they are very scary especially when you're expecting to see them. That and the beautiful yellow-and-black garden (orb) spider are our largest spiders (in Michigan).

 

If I remember from the movie Microcosmos, there's a spider (diving spider) species in Europe and Asia that constructs an air bubble in which to hide, drag its prey, and even lay its eggs. Do you have these in Sweden?

 

Cheers, Ethan

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Thanks alot Ethan. This one was tied as a display fly only, but would probably fish well since the underbody is made of foam so it would float like a cork! It takes me about an hour to do one of these guys.

 

Yes we do have these diving spiders here in sweden. If I am not misstacen it's the Argyroneta aquatica that you are refering to. Here in sweden they are called "water spiders" plain and simple. The will grow to just under 2 cm and just as you say, creates an air bubble under water in which the live, feed and breed.

 

Ulf

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Yes, that's the spider.

 

They're also interesting in that, in contrast to most terrestrial spiders, the male is larger than the female. Delores Schuetz and Michael Taborsky did some interesting research on this topic:

 

Schütz D, Taborsky M. 2003. Adaptations to an aquatic life may be responsible for the reversed sexual size dimorphism in the water spider, Argyroneta aquatica. Evolutionary Ecology Research, 2003, 5: 105–117.

 

Below is the abstract:

 

Argyroneta aquatica is the only spider that spends its whole life under water, and one of very

few in which males are bigger than females. We hypothesized that the unusual ecology of the

water spider is responsible for its exceptional sexual size dimorphism. If ecological parameters

influence optimal body size for locomotion, the size of the more mobile sex (males) is expected

to vary more between populations that vary in these ecological conditions than that of the other

sex (females). Indeed, sexual size dimorphism differed significantly between four populations

of A. aquatica studied at Vienna, and this variation depended more on variance in male size

than in female size. We found that, apart from size, body shape and the relative length of the

first pair of legs also differed significantly between the sexes.

In land spiders, among which females are usually larger than males, small male size has been

attributed to the better mobility of smaller individuals, as generally males are the more mobile

sex in spiders. In aquatic animals, larger individuals have mobility advantages over smaller

ones. We therefore hypothesized that, in A. aquatica, large rather than small size may facilitate

locomotion, and hence that males are better divers than females. This was confirmed by the

results of diving experiments. It is probable that male diving superiority is mainly due to their

longer first pair of legs. Female size determines fecundity to a large extent. We wished to

determine which size constraints could prevent females from growing bigger. Female size

may be limited by the costs of building air bells, which they use as a retreat and for brood care.

In laboratory experiments, we found that females build larger air bells than males and that

air bell size correlates with body size in females but not in males. Females need to collect air

from the surface to refill their bells more often than males. We conclude that the need for males

to move efficiently under water and the costs to females of building a retreat and breeding

shelter may be important determinants of body size and morphology. Hence the reversed

sexual size dimorphism in A. aquatica may be greatly influenced by mechanisms of natural

selection.

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Fascinating facts Ethan! I just did a google search for the Argyroneta aquatica and it's really cool to see the air "bell" it does for itself. As I understand it the spider actually gathers the air, buble for buble, from the surface bringing it down to the bell and slowly filling it with air until it is totaly filled. Amazing!

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A few lears ago, I saw one blue and one green six-spotted fishing spider at a bog near my home. They were georgous! Didn't have a camera that day but I will go back and see if there are any more there! We also have goldenrod spiders and big spiders with a cats face on their back in my garden. I love, love, love spiders!

 

That is a spectacular spider that you tied, uffepuffe.

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uffepuffe: Great spider fly!

Ethan: Impressive photos -- those fangs (I'm sure they're not proerly called that) are pretty impressive.

 

--Bill

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