Small aquatic spider?

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specious_reasons
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Small aquatic spider?

Post by specious_reasons »

I pulled a sample out of a local pond, and was very surprised to see this creature in the mix. He was completely under the water - was in fact hiding in the plant material I had collected. I didn't think that spiders were aquatic like that. Any suggestions as to what it is?

Darkfield with a 4x objective:
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Brightfield with a 10x objective:
Image

rjlittlefield
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Post by rjlittlefield »

Several groups of spiders are known to hunt and hide under water. These include certain species of Nursery Web spiders (Pisauridae), Wolf spiders (Lycosidae), and Funnel Web spiders (Agelenidae). One species, Argyroneta aquatica, is dedicated to living in water. According to The Pond by Gerald Thompson et.al.,
Argyroneta aquatica is unique in spending its life underwater without any need to come above the surface to moult, feed, mate, or reproduce.
...
A. aquatica is restricted to Europe but, in Britain it is found in ponds in many parts of the country.
I am not expert on aquatic spiders and I have no idea what this particular species is. But there is no problem with it being a spider, just because you found it in water.

BTW, the quality of images you have here, including the fact that you included a scale bar, makes them (in my view) clearly appropriate for the main Microscope gallery. You will get many more viewers there than here in the Beginners forum. If you would like me to move the topic, just say the word. :)

--Rik

specious_reasons
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Post by specious_reasons »

Thanks, both for the information and compliment. You can move it - I am my own worst critic, after all.

rjlittlefield
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Post by rjlittlefield »

Done! :D

--Rik

Cyclops
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Post by Cyclops »

Was it alive when you retrieved it,only it looks dead there in which case it could be any regular spider that fell into the water and drowned.
The only water spider i know is Dolomedes and I've yet to see one.
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specious_reasons
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Post by specious_reasons »

Cyclops wrote:Was it alive when you retrieved it,only it looks dead there in which case it could be any regular spider that fell into the water and drowned.
The only water spider i know is Dolomedes and I've yet to see one.
It mainly looks dead because it's being squished by a cover glass in these pictures. It was still moving slightly while I was taking pictures. This water sample was collected the day before I took these pictures, and the spider was found alive hiding in the water - probably hiding from me. :)

It may be a part of the Dolomedes family - it's extremely early Spring here in Illinois (below freezing today), and this may just be a very young spider.

I will be trying to get a better headshot this weekend.

Franz Neidl
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Post by Franz Neidl »

I think your pictures are very good.
As I am not a specialist for spiders I looked in a small booklet (A key to the major groups of British Freshwater invertebrates by P.S. Croft) and I found the folllowing text (p.550) wich could be useful for you:
- Animal can swim freely underwater, abdomen covered in short water repellent hairs which trap a silver layer of air when it is underwater
Order Araneae, family Agelenidae Agyroneta aquatica the water spider

- Animal unable to swim freely underwater, without water repellent hairs over the abdomen; most come from the surface film - but at least one genus can run down the bank and catch prey underwater
Order Araneae terrestial spider

Harold Gough
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Post by Harold Gough »

Dolomedes is the raft spider and lives on the surface unless startled, when it dives.

Harold
Last edited by Harold Gough on Fri Mar 13, 2009 8:11 am, edited 1 time in total.
My images are a medium for sharing some of my experiences: they are not me.

rjlittlefield
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Post by rjlittlefield »

Harold Gough wrote:Dolmedes is the raft spider and lives on the surface unless startled, when it dives.
I'm curious about the spelling. By raw count, Google finds similar numbers of Dolomedes with the second "o" and Dolmedes without the second "o", as you have it. But on closer inspection, most of the counts for Dolmedes are due to foreign language text, not references to the spider. For the spider, Dolomedes seems much more common. But I know how strongly you feel about correct spelling, so I figure there must be something interesting going on here with the names. What is it?

--Rik

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Post by Harold Gough »

#-o I thought I had typed the second 'o'. I was thinking about spiders at the time. It shows that I can't think and type at the same time.

Now corrected.

Thanks, Rik.

Harold
My images are a medium for sharing some of my experiences: they are not me.

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