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crayfish ID question

Started by Guest_SeaweedGuy_* , Jun 17 2009 04:26 PM

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9 replies to this topic

#1 Guest_SeaweedGuy_*

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Posted 17 June 2009 - 04:26 PM

Found this crayfish in a creek in the Wisconsin River drainage in Dane County, WI. Any ideas on what it may be?

Any help is appreciated.

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#2 Guest_ashtonmj_*

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Posted 17 June 2009 - 07:31 PM

Upside down?Not a chance...at least right side up if no gonopods being shown.

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#3 Guest_SeaweedGuy_*

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Posted 22 June 2009 - 07:17 PM

What kind of picture would be needed to make the ID if none of those helped?

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#4 Guest_schambers_*

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Posted 23 June 2009 - 11:11 AM

The bottom picture was probably helpful, but you also need a pic of the gonopods. They are hidden under the tail of the crayfish in your top picture. The picture in the second post is an example of what you need: Crayfish Identification

Also, here is an excerpt from this post: Invertebrate Identification Procedures

- Crayfish -
A dorsal (top) picture should show at least the carapace (head to rostrum). A ventral (bottom) picture should show a detailed picture of the gonopods (first swimmeret in males) or the annulus ventralus (receptacle in females). See this post regarding a HIGH quality image of gonopods. Other pictures such as full dorsal shots, mandibles, or claws are welcome and may be necessary.

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#5 Guest_SeaweedGuy_*

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Posted 19 July 2009 - 11:34 AM

I lost my camera for a little while, but I have it back now and hopefully got a picture of what you're looking for. If not, let me know and I'll try again.

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#6 Guest_centrarchid_*

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Posted 19 July 2009 - 07:52 PM

Good shot although if it had gonopods, then multiple aspects would be helpfull.

It is a form II / juvenile female. Species based on gross appearance in my opinion is the virile crayfish Orconectes virilis (a.k.a. northern crayfish). They have capacity for fast growth and are good eating.

Edited by centrarchid, 19 July 2009 - 07:53 PM.

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#7 Guest_ashtonmj_*

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Posted 19 July 2009 - 09:15 PM

I'm not so sure it is virle crayfish and instead a rusty crayfish. The aerola is a little wide for a virilis, the mandimbles appear smooth, and the setae/tubercles on the the chela aren't very enlarged.

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#8 Guest_centrarchid_*

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Posted 20 July 2009 - 08:52 AM

I'm not so sure it is virle crayfish and instead a rusty crayfish. The aerola is a little wide for a virilis, the mandimbles appear smooth, and the setae/tubercles on the the chela aren't very enlarged.

If not O. virilis, then I would first suspect O. propinquus before O. rusticus. Overall coloration outside of O. rusticus range for invasive populations of O. rusticus in WI but not unlike juvenile O. propinquus populations of Indiana and Illinois. The critter shown has the stripe going down the back which many O. propinquus exhibit. Aerola width can be broader in populations exposed to consistantly high oxygen concentrations. Image showing mandibles not of quality required to distinguish creniculate versus entire mandibles (need better image).

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#9 Guest_SeaweedGuy_*

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Posted 23 July 2009 - 12:56 PM

I've seen lots of rusty crayfish in Wisconsin, and this doesn't fit the coloration pattern that I'm used to for them. I can try to provide some different angles if that would help with the ID.

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#10 Guest_centrarchid_*

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Posted 23 July 2009 - 01:28 PM

I've seen lots of rusty crayfish in Wisconsin, and this doesn't fit the coloration pattern that I'm used to for them. I can try to provide some different angles if that would help with the ID.

I do not think it is a rusty or the virile crayfish I postulated earlier either, but rather a spring crayfish. Get a better shot of mouth / mandibles. Need to see if shearing surfaces straight or not. Can you catch an adult male? Even if not sexually competent, an adult male will more likely exhibit coloration consistent with its species than a juvenile animal.