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Can anyone id this crayfish?

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#1 Guest_smbass_*

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Posted 12 April 2007 - 06:19 PM

This is a big male found in a ditch that is a tributary to the Blanchard River in Ohio a week ago today. I can tell it's not a rusty crayfish, which the other 20 or more we found were, but thats about as far as my crayfish id skills go. Anyone have a guess (maybe Todd)?
Attached File  Male_Crayfish_sp1_from_an_unnamed_tributary_of_the_Blanchard_River_OH_04_06_07_by_BZ.JPG   54.15KB   3 downloads
Attached File  Male_Crayfish_sp2_from_an_unnamed_tributary_of_the_Blanchard_River_OH_04_06_07_by_BZ.JPG   47.16KB   1 downloads
Attached File  Male_Crayfish_sp3_from_an_unnamed_tributary_of_the_Blanchard_River_OH_04_06_07_by_BZ.JPG   54.75KB   2 downloads

#2 Guest_diburning_*

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Posted 07 October 2007 - 03:11 AM

Oronectes virilis

#3 Guest_ashtonmj_*

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Posted 07 October 2007 - 07:42 AM

Yes it is Orconectes virilis. A couple of the things for a positive ID on this fella are the large yellow tubercules on the claws, the chestnut color on the carapace, long thin terminal elements of the gonopodthat turn away (anteriorly?) at a 30 degree angle, and I believe a tuft of hair on setae between the movable and non movable finger. The best way to get this guy straight down to genus is look at the number of spines and elements of the rostrum and if yuo have a male the shape of the gonopods (long thin versus blunt...)

#4 Guest_farmertodd_*

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Posted 07 October 2007 - 10:33 AM

Without having it in hand, I disagree, mainly by experience in that part of the system, and knowing the hydrology present. I would say instead that it's the very closely related Orconectes immunis (papershell crayfish). I've yet to find virilis in the Maumee system outside the upper St. Joseph. I think the rest of the watershed is too warm and turbid for virilis, you only see immunis and P. acutus where prairie was the dominant land type (they can get quite abundant in those ditches), and they've been able to adjust to the hydrological changes. Otherwise, the system is completely run over (or perhaps more likely, "filled in") with rusticus.


#5 Guest_Skipjack_*

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Posted 07 October 2007 - 08:37 PM

I have seen what I believe are virilus in the Mad. Seem to be the dominant cray in this system. Am I correct on this? Todd? The cray in question here seems a bit different.

#6 Guest_farmertodd_*

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Posted 07 October 2007 - 09:00 PM

Yes, there's actually a few different species I've seen in there, and I think a lot of it is tied to the temperatures and less disturbance from the historical hydrology and community. I know rusticus is attributed to complete annihilation of the crayfish community in some WI and MN lakes... but in Ohio, I see strong evidence that their "invasiveness" is directly attributable to modifications in hydrologic period, thus bringing on higher temps, turbidity, incision, and all the harbingers of river compromise.


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