Tuesday, May 18, 2010

The Snubnose Darters At Estill Fork Are:

Mostly Tennessee Snubnoses, Etheostoma simoterum rather than the similar Black Darters, E. duryi. I base this on examining about 15 individuals I collected on May 1 with the Florida gang. The fundamental difference between the two species is that the Tennessees have a frenum (like a groove) over their "upper lip", and the Blacks don't. I finally sat down this afternoon and examined all of the individuals under a dissecting 'scope to determine frenum or not. The only Blacks in my collection were two large, colored-up males we found downstream from our typical collecting spot, across from the Baptist church. This is of interest to me because I've been hazy on which species is more common in the stream. In principle the Tennessees should be more common, since they generally dominate highland streams where their range overlaps with Blacks, while the Blacks are more common in streams with a direct connection to the Tennessee River. My intention is to examine both species for gill parasites, assuming we find enough Black Darters to make a meaningful comparison. I also have a bunch of snubnose darters we collected last Friday at our normal site to examine, hopefully tomorrow.

2 Comments:

At 3:15 PM, Anonymous Anonymous said...

Also look at the caudal spots.
There are 4 stacked. The 2 center ones are often fused on one of the species.
I was also told the Blacks are more common in higher elevations and in degraded streams. But they are too tough to seperate in the field for me. Etnier's book helps a lot.
Ive got a big frenum under my upper lip.
:)

 
At 4:30 PM, Blogger Mrs. Brighton said...

Yes, the blacks are more common in lowland streams with higher organic contents, no doubt. I feel I can separate males in peak breeding condition, but other than that I now depend on a good dissecting 'scope for a good look at the frenum.

 

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