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3. Epeorus sp. (longimanus?)

I'm pretty sure This is Epeorus longimanus but want to leave myself a little room to weasel out if I'm wrong since some Epeorus species are undescribed as nymphs in California. Among the nymphs that are described it could only be E. longimanus, E. grandis or possibly E. permagnus although E. permagnus hasn't been reported in California yet. E. grandis and E. permagnus can't be differentiated from each other as larvae. Both are much stouter in appearance than E. longimanus and the head is abruptly expanded anteriorly. These three species have the first pair of gills meeting or nearly meeting on the venter of the nymph. On the other described species of Epeorus in California the gills do not meet or even come close to meeting.

The nymphs were collected from the Russian River March 2nd, 2013 in riffles with a clean substrate of large gravel and cobble. All the photos are of nymphs in alcohol. The pictures were taken within 12 hours of collection so the color is close to that of live specimens. The nymphs are 8.5 mm long (excluding cerci).

I haven't noticed it mentioned in descriptions but grandis has much shorter and stouter tails. Could this be one of our coastal species? Though it seems to comply with the keys, E. longimanus is found higher and more inland I think. They need pretty cold water.

Kurt -



I don't see how it could be unless it's a nymph that's undescribed. I've got several vials of these little critters and they all show the same characteristics. As far as I know the only Epeorus on the west coast with the first set of gills meeting or nearly meeting underneath are E. longimanus, E. grandis and E. permagnus. The other species of Epeorus, the Epeorus albertae group don't have the first set of gills meeting underneath.



They tend to show up pretty early in the year when water temps are cooler here (40-55 F) and disappear when temperatures get much higher. They're also quite common in some of the smaller tributaries of the Russian and tend to stay there a longer period of time (possibly due to the cooler water temperatures because of the canopy on the smaller creeks).

Food for thought,
Mark

Interesting... I would think the water too warm for them, especially in the late Summer. Perhaps the eggs or early instars have adapted coping responses unique to this strain? I agree about albertae. The femoral maculae are wrong as well.

Do you have access to any descriptions of hesperus or lagunitas?

I suspect they are in the hyporheic zone, which is cooler.



Just a general description in an unpublished SAFIT account where they are lumped into the Epeorus albertae group. The key says this group does not have the gills meeting underneath.

Yeah, they have to be somewhere.

BTW, didn't mean to insinuate those other species were options - just hoping as an aside that you may have uncovered some nymph descriptions I was unaware of since we were talking about The genus. :)

Sorry -
I had a stroke the other day and haven't had a chance to answer, will
answer when I feel better.
Mark

Mark,

Hope you are better soon. Let us know when you get a chance.

--Louis

Louis-

I'm feeling much better. I'm able to type much better. Don't feel nearly as clumsy as I did. Couple more days and I should be as good as new.

Mark



Kurt-

Will attempt to answer your question as soon as possible. Should be in the next couple days,

Mark

Take your time, buddy. It's Steelhead season and this is the first chance I've had to check in anyway, so no hurry. Glad to hear you're feeling better!