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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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PaulRoberts's profile picture

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PaulRoberts on Jul 16, 2016July 16th, 2016, 4:15 pm EDT
Filmed in a freshwater pond in Colorado. It is likely a larval...something...and appears to be around a bit under an inch (20mm) in length. It appears to be nearly transparent, long thread-like tails, and a smooth gliding swimming behavior. I took a wild stab at a Gastrotrich, but an expert in Italy, Antonoio Todara, didn't think so. "Too big", he thought.

It's not a very clear video so its best viewed small -like NOT full screen. Best guesses?
Healdsburg, CA

Posts: 344
Millcreek on Jul 17, 2016July 17th, 2016, 11:17 am EDT

Maybe a water scavenger beetle? Something like these.



The bottom link you'll have to scroll down to get to the water scavenger beetles.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
PaulRoberts's profile picture

Posts: 1776
PaulRoberts on Jul 19, 2016July 19th, 2016, 11:26 am EDT
Thanks, Mark. But... I don't think so. The transparency and slow gliding movement through open water is unique. I'm at a loss.
Konchu's profile picture
Site Editor

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Konchu on Jul 23, 2016July 23rd, 2016, 6:11 pm EDT
Any chance it could have been a fairy shrimp, or some other kind of crustacean? It had that kind of movement.
PaulRoberts's profile picture

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PaulRoberts on Jul 25, 2016July 25th, 2016, 3:13 pm EDT
Hi Luke! That's the best guess so far. Long, lean, gliding, and transparent would describe both critters.

The cons are: Supposedly they don't do well with fish predators around and there are plenty of bluegills and bass in this pond. And, fairy shrimp are pretty fast swimmers, I think. The guy I recorded was cruising pretty slow.

Thanks for piping in.
Crepuscular's profile picture
Boiling Springs, PA

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Crepuscular on Jul 26, 2016July 26th, 2016, 3:13 am EDT
how about a leech? i've seen some pretty light colored ones from time to time.
PaulRoberts's profile picture

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PaulRoberts on Jul 26, 2016July 26th, 2016, 6:18 pm EDT
I don't think so -they undulate. I'm stumped. Not even sure what else to consider. Best guess so far is fairy shrimp.
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Oscoda, MI

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Jmd123 on Jul 26, 2016July 26th, 2016, 8:13 pm EDT
A transparent larval fish of some sort, perhaps a baby lamprey, or other eel-like species? Or a baby bowfin?? I mean we're talking just out of the egg here if that's what it is...??? I see a very slight degree of undulation, but not much, like the swimming leeches I saw today. I go for larval fish of some sort.

No matter how big the one you just caught is, there's always a bigger one out there somewhere...
PaulRoberts's profile picture

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PaulRoberts on Jul 27, 2016July 27th, 2016, 5:47 pm EDT
I'd considered that Jonathon. I looked at larval gizzard shad and carp (this is a warmwater pond), but I didn't see a fit. Some saltwater fish have leptocephalus larvae that free drift before undergoing metamorphosis. Shad have fairly "underdeveloped" larvae, but they didn't fit.

Unfortunate that the image is so poor.
Martinlf's profile picture
Palmyra PA

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Martinlf on Jul 29, 2016July 29th, 2016, 3:46 am EDT
Another mystery. It amazes me that for all we humans know, we still run into things that we can't explain. Oh, I assume somebody would know what this creature is, but it doesn't seem to be very easy to identify for some pretty knowledgeable folks. Love it. Thanks, Paul.
"He spread them a yard and a half. 'And every one that got away is this big.'"

--Fred Chappell
PaulRoberts's profile picture

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PaulRoberts on Jul 29, 2016July 29th, 2016, 6:14 am EDT
Thanks, Louis. A bit off-topic for a trout focused site, but I was stumped. My best stab was a Gastrotrich, so I contacted a world authority. He didn't know what it was, only to say it wasn't a Gastrotrich. I have no more guesses so I thought I'd shoot it out here where reside people who are interested and willing to delve into cool things, even those tiny and complex. Thanks for trying all. It will remain labelled "strange critter".
Entoman's profile picture
Northern CA & ID

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Entoman on Jul 29, 2016July 29th, 2016, 9:08 am EDT
Hi Paul,

Were there a a lot of tails or just a few? Were mandibles noticeable or not? Were there any noticeable legs or other appendages? If it weren't for the size I would have thought phantom midge larvae, but it still may be dipteran of some kind...
"It's not that I find fishing so important, it's just that I find all other endeavors of Man equally unimportant... And not nearly as much fun!" Robert Traver, Anatomy of a Fisherman
PaulRoberts's profile picture

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PaulRoberts on Jul 30, 2016July 30th, 2016, 3:18 pm EDT
Hi Kurt,

I have no anatomical details to offer, only the video posted. I know it's not much to go on.

Phantom midge is a good guess: transparent, elongate, open water. But the vids I watched of them show them with a twisting swimming motion, like mosquito larvae.
PaulRoberts's profile picture

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PaulRoberts on Aug 11, 2016August 11th, 2016, 7:50 pm EDT

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