Gammarus pulex - ID Help Though - Video Added

Mitch640 · Post by **Mitch640** » Sun Mar 13, 2011 6:35 pm

Is this a female with eggs or a male? It was quite large, which is why I thought male, but I can't find anything on the internet about their anatomy.

Here's a video.

fpelectronica · Post by **fpelectronica** » Mon Mar 14, 2011 10:04 am

Beautiful photographs. Good color and definition
It seems that cleaning the microscope has been successful
Francisco

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 10:49 am

Thanks Francisco. Yes, I am very happy with the way it came out. I will be doing it again very soon, using better tools to get to the lenses. I didn't really have the right stuff, but even so, it helped a lot. The fine detail now comes though.

ChrisR · Post by **ChrisR** » Mon Mar 14, 2011 10:59 am

It seems that cleaning the microscope has been successful

Even I can see the difference, well done indeed! It would make a nice pano.

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 11:10 am

Thanks Chris. No one is more relieved than me about finding out what the problem was. Except maybe all you guys who I bugged for answers. LOL

But no idea what the things on this guys belly are? I live in Wisconsin, and we have a lot of animals with things hanging down like that, but these aren't cows.

Didn't think of a Pano, although I have made one before of a Cyclops.

ChrisR · Post by **ChrisR** » Mon Mar 14, 2011 12:06 pm

Cows? I don't think we have those, I live in London.
We have Bankers, who would need something like those pouches for their bonuses...

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 12:09 pm

Ah, yes, we have bankers too, but they need much bigger pouches than these.

NikonUser · Post by **NikonUser** » Mon Mar 14, 2011 1:25 pm

Almost too much detail to make out individual bits and pieces.
I checked what texts I have and found nothing useful.
A great project would be take one of these animals apart, work out what each piece is and post photos.

In the top image the elongated sac just below the dorsal surface is the heart.
The little circles beneath the heart are where the gonads are situated, perhaps these are they.
The gut is obvious and beneath the gut is the ventral nerve cord.

Normally, in arthropods, the body segments have lateral plates. In the Amphipod Crustacea (of which this is, but not necessarily a Gammurus) the plates are small and their function (protection?) is taken over by the 1st joint of the appendages (coxa) having large plates. Possible that these are what you were thinking were eggs.

We really do need someone to take these beasts apart.

rjlittlefield · Post by **rjlittlefield** » Mon Mar 14, 2011 1:44 pm

In several of the pictures, the pouches do not appear to be associated with legs. But I can't tell whether that's an illusion.

The possibility of gills also came to mind. How do these critters breath?

--Rik

Charles Krebs · Post by **Charles Krebs** » Mon Mar 14, 2011 3:26 pm

I do believe the parts that prompted the "cow" reference are indeed gills.

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 3:39 pm

Thanks for the information NU and Rik. I spent the last couple days searching Google and YouTube with every possible search term I could think of, and came up with nothing in either description or images like these.

At first, I thought they were some kind of parasite, then possibly eggs, or gonads of the male, sperm packets, but there really is nothing I could find even remotely like it. I have even counted all the legs to discount possible leg parts. But these are extra from any of my other shots of the Gammarus Shrimp from the last 2 times I found one. In fact, they seem to be in 3 different stages.

I am sure though, that I am not equipped to dissect one.

By the way, I did get some video, in fact, thee were taken as stills during the video recording, and, the parts in question are extremely flexible. The legs were kicking them all around and from their reaction, they were attached only at the small end on the belly. Not a way to treat eggs. I did run upon one description though that says the female will beat those rear legs to provide oxygenated water to the eggs before they hatch.

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 3:47 pm

Charles, I did find descriptions of gills on the Gammarus shrimp, but no pictures, and got the impression they were near the head. I could be wrong though, not being familiar with the names of the body parts.

I did look through some of my other images from two other of these I have caught. At best, the evidence is inconclusive.

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 3:48 pm

Ooops, a double post.

NikonUser · Post by **NikonUser** » Mon Mar 14, 2011 5:18 pm

Let's be sure we are talking about the same pieces.
In Mitch's last set of 2 images; the top image shows the anterior end of the shrimp.
Each of those 3 anterior rectangular plates at the base of the appendages is a coxa plate of the appendage.
I made a Q&D prep. of the 1st thoracic segment of an Amphipod (shrimp); for all practical puposes it is identical to Mitch's image of that most anterior appendage.
(I should learn never to label images, read 'upside for 'updide')

NU11026

Mitch640 · Post by **Mitch640** » Mon Mar 14, 2011 5:35 pm

The coxal plates are visible on the first one, in this image, they seem to be to the rear of the 'cow' parts, or, they are something else entirely.

I do have some video that shows all this very clearly. I will process it tonight.