I would say it is Daphnia similis Claus, 1876 (based on habitus, rostrum, postabdomen, dorsal profile, spine length...).

Might you provide a picture of the rostrum where its tip and the antennule are more evident?

I tend to agree that it is Daphnia similis, especially based on the rostrum and postabdomen.

However at first I was shocked, because the habitus is almost identical to a clone of Daphnia barbata I have worked with for a long time (non-induced, I will attach a photo in the following days, the similarity of the habitus with the exception of the rostrum+postabdomen is really uncanny)  and very unlike to the habitus of all Daphnia similis clones I have seen so far. However the habitus of D. similis is very variable and D. barbata can be very safely excluded (beard, rostrum, different post-abdomen and has not been described in Algeria to my knowledge).

Can you tell more about the body length and do you happen to have pictures of detached ephippia?

Dear Quirin

Really I can not say which Daphnia do you have? Can you send the specimens me, please? I will have a more accurate verdict. All the best!

Alexey

Dear Alexey,

do you mean Smaoune Ghiles's samples from Algeria? The Daphnia barbata I have (or actually had in my previous lab) are sampled from Joachim Mergeay in Ethiopia, well identified and as far as I know, have also been used for genetic phylogeny studies. But if you want samples, please write Christian Laforsch. Currently, there are only non-induced life individuals, but there should be lots of samples from all three described morphotypes of this clone. Miguel Alonso also has samples of all three female morphotypes and also a number of males.

Quirin

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Regarding the similarities of the habitus, as promised, I add here an comparison with the Ethiopian barbata clone. On the left is an older female (~4-6 adult molt) on the left is an primiparous female. Headshape shifts with age towards a rounder form (it can get even rounder). I think I have photos somewhere with the similarities even more apparent, but probably you'll be able to see, why I find tha habitus very similar. However, you can also clearly see the clear differences in the rostrum and post-abdomen.

Still, I am becoming more and more unsure about the specimen in question being D. similis. The latter is rather large (with 2-4.5mm up to more than twice as large as barbata) and while it is difficult to tell without more information, the provided pictures seem to show a moderately small daphnid (

terrible fotos - but after postabdomen, and body shape it looks like D. deserti .... see foto Hudec 1993.  D. similis is really different   igor