Dear Schneider,

I'm sorry but I can't help you with this issue,

Regards

Gordon

It will not be possible to give you an identification with your pictures. We need a detailed vue of the appendages and of the abdomen, which is masked by eggs.

Best regards.

Fred

You need to carefully tease the eggs away from the animal with very fine pin vices.  Then using the same pin vices dissect the 5 pairs of legs from each other pair under a dissecting microscope.  Carefully place a cover slip over the dissected animal, then  transfer the slide to a compound microscope to identify the animal.  Depending on the Family you will need either a male or female, plus the correct taxonomic keys to ID the specimen., 

Looking at the pictures I would say this could be an Acartia spp.; perhaps (Para)Acartia grani, regarding the spine-end of the metasome. It could be a marine calanoid that supports low salinities but without any additional information it is difficult to say. You could check the 5th legs and different zooplankton guides. Hope this will help you.

Best regards,

Eneko

I am not sure, I will need to see more pics. I can risk that is a Boeckella if it was collected in freshwater.

Please, send me more pics to my email: [email protected], and may be able to help you.

It's quite difficult to identify with this pics, if you have bigger photos maybe I can help!

Could you remove the egg?

My first thought was also Acartia spp.  But, not enough info to be sure.

Best.

It looks like Paracartia, but more info is needed as there are several species it could be: P. latisetosa (I'm leaning toward this one), P. grani, and P. africana.  You would need to dissect it to make sure it is Paracartia and then key it to species. Good luck!

because you say it is freshwater, have you checked out Diaptomus? or any of its associates? for our local area in Canada: 

https://www.for.gov.bc.ca/hts/risc/o_docs/aquatic/calanoid/assets/final.pdf 

Pretty sure this is a member of the calanoid family Diaptomidae. This is as much as can be said without more information on the swimming legs (in particular P5), ideally from both sexes.

You need to provide the P5 morphology (fifth leg) to proper identification.

P5 (fifth leg), GS (genital segment), CR (caudal rami) and PLC (posterolateral corners); you will need to look at all of these to get genus and species. Look through the key in the link that I sent to get an idea of morphological attributes are important   

De acuerdo con Iris, se requiere aislamiento de un especimen macho (antena geniculada) y extraer 5º pata, esto puedes hacerlo bajo stereo; sacas una fotografía de la 5º pata usando microscopio. Disculpa pero recien he visto tu solicitud de apoyo. Si aún necesitas puedes enviar foto, y apoyarte quizás con la sp. o enviandote claves.