Obviously a copepod. 

I'm unfamiliar with the marine genera but it resembles a freshwater Lernea sp. Definitely a copepod..

There are strong evidence that it is a Copepoda of genus Pennella

It look like Copepoda of genus Pennella

 Your specimen is a pennellidae and must be a Lernaneenicus species.Any way it could be good to have others photo showing detail of the cephalosome. Lernaeeenicus has been reported  parasitic on Caranx species.  

see: Knoff. M, Walter A. Boeger.1994.  Expanded description of the female of Lernaeenicus.... Mem. Inst.Oswaldo Cruz. ,Rio de Janeiro.89(3):313-317.

Crustacea, Pennellidae, Pennella 

Maybe these links can help you

http://www.oers.ca/journal/volume7/issue1/briefCommunication.pdf

http://www.vims.edu/research/departments/eaah/programs/crustacean/_documents/2005%20Hoeg%20et%20al.%20Ecol.%20Mar.%20Parasites%20-%20parasitic%20crustaceans.pdf

http://www.marinespecies.org/aphia.php?p=taxdetails&id=237932

http://www.mapress.com/j/zt/article/view/zootaxa.4244.1.1

Best regards.

I agree, it seems to be a member of Copepoda Pennellidae, but more detail of the attachment region are need to assess its generic and specific status

It seems to be a L. longiventris  Mem. Inst.Oswaldo Cruz. ,Rio de Janeiro.89(3):313-317.

Dear Raul-Castro,

I appreciate your help and I am obliged to send more images of the cephalosome of this this Pennellid parasite of C. hippos attached herewith below.

My gratitude to everyone else all the way from Jean-Lou Justine to Marcelo Knoff and those waiting to offer assistance in this regard. 

Please, let me know what else would propel the identification quickly.

Thanks,

AKINWALE, M-M.A

Please let me known if it has only two holdfast, or there are variation in number in others specimens.

We had observed variation in some specimens of Lernaeenicus (L.longiventris) lacking some holdfast. 

Do you have more specimens in order to look them and verify some details. on the labium 

best regards

Rcastro

you can send me details to my e-mail :[email protected]

If you can send me samples in 70% alcohol we can help you.