Can any one provide key?

Let me pass it on to our guys here. Form where is this one ?

It could be an Anilocra (Malacostraca)

Hi Jayachandran

The specimen  belongs to the family Idoteidae.

Is marine, estuarine o freshwater?

sir it is estuarine species collected from south west coast of india

Hi Jayachandran

I agree with Carlos that this is an idoteid (genus Idotea and its relatives). It would not be possible to make a firm identification from the photograph but you could start looking at published descriptions of Idotea emarginata which is a likely candidate.  See the attached link.

Keith

http://www.biosearch.in/publicOrganismPage.php?id=114128

thank you Dr. Keith

You're welcome.  I would note one word of caution.  Idotea emarginata is correctly a European species.  However, there are cases of some isopod species having been moved around the world by shipping and now appearing well outside their original geographical range.  I note the Bioinformatics Centre in Goa (the link I provided) are saying Idotea emarginata is found in India but it is possible this is actually an Indian species that merely resembles Idotea emarginata.  However, we must leave that to the next taxonomist who takes a detailed look.

ok I will check its taxonomic characters and get back to you