What exactly is 大闸蟹 ?

[michfr]

Is it just "steamed crab" in general or does it refer to a special species of crab or a special way of preparing the crab or what?

Thanks.

[Mugi]

It's a variety of fresh water crab.

Check out the second entry on http://www.china-fisheries.com/data/pic.asp

It's what the Japanese call 上海ガニ (Shanhai gani). Not sure what it's usually called in English - you get all sorts of different names when you google it. Yangcheng Lake Crab seems to come up quite often though.

After further investigation: Chinese mitten crab, sometimes Chinese hairy crab.

[xiaocai]

Mostly, when talking about 大闸蟹, it means 中华绒螯蟹(Eriocheir japonica sinensis).