Kawakami

Why would it be manta?

The manta ray (Manta birostris) is an extremely large, open water ray that enjoys long swims near reefs, warm sunshine, eating plankton, and cuddling puppies. They are currently listed as "Near Threatened" and are not often captured.

While they are HUGE, their nodes are small. Not really the most desirable thing for samegawa, small nodes. Not only that, compare the number of mantas that are even sighted, let alone caught, to the number of old tsuka that show the Emperor nodes (there is only one set of Emperor/crown nodes on a fish).

Samegawa is not manta.

What is actually used?

A couple of things are actually used for samegawa: sharks (hence SAMEgawa) and stingrays (Dasyatidae). It seems that, more often than not, it is stingrays of the genus Dasyatis, and, from what I understand, Dasyatis matsubarai (the Pitted Ray found only around Japan and China) as a specific. These rays all have the large, round dermal denticles (nodes) that are desired on samegawa. Crown or Emperor nodes (Oyatsubu) generally come in sets of three and five, depending on the size and maturity of the fish.

I am inclined to think that the samegawa used on swords is almost always stingray as opposed to shark, as sharkskin is covered in sharp scale-shaped teeth as opposed to round, stone like ones.

So, there. Samegawa is stingray, not Manta ray.

If I'm wrong about the difference in Japanese shark and stingray skin, let me know. If you think I'm wrong about manta, then do more research. ^_^

Kawakami