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Animals

It's been a long time since, during a dive on the "scoglio del Dentice", near the island of rabbits, we found several shells of Argonauta.
The dive is not the most simple of Lampedusa, go down into the blue down to - 28 m on an isolated rock around with sea grass and sand. Over and around the rock, a lot of fish but most a lot of Octopuses, many octopuses.

And so, by swimming to the top of the cliff, Enio a friend of mine, has anticipated me and recovered two rare and brittle shells of Argonauta.

But why are they so rare? Why so sensitive?

 The mystery is solved soon, the Argonaut is nothing other than a cephalopod, a small octopus then.

An octopus has a shell? It just so, the female Argonauta argo, much larger than the male secretes an external shell which protects and lays its eggs.

The shell is so delicate that it seems to be made paper mache, white streaked with red-brown inside is pearly and is composed of layers of aragonite (a crystalline form of calcium carbonate, CaCO3), alternating with layers of a protein (conchiolin) that the animal develops directly from their mantle.                  

 photo credits

 

The Argonaut lives in pelagic environment and often too in shallow water floating on the surface, in association with tunicates Salpa and other jellyfish such as the famous Velella velella.

It feeds on plankton and in turn are preyed upon by pelagic fish such as tuna. The female is much larger than the male, which curiously has never been observed in nature, for he is known only to fertilize it, his organ is detached from the body and remains inside the female forever.

The video is taken from youtube and was uploaded by Alberto piras.