Spirula spirula Seashell Sea Snail Cephalopod Octopus Squid Cuttlefish Nautilus

Description

Origin : Atlantic Ocean (North Brazil)

Spirula spirula mm 20-25 Seashell Sea Snail Cephalopod Octopus Squid Cuttlefish Nautilus.
Family: Spirulidae.
Common name: Ram's Horn Squid, Common Spirula, Ram's Horn Shell.
Syn. Nautilus spirula, Lituus laevis, Spirula australis, Spirula blakei, Spirula fragilis, Spirula peroni, Spirula prototypus, Spirula reticulata.

Spirula spirula is a pelagic species (ie, deep-water, ocean, up to 700 m depth) of Cephalopod mollusc outwardly similar to a squid. The main feature of this form is the presence of a shell internally compartmentalized, which is the organ of buoyancy of the animal.
Specimens of this species are rarely observed in nature due to the environment of deep life. However, the inner shell, although small, is quite robust and its buoyancy is high because of internal gases: therefore, once the dead animal can float for a while and be beached on temperate-tropical coastlines around the world.
The shell, white and translucent, is located in the rear part of the body of the animal, entirely covered by the mantle, and is comprised entirely from fragmoconus, ie from the compartmentalized zone. It is a shell of a conical shape, with planispiral winding (a flat spiral, wrapped in the plane of symmetry of the body), giroconus type (in which the later rounds not touching) intragastric (on the ventral side of the body). The shell is divided into chambers (more than thirty adult) by septa traversed by a siphon which runs in a ventral position. The siphon is a structure of living tissue formed by an extension of the mantle, partially mineralized, which has the function of regulating the pressure of gases and liquids contained in the rooms, varying the hydrostatic equilibrium and thus the depth of the organism. The position of life of the animal is sub-vertical, head down, for the remarkable buoyancy of the shell.
The genus Spirula (signaled from Miocene) is the form closest to the extinct groups of Belemnites, although the shells is preserved rarely fossil state. It has function of support and defense of the soft parts.