Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal Mollusc shell) found in all members of the family Sepiidae, commonly known as cuttlefish, within the . In other cephalopod families it is called a gladius.
Cuttlebone is composed primarily of aragonite. It is a chambered structure that the animal can fill with gas or liquid for buoyancy control. On the ventral (bottom) side of the cuttlebone is the highly modified siphuncle; this is the organ with which the cuttlebone is filled with gas or liquid.
Depending on the species, cuttlebones implode at a depth of . Because of this limitation, most species of cuttlefish live on the seafloor in shallow water, usually on a continental shelf.
When the cuttlefish dies, only the cuttlebone remains and will often wash up on a beach.
Human uses
In the past, cuttlebones were ground up to make polishing powder, which was used by
.
The powder was also added to
toothpaste,
and was used as an
antacid for medicinal purposes
or as an absorbent. They were also used as an artistic carving medium during the 19th
and 20th centuries.
Today, cuttlebones are commonly used as calcium-rich dietary supplements for caged , , , , shrimp, and . These are not intended for human consumption.
Lime production
As a carbonate-rich biogenic raw material, cuttlebone has potential to be used in the production of calcitic lime.
Jewelry making
Because cuttlebone is able to withstand high temperatures and is easily carved, it serves as mold-making material for small metal castings for the creation of jewelry and small sculptural objects.
It can also be used in the process of pewter casting, as a mould.
Internal structure
The
microstructure of the cuttlebone consists of two components, horizontal
Septum and vertical pillars. Both components are composed predominantly of
aragonite.
The horizontal septa divide the cuttlebone into separate chambers. These chambers are supported by the vertical pillars which have a corrugated (or "wavy") structure.
The thickness of these pillars varies from species to species, but are typically a few microns thick.
The horizontal septa are typically thicker than the vertical pillars and consist of a double-layered structure. The upper layer of the septa and walls consist of vertically aligned crystals, whereas the bottom sublayer consists of
rotated with respect to each other to form a "
plywood" structure.
Overall, this chambered microstructure results in the cuttlebone having a
porosity over 90% by volume.
File:3D visualisation of μCT-data of a cuttlebone 01.jpg|3D view of part of a cuttlebone at low resolution.
File:3D visualisation of μCT-data of a cuttlebone 03.jpg|Overview of a part at high resolution, about 5 μm/voxel.
File:3D visualisation of μCT-data of a cuttlebone 04.jpg|Higher magnification.
File:3D visualisation of μCT-data of a cuttlebone 05.jpg|Detailed view at very high magnification. Wall thickness of the vertical structures is about 10 μm.
File:Flight through image stack of μCT-data of a cuttlebone, lateral view.ogv|Flight through the corresponding μCT image stack, section direction about 30°, lateral view.
File:Flight through image stack of μCT-data of a cuttlebone, top view.ogv|Flight through the corresponding μCT image stack, section direction about 30°, top view.
File:Aligned flight through image stack of μCT-data of a cuttlebone, lateral view.ogv|Flight through the aligned image stack, lateral view.
File:Aligned flight through image stack of μCT-data of a cuttlebone, top view.ogv|Flight through the aligned image stack, top view.
File:Aligned flight through image stack of μCT-data of a cuttlebone, top view, magnified.ogv|Flight through the aligned image stack, top view, magnified section.
Mechanical properties
The cuttlebone has been studied extensively due to its ability to be simultaneously lightweight,
Stiffness, and tolerant to damage. This combination of mechanical properties has led to research into cuttlebone-inspired
Biomimetics .
In addition, due to its mechanical properties, cuttlebone has been used as scaffolding in superconductors
and tissue engineering applications.
The light weight of the cuttlebone derives from its high
porosity (over 90% by volume).
The stiffness of the cuttlebone arises from the chambered structure composition of approximately 95%
aragonite (a stiff material) and 5%
Organic matter.
Since the stiffness of a composite will be dominated by the material with the largest volume fraction, the cuttlebone is also stiff. The
Specific modulus of the cuttlebone in one species was measured to be as high as 8.4 (MN)m/kg.
The most intriguing property of cuttlebone is its ability to tolerate damage given that aragonite is a
Brittleness material. The high tolerance to damage can be linked to the cuttlebone's unique
microstructure.
Deformation process
Due to the marine lifestyle of the cuttlefish, the cuttlebone must be capable of both withstanding large compressive forces from the water while avoiding sudden
Brittleness Fracture. The cuttlebone of some species under compression has demonstrated a
specific energy on par with some advanced
made from more compliant materials such as
and
.
The high energy absorption is a result of several factors.
The failure of the cuttlebone occurs in three distinct stages: local crack formation, crack expansion, and densification.
See also
Explanatory footnotes
External links
