Herklots 1859 I 2 Sepia officinalis - schelp

Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal

shell Shell may refer to: Architecture and design * Shell (structure), a thin structure ** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses Science Biology * Seashell, a hard outer layer of a marine ani ...

) found in all members of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Sepiidae, commonly known as

cuttlefish Cuttlefish, or cuttles, are Marine (ocean), marine Mollusca, molluscs of the order (biology), suborder Sepiina. They belong to the class (biology), class Cephalopoda which also includes squid, octopuses, and nautiluses. Cuttlefish have a unique ...

, within the

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s. In other cephalopod families it is called a ''gladius''. Cuttlebone is composed primarily of

aragonite Aragonite is a carbonate mineral and one of the three most common naturally occurring crystal forms of calcium carbonate (), the others being calcite and vaterite. It is formed by biological and physical processes, including precipitation fr ...

. It is a chambered structure that the animal can fill with gas or liquid for

buoyancy Buoyancy (), or upthrust, is the force exerted by a fluid opposing the weight of a partially or fully immersed object (which may be also be a parcel of fluid). In a column of fluid, pressure increases with depth as a result of the weight of t ...

control. On the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

(bottom) side of the cuttlebone is the highly modified

siphuncle The siphuncle is a strand of biological tissue, tissue passing longitudinally through the mollusc shell, shell of a cephalopod mollusc. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the li ...

; this is the organ with which the cuttlebone is filled with gas or liquid. The microscopic structure of cuttlebone consists of narrow layers connected by numerous upright pillars. 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 A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an islan ...

. 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

goldsmith A goldsmith is a Metalworking, metalworker who specializes in working with gold and other precious metals. Modern goldsmiths mainly specialize in jewelry-making but historically, they have also made cutlery, silverware, platter (dishware), plat ...

s. The powder was also added to

toothpaste Toothpaste is a paste or gel dentifrice that is used with a toothbrush to clean and maintain the aesthetics of Human tooth, teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from th ...

, and was used as an

antacid An antacid is a substance which neutralization (chemistry), neutralizes gastric acid, stomach acidity and is used to relieve heartburn, indigestion, or an upset stomach. Some antacids have been used in the treatment of constipation and diarrhe ...

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 Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

-rich dietary supplements for caged

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

chinchilla Chinchilla refers to either of two species ('' Chinchilla chinchilla'' and '' Chinchilla lanigera'') of crepuscular rodents of the parvorder Caviomorpha, and are native to the Andes mountains in South America. They live in colonies called "her ...

hermit crab Hermit crabs are anomuran Decapoda, decapod crustaceans of the superfamily (taxonomy), superfamily Paguroidea that have adapted to occupy empty scavenged mollusc shells to protect their fragile exoskeletons. There are over 800 species of hermit c ...

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

shrimp A shrimp (: shrimp (American English, US) or shrimps (British English, UK)) is a crustacean with an elongated body and a primarily Aquatic locomotion, swimming mode of locomotion – typically Decapods belonging to the Caridea or Dendrobranchi ...

, and

snail A snail is a shelled gastropod. The name is most often applied to land snails, terrestrial molluscs, terrestrial pulmonate gastropod molluscs. However, the common name ''snail'' is also used for most of the members of the molluscan class Gas ...

s. 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 Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymer ...

of the cuttlebone consists of two components, horizontal

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

and vertical pillars. Both components are composed predominantly of

. 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 nanorods rotated with respect to each other to form a "

plywood Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboa ...

" structure. Overall, this chambered microstructure results in the cuttlebone having a

porosity Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

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, stiff, and tolerant to damage. This combination of mechanical properties has led to research into cuttlebone-inspired biomimetic ceramic foams. In addition, due to its mechanical properties, cuttlebone has been used as scaffolding in

superconductors Superconductivity is a set of physical properties observed in superconductors: materials where electrical resistance vanishes and magnetic fields are expelled from the material. Unlike an ordinary metallic conductor, whose resistance decreases ...

and

tissue engineering Tissue engineering is a biomedical engineering discipline that uses a combination of cells, engineering, materials methods, and suitable biochemical and physicochemical factors to restore, maintain, improve, or replace different types of biolo ...

applications. The light weight of the cuttlebone derives from its high

(over 90% by volume). The stiffness of the cuttlebone arises from the chambered structure composition of approximately 95%

(a stiff material) and 5%

organic material Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

. Since the stiffness of a composite will be dominated by the material with the largest volume fraction, the cuttlebone is also stiff. The specific stiffness 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

brittle A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. ...

material. The high tolerance to damage can be linked to the cuttlebone's unique

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

failure Failure is the social concept of not meeting a desirable or intended objective, and is usually viewed as the opposite of success. The criteria for failure depends on context, and may be relative to a particular observer or belief system. On ...

. The cuttlebone of some species under compression has demonstrated a

specific energy Specific energy or massic energy is energy per unit mass. It is also sometimes called gravimetric energy density, which is not to be confused with energy density, which is defined as energy per unit volume. It is used to quantify, for example, st ...

on par with some advanced

foam Foams are two-phase materials science, material systems where a gas is dispersed in a second, non-gaseous material, specifically, in which gas cells are enclosed by a distinct liquid or solid material. Note, this source focuses only on liquid ...

s made from more compliant materials such as

metal A metal () is a material that, when polished or fractured, shows a lustrous appearance, and conducts electrical resistivity and conductivity, electricity and thermal conductivity, heat relatively well. These properties are all associated wit ...

s and

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

s. 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. Crack formation typically occurs in the middle of the vertical walls in the chambered structure of the cuttlebone. The location of crack formation is controlled by the waviness in the corrugated structure of the walls. The waviness of the walls in the cuttlebone provides an optimized balance between stiffness and brittleness of the overall structure. This wavy structure inhibits crack propagation, increasing the energy input necessary for failure. After sufficient damage has occurred to the walls of the cuttlebone, a process known as densification occurs whereby the walls gradually compact while fracture continues. Significant energy is dissipated in the continued cracking of the walls while densification is occurring. It has also been observed that under compressive stresses, the horizontally layered chambers of the cuttlebone will fail sequentially. While one chamber is undergoing fracture and densification, the other chambers will not deform until the

septum In biology, a septum (Latin language, Latin for ''something that encloses''; septa) is a wall, dividing a Body cavity, cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Hum ...

between the chambers has been penetrated. The septum is significantly stronger than the vertical walls due to its "

" structure further increasing the total energy needed for complete structural failure of the cuttlebone.

Explanatory footnotes

References

External links

* {{Cephalopod anatomy Articles containing video clips Cephalopod zootomy Cuttlefish Mollusc products