Gladius (cephalopod)

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Gladius, showing measurement of rachis and vane Squid gladius, showing measurement of rachis and vane.jpg
Gladius, showing measurement of rachis and vane

The gladius (pl.: gladii), or pen, is a hard internal bodypart found in many cephalopods of the superorder Decapodiformes (particularly squids) and in a single extant member of the Octopodiformes, the vampire squid (Vampyroteuthis infernalis). [1] It is so named for its superficial resemblance to the Roman short sword of the same name, and is a vestige of the ancestral mollusc shell, which was external. [1] The gladius is located dorsally within the mantle and usually extends for its entire length. Composed primarily of chitin, it lies within the shell sac, which is responsible for its secretion. [1] [2] Some species, like the bigfin reef squid, still has a gladius with some degree of mineralization. [3]

Contents

Fossilised gladius of Trachyteuthis Trachyteuthis hastiformis 01.JPG
Fossilised gladius of Trachyteuthis
Fossilised gladius of Teudopsis Teudopsis.JPG
Fossilised gladius of Teudopsis

Gladii are known from a number of extinct cephalopod groups, including teudopseids (e.g. Actinosepia , Glyphiteuthis , Muensterella , Palaeololigo , Teudopsinia , Teudopsis , and Trachyteuthis ), loligosepiids (e.g. Geopeltis , Jeletzkyteuthis , and Loligosepia ), and prototeuthids (e.g. Dorateuthis , Paraplesioteuthis , and Plesioteuthis ). [4] [5]

Variability

Gladii are shaped in many distinctive ways and vary considerably between species, though are often like a feather or leaf. Some examples are shown below.

Shape of gladiusSpeciesFamily
AncistroteuthisGladius.jpg Ancistroteuthis lichtensteini Onychoteuthidae
Architeuthis physeteris.jpg Architeuthis sp. Architeuthidae
Bathyteuthis abyssicola gladius.jpg Bathyteuthis abyssicola Bathyteuthidae
Histioteuthis bonnellii gladius.jpg Histioteuthis bonnellii Histioteuthidae
Histioteuthis reversa gladius.jpg Histioteuthis reversa Histioteuthidae
Illex illecebrosus gladius.jpg Illex illecebrosus Ommastrephidae
Lepidoteuthis grimaldii gladius.jpg Lepidoteuthis grimaldii Lepidoteuthidae
Loligo pealeii gladius.jpg Doryteuthis pealeii Loliginidae
Loliolus sumatrensis gladius.jpg Loliolus sumatrensis Loliginidae
Lolliguncula brevis gladius.jpg Lolliguncula brevis Loliginidae
Mastigoteuthis agassizii gladius.jpg Mastigoteuthis agassizii Mastigoteuthidae
Moroteuthis ingens4.jpg Onykia ingens Onychoteuthidae
Pholidoteuthis massyae gladius.jpg Pholidoteuthis massyae Pholidoteuthidae
Sepioteuthis lessoniana gladius.jpg Sepioteuthis lessoniana Loliginidae
Gladius Taningia danae.jpg Taningia danae Octopoteuthidae
Taonius borealis gladius.jpg Taonius borealis Cranchiidae
Teuthowenia megalops gladius.jpg Teuthowenia megalops Cranchiidae
Uroteuthis duvauceli gladius.jpg Uroteuthis duvauceli Loliginidae
Paralarva chiroteuthids (such as the Chiroteuthis veranyi pictured) are unusual in that they possess a greatly elongated gladius extending well beyond the fins; this supports a long, trailing tail-like structure. Chiroteuthis veranyi immature.jpg
Paralarva chiroteuthids (such as the Chiroteuthis veranyi pictured) are unusual in that they possess a greatly elongated gladius extending well beyond the fins; this supports a long, trailing tail-like structure.

See also

Related Research Articles

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An octopus is a soft-bodied, eight-limbed mollusc of the order Octopoda. The order consists of some 300 species and is grouped within the class Cephalopoda with squids, cuttlefish, and nautiloids. Like other cephalopods, an octopus is bilaterally symmetric with two eyes and a beaked mouth at the center point of the eight limbs. The soft body can radically alter its shape, enabling octopuses to squeeze through small gaps. They trail their eight appendages behind them as they swim. The siphon is used both for respiration and for locomotion, by expelling a jet of water. Octopuses have a complex nervous system and excellent sight, and are among the most intelligent and behaviourally diverse of all invertebrates.

<span class="mw-page-title-main">Squid</span> Superorder of cephalopod molluscs

A squid is a mollusc with an elongated soft body, large eyes, eight arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida. Though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting these criteria. Like all other cephalopods, squid have a distinct head, bilateral symmetry, and a mantle. They are mainly soft-bodied, like octopuses, but have a small internal skeleton in the form of a rod-like gladius or pen, made of chitin.

<span class="mw-page-title-main">Cephalopod</span> Class of mollusks

A cephalopod is any member of the molluscan class Cephalopoda such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology.

<span class="mw-page-title-main">Chitin</span> Long-chain polymer of a N-acetylglucosamine

Chitin (C8H13O5N)n ( KY-tin) is a long-chain polymer of N-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chitin are produced each year in the biosphere. It is a primary component of cell walls in fungi (especially filamentous and mushroom forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and gladii of molluscs and in some nematodes and diatoms. It is also synthesised by at least some fish and lissamphibians. Commercially, chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of the seafood industry. The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin. Chitin has proved useful for several medicinal, industrial and biotechnological purposes.

<span class="mw-page-title-main">Coleoidea</span> Subclass of cephalopods

Coleoidea or Dibranchiata is one of the two subclasses of cephalopods containing all the various taxa popularly thought of as "soft-bodied" or "shell-less". Unlike its extant sister group Nautiloidea, whose members have a rigid outer shell for protection, the coleoids have at most an internal shell called cuttlebone or gladius that is used for buoyancy or as muscle anchorage. Some species, notably incirrate octopuses, have lost their internal shell altogether, while in some it has been replaced by a chitinous support structure. A unique trait of the group is the ability to edit their own RNA.

<span class="mw-page-title-main">Cuttlebone</span> Hard, brittle internal structure found in all members of the family Sepiidae

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<span class="mw-page-title-main">Octopodiformes</span> Superorder of molluscs

Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid. All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid or modifying the tentacles into thin filaments. Octopodiformes is often considered the crown group of octopuses and vampire squids, including all descendants of their common ancestor. Some authors use the term Vampyropoda for the same general category, though others use "Vampyropoda" to refer to the total group. Another term is Octobranchia, referring to cephalopods without prominent tentacles.

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<span class="mw-page-title-main">Nidamental gland</span>

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<span class="mw-page-title-main">Mollusc shell</span> Exoskeleton of an animal in the phylum Mollusca

The molluscshell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.

<span class="mw-page-title-main">Mollusca</span> Phylum of invertebrate animals

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<span class="mw-page-title-main">Cuttlefish</span> Order of molluscs

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Teudopsis is a genus of the coleoid cephalopod family Teudopsidae, known only from Lower Jurassic gladii. It has been reported from Alberta, Canada and Europe. The life appearance of Teudopsis is probably best inferred by its close relative Trachyteuthis. A fossil with soft tissue preservation shows that this animal may have had two mantle fins, which may also be the case for Teudopsis.

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<span class="mw-page-title-main">Cephalopod fin</span>

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Eromangateuthis is an extinct genus of large plesioteuthidid cephalopod from the Cretaceous of Australia and possibly Canada.

Antarcticeras is an extinct genus of enigmatic cephalopod from the Eocene of Antarctica. It contains a single species, A.nordenskjoeldi. It is either considered the last of the "orthocone"-type cephalopods, the only member of its subclass Paracoleoidea & a descendant of the orthoceratids, and a remarkable example of convergent evolution with coleoid cephalopods, or an oegospid squid and a transitional form in the development of the modern squid gladius, of which it is the only preserved example.

References

  1. 1 2 3 Young, R.E.; Vecchione, M.; Mangold, K.M., eds. (1999). "Cephalopod gladius terminology". Tree of Life Web Project .
  2. Hunt, S.; Nixon, M. (1981). "A comparative study of protein composition in the chitin-protein complexes of the beak, pen, sucker disc, radula and oesophageal cuticle of cephalopods". Comparative Biochemistry and Physiology B. 68 (4): 535–546. doi:10.1016/0305-0491(81)90071-7.
  3. Messerli, Mark A.; Raihan, M. Jahir; Kobylkevich, Brian M.; Benson, Austin C.; Bruening, Kristi S.; Shribak, Michael; Rosenthal, Joshua J. C.; Sohn, Joel J. (2019). "Construction and Composition of the Squid Pen from Doryteuthis pealeii". The Biological Bulletin. 237 (1): 1–15. doi:10.1086/704209. PMC   7340512 . PMID   31441702.
  4. Fuchs, D.; Engeser, T.; Keupp, H. (2007). "Gladius shape variation in coleoid cephalopod Trachyteuthis from the Upper Jurassic Nusplingen and Solnhofen Plattenkalks" (PDF). Acta Palaeontologica Polonica. 52 (3): 575–589.
  5. Fuchs, D., ed. (2010). "Teudopseina". Tree of Life Web Project .

Further reading