Gladius (cephalopod)
   HOME

TheInfoList



OR:

The gladius (: ''gladii''), or pen, is a hard internal bodypart found in many
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 of the superorder Decapodiformes (particularly
squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...
s) and in a single
extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...
member of the
Octopodiformes 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 (as is the case in octopuses) or modifying ...
, the vampire squid (''Vampyroteuthis infernalis''). It is so named for its superficial resemblance to the Roman short sword of the same name, and is a
vestige Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
of the ancestral
mollusc shell The mollusc (or mollusk) shell 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 ...
, which was external. The gladius is located
dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...
ly within the mantle and usually extends for its entire length. Composed primarily of
chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...
, it lies within the shell sac, which is responsible for its secretion. Some species, like the bigfin reef squid, still has a gladius with some degree of mineralization. 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'').


Morphology

Gladii are shaped in many distinctive ways and vary considerably between species, though are often like a
feather Feathers are epidermal growths that form a distinctive outer covering, or plumage, on both avian (bird) and some non-avian dinosaurs and other archosaurs. They are the most complex integumentary structures found in vertebrates and an exa ...
or
leaf A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...
. The equivalent part in cuttlefish is the
cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal Mollusc shell, shell) found in all members of the family (biology), family Sepiidae, commonly known as cuttlefish, within the cephalopods. In othe ...
. Below are examples of gladii from various
families Family (from ) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictability, structure, and safety as ...
of squid;


See also

*
Cuttlebone Cuttlebone, also known as cuttlefish bone, is a hard, brittle internal structure (an internal Mollusc shell, shell) found in all members of the family (biology), family Sepiidae, commonly known as cuttlefish, within the cephalopods. In othe ...
* Belemnoidea * Argonaut *
Nautilus A nautilus (; ) is any of the various species within the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina. It comprises nine living species in two genera, the type genus, ty ...
* Spirula *
Mollusc shell The mollusc (or mollusk) shell 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 ...


References


Further reading

* 513 pp. * 390 pp. * {{Cephalopod anatomy Cephalopod zootomy Skeletal system