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Gladius (cephalopod)

Bodypart of certain cephalopods

Gladius (cephalopod)
Summary

Bodypart of certain cephalopods

Gladius, showing measurement of rachis and vane

The gladius (: 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). 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. 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

[[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.]] Gladii are shaped in many distinctive ways and vary considerably between species, though are often like a feather or leaf. The equivalent part in cuttlefish is the cuttlebone. Below are examples of gladii from various families of squid;

Shape of gladiusSpeciesFamily
[[File:AncistroteuthisGladius.jpg350px]]Ancistroteuthis lichtensteiniOnychoteuthidae
[[File:Architeuthis physeteris.jpg350px]]Architeuthis sp.Architeuthidae
[[File:Bathyteuthis abyssicola gladius.jpg350px]]Bathyteuthis abyssicolaBathyteuthidae
[[File:Histioteuthis bonnellii gladius.jpg350px]]Histioteuthis bonnelliiHistioteuthidae
[[File:Histioteuthis reversa gladius.jpg350px]]Histioteuthis reversa Histioteuthidae
[[File:Illex illecebrosus gladius.jpg350px]]Illex illecebrosusOmmastrephidae
[[File:Lepidoteuthis grimaldii gladius.jpg350px]]Lepidoteuthis grimaldiiLepidoteuthidae
[[File:Loligo pealeii gladius.jpg350px]]Doryteuthis pealeiiLoliginidae
[[File:Loliolus sumatrensis gladius.jpg350px]]Loliolus sumatrensisLoliginidae
[[File:Lolliguncula brevis gladius.jpg350px]]Lolliguncula brevisLoliginidae
[[File:Mastigoteuthis agassizii gladius.jpg350px]]Mastigoteuthis agassiziiMastigoteuthidae
[[File:Moroteuthis ingens4.jpg350px]]Onykia ingensOnychoteuthidae
[[File:Pholidoteuthis massyae gladius.jpg350px]]Pholidoteuthis massyaePholidoteuthidae
[[File:Sepioteuthis lessoniana gladius.jpg350px]]Sepioteuthis lessonianaLoliginidae
[[File:Gladius Taningia danae.jpg350px]]Taningia danaeOctopoteuthidae
[[File:Taonius borealis gladius.jpg350px]]Taonius borealisCranchiidae
[[File:Teuthowenia megalops gladius.jpg350px]]Teuthowenia megalopsCranchiidae
[[File:Uroteuthis duvauceli gladius.jpg350px]]Uroteuthis duvauceliLoliginidae

References

References

  1. (1999). "Cephalopod gladius terminology".
  2. (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.
  3. (2019). "Construction and Composition of the Squid Pen from Doryteuthis pealeii". The Biological Bulletin.
  4. (2007). "Gladius shape variation in coleoid cephalopod ''Trachyteuthis'' from the Upper Jurassic Nusplingen and Solnhofen Plattenkalks". Acta Palaeontologica Polonica.
  5. (2010). "Teudopseina".
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cephalopod-zootomy skeletal-system
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