Gladius (cephalopod)

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Gladius, showing measurement of rachis and vane

The gladius (pl.: gladii), or pen, is a hard internal bodypart found in many

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]

Fossilised gladius of Trachyteuthis
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 gladius Species Family
Ancistroteuthis lichtensteini
Onychoteuthidae
Architeuthis
 sp.
Architeuthidae
Bathyteuthis abyssicola
Bathyteuthidae
Histioteuthis bonnellii Histioteuthidae
Histioteuthis reversa Histioteuthidae
Illex illecebrosus Ommastrephidae
Lepidoteuthis grimaldii
Lepidoteuthidae
Doryteuthis pealeii
 		Loliginidae
Loliolus sumatrensis Loliginidae
Lolliguncula brevis Loliginidae
Mastigoteuthis agassizii
Mastigoteuthidae
Onykia ingens
Onychoteuthidae
Pholidoteuthis massyae
Pholidoteuthidae
Sepioteuthis lessoniana
 		Loliginidae
Taningia danae Octopoteuthidae
Taonius borealis Cranchiidae
Teuthowenia megalops Cranchiidae
Uroteuthis duvauceli
 		Loliginidae
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

Wikimedia Commons has media related to Gladius.

References

  1. ^ a b c Young, R.E.; Vecchione, M.; Mangold, K.M., eds. (1999). "Cephalopod gladius terminology". Tree of Life Web Project.
  2. doi:10.1016/0305-0491(81)90071-7
    .
  3. ^ Construction and composition of the squid pen from Doryteuthis pealeii
  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

  • Bizikov, V.A. (1991). Squid gladius: Its use for the study of growth, age, intraspecies structure and evolution (on the example of the family Ommastrephidae) (Ph.D.) (in Russian and English). Moscow: Institute of Oceanology, SSSR Academy of Sciences. 513 pp.
  • Toll, R.B. (1982). The comparative morphology of the gladius in the order Teuthoidea (Mollusca: Cephalopoda) in relation to systematics and phylogeny (Ph.D.). Coral Gables, Florida: University of Miami. 390 pp.
  • Toll, R.B. (1998). "The gladius in teuthoid systematics". Smithsonian Contributions to Zoology. 586 (1): 55–67.
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