Gladius, showing measurement of rachis and vane
The gladius (plural: 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 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]
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).[3][4]
Variability
Gladii are shaped in many distinctive ways, and vary considerably between species. Some examples are shown below.
See also
References
Further reading
- (Russian) 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. Thesis. Institute of Oceanology, SSSR Academy of Sciences, Moscow. 513 pp. (English abstract)
- Toll, R.B. (1982). The comparative morphology of the gladius in the order Teuthoidea (Mollusca: Cephalopoda) in relation to systematics and phylogeny. Ph.D. Thesis. University of Miami, Coral Gables, Florida. 390 pp.
- Toll, R.B. (1998). The gladius in teuthoid systematics. Smithsonian Contributions to Zoology 586(1): 55–67.
|
---|
| Shell |
Shell types | |
---|
| External features | |
---|
| Internal features | |
---|
| |
---|
| Mantle |
External anatomy | |
---|
| Internal anatomy | |
---|
|
---|
| Funnel | |
---|
| Head and limbs |
Brachial crown | |
---|
| Buccal region | |
---|
| Occipital region |
- Occipital crest
- Occipital folds (nuchal folds)
- Occipital membrane
- Olfactory organ
- Nuchal organ
|
---|
| Other parts | |
---|
|
---|
| General | |
---|
| |
|