Gladius (cephalopod)

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. 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. 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 or leaf. The equivalent part in cuttlefish is the cuttlebone. Below are examples of gladii from various families of squid;

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

Gladius (cephalopod)

Bron en licentie