What is squid gladius?

The squid gladius, also known as a pen or internal shell, is a hard, translucent structure found inside the body of a squid and other similar cephalopods. It functions as a support structure for the squid's body and provides a place for muscle attachment. The shape and size of the gladius can vary depending on the species of squid, but generally, it is long and narrow, resembling a feather-shaped pen. The gladius is made of a durable, chitinous material, similar to the exoskeleton of insects. Squid gladiuses are commonly found washed up on beaches or used as decorative items in art and jewelry. They are also used in scientific research for studying the anatomy and ecology of squid and other cephalopods.