A stylet is a hard, sharp, anatomical structure found in some

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s. For example, the word ''stylet'' or stomatostyle is used for the primitive piercing mouthparts of some nematodes and some

nemertea Nemertea is a phylum of animals also known as ribbon worms or proboscis worms, consisting of 1300 known species. Most ribbon worms are very slim, usually only a few millimeters wide, although a few have relatively short but wide bodies. Many h ...

ns. In these groups the stylet is a hardened protrusible opening to the

stomach The stomach is a muscular, hollow organ in the gastrointestinal tract of humans and many other animals, including several invertebrates. The stomach has a dilated structure and functions as a vital organ in the digestive system. The stomach i ...

. These stylets are adapted for the piercing of cell walls and usually function by providing the operative organism with access to the nutrients contained within the prey cell. The mouthparts of

tardigrade Tardigrades (), known colloquially as water bears or moss piglets, are a phylum of eight-legged segmented micro-animals. They were first described by the German zoologist Johann August Ephraim Goeze in 1773, who called them Kleiner Wasserbä ...

s, diptera and

aphid Aphids are small sap-sucking insects and members of the superfamily Aphidoidea. Common names include greenfly and blackfly, although individuals within a species can vary widely in color. The group includes the fluffy white woolly aphids. A t ...

s are also called stylets. In octopodes, the stylets are internal, needle-like bent rods within the mantle, the vestigial remnants of an external shell.

References

Nematode anatomy {{Animal-anatomy-stub