Appendage

In arthropods, an appendage refers to any of the homologous body parts that may extend from a body segment, including antennae, mouthparts (including mandibles, maxillae and maxillipeds), gills, locomotor legs (pereiopods for walking, and pleopods for swimming), sexual organs (gonopods), and parts of the tail (uropods).

The end of the pedicellaria consists of valves that give a jaw-like appearance and is thought to be used to clear the external body surface.

Tube feet form part of the water vascular system and are used for locomotion, food and waste transportation, and respiration.

In vertebrates, an appendage can refer to a locomotor part such as a tail, fins on a fish, limbs (arms, legs, flippers or wings) on a tetrapod; exposed sex organ; defensive parts such as horns and antlers; or sensory organs such as auricles, proboscis (trunk and snout) and barbels.

Changes to these genes have allowed scientists to produce animals (chiefly Drosophila melanogaster) with modified appendages, such as legs instead of antennae.

[2] A number of cell-surface appendages are found in prokaryotes – bacteria and archaea, and include archaella, flagella, pili, fimbriae, and prosthecae also called stalks.

Pili are used for attachment to surfaces, possible communication between cells enabling cell-to-cell contact allowing genetic transfer, and the formation of biofilms.