In
echinoderms an appendage called a
pedicellaria is found. 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. Echinoderms also possess podia known as
tube feet. 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.
In protostomes In
annelid worms, lateral protrusions from the body are called
parapodia. In the
class of
polychaetes,
chitinized lateral protrusions are called
chaeta. All
cephalopods, a
mollusc class, have flexible appendages known as
cephalopod limbs. They may have further extensions as
suckers. 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,
locomotory legs (
pereiopods for
walking, and
pleopods for
swimming),
sexual organs (
gonopods), and parts of the
tail (
uropods). All arthropod appendages are variations of the same basic structure (being
homologous with one another), and which structure is produced is controlled by "
homeobox" genes; alterations to these genes have allowed scientists to produce
genetically modified animals, such as fruit flies (
Drosophila melanogaster) with legs growing where the antennae would have on the head. Appendages may become
uniramous, as in
insects and
centipedes, where each appendage comprises a single series of segments, or it may be
biramous, as in many
crustaceans, where each appendage branches into two sections.
Triramous (branching into three) appendages are also possible. In the past this difference in leg development became the basis of arthropod classification, with
Uniramia being a former group within Arthropoda. ==Types in prokaryotes==