Molluscs Many molluscs have tentacles of one form or another. The most familiar are those of the
pulmonate land snails, which usually have two sets of tentacles on the head: when extended the upper pair have eyes at their tips; the lower pair are
chemoreceptors. Both pairs are fully retractable
muscular hydrostats, but they are not used for manipulation or prey capture. Molluscs have one pair of tentacles close to their mouths that hold close to their captured prey before they can consume it. Some marine snails such as
abalone and top snails,
Trochidae, have numerous small tentacles around the edge of the
mantle. These are known as
pallial tentacles. These tentacles are made of stalks of axial
nerve cords that are covered by circular transverse muscle tissue that contract in response to stimuli. There is a layer of helical muscle that helps each tentacle to twist or turn in any direction where the prey is sensed. While arms are distinct from tentacles (a definition specific to the limb featuring peduncles), arms do fall within the general definition of "tentacle" as "a flexible, mobile, and elongated organ" and "tentacle" could be used as an
umbrella term. The tentacles of the
giant squid and
colossal squid have powerful suckers and pointed teeth at the ends. The teeth of the giant squid resemble
bottle caps and function like tiny
hole saws, while the tentacles of the colossal squid wield two long rows of swiveling, tri-pointed hooks.
Cnidarians Cnidarians, such as
jellyfish,
sea anemones,
Hydra and
coral have numerous hair-like tentacles. Cnidarians have huge numbers of
cnidocytes on their tentacles. In
medusoid form, the body floats on water so that the tentacles hang down in a ring around the mouth. In
polyp form, such as sea anemone and coral, the body is below with the tentacles pointed upwards. The tentacles of the
lion's mane jellyfish may be up to long. They are hollow and are arranged in 8 groups of between 70 and 150. The longer tentacles are equipped with cnidocytes whose venom paralyses and kills prey. The smaller tentacles guide food into the mouth.
Ctenophores Many species of the jellyfish-like
ctenophores have two tentacles, while some have none. Their tentacles have adhesive structures called
colloblasts or
lasso cells. The colloblasts burst open when prey comes in contact with the tentacle, releasing sticky threads that secure the food.
Bryozoa Bryozoa (moss animals) are tiny creatures with tentacles around their mouths. The tentacles are almost cylindrical and have bands of cilia which create a water current towards the mouth. The animal extracts edible material from the flow of water.
Trypanorhynch cestodes Trypanorhynch cestodes are parasitic in fish. Their
scolex shows four tentacles which are covered by spines. These tentacles help the adult cestode to attach to the intestine of the shark or ray that they parasitize. The same tentacles are also present in the larvae. ==Vertebrates==