The siphonoglyph is a
ciliated groove at one or both ends of the mouth of
sea anemones and some
corals. The siphonoglyph extends into a
pharynx and is used to create currents of water into the pharynx. These water currents are important for
respiration and maintenance of internal pressure. The presence of a siphonoglyph (or two siphonoglyphs) in several
anthozoan
Anthozoa is a subphylum of marine invertebrates which includes the sea anemones, stony corals and soft corals. Adult anthozoans are almost all attached to the seabed, while their larvae can disperse as part of the plankton. The basic unit of t ...
s (including species from the orders
Zoantharia,
Ceriantharia
Tube-dwelling anemones or ceriantharians look very similar to sea anemones but belong to an entirely different class of anthozoans. They are solitary, living buried in soft sediments. Tube anemones live inside and can withdraw into tubes, which ...
,
Antipatharia, and
Octocorallia
Octocorallia (also known as Alcyonaria) is a class of Anthozoa comprising around 3,000 species of water-based organisms formed of colonial polyps with 8-fold symmetry. It includes the blue coral, soft corals, sea pens, and gorgonians (sea fa ...
) introduces an element of
bilateral symmetry
Symmetry in biology refers to the symmetry observed in organisms, including plants, animals, fungi, and bacteria. External symmetry can be easily seen by just looking at an organism. For example, take the face of a human being which has a pl ...
into the particular species' body plan (Beklemishev 1969). Some have argued that the presence of bilateral symmetry in these anthozoans is evidence that the ancestor to bilaterians and cnidarians may have had a bilaterally symmetrical body plan (Finnerty 2003).
References
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Anthozoa
Cnidarian anatomy
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