Siphonal notch

A shell of Acus crenulata, with the siphonal notch visible near the bottom left of the image, at the anterior end of the shell.

A live individual of the volute species Cymbiola magnifica showing the siphon extended through the siphonal notch of the shell

A siphonal notch is a feature of the shell anatomy in some sea snails, marine gastropod mollusks.

In these particular groups of sea snails the animal has a soft tubular anterior extension of the mantle called a siphon through which water is drawn into the mantle cavity and over the gill and which serves as a chemoreceptor to locate food. This siphonal opening also serves for the exit of the water that has entered by the branchial opening.

The siphonal notch is a noticeable notch situated at the most posterior part of the aperture of the shell, through which the siphon is extended when the animal is active. The notch at the posterior end of the aperture is also called the anal notch, anal sinus, anal canal or posterior canal.

Instead of a simple siphonal notch, some gastropods have an elongated siphonal canal, a hard shell tube which extends out from the anterior edge of the aperture.

References

Gastropod anatomy

Shell	Aperture Apex Body whorl Callus Columella Lip Lira Nacre Periostracum Peristome Planispiral Plait Protoconch Sculpture Selenizone Siphonal canal Siphonal notch Spire Stromboid notch Suture Umbilicus Valve Varix Whorl

Other hard parts	Clausilium Love dart Operculum Pearl Radula

External soft parts	Caryophyllidia Caudal mucous pit Cerata Cnidosac Mantle Mentum Notum Parapodium Pneumostome Rhinophore Semper's organ Siphon Suprapedal gland

Internal soft parts	Circulatory system of gastropods Crop Ctenidium Digestive system of gastropods Diverticula Excretory system of gastropods Gastric shield Hancock's organ Hepatopancreas Hypobranchial gland Nephridium Nervous system of gastropods Nidamental gland Odontophore Oesophageal pouch Osphradium Reproductive system of gastropods Respiratory system of gastropods Sensory organs of gastropods

Other	Epiphragm Pseudofeces Torsion Circumesophageal nerve ring Trochophore Tyrian purple Veliger

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Siphonal notch

See also

References