Excretory system of gastropods

The

gastropods removes nitrogenous waste and maintains the internal water balance of these creatures, commonly referred to as snails and slugs. The primary organ of excretion is a nephridium

.

Structure

The most primitive gastropods retain two nephridia, but in the great majority of species, the right nephridium has been lost, leaving a single excretory organ, located in the anterior part of the

haemolymph directly bathes the tissues, where it supplies them with oxygen and absorbs carbon dioxide and nitrogenous waste, a necessary waste product of metabolism

. From the arterial sinuses bathing the tissues, it drains into the venous sinus, and thus flows past the nephridium.

The main body cavity of most aquatic gastropods also includes pericardial glands, often located above the heart. These secrete waste into the haemolymph, prior to further filtration in the nephridium. Pulmonates lack these glands, so that the nephridium is the only major organ of excretion.

In some gastropods, the nephridium opens directly into the sinus, but more usually, there is a small duct, referred to as the renopericardial canal. In aquatic gastropods, the nephridium is drained by a

pulmonates instead have a much longer ureter, that opens near the anus

.

In addition to the pericardial glands and nephridium, excretory cells are also present in the digestive glands opening into the

faeces

.

Water balance

In aquatic gastropods, the waste product is invariably ammonia, which rapidly dissolves in the surrounding water. In the case of freshwater species, the nephridium also resorbs a significant amount of salt in order to prevent its loss through osmosis into the surrounding water.

Terrestrial species instead excrete insoluble

aestivate

during dry periods to preserve moisture.

References

Barnes, Robert D. (1982). Invertebrate Zoology. Philadelphia, PA: Holt-Saunders International. pp. 364–365.

ISBN 0-03-056747-5

.

v t e 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

Structure

Water balance

References

External links