Excretory system of gastropods

The excretory system of gastropods removes nitrogenous waste and maintains the internal water balance of these creatures, commonly referred to as snails and slugs.

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 visceral mass.

These glands have a metabolic function, somewhat similar to that of the vertebrate liver, and excrete waste products directly into the digestive system, where it is voided with the faeces.

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.

Those few species that dwell in arid environments typically hibernate or aestivate during dry periods to preserve moisture.