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Gastropods such as abalone and keyhole limpets have two gills, which is believed to be the arrangement in the earliest fossil gastropods. The water current to supply these gills is evacuated through a slit or notch in the upper surface of the shell, below which the anus opens. In most other gastropods, the right gill has been lost.
Almost all marine gastropods breathe with a gill, but many freshwater species, and the majority of terrestrial species, have a pallial lung. The respiratory protein in almost all gastropods is hemocyanin, but one freshwater pulmonate family, the Planorbidae, have hemoglobin as the respiratory protein. [citation needed]
A ctenidium is a respiratory organ or gill which is found in many molluscs. This structure exists in bivalves, cephalopods, polyplacophorans (chitons), and in aquatic gastropods such as freshwater snails and marine snails. [1]
In gastropods, it secretes mucus as a lubricant to aid movement. In forms having only a top shell, such as limpets , the foot acts as a sucker attaching the animal to a hard surface, and the vertical muscles clamp the shell down over it; in other molluscs, the vertical muscles pull the foot and other exposed soft parts into the shell. [ 19 ]
Scaly-foot gastropod Chrysomallon squamiferum, common name the scaly-foot gastropod, is a species of deep-sea hydrothermal-vent snail, a marine gastropod mollusc in the family Peltospiridae. This vent-endemic gastropod is known only from deep-sea hydrothermal vents in the Indian Ocean, where it has been found at depths of about 2,400–2,800 m ...
The scaly-foot gastropod is an obligate symbiotroph throughout post-settlement life. [24] Throughout its post-larval life, the scaly-foot gastropod obtains all of its nutrition from the chemoautotrophy of its endosymbiotic bacteria. [26] [24] The scaly-foot gastropod is neither a filter-feeder [5] [24] nor uses other mechanisms for feeding. [5]
The majority of gastropods have haemolymph containing the respiratory pigment haemocyanin. This is a copper-containing protein that helps to carry oxygen, and gives the haemolymph a pale blue colour. In the freshwater Planorbid snails, however, the haemocyanin is replaced by haemoglobin , and thus their haemolymph is red rather than blue.
In many marine gastropods where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft tissue of the siphon. This shell modification is known as the siphonal canal. For a gastropod whose shell has an exceptionally long siphonal canal, see Venus comb murex.