Sensory organs of gastropods
Encyclopedia
Sensory organs
of gastropods (snail
s and slug
s) include olfactory organs
, eye
s, statocyst
s and mechanoreceptor
s. Gastropods have no sense of hearing.
s.
In opisthobranch marine gastropods, the chemosensor
y organs are two protruding structures on top of the head. These are known as rhinophore
s.
An opisthobranch Navanax inermis
has chemoreceptors at sides of its mouth in and it can to track mucopolysaccharides from the slime
trails of prey, and of potential mates.
Freshwater snail Bithynia tentaculata
is capable of detecting the presence of molluscivorous leeches through chemoreception and of closing its operculum
to avoid predation. Vision is not the most important requirement in terrestrial gastropods, because they are mainly nocturnal animals.
Some gastropods, for example the freshwater Apple snails (family Ampullariidae
) and marine species of genus Strombus
can completely regenerate
their eyes. The gastropods in both of these families have lens eyes.
Morphological sequence of different types of multicellular eyes exemplified by gastropod eyes:
another drawing of eye of Helix pomatia
s of Haliotis asinina was found the expression
of a conserved gene (Pax-258 gene
), which is also important for forming structures for balance in eumetazoa
ns.
Sense
Senses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...
of gastropods (snail
Snail
Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...
s and slug
Slug
Slug is a common name that is normally applied to any gastropod mollusc that lacks a shell, has a very reduced shell, or has a small internal shell...
s) include olfactory organs
Olfaction
Olfaction is the sense of smell. This sense is mediated by specialized sensory cells of the nasal cavity of vertebrates, and, by analogy, sensory cells of the antennae of invertebrates...
, eye
Mollusc eye
The molluscs have the widest variety of eye morphologies of any phylum, and a large degree of variation in their function. Cephalopods' eyes are as complex as those of vertebrates; scallops have up to 100 simple eyes; and some bivalves have compound eyes....
s, statocyst
Statocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...
s and mechanoreceptor
Mechanoreceptor
A mechanoreceptor is a sensory receptor that responds to mechanical pressure or distortion. There are four main types in the glabrous skin of humans: Pacinian corpuscles, Meissner's corpuscles, Merkel's discs, and Ruffini corpuscles...
s. Gastropods have no sense of hearing.
Olfactory organs
In terrestrial gastropods the most important sensory organs are the olfactory organs which are located on the tips of the 4 tentacleTentacle
A tentacle or bothrium is one of usually two or more elongated flexible organs present in animals, especially invertebrates. The term may also refer to the hairs of the leaves of some insectivorous plants. Usually, tentacles are used for feeding, feeling and grasping. Anatomically, they work like...
s.
In opisthobranch marine gastropods, the chemosensor
Chemosensor
A chemoreceptor, also known as chemosensor, is a sensory receptor that transduces a chemical signal into an action potential. In more general terms, a chemosensor detects certain chemical stimuli in the environment.- Classes :...
y organs are two protruding structures on top of the head. These are known as rhinophore
Rhinophore
A rhinophore is one of a pair of club-shaped structures which are the most prominent part of the external head anatomy of a group of sea slugs, marine gastropod opisthobranch mollusks in the order Nudibranchia, the nudibranchs, specifically the dorid nudibranchs.- Etymology :The name relates to the...
s.
An opisthobranch Navanax inermis
Navanax inermis
Navanax inermis is a species of predatory sea slug, a marine opisthobranch gastropod mollusk in the family Aglajidae and the order Cephalaspidea, the headshield slugs and bubble snails....
has chemoreceptors at sides of its mouth in and it can to track mucopolysaccharides from the slime
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...
trails of prey, and of potential mates.
Freshwater snail Bithynia tentaculata
Bithynia tentaculata
Bithynia tentaculata, common names the mud bithynia or common bithynia, or faucet snail is a relatively small species of freshwater snail with gills and an operculum, an aquatic prosobranch gastropod mollusk in the family Bithyniidae....
is capable of detecting the presence of molluscivorous leeches through chemoreception and of closing its operculum
Operculum (gastropod)
The operculum, meaning little lid, is a corneous or calcareous anatomical structure which exists in many groups of sea snails and freshwater snails, and also in a few groups of land snails...
to avoid predation. Vision is not the most important requirement in terrestrial gastropods, because they are mainly nocturnal animals.
Some gastropods, for example the freshwater Apple snails (family Ampullariidae
Ampullariidae
Ampullariidae, common name the apple snails, is a family of large freshwater snails, aquatic gastropod mollusks with a gill and an operculum...
) and marine species of genus Strombus
Strombus
Strombus, common name the true conchs, is a genus of medium to large sea snails with an operculum, marine gastropod mollusks in the family Strombidae, the true conchs and their immediate relatives....
can completely regenerate
Regeneration (biology)
In biology, regeneration is the process of renewal, restoration, and growth that makes genomes, cells, organs, organisms, and ecosystems resilient to natural fluctuations or events that cause disturbance or damage. Every species is capable of regeneration, from bacteria to humans. At its most...
their eyes. The gastropods in both of these families have lens eyes.
Morphological sequence of different types of multicellular eyes exemplified by gastropod eyes:
Lens eyes
 |
another drawing of eye of Helix pomatia
Statocysts
In the statocystStatocyst
The statocyst is a balance sensory receptor present in some aquatic invertebrates, including bivalves, cnidarians, echinoderms, cephalopods, and crustaceans. A similar structure is also found in Xenoturbella. The statocyst consists of a sac-like structure containing a mineralised mass and numerous...
s of Haliotis asinina was found the expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
of a conserved gene (Pax-258 gene
Pax genes
Paired box genes are a family of tissue specific transcription factors containing a paired domain and usually a partial or complete homeodomain. An octapeptide may also be present...
), which is also important for forming structures for balance in eumetazoa
Eumetazoa
Eumetazoa is a clade comprising all major animal groups except sponges, placozoa and several other little known animals. Characteristics of eumetazoans include true tissues organized into germ layers, and an embryo that goes through a gastrula stage...
ns.
Further reading
- Sergei Tschachotin. 1908. Die Statocyste der Heteropoden. Heidelberg, Univ., Diss., (Zeitschrift f. wissenschaftl. Zoologie; Bd. 90; S. 343-422).
- Abraham J. Susswein, Mitchell S. Cappell & Michael V. L. Bennett 1982. Distance chemoreception in Navanax inermis. Marine and Freshwater Behaviour and Physiology, Volume 8, Issue 3 April 1982, pages 231-241.