The gastropods, commonly known as slugs and snails, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda.
Chitons are marine molluscs of varying size in the class Polyplacophora, formerly known as Amphineura. About 940 extant and 430 fossil species are recognized.
The vomeronasal organ (VNO), or Jacobson's organ, is the paired auxiliary olfactory (smell) sense organ located in the soft tissue of the nasal septum, in the nasal cavity just above the roof of the mouth in various tetrapods. The name is derived from the fact that it lies adjacent to the unpaired vomer bone in the nasal septum. It is present and functional in all snakes and lizards, and in many mammals, including cats, dogs, cattle, pigs, and some primates. Some humans may have physical remnants of a VNO, but it is vestigial and non-functional.
Cephalization is an evolutionary trend in which, over many generations, the mouth, sense organs, and nerve ganglia become concentrated at the front end of an animal, producing a head region. This is associated with movement and bilateral symmetry, such that the animal has a definite head end. This led to the formation of a highly sophisticated brain in three groups of animals, namely the arthropods, cephalopod molluscs, and vertebrates.
The tusk shells or tooth shells, technically the Scaphopoda, are members of a class of shelled marine mollusc with worldwide distribution, and are the only class of exclusively infaunal marine molluscs. Shells of species within this class range from about 0.5 to 18 cm in length. Members of the order Dentaliida tend to be larger than those of the order Gadilida.
The Patellogastropoda, common name true limpets and historically called the Docoglossa, are members of a major phylogenetic group of marine gastropods, treated by experts either as a clade or as a taxonomic order.
A parietal eye, also known as a third eye or pineal eye, is a part of the epithalamus present in some vertebrates. The eye is located at the top of the head, is photoreceptive and is associated with the pineal gland, regulating circadian rhythmicity and hormone production for thermoregulation. The hole in the head which contains the eye is known as a pineal foramen or parietal foramen, since it is often enclosed by the parietal bones.
The evolution of the molluscs is the way in which the Mollusca, one of the largest groups of invertebrate animals, evolved. This phylum includes gastropods, bivalves, scaphopods, cephalopods, and several other groups. The fossil record of mollusks is relatively complete, and they are well represented in most fossil-bearing marine strata. Very early organisms which have dubiously been compared to molluscs include Kimberella and Odontogriphus.
Odostomiinae, Odostomia snails and their allies, is a taxonomic subfamily of minute parasitic sea snails. These are marine heterobranch gastropod mollusks, or micromollusks, in the family Pyramidellidae.
Odontogriphus is a genus of soft-bodied animals known from middle Cambrian Lagerstätte. Reaching as much as 12.5 centimetres (4.9 in) in length, Odontogriphus is a flat, oval bilaterian which apparently had a single muscular foot and a "shell" on its back that was moderately rigid but of a material unsuited to fossilization.
The siphonal canal is an anatomical feature of the shells of certain groups of sea snails within the clade Neogastropoda. Some sea marine gastropods have 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. Siphonal canals allow for active transport of water to sensory organs inside the shell. Organisms without siphonal canals in their shells rely on passive or diffuse transport or water into their shell. Those with siphonal canals have a direct inhalant stream of water that interacts with sensory organs to detect concentration and direction of a stimulus, such as food or mates. In certain groups of carnivorous snails, where the siphon is particularly long, the structure of the shell has been modified in order to house and protect the soft structure of the siphon. Thus the siphonal canal is a semi-tubular extension of the aperture of the shell through which the siphon is extended when the animal is active.
engrailed is a homeodomain transcription factor involved in many aspects of multicellular development. First known for its role in arthropod embryological development, working in consort with the Hox genes, engrailed has been found to be important in other areas of development. It has been identified in many bilaterians, including the arthropods, vertebrates, echinoderms, molluscs, nematodes, brachiopods, and polychaetes. It acts as a "selector" gene, conferring a specific identity to defined areas of the body, and co-ordinating the expression of downstream genes.
Mollusca is the second-largest phylum of invertebrate animals, after the Arthropoda; members are known as molluscs or mollusks. Around 85,000 extant species of molluscs are recognized. The number of fossil species is estimated between 60,000 and 100,000 additional species. The proportion of undescribed species is very high. Many taxa remain poorly studied.
The molluscs have the widest variety of eye morphologies of any phylum, and a large degree of variation in their function. Cephalopods such as octopus, squid, and cuttlefish have eyes as complex as those of vertebrates, while scallops have up to 100 simple eyes.
Vetigastropoda is a major taxonomic group of sea snails, marine gastropod mollusks that form a very ancient lineage. Taxonomically the Vetigastropoda are sometimes treated as an order, although they are treated as an unranked clade in Bouchet and Rocroi, 2005.
Winston Frank Ponder is a malacologist born and educated in New Zealand who has named and described many marine and freshwater animals, especially micromolluscs.
The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors. Gastropods have no sense of hearing.
The nervous system of gastropods consists of a series of paired ganglia connected by major nerve cords, and a number of smaller branching nerves. It is sometimes called ganglionic.
Bathyacmaea nipponica is a species of very small, deep-sea limpet, a marine gastropod mollusk in the family Pectinodontidae.
This outline is provided as an overview of, and organized list of articles relevant to, the subject of gastropods :
