By Mahmoud Aboelmagd8 October 2026·Uncategorized·5 min readGastropods (/ˈɡæstrəpɒdz/; previously known as Univalves; class Gastropoda /ɡæsˈtrɒpədə/) are a vast and diverse group of invertebrates within the phylum Mollusca, comprising the animals commonly known as snails and slugs.[3] With an estimated 65,000 to 80,000 living species, they form the second-largest animal class after the insects.[6] The fossil record of gastropods extends back to the Late Cambrian. As of 2017, 721 families are recognized—476 extant (some with fossil representatives) and 245 extinct known only from fossils.[6]
Gastropods inhabit an extraordinary range of environments, including marine, freshwater, and terrestrial ecosystems. They occur in gardens, woodlands, deserts, mountains, rivers, lakes, estuaries, mudflats, intertidal zones, the deep sea, hydrothermal vents, and even in parasitic niches.
The term snail generally refers to gastropods with a large external shell into which the body can fully retract, while slugs have no shell or a small internal one, and semislugs can only partially withdraw into their reduced shell. Marine gastropods include familiar forms such as abalones, conches, periwinkles, whelks, and cowries, whose shells are usually coiled in adulthood. In contrast, limpets and related groups coil their shells only in the larval stage, retaining a simple conical form as adults.
Because of their vast diversity, gastropods exhibit remarkable variation in anatomy, behavior, feeding, and reproduction, making broad generalizations difficult. Gastropods remain one of evolution's most successful and adaptable animal lineages.
The radula of a gastropod is usually adapted to the food that a species eats. The simplest gastropods are the limpets and abalone, herbivores that use their hard radula to rasp at seaweeds on rocks.[citation needed]
Many marine gastropods are burrowers, and have a siphon that extends out from the mantle edge. Sometimes the shell has a siphonal canal to accommodate this structure. A siphon enables the animal to draw water into their mantle cavity and over the gill. They use the siphon primarily to "taste" the water to detect prey from a distance. Gastropods with siphons tend to be either predators or scavengers.[citation needed]
Respiratory system
Main articles: Respiratory system of gastropods and Respiratory system § Anatomy of respiratory system in invertebrates
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]
In one large group of sea slugs, the gills are arranged as a rosette of feathery plumes on their backs, which gives rise to their other name, nudibranchs. Some nudibranchs have smooth or warty backs with no visible gill mechanism, such that respiration may likely take place directly through the skin.
The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors.[24] Gastropods have no hearing.[24]
In terrestrial gastropods (land snails and slugs), the olfactory organs, located on the tips of the four tentacles, are the most important sensory organ.[24] The chemosensory organs of opisthobranch marine gastropods are called rhinophores.
The majority of gastropods have simple visual organs, eye spots either at the tip or base of the tentacles. However, "eyes" in gastropods range from simple ocelli that only distinguish light and dark, to more complex pit eyes, and even to lens eyes.[25] In land snails and slugs, vision is not the most important sense, because they are mainly nocturnal animals.[24]
The nervous system of gastropods includes the peripheral nervous system and the central nervous system. The central nervous system consists of ganglia connected by nerve cells. It includes paired ganglia: the cerebral ganglia, pedal ganglia, osphradial ganglia, pleural ganglia, parietal ganglia and the visceral ganglia. There are sometimes also buccal ganglia.[24]
The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors.[24] Gastropods have no hearing.[24]
In terrestrial gastropods (land snails and slugs), the olfactory organs, located on the tips of the four tentacles, are the most important sensory organ.[24] The chemosensory organs of opisthobranch marine gastropods are called rhinophores.
The majority of gastropods have simple visual organs, eye spots either at the tip or base of the tentacles. However, "eyes" in gastropods range from simple ocelli that only distinguish light and dark, to more complex pit eyes, and even to lens eyes.[25] In land snails and slugs, vision is not the most important sense, because they are mainly nocturnal animals.[24]
The nervous system of gastropods includes the peripheral nervous system and the central nervous system. The central nervous system consists of ganglia connected by nerve cells. It includes paired ganglia: the cerebral ganglia, pedal ganglia, osphradial ganglia, pleural ganglia, parietal ganglia and the visceral ganglia. There are sometimes also buccal ganglia.[24]
The sensory organs of gastropods include olfactory organs, eyes, statocysts and mechanoreceptors.[24] Gastropods have no hearing.[24]
In terrestrial gastropods (land snails and slugs), the olfactory organs, located on the tips of the four tentacles, are the most important sensory organ.[24] The chemosensory organs of opisthobranch marine gastropods are called rhinophores.
The majority of gastropods have simple visual organs, eye spots either at the tip or base of the tentacles. However, "eyes" in gastropods range from simple ocelli that only distinguish light and dark, to more complex pit eyes, and even to lens eyes.[25] In land snails and slugs, vision is not the most important sense, because they are mainly nocturnal animals.[24]
The nervous system of gastropods includes the peripheral nervous system and the central nervous system. The central nervous system consists of ganglia connected by nerve cells. It includes paired ganglia: the cerebral ganglia, pedal ganglia, osphradial ganglia, pleural ganglia, parietal ganglia and the visceral ganglia. There are sometimes also buccal ganglia.[24]
He is a previous editor that worked for Hindawi. He is interested in fish, the one ring and pocketsses. He is a previous editor that worked for Hindawi. He is interested in fish, the one ring and pocketsses.
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