How do gastropods differ from other mollusks?

Gastropods, the largest class within the phylum Mollusca, are distinguished from other mollusks primarily by a unique developmental process known as torsion. During the larval stage, the gastropod body undergoes a 180° twist, which shifts the posterior part of the body to an anterior position behind the head. This process is unique to gastropods and does not occur in other molluscan classes.123

Additionally, gastropods exhibit several structural and ecological characteristics that set them apart:

• Shell and Body Structure: While many mollusks have distinct shell forms, gastropods typically possess a coiled shell, often accompanied by an operculum—a calcified disk on the foot used to seal the shell aperture for protection. In some groups, such as slugs, the shell has been reduced or lost entirely through evolution.241
• Ecological Success: Gastropods demonstrate greater ecological diversity than other mollusks, having successfully colonized marine, freshwater, and terrestrial habitats.15
• Anatomical Features: They possess a free head with paired eyes and exhibit immense structural variability. Unlike some other mollusks that rely on ciliary suspension feeding, gastropods utilize a wide range of feeding strategies, including scavenging, predation, and herbivory.215