What common feature do a land snail, a clam, and an octopus share?

A mantle is a common feature found in land snails, clams, and octopuses, as it is a significant characteristic of a phylum that includes these organisms—Mollusca. The mantle is a layer of tissue that covers the body and secretes the shell in species that have one, providing protection and structural support. In different groups within the Mollusca, the mantle can serve various functions, such as facilitating gas exchange, waste elimination, and shell formation.

Land snails have a well-developed mantle that plays a critical role in producing their spiral shell. Clams possess a mantle that has two lobes that can create a shell for protection. Octopuses, while they do not have an external shell, still possess a mantle that houses most of their vital organs and aids in locomotion and gas exchange through a siphon. This shared feature underscores the evolutionary relationship among these diverse mollusks, highlighting the mantle's importance across different environments and lifestyles.