Mollusks | Mollusca
After the Arthropoda, Mollusca is the second largest phylum of invertebrate animals with members on land and sea. Mollusca is the largest marine phylum, with numerous creatures, such as squids, snails, scallops, and more, which make up 23% of all marine organisms. The defining features of Mollusca, include a soft body with a hand and a foot and a hard exoskeleton. Throughout history, Mollusca have been a source of food, jewelry, currency, tools, and even pets. However, Mollusca have also been pests to gardens and boats and occasionally invasive species wrecking havoc on ecosystems.
A mollusk’s diet may vary depending on its species. For example, mollusks that have their body between 2 shells are herbivores that eat algae. Meanwhile, squids and octopuses eat fish and other sea creatures. Mollusk snails can be either herbivores or carnivores.
The way a mollusk moves depends if it lives on land or water. Mollusks that live on land move very slowly on a foot. Mollusks that live in the water eject water out of their body to move themselves. Some mollusks, like oysters and clams, do not move but rather attach themselves to a rock or a surface.
Aquatic mollusks breath by using gills, called ctenidia that are in their mantle cavity. Mollusks that live on land do not have gills and breathe through their mantle cavity that has a surface lined with blood vessels. Diffusion of air happens through the moist skin of mollusks.