Mollusks, belonging to the phylum Mollusca, are a diverse group of invertebrates that includes snails, clams, squids, and octopuses. With a lineage dating back over 500 million years, they've evolved into various forms and sizes, adapting to marine, freshwater, and terrestrial habitats. Most mollusks have a soft body, often protected by a hard shell, and they use a muscular foot for movement. They play critical ecological roles, from acting as filter feeders to being apex predators. Mollusks also have significant economic importance, with many species being harvested for food, pearls, and shells.
Mollusks are a varied group, but most share key traits. Typically, they have a soft body encased in a hard shell for protection. They move using a muscular foot that can glide, burrow, or even jet-propel in the case of squids. While they don't have "speech," some can communicate using color changes or by releasing chemicals. Their senses vary widely: cephalopods like octopuses have complex eyes and brains, while others have simpler sensory organs. Mollusks feed in various ways, from filter-feeding clams to predatory squids. Their diverse anatomies reflect their wide range of lifestyles and habitats.
Humans have interacted with mollusks for millennia, valuing them for food, jewelry (pearls), and even currency (cowrie shells). Dishes like escargot, oysters, and calamari are culinary delicacies. In pop culture, mollusks feature in tales like "20,000 Leagues Under the Sea" or animations like "Finding Nemo."
Conservation efforts are crucial as many mollusk species face threats from pollution, overfishing, and habitat destruction. Organizations work to protect habitats and regulate harvesting to ensure sustainable populations. Marine sanctuaries and breeding programs also aid in preserving vulnerable species, highlighting the importance of mollusks in biodiversity and human culture.
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.
