MOLLUSCA: SNAILS, SLUGS, OCTOPI, CLAMS, OYSTERS, AND SQUIDS
the wolf octopus: Octopus wolfi
Snails, slugs, octopi, clams, oysters, and squid all fall under the phylum Mollusca. There are three categories into which these animals are separated:
Gastropods (snails, slugs, etc.), Bivalves (oysters, clams, etc.), and Cephalopods (squid, octopi, etc.). Mollusks have a body with bilateral symmetry. Their body structure includes a mantle, which protects the organs; gills, which allow for the exchange of carbon dioxide for oxygen; sometimes a shell; an open circulatory system, which allows blood flow into all open areas; a complex head, including a mouth and sensory organs; sometimes tentacles; and a muscular foot, which is used for movement. Their circulatory system is interesting because unlike ours, which allows blood flow only through veins, a mollusk’s blood flows in the space around their organs. This system lets the blood, which contains nutrients and oxygen, give those nutrients to all the body organs. Mollusks have two body openings, unlike previous phyla, and a one-way digestive system. This means that food and waste are not taken in and excreted through the same opening. This phylum reproduces sexually. Gastropods can be hermaphrodites but the eggs still must be fertilized sexually by another. Most assume these creatures to be unintelligent, but cephalopods can actually be quite smart. Surprisingly, octopi can learn from past experiences, as shown when an octopus taught himself how to open a jar. Octopi can camouflage perfectly in less than a second by measuring the contrast in the background, then changing the contrast in their skin to uniform, mottled, or disruptive. They can also use camouflage to mimic other animals and scare away predators. One octopus even proved his amazing memory by remembering shapes and mazes!