The octopus-like cephalopod on the left is so small that it cannot fit all the usual organs inside. It has no gills. Instead, its skin is covered with blood-rich respiratory projections to increase surface area. While it has blood, it has no heart and instead uses its other muscles to stir the blood a bit.
The cheerleader worm in the center (named for the "pom-poms" on its front end) hunts protozoa by grasping them between its "pom-poms" and pulling them into the mouth. It is distantly related to the much larger clapworms, which "clap" prey between their "hands" to stun it before pulling it into the mouth.
The two-headed daggerworm has a sharp, tough, serrated cuticle to thwart predators and parasites. Its unusual embryological development gives it segments that alternate and two heads. Each head has one simple eye capable of perceiving light polarized along a particular axis. The axis of the two eyes are set at ninety degrees from each other to help the creature better detect a specific type of algae that only reflects polarized light. It is its favorite food.
The swimming organism at the far right has four pockets to hold symbiotic algae. It often holds algae of different colors (in this case, red and green) to hedge its bets against unpredictable light levels and spectrum distribution (the Snax sun is a variable star).
The other two creatures are cool too.