Species: Sand dollar
The sand dollar does not have a cardio vascular system. It has a network of water-filled canals called the water vascular system to help circulation throughout the sand dollar, much like the starfish. One of the characteristics that define echinoderms like the sand dollar, is the water vascular system. This feature is a hydraulic system that moves the tube feet of the echinoderm. It is controlled by the porous plate on the aboral surface that periodically takes in water to replenish the system. Once the water has entered the echinoderm, it flows through the radial canal into lateral branches that connect the tube feet. For movement of the tube feet to occur it has a valve, or ampulla, that creates pressure. When the ampulla is closed, the tube foot extends and when it is open, the pressure is released to withdraw the tube feet. Like all other echinodermata, it has no heart.
The sand dollar does not have a cardio vascular system. It has a network of water-filled canals called the water vascular system to help circulation throughout the sand dollar, much like the starfish. One of the characteristics that define echinoderms like the sand dollar, is the water vascular system. This feature is a hydraulic system that moves the tube feet of the echinoderm. It is controlled by the porous plate on the aboral surface that periodically takes in water to replenish the system. Once the water has entered the echinoderm, it flows through the radial canal into lateral branches that connect the tube feet. For movement of the tube feet to occur it has a valve, or ampulla, that creates pressure. When the ampulla is closed, the tube foot extends and when it is open, the pressure is released to withdraw the tube feet. Like all other echinodermata, it has no heart.