Invertebrate Excretory Structures

Invertebrate Excretory Structures
Many protozoa and some freshwater sponges have special excretory organelles called contractile vacuoles. More complex invertebrates have excretory organs that are basically tubular structures forming urine by first producing an ultrafiltrate or fluid secretion of the blood. This fluid secretion enters the proximal end of the tubule and is modified continuously as it flows down the tubule. The final product is urine.