Table of Contents
What are Invertebrate Excretory Systems?
Invertebrate excretory systems are different from those of vertebrates in a number of ways. First, invertebrates typically lack kidneys, which are the organs in vertebrates that filter wastes from the blood. Instead, invertebrates typically use one or more of the following organs to excrete wastes:
-Gills: Wastes can be excreted directly into the water through gills. This is common in aquatic invertebrates.
-Malphigiian tubules: Wastes can be excreted into the coelom (body cavity) and then drained out through the anus. This is common in terrestrial invertebrates.
-Hemolymph: Wastes can be excreted directly into the hemolymph (blood-like fluid). This is common in some invertebrates, such as insects.
In addition, invertebrate excretory systems typically lack a bladder.
Invertebrate excretory systems vary in their complexity, but all excrete waste products in some way. Protozoa and ciliates use contractile vacuoles to pump water in and out of the cell to expel wastes. Some worms use flame cells, or nephridia, to filter wastes from the blood. Other worms use a type of gut called a rectal gland to secrete wastes into the gut. Some crustaceans use maxillary glands to secrete wastes into the gut, and insects use Malpighian tubules to filter wastes from the blood. Regardless of the method used, the goal is to remove the wastes from the body so they can be expelled.
Marine Invertebrates
Marine invertebrates are animals that do not have a backbone. These animals include jellyfish, sea stars, crabs, and shrimp. Marine invertebrates can be found in both salt water and fresh water.
One of the most common types of marine invertebrates is the jellyfish. Jellyfish can be found in both salt water and fresh water. They are usually clear or translucent and have a jelly-like body. Jellyfish use their tentacles to catch food.
Sea stars are another common type of marine invertebrate. They can be found in both salt water and fresh water. Sea stars have five arms that they use to catch food. They also have a hard shell that protects them from predators.
Crabs are another type of marine invertebrate. They can be found in both salt water and fresh water. Crabs have a hard shell that protects them from predators. They use their pincers to catch food.
Shrimp are another type of marine invertebrate. They can be found in both salt water and fresh water. Shrimp have a hard shell that protects them from predators. They use their antennas to catch food.
Invertebrates are animals without a backbone. Marine invertebrates live in the ocean. There are many different types of marine invertebrates. Some of these animals are very small while others are very large.
Some of the smallest marine invertebrates are the plankton. Plankton are very small animals that float in the ocean. They are very important because they are the food that many larger marine animals eat.
Another type of small marine invertebrate is the sea urchin. Sea urchins are small animals that live on the ocean floor. They have a hard shell that protects them from predators. Sea urchins eat algae and other small animals.
Another type of small marine invertebrate is the jellyfish. Jellyfish are small animals that live in the ocean. They have a soft body that is surrounded by a jelly-like substance. Jellyfish eat small animals and plants.
Some of the largest marine invertebrates are the whales. Whales are large animals that live in the ocean. They are the largest animals on Earth. Whales eat small animals and plants.
Contractile Vacuoles of Protozoans
Protozoans are single-celled organisms that lack a defined nucleus. They are found in a variety of environments, including fresh and salt water, soil, and the digestive tracts of animals. Protozoans have a variety of shapes, and range in size from microscopic to several inches in diameter.
One of the most distinguishing features of protozoan cells is the presence of contractile vacuoles. These small, water-filled sacs help to maintain the cell’s shape and to expel excess water and waste products. The vacuoles are powered by special muscles that contract and expel the water.
Contractile vacuoles are found in all types of protozoa, but they are especially important in those that live in aquatic environments. In these organisms, the vacuoles help to expel excess water, which can be in short supply in aquatic habitats. This helps to maintain the protozoan’s cell volume and to prevent it from sinking to the bottom of the water column.
The contractile vacuole also helps to remove wastes from the cell. Protozoans that live in soil or in the digestive tracts of animals can take up nutrients from their surroundings. The vacuoles help to expel the waste products of metabolism, which can be harmful to the organism.
Nephridia of Annelids, Flatworms, Nemertines and Rotifers
Nephridia are excretory organs that remove wastes from the body of annelids, flatworms, nemertines, and rotifers. In annelids, the nephridia are paired, coiled tubes that extend from the body cavity to the exterior. They are lined with ciliated cells that sweep wastes into the lumen, where they are eliminated from the body. In flatworms and nemertines, the nephridia are simple tubes that open to the exterior. In rotifers, the nephridia are small sacs that open to the exterior on one side of the body.
