Smaller Ecdysozoans Unit 4.2

Ecdysozoans Many protostomes possess a cuticle. Non-living outer layer secreted by epidermis. Cuticle restricts growth and must be molted via ecdysis. Members of Ecdysozoa include: Phylum Nematoda Phylum Tardigrada Phylum Arthropoda

Phylum Nematoda: Roundworms About 25,000 species of Phylum Nematoda, also known as the roundworms, have been discovered and described, but as many as half a million may exist. They can be found in virtually all habitats in all biomes. The topsoil may contain billions of individuals per acre.

Phylum Nematoda: Roundworms Free-living nematodes feed on bacteria, yeasts, fungus, and algae. Predatory nematodes eat rotifers, tardigrades, small annelids, and other nematodes. The are also important ecologically as food for mites, insects, larvae, and fungi.

Phylum Nematoda Some species of nematodes are important parasites of plants and animals. Nematode parasites exist in nearly all animal and plant species. https://youtu.be/Z9RJHkzQtXc

Phylum Nematoda Members of Phylum Nematoda are triploblastic Pseudocoelomates. They have a cylindrical shape, and used a hydrostatic skeleton to move through their environment. They are nonsegmented and lack cilia or flagella

Phylum Nematoda The cylindrical bodies of nematodes are covered by a tough coat called a cuticle. The Cuticle is shed between each of four juvenile stages.

Phylum Nematoda Unlike the flatworms they have a complete digestive tract with a separated mouth and anus They lack circulatory or respiratory systems.

Phylum Nematoda Nematodes are dioecious, meaning they have separate sexes. Individuals are either male or female. The females are larger than their male counterparts Members exhibit internal fertilization, and the fertilized eggs are stored in uterus until deposited.

Phylum Nematoda Some larvae are free-living, while others require an intermediate host. Parasitic nematodes of humans include: Intestinal roundworm (Ascaris) Hookworm Pinworm Trichina worm Filarial worm

Phylum Nematoda: Intestinal Roundworms They found in the digestive system of most humans and don’t often cause any symptoms unless found in large numbers. An intestinal roundworm infection, also sometimes known as ascariasis, can occur if you swallow the microscopic ascaris eggs in contaminated food or water. These roundworms can grow up to 30-35 cm long, and reproduce very quickly.

Phylum Nematoda: Pinworm Humans are considered to be the only hosts of E. vermicularis, also known as human pinworm. Understanding the lifecycle of these worms helps us prevent further infection.

Phylum Nematoda: Trichina worm Trichinella is an ovoviviparous parasite that commonly infects pigs, horses, bears and humans, and is responsible for the disease trichinosis. It is sometimes referred to as the “pork worm” due to it being found commonly in undercooked pork products.

Phylum Nematoda: Filarial worms Elephantiasis is caused by a filarial worm. The adult worms only live in the human lymph system. These worm larvae spread throughout the blood stream and block the system, causing massive swelling. It affects over 120 million people in the world but is most common in Asia, Africa, the Caribbean and South America and spreads by mosquito bites. They are NOT found in the U.S.

Phylum Tardigrada Members of Phylum Tardigrada, also known as the water bears, are less than a millimeter in length. Freshwater or marine Live in spaces between sand grains.

Phylum Tardigrada These eight-legged, water-dwelling animals have been found everywhere on Earth. They are considered the most resilient animal and can survive extreme conditions that would be fatal to nearly all other known life forms. Temperature Ranges: from −272 °C to 150 °C Can live in the vacuum of outer space Can go without food or water for more than 30 years https://youtu.be/u2lkPq3Cil0

Phylum Tardigrada They share many characteristics with arthropods. But legs are unjointed. Non-chitinous cuticle that is molted.

Phylum Tardigrada Gas exchange occurs at body surface. Like the Nematodes they have no circulatory or respiratory systems. Gas exchange occurs at body surface. Brain is relatively large.