Roundworms

• These are tiny cylindrical worms usually less than 2.5 cm long. But even though they are small, they are plentiful. One shovelful of water could contain a million roundworms. They live in practically all environments and every living thing. 
• They also can live in places where nothing else likes to live such as the arctic, hot springs, mountaintops, and deep parts of the ocean. They are super durable, the most durable of the animal kingdom.
• Specific roundworms like specific hosts. 
• A Typical Roundworm: Ascaris
• The body structure is basically a tube within a tube. Epidermis and cuticle (non-cellular secreted by the epidermis)
• This is the first phylum we have seen that has an anus.
• Ascaris is supported primarily by the organs and the fluid that fills the space between the two tubs. 
• It only possess longitudinal muscles, so it moves in frantic thrashing motions.
• It feeds on digested food matter found in its host’s intestine. It sucks food into its digestive tube where it is absorbed. 
• Respiration and circulation are accomplished on a cellular level. 
• Roundworms reproduce only sexually, but they are the first type of worm we have seen that has specific males and females. The female lays eggs at a rate of 200,000 a day and are egested daily in the host’s feces.