1. Abby Griffin feat. Jacob Ulery
Phylum Nematoda
Abby Griffin feat. Jacob Ulery

2. General Characteristics
Nematodes are commonly known as roundworms.
They are bilaterally symmetric.
The name of the worm derives from the Greek word for “thread”.
They are microscopic and unsegmented.
Nematodes can be found in an abundance of ecosystems, including land, freshwater and saltwater.
There are two main types of nematodes: free-living and parasitic.

3. External Features Nematodes have a relatively simple exterior
The epidermis covers the outer side of their body
The cuticle lies underneath the epidermis and is shed as it reaches the next life stage
Muscle exists beneath the cuticle and the body cavity
There are two excretory canals located on both sides of the worm

4. Internal Features
The cuticle - secreted by the epidermis and shed by the worm later in life - resembles the skeleton of a nematode.
It is used for support and movement.
Muscles underlie the cuticle to aid in movement
The pseudocoelom - not a true body cavity - lies beneath the cuticle.
The intestine, which aids in digestion, runs the length of the internal cavity.
The nerve ring is connected to the nerve cord that runs through the roundworm’s body.
The roundworm’s reproductive organ takes up a large portion of the body
The pharynx, similar to an esophagus, forces food into the digestive tract.
The roundworm is round due to its round cross section and the high pressure within the worm

5. Feeding & the Digestive System
Nematodes have a true digestive tract that is open at both ends
There are separate openings for food intake and excretion.
Food enters through the mouth, through the pharynx and into the buccal cavity.
The food then travels through the intestine, the round structure that runs the length of the roundworm’s body.
Enzymes are produced within the intestine to help digest the nutrients
Nematodes do not possess the muscles to force the food down so they rely on outward pressures and body movement in order to digest the food.
Waste exits the body through the posterior end.
Feeding & the Digestive System

6. Feeding & the Digestive System (continued)
Nematodes commonly eat bacteria, fungi and protozoans.
Some are filter feeders as well
Their feeding habits differ based on what group they fall into:
Free-living (non-parasitic)
Feed on algae, fungi, bacteria or even other nematodes
Zooparasitic nematodes
Rely on host animals for food, infiltrate various organ systems of the host (digestive, respiratory, etc.)
Plant parasitic nematodes
Feed on the host plant and are very dangerous to crops
They attack almost every part of the plant
Feeding & the Digestive System (continued)

7. Other Organ Systems Nematodes have a simple nervous system
The main nerve cord runs the length of the ventral side of their body
At the anterior end of the roundworm are amphids - sensory structures.
The sensory structures on the posterior end are known as phasmids.
Nematodes lack a respiratory system
They obtain oxygen by diffusion through their skin
Roundworms take in the oxygen, diffuse it throughout their body and produce carbon dioxide as a result
Nematodes also lack a circulatory system
For the purpose of circulating substances throughout the body, roundworms use diffusion as well.

8. Reproduction and Development
Most nematodes are dioecious, meaning the sexes are separate.
Some are hermaphroditic, meaning that they have both male and female reproductive parts.
For the dioecious, the spine of the male is used to open the female’s reproductive part and to inject sperm.
The sperm is unusual because it does not have a flagella. It moves by a crawling motion to get to its destination.
Most species lay eggs. When fertilized, the eggs escape through a hole in the female’s system known as the gonopore.
Every species is given the exact same amount of cells. This is called eutely.

9. Reproduction and Development
The life span of a nematode is made up of 4 larva/juvenile developmental stages before reaching adulthood.
The nematode begins as an egg, goes through 4 juvenile stages marked by the shedding of the cuticle and then reaches adulthood.
Different nematode species may reside in a host or even more than one during various life stages.
For example, the Enterobius (Human Pinworm) begins its life as an egg in a host, is free-living in the first larval stage, and returns to living within a host for the remainder of its life span.

10. Nematode Life Cycle
Molting occurs when the roundworm sheds it cuticle which covers the exterior.

11. Nematode Parasites The Filarial Worms (Filarioidea)
Superfamily of parasitic nematodes
Can cause a disease known as filariasis in which adult worms reside in the human lymph system
Spreads through mosquito bites - worms pass from blood to mosquito back into the bloodstream
Giant Intestinal Roundworms (Ascaris lumbricoides)
Most common parasite in humans
The roundworm infects the intestines
It is found mostly in tropical regions - common in areas of poverty
Human Pinworm (Enterobius)
Typically white in color, less than half an inch long
Infest the intestines of the host and lay eggs
Infection is highly contagious

12. Nematode Parasites (continued)
The New World Hookworm (Necator americanus)
Can be commonly found in cats, dogs and humans
Typically resides in tropical areas and the southern half of the U.S.
Females can reach a length of .4 inches
Grows rapidly, one developmental stage can take only 10 days
Can move throughout the bloodstream to various parts of the body
Leaves the human host after it reaches 1 or 2 years of age for a secondary host
The Porkworm (Taenia solium)
Can cause an infection known as taeniasis from eating undercooked pork in which the worms are present
Taeniasis is an infection of the intestine as an adult worm resides there

13. Habitat Nematodes can live in a variety of habitats.
They can live from the bottom of the ocean, to the tops of mountains, from tropic to polar regions.
It is said that if all Earth were to disappear except Nematodes, they would be the outlines of everything because of their large population.
Soil is a common habitat for nematodes
Several thousand of them can be found in a small portion of soil
Parasitic nematodes can also live in various amounts of land and sea creatures, such as fish, and/or mammals and humans.
Habitat

14. Works Cited
Nematoda. (n.d.). Retrieved March 20, 2017, from
Nematode. (n.d.). Retrieved March 21, 2017, from suggestion/wpcd_ _augmented/wp/n/Nematode.htm
Learning About Nematodes. (n.d.). Retrieved March 21, 2017, from
The Phylum Nematoda. (n.d.). Retrieved March 20, 2017, from
Writer, L. G. (2013, September 19). What Are the Main Characteristics of Nematoda? Retrieved March 20, 2017, from html