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

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.

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

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

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

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)

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.

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.

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.

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

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

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

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

Works Cited Nematoda. (n.d.). Retrieved March 20, 2017, from http://www.ento.csiro.au/science/nematodes/introduction.html Nematode. (n.d.). Retrieved March 21, 2017, from https://www.cs.mcgill.ca/~rwest/link- suggestion/wpcd_2008-09_augmented/wp/n/Nematode.htm Learning About Nematodes. (n.d.). Retrieved March 21, 2017, from http://nematologia.com.br/wp-content/uploads/2011/09/whatare.pdf The Phylum Nematoda. (n.d.). Retrieved March 20, 2017, from http://www.earthlife.net/inverts/nematoda.html Writer, L. G. (2013, September 19). What Are the Main Characteristics of Nematoda? Retrieved March 20, 2017, from http://animals.mom.me/main-characteristics-nematoda- 8326.html