Range: Cosmopolitan Habitat: Varies by species Size: Microscopic to several inches long on average; Up to 30 feet (9m) long Diet: Nutrients from plant and animal hosts, algae, fungi, and more Threats: Small fish, copepods, flatworms, mites, nematodes, and more Life span: Varies by species

Transcript:

Today on Animal Fact Files we’re discussing nematodes. Nematodes are also known as roundworms. Their name comes from the mix of Greek and Latin words that mean “resembling thread”, which is an apt way to describe them. Nematodes are bilaterally symmetrical and have a cylindrical shaped body; hence the name roundworm. They’re described as a “tube within a tube” as their body wall is separated from the inner digestive tube by a fluid filled cavity. There are currently over 20,000 described nematode species, but estimates on the amount of living species reach from half a million to more than double that. This means that they rival arthropods in the most species rich animal group! Because of this species richness, this episode will be more general in nature because there are just so many nematodes out there.

Nematodes are found everywhere. From icy Antarctica to hydrothermal vents, from the bottom of the ocean to bottom of beer coasters, from plant roots to the hearts of dogs - they truly live just about everywhere. And there are estimated to be somewhere around 60 billion nematodes for every human alive on earth, which means there are an incomprehensible amount of nematodes living all around us. There are free living nematodes which may be seen in water and soil. Other nematodes are parasitic and may live inside, as endoparasites, or on, as ectoparasites, just about every type of plant or animal alive today. Humans aren’t exempt from this. The ways nematodes affect humans range from causing mild issues to fatal conditions depending on the species. They can also affect our pets. Many cat and dog owners are likely familiar with heartworm disease. This is caused by nematodes!

Most roundworms are microscopic but some can be inches long and seen flopping around in water. Their bodies are typically tapered on each end. one being the mouth the other the anus. Depending on the type of nematode, they may have a stylet. This is a needle-like projection which is used to puncture plant cells and specific to plant parasitic nematodes. Others are classified based on what they eat, how they move, and the types of problems they can cause to other organisms. The largest nematode can reach nearly 30 feet (9m) long and lives in the placenta of sperm whales.

Nematodes start out life as eggs. Females may lay hundreds of thousands to millions of eggs in a single day depending on the species. They may hatch as either male, female, or hermaphroditic. Mating is done sexually between males and females or asexually with a single nematode producing offspring via parthenogenesis, or reproduction without fertilization. Larvae hatch from the eggs and, like arthropods, nematodes molt. Their bodies are covered in a non-cellular cuticle that must be shed four times in their lives before they become adults.

Predators to nematodes include small fish, copepods, flatworms, mites, as well as other nematodes and more. In turn they gain nutrients from their hosts or eat algae, fungi, and more. In one study, more than 90,000 individual nematodes were recorded living in a single rotting apple! They may live a year or many years depending on the species and the environmental conditions. Like tardigrades, nematodes can enter cryptobiosis in which they are in a nearly indestructible state while they wait for more favorable conditions to emerge. They can stay like this for years.

For more facts on nematodes, check out the links below. Give a thumbs up if you learned something new today! Thank you to our Patrons SpikeSpiegel93, Dad, and everyone else for their support of this channel! A special thanks for today’s request! And thank you for watching Animal Fact Files!