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Major Animal Phyla

All animals are part of the Kingdom Animalia, which can be further categorized into phyla. Which phyla do you recognize?

Special thanks to Journey to the Microcosmos for their incredibly detailed videos on microscopic animals.
Check out their YouTube channel for more microscopic adventures.

Table of Contents

Porifera (Sponges)

Cnidaria (Cnidarians)

Ctenophora (Comb Jellies)

Comb jellies are not true jellyfish.
Here are some important differences between Comb jellies and jellyfish:

  1. Comb jellies do not naturally produce nematocysts (the stinging cells of jellyfish). This means comb jellies do not sting.
    Instead, Comb jellies have colloblasts, which produce glue. This glue is used to trap prey.

  2. Comb jellies do not have the same life cycle as jellyfish. They do not have a polyp stage.

It is worth mentioning that there is one type of Comb jelly with stingers. However, this Comb jelly gets its stingers by recycling the nematocysts from jellyfish it eats. 

Platyhelminthes (Flatworms)

The Class Turbellaria includes planarians and marine flatworms. Most of them are free-living, which means they do not live on the body of another animal. Some planarians are capable of regenerating their entire body from a small fragment. The marine (ocean-dwelling) flatworms can be colorful and beautiful.

The Class Monogenea includes external parasites of fish. They feed on the fish’s skin and gills. These parasites are commonly called Skin Flukes or Gill Flukes, but they are technically not flukes. Aquarium fish are sometimes infected by these parasites, and one symptom is that fish will try to scratch themselves on aquarium decorations.

The Class Trematoda includes flukes, which are internal parasites of mollusks and other animals. The primary host is almost always a mollusk like a snail. The secondary host is a different animal. Some trematodes are spread through aquatic vegetables. Humans can become infected by eating contaminated seafood or contaminated aquatic vegetables.  

The Class Cestoda includes tapeworms, which are internal parasites of vertebrates. The tapeworms that infect pets cannot be transmitted to humans unless a human ingests an infected flea. The human tapeworm is transmitted through contaminated meat. The tapeworm remains inside the body, and tapeworm segments can exit through feces. The worm does not enter or exit through the skin. 

The best way to prevent parasitic infections is proper food hygiene and not consuming undercooked meat.

Nemertea (Ribbon Worms)

The Ribbon Worm is also known as the Proboscis Worm because it can shoot out its proboscis to catch prey. They are free-living marine worms.

Rotifera (Rotifers)

Rotifers are microscopic animals that live in water.

Gastrotricha (Gastrotrichs)

Gastrotrichs are microscopic aquatic animals.

Nematomorpha (Horsehair Worms)

Horsehair worms are parasites of insects. Adult Horsehair worms are free-living in water. Baby worms must enter inside an insect to grow up. The baby worm feeds on the inside of the insect until it becomes an adult. Then, the worm controls the insect’s mind and makes it go to the water, where the worm will emerge as an adult and swim away.

Horsehair worms do not target humans.

Nematoda (Nematodes)

Nematodes are worms that live in soil or water. Most of them are free-living. However, some of them are parasites of plants and animals. Most soil nematodes are beneficial for plants because they recycle nutrients in the soil. Some nematodes parasitize plants, and farmers have to find ways to keep these pests under control.

The nematodes that infect humans include the Roundworm, the Hookworm, the Pinworm, the Guinea worm, and the Giant Kidney worm. These parasites are usually spread through contaminated soil or water. It is important to wash your hands whenever you touch soil or outdoor water. If you have a pet, keeping them worm-free is the best way to protect yourself from getting infected.

The Dog Heartworm is a parasitic nematode that affects dogs. This parasite is transmitted when a mosquito sucks the blood of an infected dog and then bites another dog. Because this parasite is only transmitted by mosquitoes, a pet cannot spread heartworms to a human. If a person is bitten by an infected mosquito, usually nothing happens because heartworms cannot survive in humans.

Bryozoa (Bryozoans)

Bryozoans are also called “moss animals”. They form coral-like colonies. Some bryozoans secrete a calcium carbonate skeleton. Unlike corals, they do not have stinging nematocysts. Bryozoans use tiny tentacles to filter feed, but they do not sting.

Tardigrada (Tardigrades)

Tardigrades are also called “water bears”. They are known for surviving in some of the most extreme conditions on Earth and even in outer space. Tardigrades can also go over 100 years without food or water. Tardigrades accomplish these feats by undergoing cryptobiosis, which makes them extremely resistant to negative conditions. In cryptobiosis, the tardigrade’s metabolism slows down to an extremely low level. As a result, the tardigrade uses almost no energy, and therefore, it doesn’t require food or water. 

Cryptobiosis does not last forever. Depending on the negative condition the tardigrade is experiencing, it may not last a very long time. Although the tardigrade can survive extreme conditions, it cannot live normally. It is forced to enter cryptobiosis, and it will die if its environment does not return to normal.

Brachiopoda (Brachiopods)

Brachiopods are filter feeders. They can resemble bivalves like clams, but there is an easy way to tell the difference:

  • Brachiopods usually have vertical symmetry while bivalves do not. One exception to this is the scallop (as pictured below).
    Scallops are bivalves even though they have vertical symmetry. 
scallop real

This is a scallop. Scallops are easy to recognize with their fan-shaped shell.

Mollusca (Mollusks)

Annelida (Segmented Worms)

The annelids include earthworms, leeches, and polychaetes. Polychaetes are marine worms such as bristle worms. Annelids have a segmented body.

Arthropoda (Arthropods)

Echinodermata (Echinoderms)

Onychophora (Velvet Worms)

Velvet worms have a pair of antennae.

Hemichordata (Acorn Worms)

Acorn worms eat sand, digesting the organic material and pooping out the inorganic material. The way they eat and poop sand is similar to lugworms.

Chordata (Chordates)

Diamond-tier Videos

Here are some great videos you can watch on YouTube about fantastic wildlife.

1. Cool Sea Creatures Part 1

2. Cool Sea Creatures Part 2