Day 12 Sea Worms
There are Four major phyla of worms
Phylum Platyhelminthes: The flatworms
Phylum Nemertea: Ribbon worms
Phylum Nematodes: Roundworms
Phylum Annelida: Segmented worms
Kate Terbush
A couple other phyla that are common but we do not talk about are:
-Sipuncula: Peanut worms
-Echiurans
They are interesting marine worms. Feel free to learn more about them if you like.
Watch this video on Sea Worms. Create a box in your sketchbook, title it "Sea Worms" and take notes, write down interesting things that you learn from the video and include an image in your sketchbook. Make sure you understand the characteristics of Sea Worms.
Phylum Platyhelminthes
Characteristics
-Bilateral symmetry
-Unsegmented
-They have a central nervous system
-Simple brain (Aggregation of nerve cells in the brain)
-Has an actual mesoderm (middle layer) making them a triploblastic animal, having 3 layers.
-No anus. They do not have a complete digestive track. They have one opening where food enters and waste exits.
-They have a flat body shape
-Their flat body shape allows oxygen and water to enter their body due to diffusion and osmosis. They do not have osmoregulatory organs.
-Flatworm anatomy is very simple. The flatworms have an organ called protonephridia. The protonephridia is a series of folds that absorb small molecules. In this manner they act like simple kidneys.
-The flatworm has a pharynx in the middle of its body. It uses the pharynx as both a mouth and an anus.
-20,000 known species
Class Turbellaria
-Most common marine species are from the class turbellarians
-The turbellarians are free living (not parasites) carnivores
Here are some videos of flatworms swimming. Just watch 10-30 seconds of each video to get a good idea of what Turbellarians look like and how they move
Phylum Nemertea
Characteristics
-They are triploblastic
-They have bilateral Symmetry
-They have a complete digestive tract with mouth and anus
-They are ribbon shaped
-They have a simply circulatory system
-They have a large Proboscis
-A proboscis is a long feeding tube that sticks out of the mouth. On nemertean worms the proposcis has a sharp spear like end that can puncture the flesh of an animal and then be used as a straw to eat the animal.
-There are about 900 species of nemertean worms.
This is just a short video to give you an idea of the length of a nemertean worm.
Phylum Nematoda
Nematode Characteristics
About 80,000 species have been described
-They are Triploblastic
-They have bilateral Symmetry
-They are round in shape
-They have an Ecdysis, a tough cuticle that molts (molting as they grow) similar to insects.
-Complete digestive tract. They have a mouth and an anus
-Mouth usually surrounded by lips that have sense organs
-Body wall only has longitudinal muscles
-Do not posses cilia or flagella in anyway (even their sperm is amoeboid)
-Nematodes are mostly parasitic.
-This means that they infect a host. Usually they will live inside another animal and live off of it.
-Round
-25,000 species
-At risk if you eat Sashimi or Ceviche
Phylum Annelida
-They are Segmented
-They are Triploblastic
-They have bilateral Symmetry
-Closed circulatory system (Meaning they have veins)
Class Polychaetes
-Has a pair of Parapoda on each segment
-Sharp bristles called setae
-Gills
This is an optional video that goes through the taxonomy and anatomy of Polychaetes.
The Annelids have trochophore larvae
This is just a short video to help you understand how polychaetes move
Watch this video on the bobbit worm.
Christmas tree worms (a type of polychaete)
This is just a short video of a Christmas tree worm spawning.
Watch this video on deep sea worms. Create a box in your sketchbook, title it "Deep Sea Worms" and write down anything you find interesting. Include an image in your sketchbook.
This video is optional. This is not the most exciting video but it is informative of polychaetes.