1. By: Brian Jones, Owen Klassen, Sean Stoqua
Chaetognatha
By: Brian Jones, Owen Klassen, Sean Stoqua

2. Introduction Phylum Chaetognatha are often called ‘arrow worms’
Live in marine ecosystems
Most are planktonic (80%) while some are benthic (20%)
Most abundant type of animal present in many deep sea environments
120 modern species that range in size from 2 to 120 mm
One of the earliest Bilaterians
-but the name is actually derrived from latin, meaning “hair jaw”
-planktonic – small organisms that float or drift in great numbers in fresh or salt water
-benthic – meaning that they live near the floor of the sea
-characterized by bilateral symmetry (they have a front and back end, as well as a topside and downside

3. Evolution
While early fossils have been found .. Their fossils do not preserve well …
Have been around since the Cambrian time period
It has been hypothesized that they are linked to the deuterstome phyla or acanthocephalan worms
Early fossils (300 million years)
Deuterstome phyla – this view is based on certain embryological features that are shared between the two groups
Acanthocephalan worms –based on the presence of an unusual cuticle structure

4. Characteristics Transparent or translucent torpedo shaped invertebrate
Body is made up of three sections
There is a fin on the tail as well as two sets of lateral fins
They have a circulatory system, gaseous exchange organs or excretory system
Hermaphroditic
Gets its name from ‘grasping spines’ around its mouth
Fins – tail fin is used for motion
Lateral fins are used for stability
An intestine runs the length of the trunk (where digestion occurs) ending in an anus just before the tail
Hermaphroditic – carry both eggs and sperm
Grasping spines – used to hunt, are covered up by a flexible hood (during swimming)

5. Interesting Facts Some have bioluminescent organs in their fins
Some feed on freshly hatched fish and other arrow worms
Contain neurotoxins used to paralyze and kill their prey
They were around during the same time period of the dinosaurs
Today they can be found in every ocean in the world

6. More Facts They are all carnivores
Although they have been around for 300 million years, they are still abundant in numbers
Considered a useful model for examining ancestral bilateran
Their nervous system is relatively simple and resembles that of a protosome
Also known as “glassworms”

7. Video https://www.youtube.com/watch?v=PkGhxtpK7IU
The first 40 seconds of this video demonstrates the movements of the cool grasping spines of the chaetognatha

8. Sources