1. Polychaeta worms

2. Some basic facts Polychaetes come in all shapes and sizes
All polychaetes can regenerate lost segments
Some species are bioluminescent
More than 10,000 species
Only 2% are freshwater dwellers

3. Basic Structure
Polychaetes share few common characteristics, they all have a Head tail and segmented body.
Each segment has a pair of leg-like segments called parapodia
The body is basiccally a tube within a tube
Due to such diversity in lifestyles, many parts of the body form and function differently in order to accommodate the species needs.
Generaly less than 10cm but range from 1mm to 3m

4. Head
Body
Tail
Most have 4 kinds of appendages on the head, antennae,palps, cilla, and tentacles
Usually 2-5 tentacles which are used for sensing
The body usually consists of thousands of segment with parapodia on each side.
In most worms the parapodia is used for movement but some species have almost non-existant parapodia because the attach to something.
The body has no hard parts for the muscles to act against when moving so they have hydrostatic skeletons. (best example of a hydrostatic skeleton is an earthworm)
In some species the tail is used as a means of reproduction, it will grow independent and full of sperm or eggs and then detach.

5. Reproduction
Most polychaetes sexually reproduce by releasing eggs and sperm into the water column. However many species reproduce differently.
Some asexually reproduce by 'multiple fragmentation' which is splitting into multiple pieces and having each piece grow into another organism.
Others go through "stolonization' which is when the tail grows and is filled with sperm or eggs, then detaches from the 'parent' and releases all the eggs or sperm at the surface of the water.
A small group of polychaetes go through a process called epitoky. epitoky is when the whole animal can transform into a swimming form capable of breeding.

6. Diet
Some Polychaetes are active predators who hunt and capture prey with powerful jaws, usually eating anything it can catch.
Others are herbivore who eat organic matter such as algae off the sea floor, also some species are filter feeders.
There are five species of polychaetes that eat whale bone, the eat it by breaking it down with an acid produced on their skin.

7. Habitat
Polychaetes are in every ocean at all depths, and the temperature ranges from arctic waters to extremely high temperatures in hydrothermal vents
Some swim out in open ocean while others burrow in mud on shorelines, they also make homes in reefs, but most live in the deep sea.

8. Fossil record The earliest fossil is 520 million years old
Most fossils are jaws and calcified dwelling tubes
Throughout time polychaetes have survived 5 mass extinctions, including one which wiped out 96% of marine life

9. Citations
worms /?no-ist