Phylum: Platyhelminthes – Flatworms
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Flat worms are a very simple life form, with no respiratory or circulatory system and no body cavity other than the gut opening.
Oxygen absorption takes place through the body wall and the gut opening lets in food and excretes waste.
They are often mistaken for Nudibranchs, mimicking them as a form of defence, although some do have toxic properties obtained from their food source.
Image 2 (right) shows a flatworm mimicking a highly poisonous Sea Slug – P. pustustulosa – image 3.
As their name suggests they are totally flat with no external gills.
They are hermaphroditic and when two mate they exchange sperm so both become fertilized. The majority are carnivores.
There are approximately 20,000 identified species worldwide. They are quite fast movers and swim through muscular movement displayed in image four.
A fascinating attribute of the Flatworm is their ability to regenerate large body parts very quickly.
Image four show bite marks on the lower left side, these injuries are a result of aborted feeding attempts from predators.
Within a few days these marks will have healed and completely vanished.
Pylum: Annelid – Worms
Spirobranchus giganteus – Christmas Tree Worm
Abundant and easily spotted it was once thought these colourful tube dwelling worms bore themselves a hole inside the surface of coral.
However recent studies conducted on the Barrier Reef – Australia suggest the larvae settle on corals and the coral grows around it, living in harmony they grow at the same rate.
With just the tentacles visible, clearly illustrated here, two cone-like spirals are used to filter the water for particles on which it feeds.
They quickly retreat into their burrow if disturbed but within a minute or two emerge again.
Sabellastarte magnifica – Tube Worm
Also refered to as Fan Worms or Feather Duster, a common sight on coral reefs with many species, found throughout the worlds oceans even close to deep sea vents.
Burying their body in a self constructed tube and generally prefering harder substrate than softer sand which can be moved by surge and current.
They use their plant like braches to gather passing plankton on which it feeds. Some species have eye spots along the tentacles.
Tube worms are often confused with the Tube Anemone pictured to the right however they are a completely different animals having absolutely no relationship to one another but look incredibly similar.
For more information on Tube Anemones please visit our Anemone page.