| Segmented Worms - Phylum Annelida | ||||
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Annelids are soft bodied worms with numerous segments dividing the body.
They range in size from less than 1 mm to more than 3 m long. To move,
they contract muscle layers which, using hydrostatic pressure, forces
the body to move in certain directions. Movement is also assisted by
lobes and bristles found on each segment. There are approximately 20 000
species named, though there are likely to be a lot more that are
undescribed.
There are several classes, the Oligochaetes (including earthworms and many marine forms), Hirudineans (leeches) and Polychaetes (almost exclusively marine worms). The Class Polychaeta contains many weird and wonderful species, often brightly coloured and sometimes possessing fairy like tentacles around the mouth (fan worms - the Sabellids). They have paddle shaped appendages on each segment called parapodia, which can be used for gas exchange and have spines (chaetae) attached. These are arranged in many different ways, with each individual's and species chaetae differing. This provides for some interesting identification! There are tube dwelling Polychaetes (Sedentaria) and free living polychaetes (Errantia). The most common Polychaete found by staff at the Centre is the tube worm:
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