Polychaete “worms” are a ubiquitous part of the invertebrate fauna inhabiting coral reef ecosystems. They play a variey of roles in the reef community, with species that feed as carnivores, filter-feeders, deposit-feeders, and/or omnivores
Polychaete “worms” are found in a broad array of marine habitats.
They are common on and in the hard reef framework as well as within seagrass meadows, mangrove forests, coral rubble, and sand plains.
Polychaetes play a variety of roles in coral reef ecosystems. As well as the variety of feding methods employed by these creatures, many species represent an important food source for other animals, particularly certain fishes. Other coral reef polychaetes participate in the erosion of dead coral.
As a group, the polychates can be divided into two main types based upon their respective lifestyles; those that permanently attach to a particular place and remain there (sedentary or sessile forms), and those that move about freely (mobile or motile forms.
Sedentary reef dwelling polychaetes generally build tubes within the substrate, and enlarge these homes as they grow. Some of these burrow into living coral colonies to form their homes.
The most familiar such coral reef polychaetes are the brightly colored feather dusters and Christmas tree worms that extend ornate feeding tentacles from concealed tubes within living coral colonies (see photo, left).
The tentacles, used to capture plankton, are quickly withdrawn if a diver or fish approaches too closely.
In contrast to their sedentary bretheren, many of the mobile free-living coral reef polychaetes are voracious predators feeding upon a variety of other small invertebrate animals, sometimes including corals.
The notorious fire worms and bristle worms are (at least to scuba divers) among the best known examples of this group of polychaetes because they are quite painful to the touch.
The vast majority of motile coral reef polychaetes spend most of their life cycle as bottom dwellers, with most living in dead coral rubble or sand. However, some types undergo a dramatic shift in behavior as well as profound changes in physical characteristics when in the reproductive phase.
At this time, normally subsurface dwellers may develop swimming appendages and greatly enlarged eyes. On some unknown cue, they ascend in countless numbers up into the water column on a few consecutive nights to reproduce, some even reaching the sea surface.
In some regions of coral reef development, representatives of a few of the other major groups (Phyla) of worms such as the flatworms (Phylum Platyhelminthes) and ribbon worms (Phylum Nemertea) may also be common and readily observed by divers and snorkelers.
For more information on these groups readers are referred to more comprehensive guides to coral reef invertebrate animals.
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