Rristleworms come in a variety of shapes and sizes. Some species can be several centimetres in length, while others are less than 1 cm (0.4 in.). Most are elongated in shape, having a typical worm-like appearance. The body is segmented, with each segment sporting a pair of fleshy appendages called parapodia. It is from these appendages that the characteristic "'bristles7*, or setae, of polychaetes arise. In some species these setae are short and few while in others, such as the infamous Fire worm, Hermodice carunculata., they are long and numerous, and pack a painful sting.
The head of polychaetes (the prostomium) may bear several appendages such as tentacles, palpi, chitonous jaws and/or a protrusible pharynx, depending on the species. Those with jaws tend to be larger and are the most dangerous forms in the aquarium.
Polychaetes can reproduce sexually or asexually depending on the species. Those that reproduce asexually can quickly multiply in aquariums, especially those with a thick bottom material. Many sabellid fanworms reproduce asexually, and multiply quickly in most reef aquariums. Polychaetes also have amazing regenerative powers and this can come into play when trying to remove them from the aquarium. If only sections of the worm are removed, the remaining section can regrow into a new individual.
Polychaetes can be divided into two basic ecological groupings. Those that live in tubes or burrows do not move about much once they have found a home and are called sedentary. Sedentary polychaetes are predominantly detrital feeders. They trap food particles either by filtering them from the water column with feather-like appendages or by trapping them on mucus covered tentacles that may extend several centimetres over the substrate. Examples of sedentary polychaetes include the well-known Fanworms (Sabellidae and Serpulidae families) and the Spaghetti worms of the Terebellidae family. Some burrowing polychaetes are more active and wall burrow into sponges, eating sponge tissue as they go. Others such as Eunice schemacephala and Dodecaria coralii burrow into stony coral heads, damaging living coral tissue ( Gosner, 1971; Kaplan, 1982 ) and some polychaetes apparently feed on the tissue of living corals; both healthy and damaged (J. Sprung, pers. obs.). Other species of polychaetes (Eunice spp.??) can burrow
Below: Oenone fulgida (Lamarck, 1818). This horrible but fascinating polychaete worm, Order Eunicida, Family Oenonidae, eats snails and clams. The size is about 0.25 cm (0.1 in.) diameter and 10 to 30 cm (4-12 in.) long. Note characteristic bright orange colour and copious mucus secreted by the worm. It traps and suffocates snails by secreting a mucus blob over them. When the snail dies, the worm pops off the operculum and eats the tissues. It also bores perfectly round holes in clam shells (as oyster drills do) and feeds on the
tissues of the still living clam. It can retract into the live rock and return to have a snack of clam meat via the same hole, or bore a new one. A healthy clam can plug up the hole with a protein matrix and seal it with new calcareous shell. Weakened by the worm's feeding, however, clams eventually succomb to infection and die. This worm is a serious pest! It is fairly common in live rock. The only way to remove it is to take out the rock into which it retreats. J. Sprung.
Far Right: View of outside of shell showing the bore hole. This is the typical location where the worm or oyster drill snails pierce through clam shells. J. Sprung.
into soft corals, especially Sarcophyton, Lobophytum, Sinularia and Clacliella. They begin by eating trails on the outer surface of the coral and eventually move into the body column (Wilkens and Birkholz, 1986). There are also polychaetes that burrow into the shells of oysters and clams, so the potential exists for polychaetes that can damage tridacnid clams too (Gosner, 1971).
The errantia, or free-living polychaetes contain the main wormy pests of the marine aquarium. Many of these polychaetes possess strong, chitonous jaws that can be extruded from a protrusible pharynx. In some cases these jaws are used to cut algae strands for food, but most errant polychaetes are carnivores or omnivores. The two main genera of concern are Eunice and Nereis. The larger species in these genera reach up to 50 cm (20 in.) in length and
A large, predatory tireworm, Hermodice carunculata. S.W. Michael.
can cause a great deal of damage in the aquarium. These large worms are easily recognized by their pronounced body segmentation, parapodia and setae. Mainly active at night, they are introduced into the aquarium concealed in live rock. Both genera will feed on corals, clams, and small, sleeping fish (Wilkens and Birkholz, 1986). On stony corals, the sudden loss of tissue in a localized area, exposing the skeleton as a white spot, can be caused by a tiny polychaete in the rock below it, and the coral should be moved to a new location. The previously mentioned Fireworm, H. carunculata, is also a voracious predator of corals, anemones and clams, and should be removed as soon as possible if it is ever seen in the aquarium ('see White Band Disease).
In aquariums with a thick substrate large populations of smaller polychaetes can multiply very quickly. These species do not usually cause much of a problem and actually help to cycle detritus, clean-up uneaten food, provide a source of planktonic larvae, and aerate the substrate through their burrowing actions. Most are desirable additions to the aquarium ecosystem. However, some species may irritate some corals such as Fungia, Heliofungia, Herpolitba and Polyphyllia that live on the substrate.
Removal: Of course the easiest way to deal with polychaetes is not to introduce them in the first place. Since live rock is the main source it would be prudent to screen the rock before placing it in the show aquarium. Please remember, always wear thick gloves when working with live rock; some of the animals contained on and in it can give you a nasty bite or sting! The best method is to store the rock in a separate holding system and remove the larger
worms with long handled tweezers as they appear. Once you feel confident that you have removed all the worms, you can place the rock in your main aquarium. This is of course the ideal situation and not everyone has the facilities or time to do this. Therefore we offer the following removal techniques.
The larger species of polychaete are by far the most dangerous to your aquarium inhabitants and should be removed as soon as possible. Unfortunately, these larger polychaetes are also the more difficult ones to remove. There a number of methods that can be used with varying success. Since they only become active at night, the best time to find and remove polychaetes manually is after the lights have gone out. These animals are very sensitive to movement and vibration, making them extremely difficult to catch out in the open. Often they will only extend far enough to feed and will quickly withdraw back into the rock when disturbed. In this case a neat trick is to not feed your aquarium for a week or two, then introduce some fresh shrimp or scallop just before the lights go out. Within a few minutes after the lights have gone out the hungry worms will begin moving out towards the prey. If you placed the bait well away from their hiding place they will usually move completely out of the rock. Once this occurs it is a simple matter to pluck them off the bottom with a net or a pair of long handled tweezers. Be very careful when handling these worms, they can deliver a nasty sting or bite, and you could also quickly, and painfully, learn why they call some of them Fireworms! The other danger with this technique is that if you attempt to grab the worm and only get a piece of it, the leftover piece may simply regrow. This method is also very time consuming and tedious.
An alternative is to use a trap. There are a number of such devices available commercially, and they work! You can also build your own quite easily by using a section of PVC pipe, 2 or 5 cm (1 or 2 in.) in diameter. There are two designs that have proven successful. The first involves placing removable caps on both ends of the pipe and drilling several holes into the tube that are just large enough for the worms to enter. Bait the trap with cut shrimp or scallop and place it horizontally on the bottom of the aquarium, just before the lights have gone out. Not feeding the aquarium for a few days enhances the lure of the trap. The next day simply remove the trap and empty it into a bucket. If the worms were hungry enough to enter the trap and eat the bait, they will have become too large to fit through the holes to get back out (G. Smit, pers. comm.). The other option is very similar to the commercial
traps. In this case, only one end of the PVC pipe is capped. In the other end glue a narrow bore funnel and cut off the majority of the
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