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Reefkeeper's Guide to Invertebrate Zoology: by Rob Toonen Aquarium.Net January 1998

Potentially Dangerous Errant Polychaetes, Aquarium Net has numerous articles written by the leading authors for the advanced aquarist

Reefkeeper's Guide to Invertebrate Zoology:

Part 11: Potentially Dangerous Errant Polychaetes.

By Rob Toonen

Last month, I ended the article on sedentary (an archaic classification term which is still functionally useful because it is loosely equivalent to "tube-building") polychaetes with an introduction to the errant (loosely equivalent to "free-living") polychaetes. If you read that article, much of this paragraph will be familiar, but I want to reiterate several things that I mentioned at the end of that article here. I pointed out that unlike the sedentary polychaetes, of which few are any threat to a healthy reef tank, some errant polychaetes can be a substantial threat both to your tank and to you as well.

Having said that, there are, of course, some polychaetes that you will want to eradicate from your tank (such as Hemodice or Eunice ), but the sight of a small bristled worm crawling across a section of your live rock (or even your prized clam or coral) is NOT cause for panic or overreaction. More often than not, these worms turn out to be harmless scavengers that are scrounging around for organic detritus and prove to be beneficial rather than detrimental to your tank. My immediate advice is to relax, keep a close eye on the potential trouble-maker, and see whether or not anything in the tank seems to suffer from the presence of the worms before you start looking for ways to blindly eradicate them. Of course, having a bit more knowledge of the various classes of polychaetes and the relative risk involved with the presence of a Syllid versus a Glycerid in your tank will help you to make a more informed decision on the likelihood that the worm you have just seen crawling on the mantle of your favorite Tridacna is going to be a problem.

In keeping with the style of the past couple of articles on the sedentary polychaetes, this article will again be pretty much a march through the classes of errant polychaetes with a brief description of each group, and a quick synopsis of the typical feeding modes that species in each group employ. I've tried to include a representative picture of each group in the hopes that you can use general similarities between temperate Californian species (and my abbreviated character list) to identify the worms you see in your aquarium to make at least a Family-level identification, and from that can make an informed assessment of the risk that worm is likely to represent to the inhabitants of your tank. I'll start with the typical "bristle-worms" to which you should pay close attention this month because they pose a potential risk to either you or your tank inhabitants, and will then continue with the groups that are unlikely to be of much threat in your aquarium with the next article.

Amphinomidae (amf-in-o-mid-ay)

This is the family of polychaetes which is primarily responsible for having given "bristle-worms" a bad name. Aside from the fact that these animals are voracious predators, and some are capable of ingesting entire branches of Acropora and digesting all the tissue from the skeleton, it is also to this family that the dreaded "fireworms" ( Hermodice carrunculata and Eurythoe complanata ) belong. These bright orange worms with a row of brilliant white bristles adorning each side of the animal deserve the bad reputation which they have (undeservedly) passed on to the rest of their relatives. Although these worms are generally a bright reddish-orange color, it is not the color that gives them the name "fireworms," but rather the action of the toxin injected by the fine, hollow setae (needle-like bristles, described in more detail in the Part 6 , an introduction to the Phylum Annelida and the Part 7 , the first complete annelid article in this series) lining the sides of the worm. If you have ever been misfortunate enough to have picked up one of these worms by mistake, you will certainly remember the lasting sensation left long after you have tried to remove all the brittle, glass-like setae from your fingers. Once imbedded the setae cause inflammation, irritation, itching and numbness (usually associated with the toxin they contain, but also commonly due to infection). In their 1980 book, Morris, Abbot and Haderlie report that some unfortunate people have required amputation of digits following encounters with certain species of fireworms. Just to make things worse, the brittleness of the setae make them very difficult to remove, and if you try to remove them with tweezers, they just break off (usually below the level of the skin), and usually make the burning irritation worse. So, if you discover a polychaete in your tank that looks like a 'wooly-bear' caterpillar (like the two species of fireworms pictured here), please don't touch it with your bare hands ! A new pair of rubber dishwashing gloves (PLEASE get a new pair for this purpose -- don't put the soapy pair from the kitchen into your tank!) is all that is necessary to protect yourself from a painful, and potentially dangerous injury. (At the same time, I have yet to hear of anyone being hospitalized for treatment of a fireworm "sting" in relation to a reef aquarium, although divers and snorkelers often suffer from encounters with Hermodice carunculata and Chloeia viridis .)

Hermodice carrunculata (left) and Eurythoe complanata (right) two of the most common species of the dreaded "fire worms."

If you do find yourself in the unenviable situation of discovering first-hand why these animals are called "fire-worms," DO NOT rub or scratch the injured area (you'll only make it worse, and likely spread the irritation by breaking and transferring bristles around on your skin), and do not try to remove the setae (bristles) with your fingernails or a pair of tweezers (some first aid texts suggest tweezers, but even with a stereo scope, this is a very tricky endeavor). Allow the area to dry, and then use a piece of masking or duct tape to carefully remove all the bristles you can by dabbing the sticky side of the tape onto the protruding setae and lifting them out of the skin. Turn the tape to a clean area and repeat, until all visible bristles have been removed. . Then soak the affected area with rubbing alcohol (~40% isopropyl alcohol), vinegar, or better yet, a dilute ammonia solution (10 parts water to 1 part household ammonia) or sprinkle generously with meat tenderizer, in order to denature the toxin as best possible -- this will make the burning sensation subside much more quickly than would be the case if you simply remove the bristles and wait (which usually takes several days to a week). Once cleaned and dried, a soothing lotion (such as calamine lotion, or something containing benzocaine) can be applied to the injured area to ease the pain, and it would be a good idea to apply an antibiotic (such as Safeway's triple antibiotic ointment: Bacitracin, Neomycin & Polymyxin B) to reduce the risk of secondary infection (common with fireworm stings). If pain and/or swelling persists, or the area becomes infected, you should seek the care of a physician.

Obviously, these worms should be carefully removed if possible when discovered in your tank, but for small species that breed rapidly, such as Eurythoe complanata , that can often prove a difficult task. I provided pictures of some of these species and suggested a number of alternative strategies for eradication of problem polychaetes in Part 8 , the first polychaete article in this series.

Phyllodocidae (phil-o-doe-sid-ay)

Phyllodoce novaehollandiae , A large phyllodocid polychaete worm common in Australian estuaries and mudflats.

The phyllodocids are named for their unusually large phyllopodous (leaf- or paddle-like) limbs. The parapodia (paired limbs characteristic of polychatetes, as described in Part 7 ) of phyllodocids are large and obvious -- you cannot help but notice the large fleshy paddle-like limbs projecting from each segment along the body of the worm. Coupled with those obvious parapodia are a number of large and obvious antennae, tentacles, and cirri (all various head appendages) that give phyllodocids a disticnctive appearance (as shown in this picture).

These worms can become quite large, and are probably the single most common epibenthic predator on solid substrata (such as live rock, for example), and so are among the most likely inhabitants of your reef structure. However, despite the fact that the group is almost entirely predatory, and that some can become quite large, they generally seek relatively small prey, and are, in general, unlikely to be a substantial risk to most of your tank inhabitants. Having said that, however, their primary prey items tend to be other worms, small crustaceans and tiny molluscs, so if you are trying to culture copepods, amphipods or other small prey for your Mandarin "Goby" ( Synchiropus splendidus ), you may have a difficult time doing so with a large standing population of phyllodocids in the aquarium.

Although I have phyllodocids in every one of my reef tanks, I have yet to see any evidence that they are causing any real problems in my own tanks, however. More often than not, the phyllodocid worms that are found in reef tanks are the small (and therefore more easily hidden and transported) species, such as Eteone or Eulalia , and although they can become surprisingly abundant in tanks which are chronically overfed (such as my Cassiopea  tank), they generally are not a problem in a well-balanced and carefully maintained reef tank.

Glyceridae (gly-sear-id-ay)

These worms look relatively innocuous, but can be surprisingly voracious. An unprovoked worm looks for all the world like the earthworms that you buy at your local bait store for a weekend of fishing (and in fact these worms are often sold in coastal areas around the Pacific Northwest as bait for marine anglers), but that harmless appearance can be very misleading. Unlike their oligochaete (another class of annelid worms, originally discussed in Part 7 , to which the earthworms belong) cousins, the glycerids have an eversible proboscis (a hidden set of muscular jaws that can be suddenly shot out to grab prey items or "bite" larger creatures that threaten the worm) armed with four Rattlesnake-like fangs (in that each has a poison gland associated with it, and a bite from the animal allows injection of a debilitating venom that enables the animal to subdue its prey or fend off potential predators). Although the venom of a glycerid poses no real threat to us, and indeed the jaws are not powerful enough to pierce the toughened skin of most people's hands, on the odd occasion that one slips between your fingers, and manages to sink it's jaws into the sensitive area between your fingers, the venom causes a sharp burning sensation and you will not soon forget that bite.

Left, the everted proboscis of Glycera americana , a common glycerid polychaete worm from the US Pacific coast, showing the black poison fangs and the muscular pharynx used for prey capture. Right, the same worm without the proboscis everted.

Unlike us, most of your aquarium inhabitants are not large enough or tough enough to withstand the bite without suffering any ill effects. These worms are typically only found burrowing in sandy bottoms, and so are unlikely to occur in a "Berlin-style" reef, but could easily be found in a "Jaubert-style" reef, especially one which was stocked by purchasing wild-collected or seeded "live-sand." As shown in the picture, these worms look surprisingly like terrestrial earthworms (with the exception of the jaws, which are not normally seen), but as I just explained, this appearance is deceptive. A small glycerid is unlikely to do much harm, but is most likely preying on other animals that are desirable in your sand bed, and so it is usually a good idea to remove any glycerid polychaetes that you discover.

Eunicidae (you-nis-id-ay)

Eunice aphroditois , a common eunicid polychaete.

These thin predatory polychaetes can become surprisingly long: some specimens exceed 10 FEET in length (Brusca & Brusca 1990). Although able to attain amazing lengths, most of these worms are relatively thin, and rarely pose any real threat to reasonably large tank-mates. Although many species are omnivorous scavengers, the majority of species in this family are predatory, and their pharynx (muscular jaw apparatus, described in the original article on polychaetes) is equipped with a complex set of jaw plates capable of crushing small prey.

Like phyllodocids, these worms generally seek relatively small prey, and are, in general, unlikely to be a substantial risk to most of your tank inhabitants. Again, however, they do have well-developed jaws, and their primary prey items tend to be other worms, small crustaceans and tiny molluscs, so if you are trying to culture small crustaceans or worms in your tank for some other reason, you may have trouble finding much success with a large population of eunicids.

Nereidae (near--id-ay)

A nereid polychaete -- Australonereis ehlersi , one of the most common polychaete worms in Indo-pacific sediments.

Nereids tends to be relatively large worms with a well developed head, and well developed parapodia for both walking around on the surface of rocks, algal holdfasts, mussel beds, etc., or burrowing through soft sediments. Although many species are commonly found burrowing in soft sediments, the majority of species in this group are typically found cruising hidden surfaces (cracks in rocks, under rocks or crevices in between critters on the rocks) on hard substrata in area that are not constantly exposed to wave pounding. Members of this group are equally likely to be found in "Berlin-style" and "Jaubert-style" reefs, and are almost entirely opportunistic predators. Worms in this family have a single pair of large, curved pharyngeal jaws (they look fairly similar to the jaws of an ant, really) which are used to subdue prey, but only large individuals are likely to pose a substantial threat to most aquarium inhabitants.

Again as with phyllodocids, and eunicids, size is generally a good indicator of the risk associated with the presence of a given animal in your aquarium. In the simplest possible terms: the larger the animal, the larger and more prey items it is likely to consume.

Alciopidae & Tomopteridae

I mention these two families, not because you are likely to ever encounter them in the reef hobby, but simply because they are an interesting alternative to most worms that aquarists are likely to encounter in their tanks (and that we have been discussing in these articles). Both the Alciopiods and Tomopterids are planktonic, strong-swimming predators. These worms are transparent, with large complex eyes and a well-developed head. They often have large, fin-shaped parapodia for actively swimming and chasing down their prey. I don't have any pictures of these worms, and it wouldn't be a very good generalization anyways, because these worms can range in shape from short and short and flat to long and slender. In any case, they tend to be very efficient predators. Although they are unlikely to ever been seen in the reef trade, they could make an interesting aquarium display on their own, if one were so inclined to make a planktonic "blue-water" tank.

If however, you were to ever encounter a transparent (perhaps with a few large pigment spots) worm that spent all its time swimming around your tank, you probably want to remove it, just in case. Of course, the fact that the worm is swimming does not mean that you need to remove it -- many species reproduce by producing epitokes (described in Part 8 ) which swim around in the water column for some period of time before "exploding" and releasing gametes (sperm or eggs), which can provide a rich source of food for filter feeders in your tank.

In the next article, I will continue to discuss the errant polychaetes, but will focus on the groups which are unlikely to pose much threat to your tank inhabitants. Although there are many worms that superficially resemble one another, relatively few are likely to be trouble-makers. If you are unsure whether the worm you just saw in your tank is a glycerid (which you should remove) or a lumbrinerid or an opheliid (both of which will be discussed in the next article, and are unlikely to cause any problems), you probably should base your decision to leave it alone or remove it on the size of the worm itself. It is generally a good idea to remove any large polychaete from your tank, because it is very likely to be predaceous, and large predators are almost always an unwelcome guest in reef aquaria. When I say "large," I mean something approaching pencil-sized in diameter (length per se is relatively unimportant to determining size, because many innocuous worms can reach lengths over a foot or more, but be only a millimeter or two in diameter). On the other hand, some species (such as Oenone fulgida ) are quite thin, but despite their small diameter, they can kill relatively large prey by suffocating them with a viscous mucus (Shimek, 1996), and can apparently kill animals as large as Tridacna clams by boring into the clam and feeding on the body (Delbeek and Sprung 1994). In any case, it is always a good idea to keep a close eye on any animal you think may pose a potential threat in your tank, and if you see any evidence that critter is actually causing damage, I'd suggest removing it as quickly as possible.

Literature Cited:

Brusca, R.C., & G.J. Brusca, 1990. Invertebrates. Sinauer Associates, Inc. Sunderland, Mass. 922 pp.

Delbeek, J. C. and J. Sprung. 1994. The Reef Aquarium . Ricordea Publishing. Coconut Grove, FL. 544 pp.

Ruppert, E.E. & R.D. Barnes, 1994. Invertebrate Zoology, 6 th Edition . Saunders College Publishing, Harcourt Brace College Publishers, Orlando, FL. 1056 pp.

Morris, R.H., D.P. Abbott & E.C. Haderlie, 1980. Intertidal Invertebrates of California . Stanford University Press, Stanford, CA. 690 pp.

Shimek, R. 1996. Segmented and Vermiform, it's a way of life..  Aquarium.Net Cybermagazine. October Issue, 1996.

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