Several types of marine worms produce tubes to live in and are known as tube worms. Of these, some also have feathery structures that are extended from their tubes and are typically called feather duster or fan worms. There are several different types of fan worms, which differ in their appearance, tubes, and lifestyles. In this article, I'll be covering one group of them known as the sabellids.
Basic Biology and Common Types
The sabellid worms form a tube to live in, which is made of a tough but flexible material and sometimes coated with a layer of detritus, mud, sand, and/or small shell fragments. Some non-sabellid worms, like the Christmas tree worm (Spirobranchus spp.), also produce something of a trapdoor structure that can be used to close their tubes, but the sabellidae do not.
The sabellid worms have specialized feather-duster-like structures called crowns, which are the worms' gills and can be extended from their tubes to collect food particles. The crowns are made up of numerous feathery branches called radioles, and the radioles themselves are covered by even smaller branches; it's easy to see where their nickname comes from.
The underside of each radiole is also covered with tiny but numerous hair-like cilia that can create a flow of water by waving rhythmically and rapidly. They draw water from the underside of the crown up through the radioles. The lop side of each radiole is grooved, and as water passes by, lint particulates can be captured in the eddies that form over the radioles and passed down the grooves by other cilia into the worm's mouth. Some selection and sorting goes on in this process, and particles that are inedible are rejected.
Some sabellidae are relatively large, and Sabellastarte magnified and S. spectabilis are the two species most commonly seen for sale. You can't tell which is which by looking at their crowns, but S. spectabilis comes from the Indo-Pacific region while S. magnified is collected in the Caribbean. Both of these species produce leather-like tubes that can reach 8 inches or so in length. The tubes are also coated with mud/detritus particles but not sand or other larger sediments. Their crowns can also get up to about 4 inches in diameter and are typically nicely colored and/or patterned.
On the other hand, some sabellidae are relatively small, like the cluster dusters. These typically come in tightly spaced clusters made up of numerous individuals, with each tube being less than 2 inches in length and having crowns that are typically less than 1/2 inch across. The Caribbean species Bispira brunnea is the most commonly available of the cluster dusters.
As strange as it might sound, these can reproduce asexually by breaking off the rear end of their body, which can then grow its own crown and produce its own tube to live in. Under optimal conditions, you can end up with more and more of these worms.
Aquarium Care
When it comes to aquarium life, the first thing to note is that there are several things that will eat sabellids. Before going any further, and especially if you want to put a sabellid in a non-reef aquarium, you'll need to think about any potential incompatibility issues first. Many butterflyfishes will eat sabellidae, especially small ones like cluster dusters. A lot of hawkfishes, wrasses, and some crabs will eat them, too. Oddly enough, l remember hearing that some serpent stars will feed on them as well, so 1 wouldn't try mixing any of these with a feather duster worm. Of course, most of these aren't typical reef-aquarium picks, with the exception of some hawkfishes, so reef aquarists should be fine for the most part.
Next, sabellidae, especially small ones, are prone to starvation in aquariums. As covered above, these worms feed on particulate matter, but many aquariums simply cannot support them because sabellidae can be very-picky about what they eat. If you have a reef aquarium with a deep sand/mud bed or some sort of refugium set up, a worm may be okay, but for most aquarists, there is no sure-fire way to keep one alive.
Even using high-quality planktonic/ particulate foods may not work either, as one type of worm may do well with one type of product at one size but may not take the same food when it gets larger. Different worms have preferences for different foods, thus there is no perfect food for all of them.
What I can tell you from personal experience is that some worms, especially smaller ones that eat relatively small particles, have reproduced rapidly in one reef aquarium when fed nothing extra, while the same species slowly starved to death in many others' tanks with essentially the same setup. You might end up trying several worms of different sorts and different sizes and have success with a few and fail with some others. About the only thing you can do to increase your chances of success with many of them is to add several different foods to an aquarium and see what works best. This means that unless you're willing to put the money and effort into feeding them, you’re probably better off leaving them alone.
Lastly, with respect to foods and feeding, keep in mind that sabellidae create a current that moves food particles from the underside of their crown to the lop of their crown. If you want to try target feeding one of them, you'll need to gently squirt some food just underneath their crown rather than directing it at their topside.
A gorgeous feather duster the author found at a shop in Japan; feather duster worms consume fine particles and can be difficult to feed in the aquarium.
Moving along, placing a sabellid in a good location can be difficult at times, as they need to be in a spot where they'll stay put and where currents aren't so strong as to prevent them from fully extending their crowns. Larger specimens should be placed in the rockwork where they will stay put or should have part of their tube buried in sediments to hold them in place, but smaller ones, like cluster dusters, should be glued to a rock.
Looking closely at a sabellid radioles makes it easy to see the fine branches that cover them and make them look like feathers.
When placing a large sabellid in a gap or crevice in the rockwork, you'll need to make sure that you don’t bend or pinch the lube somehow in the process. This could obviously hurt the worm inside the tube and/or keep it from being able to extend its crown. Depending on the worm's size,
you'll also need to make sure that at least a couple inches of the tube still sticks out in such a manner that the crown can be fully extended without having it in direct contact with the rock. Of course, if you have a deep enough sand/gravel bed, you can also bury a worm’s tube, again leaving some of it sticking out of the substrate to allow extension of the crown.
A clump of the common cluster duster, Bispira brunnea.
Cluster dusters, on the other hand, can be stuck to a rock using the same cyanoacrylate glue that many hobbyists use to secure coral fragments. A clump of them can be dabbed on the underside with some of the glue and then stuck in place wherever seems to be a good spot for them. Do make sure that you don't inadvertently glue the worms' tubes shut, or glue them to your fingers.
Challenges
Even if you place a sabellid the right way and in what seems like a good spot, every once in a while, one may decide to leave its tube and crawl around. If this happens, and you spot it, do not try to stick it back into its lube. There’s no good reason to put it back where it doesn’t want to be, and you might end up injuring or even killing it in the process. These worms are especially vulnerable to predation when out of their tubes; if one decides to bail out of its home, there’s probably a very good reason for it to do so. Reasons may range from unfavorable currents that prevent them from capturing food to being attacked by a predator, but fortunately, if nothing eats them while out and about, they can build a new tube if they find a more favorable spot themselves. As bad as it might sound, the best action to take is typically to take no action and hope for the best.
Cluster dusters belonging to the genus Bispira
On occasion, a sabellid might also decide to get rid of its crown in its entirety. When this happens the whole crown separates from the rest of a worm’s body, so you might find a crown sitting around sometime and think your worm is surely dead. However, these worms can actually grow a whole new crown if they need to, so don’t throw out the tube unless you're sure there’s nothing alive inside it. You might have to wait a couple weeks, but I’ve patiently waited from time to time myself and eventually seen a new (but much smaller) crown emerge from a tube. Over time, it will grow back to its normal size if the worm is otherwise in good health. 1 haven't been able to find a reason for this behavior, but sometimes they do it.
Shopping Tips
If you decide you want to try one of these despite their common troubles, choosing the best possible specimens is always a good way to start. I've got some shopping tips to wrap things up. If you’re going to purchase a sabellid, the first thing to look for is a specimen(s) with a fully extended crown. If a specimen’s crown is only partially extended from the tube and/or is not fully fanned out, skip it. If its crown is extended and spread, you should then give it a close inspection. Check for any damaged or missing radioles.
A common-looking sabellid specimen of the genus Sabellastarte with its crown and tube on full display.
Be sure to take a good look at a specimen’s tube. Many soft-tubed specimens may have some minor damage to their tubes, which they can repair themselves. However, if a specimen’s tube has some sort of significant damage, then the worm inside may also have unseen injuries from whatever did the damage to the tube.
If you find one that passes the visual inspection, you should also try to test how it reacts to a disturbance. Sabellids’ crowns have primitive eyes of various complexity here and there, and they’re also very sensitive to touch. If healthy they should respond to a shadow-passing overhead by quickly retreating to safety in their tube. They should do the same if touched lightly. If a specimen doesn't react quickly, there may be trouble, and again, it's better to just move along and skip it if there are any questions about its health.
 |
Author: James Fatherree
About the author: James Fatherree, MSc. is a physical and environmental sciences professor in Tampa, Florida. He has been an aquarium hobbyist since childhood, a reef aquarium hobbyist for over 20 years, and has spent many days diving in Florida, Hawaii, the Bahamas, Japan, and Indonesia In the past he has managed a large retail aquarium store, owned and operated an aquarium design, installation, and maintenance business, and spent a summer working for an aquarium livestock collector/wholesaler in Florida. James has also published numerous articles in the U.S. and Europe, and has written and illustrated several hooks on the topics of reef organisms and marine aquariums, the latest of which is Giant Clams in the Sea and the Aquarium.
|