Worms! Ugh. A normal reaction when we think of the slimy earthworms familiar to most of us. But the marine worms are often quite different, and ignoring those which are writhing, crawly creatures, we can discuss those that are of potential interest to the aquarium keeper, some of which may even be described as “beautiful”. The beautiful marine worms are probably best represented by the prolific little tubeworms which live within the strong protection of enclosing massive stony corals, like some porites species. But other interesting and attractive tube worms secrete a mucus to form their own encasing tube, preferring to live with their tube-homes buried in soft mud or fine sand. Another group construct a calcareous casing which forms part of a communal construction, looking very much like a stony coral at first sight. Yet more of these nicely coloured worms will form calcareous tubes bonded to coral skeleton or coral rock. These species of worm are sedentary, and permanently situated where they are found. They do not move around from one location to another. They extend their feathery tentacle-like heads to gather food, and disappear with extreme rapidity into the safety of their concealed or fortified tubes when disturbed.
Other species are very mobile indeed. The bristle worms, which are so easily introduced into the marine aquarium with “living rock” or soft corals attached to coral rock, are fast movers when they want to be. Others use their slower mobility to find a host animal they can attach to, and live out their lives in association with their unwilling host. One spectacular worm keeps its main body anchored within a rocky hole but extends tentacles for an amazing distance across the sea bed in all directions to gather in food. Flatworms can be decorative and mobile, while others may be boringly plain, fairly sedentary, and terrible pests in the aquarium. So there is a lot of variety of form and behaviour between the many sea animals we know as “worms”.
The best known and most frequently available worms available to the aquarium market are those which are popularly known as “Feather Duster worms” or “Fanworms”.
There is a great deal of variety available from the large group of Sabellid worms, which has a total of 300 species in the family. But the aquarium hobby is supplied with a relatively restricted number of tropical species. Two very similar looking species of “Feather Duster” are the most commonly available. Sabellastarte magnifica comes from the Caribbean, and Sabellastarte sanctijosephi is from the Indo-Pacific region. The paper-like parchment tube is formed by secretions from the worm, and is usually buried in a fine sand or mud sea bottom. The feathery gills which form the fluffy head of the worm extend into the water to accumulate nutrients which are “sifted” from the passing currents. The author has also seen these feathery gills spread out across sand when the tide has gone out and just a trickle of water continues to feed them, although they are virtually exposed to the air. But if the worm senses danger indicated by some close disturbance causing worrying vibrations, or a sudden change in the light strength falling on its extended gills, it will withdraw into the tube with lightning speed, contracting its body bulk and tucking itself deep down away from the tube opening. Feather duster worms will sometimes drop their decorative heads. This may be in direct response to their being troubled by inquisitive fish, or after being moved and consequently stressed. The actual cause is not always obvious. The dropped head should be removed to prevent pollution, but the remaining worm body inside the tube will often re-grow a set of gills, albeit into a less decorative form than the original array.
Occasionally more colourful specimens of Feather Duster worms are seen. A Red and white banded species is particularly attractive, but seems to be more delicate than its banded relatives. Also from time-to-time the Caribbean species, S. magnifica, can be found in clear colours, and the Indo-Pacific S. sanctijosephi is capable of displaying itself in colourful variations.
Other tube worms of the genus Bispira have an array of feathery gills which are usually
a little more compact than those of the above species, and as the name suggests they are arranged in a gentle spiral fashion. Another notable differing feature of these spiral worms is that they are more likely to be found in close association with one another. Colours, once again, are quite variable.
Other Sabellids will form such a close association with their own kind that they are termed “colonial”. These species of Sabella worms have gills which are generally quite a lot smaller than the previously mentioned species, and are frequently bi-coloured, giving an impression of a bunch of flowers. Where they occur they may be quite abundant, and are usually established within the shelter of an adjacent rocky surface or slight overhang of coral rock. Like their larger relatives these colonial species also live in a parchment tube which is largely buried out of sight in the silted bottom.
One truly colonial type of tubeworm has even smaller gills extending from calcareous tubes which they manufacture, progressively building up a structure which at a glance looks very much like some strange hard coral with its polyps extended to show a red base area finished off with fine white feathery tips. But a closer look reveals a very different subject. This colonial tube worm may have even several hundred individual worm tubes fused together into a considerable form, but that is less common. A single column might have 50 or 60 worms in its construction, and three or four of these columns may themselves be joined together. This intricate sociable worm is called filogranella elatensis and would make a superb feature in a reef aquarium. But it is not common and could not expect to be freely available to the hobby. The calcareous tube construction is quite delicate and easily damaged if handled without due care.
Another species in the same genus is also found in the Indo-Pacific regions. This is Filogranella implexa and is far less impressive than its related species. The exposed worm gills are white, as are the calcareous tubes, but those tubes are not compact but are quite haphazard in the way they are bundled together. They straggle across an adopted surface of sponge or rockwork in an untidy manner, and would be difficult to collect as a colony. However they would not have anything like the same appeal as elatensis even if they were collectable, and would only appeal to someone with a particular interest in collecting the various species of tubeworm.
There are about 350 species of Serpulid worms, and just a few of these will be seen in aquarium culture. The amazing “Bottlebrush” or “Christmas Tree” serpulid worm Spirobranchus giganteus is the most frequently seen, and these are often collected for the aquarium hobby. They are found in both the Indo-Pacific region and the Caribbean. This species comes in many different colours and it is possible to acquire a modest sized piece of porites coral with a whole collection of these beautiful worms in situ. Some have pure single colours while others may be bi-coloured. There are bright yellow, red, and orange ones to be seen, alongside others of red with white, pure white, royal blue, and many more shades and combinations. There are also different sized worms available, depending on their original location. The tube is completely unseen, embedded right into the mass of the host coral. The head of this worm is made up from two spiralling sets of “tentacles”. A “tongue” (actually an operculum) projects from below the extended head of the worm, and when alarmed the head retracts in a flash, bringing the operculum smartly down to cover the entrance to the tube, forming an effective protective “door”.
A larger Serpulid worm is found within a very hard calcareous casing which may be only partially buried into rockwork, or quite often cemented to the rock’s outer surface. This tube worm is often marketed in the UK as a “Koko” worm. To science it is known as Protula magnifica. Like the Christmas Tree worm this very much larger species has a double headed set of gills, but it lacks the operculum to seal off the top of the tube when it is retracted. There are different coloured Koko worms available, although they never display the bright colouring their much smaller relatives can. White or pale pink are the most frequently seen colours, but occasionally bi-coloured specimens in red and white are collected. There is also some variation in the length of the gill filaments. Some specimens have distinctly longer filaments, and are consequently rather more ornamental. In the aquarium these Serpulids tend to be on the delicate side, and not as easy to maintain as the smaller species. Like the Feather Duster worms, this species may also shed its head from time to time and regenerate a new one from the retained body. A hazard for both the above mentioned species of worm is that of unchecked choking stringy algaes which may infest the coral or stony casing surrounding the worm.
Spaghetti worms Eupolymnia nebulosa are found in both the Indo-Pacific and Caribbean regions. It would need a large reef aquarium to properly accommodate these curious worms, and they do not boast any sort of beauty to attract anyone other than the collector/enthusiast as a potential aquarium subject. The body is tucked away unseen, but is said to be orange with white spots. All you will ever see, however, are the extremely long tentacles reaching out from the buried mucous tube across the substratum of the sea bed. These tentacles catch food particles and these are taken along a groove, moved by the action of cilia, to the body back in its tube. As the tentacles can reach for distances up to about 3 or 4 feet and are fine enough to penetrate even very narrow crevices, the Spaghetti worm could possibly be considered an efficient scavenger in the larger reef aquarium as well as having assured novelty value!
One of the fascinations of combing through some of the less visually appealing marine environments, an activity popularly known as “muck diving”, is finding creatures living on other creatures! Such freeloaders are likely to end up in the reef aquarium by stealth. An acquired sea cucumber, for example, might have a mollusc or worm attached to its underside and be imported into the reef aquarium without being detected. One such uninvited guest might be a specimen of Scale Worm Gastrolepidia clavigera which attaches itself quite firmly to the body of some unsuspecting holothurid sea cucumber. This is a member of yet another huge family with about 600 members. The scale worm lives commensally with the cucumber and will assume the same matching colouration so that it becomes quite difficult to detect without very close examination. If the host animal is quite large there seems to be little cause to remove the scale worm, and it will be a source of some interest when showing off your reef exhibit to some admiring friends. A more ornate species Asterophilia carlae from the same family is occasionally found in association with cucumbers or very large starfish, whose feet it is said to resemble. With a bit more than a little imagination you might agree with this theory(?). The peculiar little extensions pushing up from each of the scales which help to form the body, have globular yellow tips to them, and gives this animal a totally different profile to that of its relative mentioned above.
A very beautiful worm which is unlikely to reach the aquarium trade is known colloquially as a “Caribbean Bobbit Worm” Eunice species (aphroditois?). Being nocturnal and secretive it would hardly fit into the normal reef aquarium. But for the collector or specialist this would make a fascinating creature to observe. This worm is the member of a family which includes some of the very largest of all worms, but this particular species does not appear to grow beyond the approximated length of the specimen pictured, at about 5 cms. (Its Indo-Pacific relative, which coined the popular name of “Bobbit Worm” originally, can grow to a massive nine metres long, with more than 600 body segments, and live for up to 100 years!). The natural diet is composed of algae and swimming crustaceans. Passing prey are snatched by the worm leaping (yes, a leaping worm!) from its hole and grasping the prey in its powerful and intricately formed jaws which are equipped with a locking mechanism. The rainbow spectrum of colours is the remarkable feature of this agile worm. These colours are iridescence produced by the arrangement of muscles under the skin, and is typical for the eunicids. The author observed one of these worms during a night dive and was amazed to note how repetitively and swiftly it snatched passing swimming worms and retreated back into its hole, then very quickly re-appeared to grab still more prey. It posed the question of whether it was storing the food for consumption later, or was it rapidly consuming its catch there and then? When a large bristle worm carelessly wandered into the territory it was immediately attacked by the Eunicid worm, but could not be vanquished. After quite an intense battle the bristleworm managed to clear the area without either party suffering any damage as far as could be seen.
Bristle, or Fire Worms Chloeia, Hermodice, and Pherecardia species are unwanted pests which almost routinely find their way into reef aquariums via the “living rock” used to build the “reef” structure with. Being cosmopolitan they are likely to arrive in this calcareous rock wherever in the world it might be taken from. It has to be said that some species of Bristle worm are undeniably quite handsome creatures, but when you have accidentally grasped one attached to a piece of rockwork you are rearranging, you are not likely to be admiring the perpetrator of much pain and irritation from the bristles (setae) you will have sticking into your fingers! The Indo-Pacific species are more usually encountered in nature at night, but in Caribbean areas they may be seen at any time, and sometimes in plague proportions. Although efficient scavengers it has been suggested that Bristle Worms may attack the pedestal foot of anemones, but this is unsubstantiated as far as the author knows. Any carrion like dead fish, for example, will be searched out quickly and fed upon.
Another worm which manages all too often to steal its way into the reef aquarium with unsightly results, is an Acoel species, the “Plague Flatworm” cf. Waminoa, . These minute rust-brown simple worms are adept swimmers and move freely around the aquarium, infesting almost any surface to the point where they form a complete coating. Reproduction is exceedingly rapid and control is not easy to achieve. Some fish are seen to eat them (Callionymids like Mandarin Fish, and juvenile batfish for example) but their picking at them hardly solves the problem of such a fast reproducing menace. If damaged they are able to regenerate easily. They are said to reproduce asexually by fragmentation in an almost continuous fashion throughout the year.
However, there are other species of flatworms which may be regarded as prize specimens in the reef aquarium. They are not the hardiest of animals, for sure, but there is a better chance of keeping these alive in captive conditions than the many species of often similar looking nudibranchs (Sea Slugs) brought in occasionally. Polyclad Flatworms have numerous eyes and occasionally horn-like extension on the head. The eyes are certainly never obvious, and the “horns” vary from miniscule to prominent, depending on the species. Unlike Nudibranchs which are very selective in their dietary needs, flatworms tend to be non-specific, and this makes them a potential aquarium subject by contrast with the nudibranchs. Their diet includes squirts, small benthic crustaceans and other detritus feeders, and they may attack their own kind in certain circumstances. Many of the Polyclad Flatworms sport bright colours which warns would-be predators they are foul-tasting and best left alone. The displaying of bright warning colours in this fashion is known as aposematic behaviour, and is utilised by many sea creatures. Some of the flatworms take off and swim with a lovely undulating motion, similar to the flambuoyant Spanish Dancer nudibranch, which is a delight to witness. As soon as they land they immediately set off in their crawling mode, exploring new territory for some tasty meal.
With such a diverse range of worms to consider, there is probably something among them which would appeal to the marine reef aquarium keeper. Certainly, there are some which are very interesting species to observe but rarely if ever reach the market. Not all are suitable for inclusion in the reef aquarium but have sufficient points of interest in themselves to deserve a species tank for the dedicated collector or for public display. And just a thought : With so many of the invertebrates of the tropical coral reef being nocturnal creatures, it would make a fine exhibit for a public aquarium to stage a darkened display area with low reddish lighting over the aquariums to show these fascinating subjects going about their natural waking hours activities. During our night-time the lighting for these tanks could then be changed over to a daytime mode to ensure the creatures would retire and rest, ready to make their appearance next day to delight the viewing public when they are switched over to night-time mode again. The same darkened room could accommodate the nocturnal reef fish species in their preferred lighting conditions too, as opposed to relying on them being conditioned to being viewed in daylight brightness. Diurnal invertebrates could continue to be displayed out in the brightly lit area. This would equate to the specially staged and very popular nocturnal animal exhibits at many zoo parks these days.
This is the colour form of Feather Duster tube worm the aquarium hobby is most often supplied with. Note the exposed parchment tube. There is about twice as much of the tube buried into the substratum.
The Caribbean magnifica Feather Duster may be found in attractive colours, like this canary yellow specimen. The feathery gills are poking through the protective cover of a sponge with adjacent algae growth.
This red and white “Feather Duster” is quite often imported for the the reef aquarium. It is a little smaller than the regular species, and tends to be quite delicate by comparison.
An attractively coloured form of the Indo-Pacific species of Feather Duster tubeworm which is able to spread out its gills above the surrounding sponges and crinoids, but when retracted it is able to disappear completely within their cover .
The Bispira species of tube worm have much finer cilia in their gill construction, and they have a gentle spiral formation which is quite different to the more frequently seen Feather Duster tubeworms.
These Caribbean Sabellid worms prefer to form quite dense colonies. Mabe it is because they are so congested and have a need to compete with their neighbours to reach up for nutrients that their tubes are quite long and exposed (?).
Filogranella elatensis is a lovely colonial tube worm, which builds a delicate calcareous tube alongside eachother. The whole colony at first glance looks just like a hard coral with its polyps extended.
Filogranella implexus is an untidy relative of elatensis and similarly contructs its tube in a colonial fashion with others, but lays it flat on a convenient surface, resulting in a straggly and less secure form.
Bottlebrush tubeworms may be found in large numbers and in close association with one another, usually embedded in massive porites coral species. The colours are highly variable.
This close-up of a bottlebrush tubeworm shows the spiral form the head takes, ending in a very tight formation at its highest point.
These large headed tube worms build a tough carcareous tube for their residence. The worm is twin-headed, like its smaller relatives, but lacks the variety and generally the brightness of colouring. They are traded in the Uk as “Koko worms”.
This Protulid “Koko worm” has a bi-coloured form to suit its very colourful adjacent environment, including a red colonial squirt and fire coloured cauliflower coral.
The Spaghetti worm is tucked securely in its tube which in turn is firmly held within a rocky crevice. The tentacles extend far away from the body of the worm, and pass gathered food particles back along their considerable length.
Scale worms are often found in commensal association with larger invertebrates. This one is G. clavigera riding on a large sea cucumber. It is able to cling on to any part of the host animal, including its underside.
This Scale worm is A. carlae which is said to mimic the feet of large starfish it is often found attached to. Interestingly there is a small shrimp riding on the Scale worm and may be seen about halfway along the body. So the three creatures are in commensal association in one package!
The Caribbean Eunicid worm is nocturnal, and spends the night with its rear part securely fixed in its burrow with just the head showing. When a prey chances by it thrusts just its head end out of the hole to grasp the unfortunate creature, then retreats very rapidly back ino the hole.
This species of Bristle or Fire Worm was very common over a wide area of reefs off the Caribbean island of Dominica. It is really a very handsome creature with its fearsome bushes of white bristles with red bases where they project from the bronze body.
Indo-Pacific bristle worms are usually found only on night dives, and then in quite barren areas of mud or open sand. This specimen sported some exceptionally long “bristles” all along its 5 cms length.
This is the result of unplanned contact with a bristle worm! Waminoa flatworms are a dreaded pest in the reef aquarium. Here they are seen greatly enlarged as they begin to infest a colonial disc anemone, popularly known as “Mushrooms”. In just a few days they would smother the entire anemone.
Polyclad Flatworms can be very beautifully coloured creatures, and are able to be maintained in a reef aquarium provided there are no predators to worry them. They come in a big range of colours, and in different forms.