The beautiful Coco Worm (Protula magnifica) is a difficult animal to keep long-term.
Tube worms are beautiful, fascinating members of the class Polychaeta. They are also the most popular polychaetes available to aquarists. Larger species are intentionally purchased and added to the reef tank because of their elegant form and or their lovely colors, while smaller species often come in with live corals (i.e., living on the rocky bases that the corals are growing on). Unfortunately, the larger species often don’t fare as well as their much-malign brethren, the bristle or fire worms.
Unlike the fire worms (and many other species in this group), the tube worms are sedentary. They form a tube in which the body is hidden and have a spiral crown that projects from the tube. The crown, which is comprised of feather-like structures called radioles, is used for suspension feeding and for respiration. While they have cilia on the feather-like structures to direct food down each appendage into the mouth, they also depend on water currents to bring them tiny food particles. When the worm “feels” threatened, the radioles are rapidly rolled up and pulled into the tube. Even though they can withdraw the crown very rapidly, the radioles are sometimes nipped off by fish species before they can be retracted. The body tube, which is created by the worm, is comprised of sand grains and mucous in many sabellids (e.g., feather duster worms [e.g., Sabellastarte]), or is calcareous in the serpulid worms (e.g., Christmas tree worms [Spirobranchus], coco worms [Protula]).
The Christmas tree worms (Spirobranchus sp.) are beautiful coral obligates that may help coral colonies survive attacks from crown-of-thorn sea stars.
“Oh Christmas Tree”
The Christmas tree worms (Spirobranchus spp.) have an operculum that plugs the end of the tube when the worm withdraws into it. Their larvae settle out of the plankton (larval lifespan is about 12 days) on to a preferred host coral and begin creating their tube. The type of coral they live will impact their overall size and hence their reproductive success (i.e., larger worms, produce more gametes), so they are selective about who they settle on! In some cases, there will only be one or a few of these worms per coral colony, but in some cases, a coral head may be covered with Spirobranchus. Densities of up to 414 worms per 10 square feet have been reported on some heavily infested colonies. Not only do the calcareous tubes these worms produce provide shelter for the individual polychaetes, the empty serpulid tubes serve as a home for tube blennies (family Chaenopsidae) and the coral hermit crab (Paguritta spp.). Some members of the genus Spirobranchus are simultaneous hermaphrodites (they have both functional male and female sex organs), while others are gonochoristic (are either male or female). While many simultaneous hermaphrodites do not engage in sex fertilization, these worms can and do and the resulting embryos are viable.
One more quick note about Christmas tree worm taxonomy. There are many different species in this genus, although most are labeled in the popular literature as Spirobranchus giganteus. They are difficult for aquarists to tell apart without killing the animal and examining the hidden parts as well as the operculum.
The fan or feather duster worm is a demanding animal that will have to be fed suspended foods frequently. Avoid purchasing individuals that have lost their crowns.
Tube Worm Husbandry
If you purchase a larger sabellid feather duster worm, the first thing you need to consider is placement in the aquarium. I would recommend drilling a hole in a piece of live rock (with a masonry drill bit) and placing the sedimentary or soft tube into the hole. You could also place the tube in preexisting holes or crack in the hard substrate. While they need current to push food items past their radioles, a strong, direct water jet can damage them and/or prevent them from unfurling the feeding crown. When selecting a feather duster, never purchase an individual that has crawled completely or even partially out of its tube. These individuals are not likely to live long.
The key to keeping these animals healthy is feeding. If you are not willing to frequently feed your tube worms (of any species), you should avoid purchasing these animals as they are going to slowly starve to death in your aquarium. The larger species of feather duster and Coco worms feed on phytoplankton, small zooplankton (including ciliates, rotifers and invertebrate larvae), and suspended organic detritus. The smaller species, like the Christmas tree worms, ingest bacterial floc (i.e., a chemical precipitate) and minute particles of suspended organic detritus. The best way to provide nutrients in the aquarium is to feed phytoplankton, small zooplankton, and liquid foods for suspension feeders (larger worms need larger food items). Smaller species of feather duster worms (those that often come in on live rock) tend to do better in home aquariums than larger species, which tend to have higher metabolic needs and thus need to be fed frequently. When target feeding, direct the food to the side and slightly below the feeding crown, do not direct it into the center of the feeding crown.
These worms are sometimes fed on by shrimps and crabs. Sea urchins have been implicated in chewing through the sedimentary tubes of Sabellids. If stressed, the tube worms will shed the feeding tentacles, which will typically regrow in several weeks’ time. They may lose their feeding tentacles if underfed, in which case the regenerated tentacles will be smaller. These worms are good plankton-feeding indicator species because they are so effective at suspension feeding - if your feather dusters are starving, then any other animals in the tank that rely on this feeding strategy will be in even worse shape.
While the beautiful Christmas tree worms which are offered along with their coral associate (often Porites spp.), may live a long life in the wild (20 years or more), they are typically short-lived in captivity because they tend not to get enough to eat. One common misconceptions it that Christmas tree worms rely on their coral host for food and if the coral dies, the worms are soon to follow. While they are an obligate stony coral associate (some also live on the hydrozoan, Millepora – i.e., fire coral), they will continue to live even if the coral colony dies. So do the worms benefit the coral at all? Recent studies have shown that the worms may actually protect colonies of Porites coral from being totally consumed by crown-of-thorns sea stars (Acanthaster planci). These sea stars are infamous for occasionally appearing in large numbers in the Indo-Pacific and wiping out swaths of coral reef. It turns out, that portions of Porites colonies that harbor Spirobranchus are apparently protected by the presence of these worms and thus can regrow. The tube feet and/or inverted stomach of the crown-of-thorns is thought to be irritated by the worms, which results in an area of live coral tissue being left beneath the branchial crown of the Christmas tree worm (this section is usually 3 to 5 cm in diameter). This ensures the survival of the colony.
© Scott W. Michael - Reef Tectonics