Most of the bristle or polychaete worms
discussed in this month's column are small members of the
"clean up" crew, a group of animals that specialize
in "getting rid of the evidence." Sometimes, as
the following piece of doggerel describes, they have the task
of getting rid of dead meat, among other things
Don't you ever laugh
as a hearse goes by,
For you may be the next to die.
They wrap you up in a big white sheet,
And cover you up from your head down to your feet.
They put you in a big black box,
And cover you up with dirt and rocks.
All goes well for about a week,
And then your coffin begins to leak.
The worms crawl in, the worms crawl out,
The worms play pinochle on your snout.
They eat your eyes, they eat your nose,
They eat the jelly between your toes.
A big green worm with rolling eyes,
Crawls in your stomach and out your eyes.
Your stomach turns a slimy green,
And pus pours out like whipping cream.
You spread it out on a slice of bread,
And that's what you eat when you are dead.
Well, maybe not quite like that; few worms
can play pinochle
poker, maybe; pinochle, never. Still,
some worms, particularly the fireworms, are scavengers
on carrion. Others however are predatory and still others
are detritivores, specialized to eat particulate organic material
of various origins.
Before describing the worms themselves,
I would like to discuss the role they play in the "natural
history" of a reef aquarium. Most of these animals live
within various components of the substrate, either the unconsolidated
substrate such as sand or crushed coral, or the rocks. If
they live in the rocks, they often live in holes or burrows
generally excavated by some other organisms, although a few
worms may be capable of excavating their own burrows. Those
worms that live in the sediments may burrow through the sediments
leaving no trace. Alternatively, they may exist in tubes or
burrows that may be either permanent or quite temporary.
The vast majority of polychaete worms are
tube-dwellers, living in some sort of burrow, and often that
burrow is considerably longer than the worm itself. Generally,
these tubes are at least stabilized by a mucous lining secreted
by the worm. Such a lining is smooth and non-abrasive and
allows the worm to move freely within the tube. Many tubes
are strengthened even more fully by the presence of embedded
sand grains or other particulate material. In some cases,
the sand grains are cemented together into hard structures,
and masses of these tubes may even form reefs. Sabellarid
worm reefs in the Northeastern Pacific as well as in some
tropical areas may be several hundred feet long, and over
one hundred feet in height. The "ultimate" in "designer"
tubes are secreted by some species of feather duster worms,
in the group known as the Family Serpulidae. Serpulids secrete
calcareous tubes that are typically white and quite rugged.
In many cases, knowing the type of tube the worm secretes
can be of assistance in its identification.
Most of these kinds of worms in aquaria
are quite small, generally less than an inch in length, and
their normal aquarium habitat is more like a natural habitat
than perhaps any other reef aquarium biological component.
Aquarists typically pay these small worms no heed, and they
largely exist independently of the aquarists' efforts to manage
their tanks. The sediments or rock rubble habitats have their
own microhabitats, and food webs, that mimic the natural world
The small polychaetes that live in the
substrate form a diverse group, one that is probably different
in detail in each aquarium, but also one that has general
similarities in each system. These worms act to break down,
utilize, and mobilize organic materials. In doing so, they
move excess chemical energy and biological nutrients through
the system, eventually allowing for the export of these excess
materials. The food, or energy and materials, that they eat
goes to make more worms and, in the process, some of the material
is released as waste material, gases, or soluble nutrients
which may be either exported from the system or recycled even
All feeding types are found in this group
of worms; there are predators, herbivores, and omnivores,
as well as animals specialized to eat detritus and sediments.
In natural marine ecosystems, any potential food item has
several specific types of worms specialized to eat it. Many
of these worms have found their way into aquaria, so the array
of small worms that may be found in our systems is quite large.
I will try to deal with some of the more common ones.
I have grouped the types of worms into
functionally similar groupings that you may use to identify
them. I will briefly discuss each worm type, telling a bit
about them. More detailed information may be found by either
searching for web sites or by going to a library and using
print references. Although there are some larger species in
each of these groups, with the exception of the feather-duster
worms, most of the animals likely to be encountered will be
tiny. You will need a good magnifying glass, hand lens, or
microscope to be able to examine them in enough detail to
The Feather Dusters
Permanent tube-dwelling worms are exemplified
by the feather dusters, one group of polychaete or bristle
worms welcomed by most aquarists. The feather duster worms
are the only worms discussed in this month's column that are
likely to be intentionally added to a reef aquarium. These
worms construct a permanent burrow that they will never willingly
leave, albeit they may bail out if environmental conditions
get quite bad. As these worms never leave their burrow, they
don't really have much in the way of locomotory capabilities.
Once they start to secrete their tube, their options for movement
are decidedly limited. In effect, they can move toward the
opening of the tube or they can move away from it. Generally,
the tubes are open only at one end. The worm's head faces
toward the open end. As the worm isn't really ever going to
go anywhere, it makes no sense for it to have a lot of purely
sensory tentacles and structures originating from the head.
Likewise, if the worm is removed from the tube, the parapodia
or appendages down the side of the body will be seen to be
quite reduced. The worm can move up and down in the tube efficiently
and, in some cases, very rapidly, but that is really all that
it can do.
These worms are unable to go out and hunt
for food. But, they really don't have to go out for dinner
since it comes to them. One of the characteristics of most
shallow water marine environments is the present of a great
amount of small particulate organic material in the water.
Most of this stuff is edible. In fact, some of it is quite
nutritious and these worms are all well adapted to capture
it. The heads on representatives of all of these families
have been modified as suspension-feeding organs. These modifications
vary in detail amongst the four families constituting this
assemblage of worms, but in most of them, there is an array
of tentacles that extend from the head out into the water.
In many of these worms, the tentacles are branched, with smaller
sub-branches being found extending from the main tentacle.
These branches are arranged in a "pinnate" manner;
in other words, with each of the smaller branches being found
opposite another small branch on the other side of the main
tentacle axis. This branching pattern gives the tentacles
the appearance of a bird's feather, and the whole array of
feeding tentacles can look like a miniature version of a feather
duster. This appearance has given the entire group the name
of "Feather-Duster Worms".
1. Spirorbis on a rock. The small, coiled
white shells are characteristic of this type of worm.
Feather-duster worms are not all alike,
yet there are sufficient similarities for most taxonomic authorities
to put them in the same general group. They are all robust
worms, rather broad for their length. Inside the tube the
body is regionated. There is a head region, defined by the
feeding tentacles called "radioles." Below the head
is a region called the "thorax." The major function
of this region appears to be that of providing locomotion
up and down in the tube. Although the body appendages are
reduced from what is seen in free-living worms, they still
bear large and evident bristles, which are mostly modified
into rows of small gripping hooks.
As far as aquarists are concerned, the
worms differ primarily in the construction of their tubes
and their sizes. The distinguishing characteristics of feather-duster
worms, by family, are:
Family Spirorbidae: small calcareous
tubes, tube arranged in spiral on aquarium rocks or wall;
the coiled tube is less than one fourth of inch across.
They are common hitchhikers into marine aquaria. The most
common genus found in reef aquaria is likely Spirorbis.
They reproduce well in aquaria and sometimes become very
Family Serpulidae: commonly known as
"hard-tube" or "calcareous" tube feather-duster
worms, these worms have calcareous tubes. The tubes are
not in a spiral pattern, but elongated and linear. These
may be quite large worms with the tubes being up to about
an inch in diameter and over a foot long. Smaller individuals,
however, are much more common. Some serpulids, such as
the "Christmas Tree Worms," burrow in living
coral heads. Smaller worms with exposed tubes are common
on reef rubble and on loose rocks. Serpulids often have
a hard plug or operculum to fit into the ends of the tubes.
Some serpulids, such as the Christmas-tree worms, Spirobranchus
gigantea, and the large hard-tubed, feather dusters
in the genus Bispira, are quite attractive and
are often purchased by reef aquarists.
Family Sabellidae: worms in this family
are the "true" feather duster worms. They secrete
a proteinaceous tube that has been called "parchment-like"
in consistency. While most of the sabellids are small,
about the diameter of a thick pencil lead, some of them
do get quite large; feather duster worms in excess of
two feet long with a dense tentacle crown four or more
inches in diameter are known from some temperate regions.
Larger feather dusters such as Sabellastarte magnifica
are commonly sold for the hobby, but smaller species also
appear frequently in with some live rock.
The Family Sabellaridae: these worms
construct their tubes out of cemented sand grains. Even
though this sounds like an impermanent type of structure,
in practice, these are the most rugged of all worm tubes.
These worms are gregarious and preferentially settle and
metamorphose out of the plankton on to tubes of their
same species. These can result in huge reefs with an outer
husk of living worms on their outer surfaces. Sabellarids
are not commonly found in reef aquaria, but occasionally
are imported as hitchhikers on live rock.
2. Apomatus, a temperate serpulid worm. Note
the calcareous tubes, including the fractured tube to
the upper left. The operculum, or plug for the tube
is the spherical object above the crown of feeding tentacles.
The tube to the upper right is from a smaller species
3. Smalcina tribranciata, a small serpulid
that is gregarious and forms masses of intertwined,
twisted tubes. These individual tubes are about 1/50th
of an inch across; the entire clump of worms pictured
here is about a third of an inch long.
4. Spirobranchus gigantea in a Porites
colony. The white scars are due to parrotfish bites.
This serpulid worm has a calcareous tube that extends
into the coral head. The operculum that plugs the tube
is the funnel-shaped object at the bottom of each feeding
5. A common small sabellid, possibly an individual
in a species of Sabella, photographed through
the wall of a reef tank. Note the non-calcareous nature
of the tube, with the worm visible inside it. The dark
spots on the tentacles are eyespots and allow the worm
to rapidly withdraw should the illumination rapidly
change, such as when a fish approaches. The tentacle
crown is about half an inch across.
6. Eudistylia vancouverense. This temperate
sabellid has a tentacle crown about six inches across,
and the tubes may extend over three feet out of the
sediments, and several feet into them. These worms form
patch reefs that persist for years. The worm tubes may
become covered with barnacles and mussels.
7. Sabellaria cementarium, a feather duster
worm with a tube formed of sand grains cemented together.
The tentacle crowns are about half an inch across.
8. A portion of a reef formed by Sabellaria cementarium,
the species illustrated in Figure 7. The various worms
and some bryozoan colonies are indicated. This reef
was over 300 feet long, 100 feet wide and extended in
depth from 25 feet to about 125 feet.
Worms With Two Tentacles
There are a number of families of tube-dwelling
worms that feed by extending two tentacles, often called palps,
from their tube out into the water. They feed on small particulate
material, and probably also absorb some dissolved organic
matter. Representatives of only two of these families are
likely to be found commonly in aquaria, however; these families
are the Spionidae and the Chaetopteridae.
9. A chaetopterid worm feeding by extending its
two tentacles from its tube. Spionid worms would look
much the same and could not be distinguished without
removing the worm from the tube.
Although much more common than chaetopterids
on real reefs, spionids are somewhat rare in reef tanks. They
may make an appearance by extending their paired tentacles
from a small hole in a piece of reef rock or perhaps a gorgonian
or snail shell. They often extend their burrows into the non-living
parts of corals and other animals with a calcareous shell.
Many spionids are naturally found in sediments, but these
particular worms do not seem to be particularly common in
reef tanks. Without microscopic identification, it is hard
to definitively identify spionids, but they may be distinguished
from the following group by examining the worm's body. Spionids
typically have a head, but lack other body regions; the front,
middle, and back parts of the worms tend to look alike.
The similarity of the body regions is not
the case with the chaetopterids, and at least one member of
this family may be very abundant in reef tanks. This abundant
worm is placed in the genus Phyllochaetopterus. Phyllochaetopterus
individuals build a tube out of "hardened" mucus
in which they cement sand grains. These tubes can be up to
an inch or so in length and are about the diameter of a thin
piece of pencil lead. They will be oriented vertically in
the sediments or occasionally found filling pre-existing holes
in rocks. The worms themselves are quite small, less than
a quarter inch long; in fact, in most cases less than a tenth
of an inch. Consequently, their typical tube provides them
with quite a spacious home. The tentacles are often five to
ten times the length of the rest of the worm, and when examined
with a hand lens or good magnifying glass, the various regions
of the worm may be seen to have distinctly different appearances.
Phyllochaetopterus is generally
a benign member of the detritivore group found in reef tanks
and they are pretty good scavengers; any particulate material
that strikes their tentacles is pulled into the tube and eaten.
However, they are gregarious and reproduce well in reef tanks.
These two properties may, in time, cause some problems. The
worms can form quite large mats with literally hundreds to
thousands of tubes all cemented together. These mats quite
efficiently exclude other worms from the area, and can seal
off the sand bed surface. This, in turn, can cause the emigration
of other animals out from under such a patch, which can result
in the cementation of sediments under the patch and the failure
of the sand bed biological filtration under the patch of worms.
Such worm masses need to be periodically broken up or removed
from the system, otherwise they may cause the complete failure
of a deep sand bed. The reproduction and subsequent patch
growth can occur with surprising speed. In a 60 gallon hex
tank I once had, I introduced some of these worms and, within
about three months, they had literally paved the sand bed
surface with their tubes. I attempted to remove them all,
and it was not an easy task.
10. Phyllochaetopterus sp. Left: Animal
in the tube with its tentacles extended. Right:
Animal removed from the tube. Note the small regionated
body and large tentacles.
Worms Having Many Tentacles
Several kinds of worms with more than two
tentacles are common on natural reefs, but only two types
of these occur frequently in marine reef aquaria. These are
the worms in the Families Terebellidae and Cirratulidae, represented
in aquaria by spaghetti and hair worms, respectively. These
two types of worms are easy to distinguish; the spaghetti
worms live in a well formed, permanent tube and while they
may move in the tube, those tubes are typically fixed in position
and immobile. The hair worms are found living in the sediments,
or occasionally on the rocks, and while never especially speedy,
they are capable of moving from place to place. I have written
a detailed discussion about these types of worms and interested
readers should go to that column
for more information.
There have been representatives from quite
a number of more actively mobile worms found in aquaria, but
only those from two families seem to become either very common
or appear to be distributed widely. Representatives of these
two groups, the Family Syllidae and the Family Dorvilleidae,
have been found in a number of aquaria from around the world.
They are not easy for the average aquarist either to identify
or distinguish between. In fact, even for seasoned polychaetologists,
the syllids are difficult to work with, and identification
is difficult; there are a vast number of species and their
biological attributes are very poorly known. Dorvilleids are
also poorly known biologically, however, they are fewer in
number and less diverse than are the syllids.
Syllid polychaetes have three antennae.
One antenna is located on the mid-line at the top of the head,
the other two are each located some distance laterally to
the center one. These worms have a strong muscular proventriculus,
or gizzard; presumably it is used to mash and grind food.
The proventriculus is a good character to use in identifying
an unknown worm as a syllid as they all have it. The proventriculus
is quite evident as a dark structure found around the front
part of the gut when light is shined through the body. There
may, or may not, be slender tentacles arising from the parapodia
on each side of the body. If there are such tentacles, they
often will have the appearance of a string of beads. Much
of the taxonomy of the syllids concerns the shapes and distributions
of the various types of bristles. As these shapes may only
be seen clearly with magnifications of 1000x or more, this
level of identification is well out of our league. Nonetheless,
if you have a small slender worm with an evident gizzard,
is likely a syllid. If it has beaded tentacles you may be
sure of your identification, as such tentacles are not likely
to be found on any other polychaetes. Syllids are generally
considered to be predatory, but many species symbiotically
live with other animals, such as sponges and soft corals.
Whether or not these symbioses are commensalistic, mutualistic,
or parasitic is unclear. Free-living syllids are generally
regarded as being predatory, mostly on other worms.
11. A juvenile syllid collected from my aquarium.
Note the tiny antenna in the middle at the front end
(on the right). The gizzard and the beaded tentacles
are labeled. The worm was about 1/25th of an inch long.
Dorvilleid polychaetes are related to the
big eunicid worms discussed last month, but instead of five
antennae they have only four. As with the rest of the eunicids,
dorvilleids have jaws. They are typically short-bodied worms
with a blunt front end, and the appearance of a rounded front
end with four small antennae arising from it is quite characteristic
of this family and may be regarded as distinctive. However,
these are quite small worms, only a few millimeters long,
and this small size makes the characters difficult to discern.
If you can shine a light through such a small worm and see
the small black jaws internally, you can be reasonably sure
you are dealing with a dorvilleid. These animals have been
characterized as predatory, but some aquarium forms have been
seen to use their jaws to cut off pieces of algae.
12. A dorvilleid worm collected from my aquarium.
Note the rounded "nose," black jaws, four
antennae (one on the right side is obscured) and the
paired eyes. This animal was about one tenth of an inch
There are many other types of bristle worms
found in marine aquaria, and I am sure the number of reported
types will increase in the future as people start to use less
toxic water mixes, and as shipping of live rock and live sand
gets less traumatic for the animals in them. In this series
of columns, I have given both the characteristics for identification,
and some descriptions of the common polychaetes found in reef
aquaria. Almost all of them are either beneficial or, at least,
harmless, and should not be looked upon with dread and foreboding
by any aquarist. They are supremely well-adapted for their
way of life; that is as a crawling animal able to exploit
small spaces between and among rocks.