Last month, I discussed some of the characteristics
that are used in the identification of the so-called "bristle,"
or polychaete annelid, worms. This month I will discuss and
illustrate some of the larger worms, those which routinely
reach lengths of an inch or more and which live, or at least
occasionally prowl, on the sediment or rock surfaces. Next
month, I will deal with the greater diversity of smaller worms,
and those worms that live, generally, within the sediments.
In this column, I will describe both the most common and quite
beneficial worms, as well as a couple of the nastier types
of harmful worms found in marine reef aquaria. I had hoped
to have a large number of good, and exceedingly flashy, photos
of each worm to allow to a lot of details and variety for
ease in identification. Unfortunately, I couldn't find a lot
of good wormy photos that show the necessary discriminatory
characteristics. Reefkeepers, it appears, largely do not photograph
the worms in their tanks. I suppose they think that they have
other, more beautiful, animals to spend their time photographing.
In such they are remiss; some of these animals are indeed
The Common Large Worms
Other than the decorative feather-duster
worms, the majority of the larger worms found in reef aquaria
are found within one quite cohesive and well characterized
taxonomic group, the Family Amphinomidae. The primary and,
quite obvious, definitive character for this group are the
regularly spaced tufts of bright white bristles located along
the worms' sides. These tufts are very easily seen, but, more
to the point, they are also detectable by tactile means. The
squishing method of tactile worm examination employed by many
hobbyists has given these animals the apt common name of "fireworms."
Amphinomids are polychaete annelids that,
using the language of the taxonomist, "have a distinct
prostomium and they possess a caruncle, and have one to five
antennae. Jaws are absent, although the pharynx has an eversible
rasplike ventral pad. Notosetae are spinous protective setae,
and the branchiae are in branching tufts (Fauchald, 1977)."
Translated, the above jargon tells a reader that such worms
have a distinct frontal region prior to the mouth (= a distinct
prostomium). The head region extends backward in a sensory
or glandular patch (nobody really knows what it is for) in
the "neck" region (= possess a caruncle). Depending
on the species, they possess one to five tentacles coming
from the front of the head (= have one to five antennae).
They don't have any hard biting or pinching or cutting jaws.
The lower part of the throat region can be pushed out of the
mouth, and on the inside bottom region of the mouth, about
where a tongue would be, it has a roughened area that can
act as a rasp (= pharynx has an eversible rasplike ventral
pad). The uppermost patches of bristles on each side of each
segment are spiny and protective (= notosetae are spinous
and protective), and the gills (= branchiae) are found in
1. Eurythoe complanata, the large fireworm
common in most reef aquaria. The animal pictured here
was about six inches long, and about the diameter of
a human finger. It appeared to be a purplish grey in
the tank, but when properly illuminated the beautiful
iridescence seen here became evident. A. The
front end of the worm, with the head at the bottom.
The labeled structures are explained in the text. B.
The top of the body in the region of the head showing
the caruncle. Differences in the caruncle are important
in distinguishing species. Eurythoe is a very
beneficial scavenger and is distinguished by its large
size, and smooth caruncle. C. The head region
closer to the substrate showing the sensory tentacles
or antennae used to find food.
Fireworms are really common in reef aquaria.
They probably account for ninety or more percent of the worms
seen in reef aquaria. Most fireworms are scavengers in tropical
marine environments, albeit a few of the about 120 species
are predatory, and one or two are parasitic. The fireworms
that are most frequently found in aquaria may be very abundant.
Even a small aquarium may have thousands of them, and they
are beneficial scavengers.. One species, common in nature
but rarely found in aquaria, is of concern to aquarists. This
species, Hermodice carunculata, is predatory on stony
corals and gorgonians. Fortunately, individuals of this species
may be easily distinguished and removed from the system.
Some fireworms often reach quite substantial
sizes and aquarists are sometimes astonished to find that
their tanks may contain worms over 18 inches (60 cm) in length,
and with the diameter of a pencil. Most of these giants are
probably individuals of the common Caribbean species, Eurythoe
complanata, and are exceptionally diligent and beneficial
members of the guild of scavenging animals found in our aquaria.
Large Eurythoe individuals are adept at remaining out
of sight in the interstices and internal cavities of reef
aquarium rock work; it is often only when the tank is being
remodeled or broken down that the big worms are found. These
worms reproduce well in our systems and they are occasionally
seen spawning copious amounts of pink sperm and eggs into
the tank waters in a veritable vermous orgy. These spawning
events produce a lot of gametes which are consumed by corals,
soft corals and other filter feeding animals. Nonetheless,
the odds of some reproductive success appear to be quite good,
and Eurythoe seems to be able to maintain stable populations
in aquaria indefinitely. The reproduction of the smaller fireworms
that are also common in our systems, in the genera Linopherus
or Pareurythoe, is less obvious, but they also can
maintain quite stable and large populations in our systems.
Most of the fireworms found in our tanks are in these latter
two genera, and these animals occupy burrows in the sediments
as well in holes in the rockwork. If not hassled by fish or
crustaceans, they may be seen commonly during the day looking
for food and doing their other wormy activities. These smaller
species may reproduce more frequently by asexual than sexual
means as indicated by the abundance of worms that are regenerating
either front or back ends. As with the small starfish that
are common in some reef aquaria, these worms reproduce asexually
by fission, after which both halves produce the missing component.
2. An individual of a species of Linopherus.
This is one of the common small fireworm scavengers
in our tanks. Many tanks have thousands of these animals
as a major component of the clean up crew. A.
This worm was about an inch long. The white, venom-filled,
protective setae are evident on each side. B.
A close up of the head. Note how the caruncle and the
gills differ from that of Eurythoe in Figure
1, and note the relatively large and evident eyes.
C. These worms asexually reproduce by splitting
in the middle, the rear portion regenerates a head as
shown here. The front portion regenerates a tail end.
Fireworms are great scavengers, and even
the bigger species are occasionally seen prowling around during
the day, particularly after food has been added to the tank.
Unlike most worms, they are well protected against fish predators.
This protection is found in the obvious bright white bristle
tufts. Most polychaetes have bristles made of chitin, a chemical
with properties somewhat akin to cellulose, and the bottom
bristles of fireworms are made of this material. The upper
bristles, however, are made of something quite different,
good old calcium carbonate, which accounts for their white
color. The white color also functions to stand out against
a dark background and acts like a sign telling the potential
predators to stay clear. Such a coloration pattern is called
aposematic or warning coloration and is common in well-defended
animals (such as nudibranchs, skunks, or yellow-jacket wasps)
in all habitats. These calcareous protective bristles have
more than a warning function, however, and are protective
as well as informational. They are barbed, hollow, and filled
with a rather nasty irritating venom. Having been shaped by
aeons of natural selection, they perform their defensive duties
quite well. The bristles penetrate the flesh of any fish that
tries to bite the worm. They fracture in the wound releasing
the venom into the predator's tissues, and the bristles hold
them in the wound increasing the irritation factor. The poison
is not designed to kill anything, but it is designed to severely
irritate the fish. As many fish can learn to avoid unpleasant
stimuli, the bristles function to deter the predator. The
bristles are eventually absorbed by the predator (or the aquarist)
over a period of a couple of days, with no lasting harm, but
leaving the potential predator with a real strong desire not
to do that again. Most reef fishes are quite long-lived
after they have reached maturity, and a deterrent is far more
effective than a lethal toxin in such a situation. The fishes
may learn not to attack the worms (although this will vary
from fish to fish; my mature Premnas female either is a masochist
or has intelligence measured in negative numbers as she continues
to persist in attacking the worms) and such learning is likely
good for years. Learned deterrents, such as this, result in
fewer attacks and reduced damage to the worm than if the fish
were killed and the whole attack process had to be repeated
In contrast to the other large beneficial
fireworms found in our tanks, one species decidedly presents
problems for a reef aquarium. This species, Hermodice carunculata,
is a fireworm species commonly found in the Caribbean, although
other species in the same genus are found throughout the tropics.
It is the only potential "problem" fireworm in aquaria
because it eats stony corals and gorgonians in its natural
habitat, but may also prey on Indo-Pacific soft corals in
the aquarium. As with all fireworms, this species has no jaws
to bite off chunks of food, rather it must lick them to death.
As the worm lacks the jaws to sever the pieces of its prey,
feeding in Hermodice is a prolonged process. When they
feed, Hermodice individuals typically swallow the ends
of a gorgonian or soft coral and then proceed to lick the
flesh off of it, while the ends are still attached to the
colony. Such feeding is a lengthy process; it takes hours.
During this period the worm really isn't going to go anywhere,
it is tethered to its dinner. This species is also an obligate
predator of these prey, although it may scavenge a bit, it
will not, - in fact, it cannot, - eat other prey. If you have
a Hermodice in your tank, you will either eventually
find it on a prey organism munching away or see it crawling
across the substrate. Remove it with a pair of forceps, tweezers,
or tongs, and dispose of it.
3. A predator to avoid; the worm illustrated here
is Hermodice carunculata, the large predatory
fireworm commonly found in the Caribbean. It is very
rarely found in reef aquaria. A. A scanning electron
micrograph of the front end of a Hermodice individual;
(M= the mouth, P= the parapodia, and C= fringe-like
tentacles found on the caruncle). Note that that fringe
is evident as bright red patch in the other images;
also compare with Figure 1, and see that the fringe
is absent on Eurythoe. If all else fails, if
the worm has a bright red spot on the top of the head,
it is likely a Hermodice. B. A large Hermodice
individual approaching a dead crab or crab molt. Even
predators sometimes scavenge. C. An individual
eating the tissue off a gorgonian branch; it has swallowed
the end of a gorgonian branch and will rasp the tissue
off it. Images in B and C are courtesy of James Wiseman.
All other fireworms in our tanks are content
to gum food or dead animals. They do not perceive of live
animals as prey, and in particular, they will not eat or enter
Tridacna as susupected commonly by aquarists. In nature,
as well as in some reef aquaria, fireworms will aggregate
under these large clams. It simply is a good haven for them.
If the clam dies, they may gnaw on the corpse, but they won't
attack and kill it. In fact, as they determine their prey
by odor, they won't even perceive of any healthy animal as
a food source, nor will they attack it.
Other Big Worms
Only two other groups of polychaetes, the
Family Eunicidae, and the Family Lysaretidae contain large
worms that are commonly found in reef aquaria. The first of
these groups, the eunicid worms, is a large diverse group
with over 200 species. The second, the lysaretid worms, is
a small group with only about ten or fifteen described species;
unfortunately, the lysaretid worms are predatory and deadly
to many reef aquarium inhabitants. Even more unfortunately,
they are reasonably common in live rock.
How To Max Out Your Worm Quotient
Eunicid worms are formidably complex animals.
They are described as having an eversible pharynx, meaning
they have an extensible tube that projects outward from the
mouth. This tube is armed with two to five pairs of large
forceps or pincher-type lateral jaws and one pair of additional
jaws that are ventrally situated. This group contains the
largest polychaete worms. There are some reliable reports
of eunicid worms being an inch in diameter and fifty feet
long, although the largest confirmed specimens are
smaller. Specimens in excess of six feet long are common in
nature, and occasionally such giants are found in marine aquaria.
They are also long-lived. I have had one for several years
now; transferring it from tank to tank during remodels and
revisions of my system.
The eunicid worms found in aquaria all
have five antennae, with a large pronounced antennae arising
from the center of the "forehead." Large eunicid
worms from two distinct groups are found in aquaria. Both
enter the tanks hidden in live rock. The most distinctive
of these are worms in the genus Palola. These are rock-inhabiting
worms that reach lengths of three to six feet. They are generally
dark green to blue to black and are largely nocturnal. They
will extend from rocks to feed and appear to be mostly scavengers
or detritivores. However, little is known about their diets
in nature, and if any are found in aquaria, they may well
be able to eat small fish or shrimp. On the other hand, there
is no hard data that they do so. Palola is a genus
whose synchronous spawning is legendary. Prior to such spawning
events, the rear portions of the animals are filled with eggs
and sperm and, when the time is right, they spawn. The spawning
cues appear to be lunar and tidally influenced, but whatever
the trigger, most of the worms in large geographical areas
spawn within a few minutes. The rear portion of the worm separates
from the front portion and swims to the surface where it writhes
around and ruptures. With millions of worms spawning at once,
the sea literally becomes covered in a wriggling mass of large
worm fragments. It is thought that mass spawnings of this
nature occur because although predators will be attracted
to such spawns to eat the worms and their gametes, there will
be so many animals spawning that the predators get sated,
and many of the eggs escape to become fertilized, and undergo
development into juveniles. Palola worms are probably
harmless in most reef tanks, but if one does spawn, it may
produce enough gametes to seriously foul the tank. They are
often found dead or dying in uncured live rock.
Worms in the genus Eunice, sometimes
called "bobbit" worms are, if anything, more impressive
than their Palola cousins. Eunice is a large
genus, with well over 150 species, and it is hard to generalize
about them. As with the Palola, they have five antennae,
including one in the center of the forehead and they all have
jaws, in some cases wicked, scimitar shaped hooks with accessory
spines and hooks. These are not jaws for chewing the prey
or food item, but rather are jaws designed to ensure the food
that, once seized, never gets away. Some of these worms get
very large; the largest I have seen reported from reef tanks
was in excess of 6 feet long, and individuals of Eunice
aphroditois may be much larger. Eunice individuals
tend to live in mucus-lined borrows in rock or sediments and
may have several entrances to their tubes. Two distinct kinds
of worms seem to be represented in this genus. One kind, which
is benign in reef tanks, seems to be mostly scavenging its
food. It lives in a burrow in the sediment, or more rarely,
in a burrow in the rocks. When feeding, one of these worms
will slowly extend from its burrow. They typically have four
to six eyes and are quite capable of detecting motion outside
the aquarium, and across the room. It will slowly search the
surrounding area for food and if bothered by a fish, or its
own shadow, will retract into its burrow with a velocity that
has to be seen to be believed. Contraction back into a burrow
has been clocked in excess of 20 feet per second, and if only
a couple of feet of the worm are visible while it is foraging,
that worm can disappear, quite literally, in the blink of
4. This is "Max," the large Eunice
individual that I have had in my aquaria for about five
years. A. The head, note the characteristic five
head tentacles from the head, and specifically note
the one arising directly from the center of the "fore
head." The worm is about half an inch across. Note
the complete lack of visible setae or bristles; eunicids
do not have the white protective bristles found in fireworms,
and they often keep their other bristles withdrawn.
B. In August of 2002, I had to move Max from
one tank to another, and he broke into three fragments.
His total length was over four feet long. He has recovered
from this and is living in my present tank. He is shorter,
but I anticipate he will grow to his former length.
C. Note the gills and compare them to the ones
on Eurythoe in Figure 1.
All of the large Eunice individuals
that I have heard about in reef aquaria seem to be scavengers.
However, the largest Eunice individuals seen in nature
are impressive predators. Individuals have been reported to
strike upward from the sediment surface, grab a four-inch
long fish swimming above the sediment, pull it under the sediment
and presumably snack on it at its leisure. Such worms are
also reported to be an inch in diameter and about thirty to
fifty feet long, making them a bit larger than most home aquaria
There are also smaller species of Eunice,
and these seem to be reported from time to time in aquaria.
They generally appear to be harmless scavengers, however,
even I, a self-proclaimed vermophile, would consider them
amongst the "usual suspects" if some small fish
such as fire fish or small gobies disappeared without a trace.
Regardless of the size of its individuals,
the major characters for identification for the identification
of eunicid species would be the absence of white tufts of
setae, and the presence of five large and visible antennae
(large relative to the worm, not the aquarist), such antennae
are typically about two to three body diameters in length.
Colors are secondary characters with these animals, but the
Palola worms are often dark colors, while the Eunice
individuals are, typically, shades of brown.
The only other large worm likely to be
found in aquaria is the lysaretid polychaete Oenone fulgida.
These animals are related the Eunicids, and, like them, possess
jaws. They have three small antennae tucked in the groove
between the two segments that make up the head, and a single
dark eyespot may be visible on either side of the head.. Oenone
fulgida has been reported to be circumtropical, and is
quite variable for a single species. These studies date from
the 1920s and it is quite likely that modern research, supplemented
with genetic analyses, would show that what was thought to
be one species eighty years ago is really several different
species. The poorly studied nature of Oenone works
against us, unfortunately, as it is relatively common in aquaria.
Whatever its status, animals that we presently
refer to as Oenone fulgida may be easily recognized.
As with the rest of the eunicid group, these worms lack the
white tufts of setae characteristic of the fireworms. In fact
these lysaretids tend to look relatively smooth, often without
obvious appendages on their sides. This is an illusion, however,
as they do have good appendages off of each side of each segment.
The three antennae on the top of the head are small and often
not visible, so the head looks smooth. In this particular
case, color is a reasonably good characteristic to use in
identification. Oenone individuals are typically orange,
ranging from a dull, purplish orange to a brilliant blaze
orange. They may be large worms, fully-grown adults often
extend out of their burrows for two feet or more, and when
fully extended they may be one quarter to one eighth of an
inch in diameter. They typically live in burrows in rocks,
but also may be found in tufts of algae or inside the water
channels of large sponges. They are quite adept at detecting
movement and will rapidly withdraw into their burrow if they
are startled. Their withdrawal response, however, is not as
rapid as that of Eunice individuals.
Oenone are nocturnal predators on
snails and clams, and perhaps some other animals. They appear
to extend from their burrow, and as they approach their prey
they apparently secrete some mucus that covers the prey. This
mucus may simply smother the prey, or it may contain some
venom or narcotizing agent. After the prey is immobilized
the worm extends a proboscis from the bottom of the head into
the mucus and the jaws grasp the body of the prey. The jaws
may also cut the attachments of the body to any shells, or
alternatively the mucus may contain an agent that chemically
severs the attachment. In any case, the prey's body is ingested.
When the aquarist investigates the scene the next morning,
all that typically remains is an empty snail or clam shell
covered in a blob of mucus. Not many other predatory animals
in marine aquaria typically leave behind such remains, consequently
a dead, empty, shell covered with mucus is considered to be
good evidence of the presence of an Oenone.
5 . This is the front end of a small individual
of Oenone fulgida. Note the basic orange cast
to the worm. This worm was about four inches long and
about a quarter inch wide. A. Note the round
"snout," or prostomium, and the three small
tentacles at the top of the head. This configuration
of snout and tentacles differs from the Eunice
species (see Figure 4) and the fireworms (see Figures
1-3) and it is visible with a magnifying glass or hand
lens. Note the relatively narrow segments as well; these
make the worm appear smooth and lacking segments when
viewed from a distance of about eight or ten inches.
B. This is a lateral view of the head and front
end of a preserved specimen. Note the proboscis is protruded
from the mouth. These worms use the jaws located in
the proboscis to grasp and manipulate food. C.
This is a view of the head from directly above, showing
the characteristic three tentacles. There is a single
dark eye normally visible on each side of the head,
but the eye pigments have faded in the preservative.
Oenone fulgida are not too hard
to remove from a system, but it takes diligence. They most
often live in burrows in rock, and enter aquaria in uncured
rocks, and being nocturnal, the hobbyist has to search for
them in the middle of the night. Using a red flashlight is
best, as they will rapidly withdraw in the beam of a normal
flashlight. They will appear as long worms stretched out and
over the rocks. Once an Oenone individual is presumed
to be living in a tank, the hobbyist must watch it withdraw
in order to see where its burrow is found. After the rock
with the burrow is located, the rock must be removed and the
animal flushed from its burrow using a flood of carbonated
water (soda pop works well). The worm is then discarded, and
the rock replaced in the aquarium.
Few other large worms are found in aquaria,
although they may be quite common on reefs. I have occasionally
seen reports of two other types of large worms found in aquaria.
These are scale worms, and phyllodocid worms. Although unrelated,
these worms have some similarities of appearance. The small
appendages off of either side of a segmented worm's body are
called parapodia, and these often have several fleshy lobes.
In the scale worms, the uppermost of these lobes may have
a secondary lobe on it that grows quite large and lies on
the upper surface of the animal. These large lobes look like
large fish scales, and give the worm their common name. There
are quite a large number of scale worm species, and they belong
to several different, but apparently related, groups of species.
The distinctions between them seem to be manifested in the
amount of the upper part of the worm covered by the scales
and by the pattern of the scale arrangement. Scale worms are
generally quite small and rather "compact" worms,
but some species reach lengths of about a foot or more, and
a few of these larger individuals have been sighted in aquaria.
Scale worms are often found as commensals or symbionts on
echinoderms. Other species seem to be mostly predatory. None
of them seem to persist in aquaria, probably because their
preferred and necessary foods are absent from the aquarium
6 . Scale worms. A. A small free-living scale
worm about an inch long. Note the scales covering the
upper surface. One scale is found between ends of the
yellow lines. Scale worms often appear flattened. B.
A commensal scale worm found living in and on a sea
star. The worm's back end is situated in the sea star's
mouth. The scales are quite evident covering the dorsal
surface. This worm is reported to attack any predators
attacking its sea star, and it has sufficiently large
jaws to, on occasion, drive off the predators.
Phyllodocid worms are also predatory, but
unlike scale worms they are typically long and slender worms.
The upper lobes on their parapodia are enlarged and shaped
like a large simple plant leaf. These parapodial lobes generally
do not extend over the worm's body, but overlap the parapodia
behind it. In addition to these large parapodial lobes, the
heads of these worms are quite distinctive. They typically
have one or two pairs of large and evident eyes. Unlike the
eunicids, phyllodocids do not often show a flight response
and one often sees them out hunting in daylight. It is possible
that they have a noxious taste or some other predator defense,
but that has not been tested. Elsewhere on the head are several
pairs of long tentacles extending forward of the worm and
out laterally on each side of the head. Phyllodocids lack
the "forehead" tentacle characteristic of the eunicids.
They are active predators, often on other worms, and hunt
down, attack and kill their prey. They have been seen infrequently
in reef aquaria, but reports of their presence seem to be
increasing. Some species reach lengths of a couple of feet,
but most are a few inches long. As with the scale worms, they
don't seem to persist in reef aquaria, presumably as such
aquaria cannot support the diversity of prey necessary to
7. Phyllodocid worms are predators; these worms
were photographed while "out on the prowl."
A. This worm was about five inches long, but was only
about a sixteenth of an inch across. The enlarged dorsal
parapodial lobes look like flaps along the side of the
animals and are the identification characteristic of
the animals. B. Another, smaller, phyllodocid worm.
This animal was about one thirty second of an inch across,
but it was still about four inches long. Note the foraminiferan
for a size scale. The large eyes and extended sensory
tentacles characteristic of these predators are also
evident in these images.
Large polychaete worms, as with large animals
of any taxonomic persuasion, require lots of food and large
amounts of suitable habitat space. It is interesting that
reef aquarists have inadvertently built such habitats in their
tanks. The fireworms, in particular, seem quite pre-adapted
for reef aquarium existence, and their populations in reef
aquaria are thriving. The number of these worms in such systems
is quite large, and for the fireworms in particular, their
numbers probably dwarf those of all other species the same
size or larger in reef aquaria. We might, with a great degree
of accuracy, refer to our tanks not as coral reef aquaria,
but rather as tropical reef worm habitats. The success aquarists
have keeping other animals is to a great extent dependent
upon their success at keeping thriving populations of these
Next month, I will conclude this series
on the segmented worms of reef aquaria by discussing the smaller
species that occupy the sediments of our systems.