The May column of 'Fish Tales' will present
the often-overlooked fish of the family Siganidae, affectionately
called Rabbitfish throughout the ornamental marine fish trade,
unless you are Australian, which in that case you probably
prefer the name Spinefoot. Most hobbyists tend to look first
towards surgeonfish for a larger herbivore, and in doing so,
completely miss the best fish herbivore the hobby has to offer.
Usually hobbyists will not 'discover' Rabbitfish until after
many years of enamored by surgeonfish. Once discovered, however,
they quickly learn that rabbitfish are a hardier choice, display
more personality, and will vigorously consume certain algae
that surgeonfish would not even consider. The end result is
usually a hobbyist wondering why they didn't look into Rabbitfish
sooner.
Siganus (Lo) vulpinus decided to stop and smile for
the camera.
Notice the lack of a spot on the rear of the body. Photo courtesy
of Greg Rothschild of Mother
Nature's Creations.
Meet the Family
Today, twenty-seven described species and
two sub-species, all of which can be located in one genus,
Siganus, represent the fish family called Siganidae.
However, two sub-genera are in use: Siganus and Lo.
The primarily distinguishing feature is the extended snout
of Lo. Five species possess this feature, with the
remaining twenty-two species being found in Siganus
(Woodland, 1990). It wasn't always this simple, however.
§magnificus |
§niger |
§vulpinus |
§unimaculatus |
§uspi |
§argenteus |
§canaliculatus |
§corallinus |
§doliatus |
§fuscescens |
§guttatus |
§javus |
§labyrinthodes |
§lineatus |
§luridus |
§puellus |
§puelloides |
§punctatissimus |
§punctatus |
§randalli |
§rivulatus |
§stellatus
|
§sutor |
§spinus |
§trispilos |
§vermiculatus |
§virgatus |
|
Woodland, 1990
|
A few notes regarding the taxonomy
used above:
I have used Woodland (1990) as the reference
for taxonomy. However, it should be noted that Kuiter and
Debelius have recently published a book on Acanthuroidei entitled:
Surgeonfishes, Rabbitfishes and Their Relatives: A Comprehensive
Guide to Acanthuroidei (Marine Fish Families S.). In this
book Kuiter and Debelius raised the subspecies to species
designation, and also named a few additional species. In the
book they choose to not include any notes on the new species,
only photographs. Kuiter and Debelius believe if a color variation
is noted to a scuba diver, it is worthy of a species designation.
Woodland (pers. comm.) isn't so willing to hand out species
designation - only after extensive gene-flow research does
he hand out designation.
Additionally, Woodland is also ready to
name one additional species that closely resembles S. sutor.
Although confirmed, it still remains unnamed and is not described.
It seems all that is needed to officially name this species
is color photographs.
Lastly, Kuiter and Debelius recognized
two additional species above the already described and drab
colored S. canaliculatus and S. fuscescens.
Genetic screening by Woodland has revealed at least one of
the species is in fact a newly described species. At this
time, the second recognized species by Kuiter and Debelius
is not recognized, as more genetic research will be required.
However, Woodland is hopeful that further genetic testing
of the drab colored species may reveal another two or three
more species. So, although Siganidae currently stands at twenty-seven
species, it could conceivably reach thirty-five species in
a couple of years.
Siganus species are all remarkably
similar to each other in most of the features that fish taxonomists
use to differentiate between species. All species possess
thirteen dorsal fin spines, and seven anal fin spines. The
genus Siganus is also unique among marine fish having
two pectoral spines which are separated by three soft rays.
These twenty-four spines, plus the one procumbent spine in
front of the first dorsal spine, which is part of the proximal
pterygiophore (laymen version: the cartilage on the outer
end of which sits the median spine) and can be completely
embedded or sometimes protrude from a small groove, collectively
make up the main defense for this fish - the spines are poisonous
(more on this later) (Woodland, 1990). The teeth are also
remarkably similar to each other. The number of teeth, and
the overall shape, are classified as "identical."
Within a single row of both the top and the bottom jaw lie
very compressed, incisiform shaped teeth. The teeth also overlap,
and are individually spade-like and pointed.
Gill-raker and scale counts are another
usual method of classification. However, gill-raker counts
and scale counts, not only vary greatly among species (which
is generally good for classification), but also greatly vary
within the same species (which is bad). This irregular variation
makes gill-raker and scale counts useless for classification.
Siganus (S.) doliatus can make a stunning display fish
in the home aquarium.
Photo courtesy of Greg Rothschild of Mother
Nature's Creations.
A juvenile Siganus (S.) virgatus. The adults will have
the blue spots
extend through the yellow, except on the tail. Photo courtesy
of Greg Rothschild of Mother
Nature's Creations.
Ironic in a sense, if you think about it,
these fish are so remarkably identical in some aspects, and
so vastly different within-species in other aspects, that
classification has become troublesome. Despite these difficulties,
taxonomists still must classify these fish. Luckily, most
rabbitfish vary in coloration, making most of the species
easily identifiable. However, some species, particularly those
of the sub-genus Lo, are particularly difficult to
identify due to similar coloration. Toss in the amazing ability
to regulate pattern and color change seemingly at will (more
on this later), and it is understood why some ichthyologists
as well as hobbyists can have a tough time getting a correct
identification.
An adult Siganus (S.) corallinus is seen here. Juveniles
can be entirely
yellow and lacking the blue spots from the thorax through
the tail. Seen
here in a darker color pattern. Photo by Henry C. Schultz
III.
Siganus (S.) corallinus seen here in
a lighter color shade.
Photo by Henry C. Schultz III.
Siganus (S.) puellus is seen here awaiting purchase
at a local fish store.
Adults may feed upon sponge in the reef aquarium.
Photo courtesy of Henry C. Schultz III.
The end result was the same fish from different
locales receiving different names. Even the genus name couldn't
be agreed upon. In 1776 (Linnaeus) the original published
description lead to the given genus name Teuthis. Unfortunately,
Linnaeus decided to apply this name to two species, T.
hepatus (now Paracanthurus hepatus) and T. javus
(now Siganus javus). Subsequent years of confusion
followed with Houttuyn (1782) defining Centrogaster and Schneider
(1801) defining Amphacanthus. Finally, Cuvier (1829)
came along and determined all the previous generic names were
synonyms and gave name precedence to Siganus. After
nearly a century of confusion within the International Commission
on Zoological Nomenclature (ICZN), Nielsen and Klausewitz
(1968) applied to the ICZN to have Siganus recognized
as a valid generic name. You may wonder where Siganus originated.
Well, one year before Linnaeus erroneously named two separate
fish Teuthis, Forsskal (1775) described the genus Siganus
and two species (S. rivulatus and S. stellatus).
Although Forsskal did not define Siganus, he did describe
the two unique characteristics unique to all Siganids - the
procumbent spine before the first dorsal spike and the outer
and inner spines of the pelvic fins. Unfortunately, Forsskal
died of malaria during an expedition of Arabia before he could
publish his work. Carsten Neibuhr was the only survivor of
the six-man expedition, and it was he who edited and published
Forsskal's work (Klausewitz and Nielsen, 1965).
In 1906, Seale named the newly erected
genus, Lo. His basis for this genus hinged strictly
upon how tubulate the snout of the fish is. However, subsequent
revisions by Fowler and Bean (1929), de Beaufort and Chapman
(1951), Gawel and Woodland (1974), and Woodland (1990) regarded
Lo as sub-generic status, with the second sub-genera
Siganus acting as a repository for those fish not fitting
into Lo.
Siganus (S.) stellatus stellatus is the Red Sea
color variation of Siganus (S.) stellatus. The
more common Siganus (S.) stellatus laqueus is
minus the yellow found on the tail, pectoral fins, and
at the posterior of the dorsal fin just above the caudle
pundcle. Instead, its tail is margined by white, and
otherwise is identical to Siganus (S.) stellatus
stellatus. The owner of this fish noted it cleared
his aquarium of hair, turf, and bryopsis algae.
Photo courtesy of Dwayne Sapp.
|
A correctly identified Siganus (S.) punctatus is seen
here. In some books or
online websites this fish may be listed as Siganus (S.)
guttatus. A Siganus
(S.) guttatus will have a very apparent yellow circle
directly in front of
the caudle peduncle. Photo courtesy of Henry C. Schultz III.
Siganus (S.) fuscescens is the most studied Siganid
due primarily to its use as an aquacultured food item.
It is a finicky eater, eating only 11 species of the
101 that it was offered. Filementous algae was the bulk
of its diet, and even then it prefered the fresh, new
growths. Photo by Henry C. Schultz III.
|
All the while this was going on, additional
disagreements on the suborder prevailed. It was generally
accepted that Zanclidae (Moorish Idol), Acanthuridae (Surgeonfish),
and Siganidae were all related. However, Starks (1907) set
out to prove it. His final decision only added to the confusion:
he was undecided. Berg (1940) chose a separate suborder, Siganoidae.
Later, Gosline (1968) argued that all three aforementioned
families belonged in the single suborder Acanthuroidei. Later,
on the basis of larval morphology, Leis and Richards (1984)
concluded in agreement with Gosline; however, they also added
a fourth family to the suborder, Luvaridae. Finally, extensive
research on the osteology and larval morphology of these families
by Tyler et al. (1989) revealed that Leis and Richards were
correct. Additionally, it showed that Siganidae was the oldest
of the four families, as was it more specialized in aspects
related to their anatomy than their cousins.
In the Wild
Siganidae can be found throughout the tropical
and subtropical Indo-Pacific. The family might be widespread
in the Indo-Pacific, but some species tend to remain fairly
geographically limited, while others are widespread. Hawaii
and Easter Island somehow got snubbed; there are no Siganidae
hailing from these locales (Woodland, 1990). Siganus argenteus
has the widest distribution. At one time its longitudinal
distribution was as great as the family's. Note I said "at
one time." The Red Sea natives S. luridus and
S. rivulatus invaded the Mediterranean via the Suez Canal
(Ben-Tuvia, 1964), which subsequently widened the longitudinal
range of Siganidae. Those Siganus species with the
widest distribution are those species that relate to coral
reefs. This habitat is plentiful throughout the Indo-Pacific,
and thus results in the wide distribution. Those Siganus
species that are geographically limited are limited due to
their habitat preferences. Species such as S. vermiculatus
relate to mangroves, and as such, distribution is limited
to those areas where mangroves are found.
With the exception of two species, rabbitfish
are primarily found in shallow water, usually less than 15
meters. This shallow depth should be expected from a family
that is almost entirely herbivorous because algae is more
prevalent at shallow depths. A single row of flattened, close-set
teeth is key for rasping at meatier seaweeds. As with most
herbivores, an inefficient stomach is present, and instead
long intestines are employed. The mouth is specially designed
to aid in the removal of algae from in between rock crevices,
or coral branches. The upper jaw is fixed, with only the tip
of the mouth being able to move up or down (Starks, 1907).
In effect, this creates a nibbling action.
Siganus (S.) doliatus is found in 3 to 4 feet of water
as a juvenile,
but moves out to around 10 feet as an adult. Photo by Henry
C. Schultz III.
Mating occurs in synchronization with the
lunar cycle for at least some of the rabbitfish. Siganus
canaliculatus spawns four to seven days after the new
moon in both Guam (Bryan et al., 1975) and Palau (Hasse et
al., 1977), with similar results observed with other rabbitfishes
(Rahman et al., 2001). Research of the schooling rabbitfish
within mariculture facilities (Lam, 1974; Coche et al., 1979)
indicates that the eggs are adhesive, though not demersal,
with hatching occurring within one to three days (Lam, 1974).
After only four weeks of a pelagic lifestyle, the larvae settle
and begin feeding upon filamentous algae. It is interesting
to note S. argenteus, with the largest distribution,
also is the only Siganidae with a "pre-juvenile"
stage, a stage directly in between the juvenile and adult
stage. This pre-juvenile stage is specifically adapted to
the open water lifestyle (Hubbs, 1958; Woodland, 1990). By
one year of age the fish will have grown to six inches or
more, is sexually mature, and feeding upon meatier algae.
Siganus (S.) doliatus is seen here in a local fish
store awaiting sale.
Generally, these fish stick close to thickets of Acropora
species that
are choked with seaweeds. Adult pairs are rarely more than
1m from
each other. Photo by Henry C. Schultz III.
Juvenile Siganids school in large numbers
for safety. As can be expected with herbivores, some rabbitfish
will remain as schooling fish throughout their lifetime. However,
a large number of Siganids also move into pairs as adults.
Coincidently, the schooling Siganids are also an important
human food source for the tropical Indo-Pacific, and also
the Mediterranean. Most islands, and even Kuwait and Israel,
consider the meat from S. vermiculatus a premium.
Social
Behavior of Siganids As Adults:
Schooling
|
Pairs
|
argenteus
|
corallinus
|
canaliculatus
|
doliatus
|
fuscescens
|
magnificus
|
guttatus
|
niger
|
javus
|
puellus
|
labyrinthodes
|
puelloides
|
lineatus
|
punctatissimus
|
luridus
|
punctatus
|
randalli
|
stellatus
|
rivulatus
|
trispilos
|
sutor
|
vulpinus
|
spinus
|
unimaculatus
|
vermiculatus
|
uspi
|
|
virgatus
|
Rabbitfish possess two defensive mechanisms,
though one is arguably more effective at getting their "point"
across. First, all rabbitfish have the ability to camouflage
themselves when in the time of need. Such times would include
when threatened, sleeping, or anytime the fish wishes to blend
into its surroundings. This "fright" color stage
is rather similar throughout the family. It will consist of
six dark and six pale zones of color. The zones will be irregularly
shaped, and descend downward along the body. A brown bar also
passes through the eye with three additional dark bars passing
across the isthmus and thorax. When the "camo" fails
the fish, the poisonous spines will definitely be adequate
defense. The fish delivers the venom via one or more of its
twenty-five spines. The spines, when viewed as a cross-section,
appear shaped as a "Y," with the leg of the "Y"
facing anteriorly. The venom is stored in glands located in
the distal third of the "Y" (Halstead and Courville,
1970). The spines are not hollow, and there are no special
venom storage sacs. The venom enters the victim once the spine
is traumatized by the puncture (Woodland, 1990).
The infliction can most likely be compared
to a Bee or Wasp sting. Initial pain is intense, usually persisting
for several hours. Swelling and soreness may remain for several
days. In the case of puncture wounds from several spines,
swelling of the lymph nodes has been indicated. Nonetheless,
it is probably prudent to seek immediate medical attention
if you happen to get stung by your pet rabbitfish. For those
curious, incidents of Ciguatera poisoning is rare, though
not unheard of in Siganids. For those unfamiliar, Ciguatera
poisoning is usually associated with bottom-dwelling shore
reef fish; it the most common fish-borne seafood intoxication.
These fish feed on toxic dinoflagellates and the causative
agent, ciguatoxin, becomes concentrated in the meat of these
fish. Humans eat the meat, and the ensuing sickness is called
Ciguatera poisoning. Severe reactions can lead to seizures
and respiratory paralysis (Raiklin-Eisenkraft and Bentur,
2002).
In the Home Aquarium
As a whole, rabbitfish are relatively hardy
once settled into a home aquarium. A few general requirements
need to be met in order to ensure the well being of the fish.
First and foremost are obviously the water parameters of the
aquarium. Rabbitfish do well in various water conditions,
thanks to their large natural area of distribution. Rabbitfish
have successfully adapted to the higher salinities of the
Red Sea, as well as the lower salinities of the mangrove habitat.
One species is even noted as being found in brackish water.
Temperature range distributions are variable as well, but
are limited to the warmer temperatures associated with reefs
due to the shallow water they inhabit.
Food is another obvious area of concern
for the aquarist. The relatively inefficient stomach of rabbitfish
causes a need for a relatively large quantity of food. For
most rabbitfish, pretty much all of them encountered in the
hobby, this means algae, and a lot of it. Typically, rabbitfish
will graze nearly the entire afternoon. This can be a blessing
and also a curse, depending on your aquarium. Hobbyists with
problematic algae issues might be wise to invest in a rabbitfish.
Chances are favorable that your newly acquired rabbitfish
will eradicate your problem algae. However, aquariums without
excessive algae growth will require large amounts of additional
foods to be added. Any foods geared towards marine fish herbivores
will be sufficient, though it is recommended that you maintain
a large selection and diversity for these fish. Dried algae,
also known as nori, should be the staple of the diet, with
pellets, flake, or even frozen/thawed foods rounding out the
rest of the menu. In aquariums void of naturally growing algae,
it is essential to have nori available for grazing throughout
the daylight photoperiod. Selecting what type of rabbitfish
will depend on your problematic algae: filamentous algae will
require a juvenile rabbitfish while Caulerpa species
and other tougher, meatier algae will require adults. Unfortunately,
experience has taught me that no two rabbitfish species or
individuals will always eat the same algae. Despite their
rather large appetite, they can, on occasion, become "picky"
or "choosy" eaters. If your rabbitfish isn't eating
your problematic algae, it might be worth a shot to trade-in
the fish for another rabbitfish, even if it is the same species.
It should also be noted that rabbitfish are rather messy fish.
It should be well understood that as fast as the food enters
the fish, it also exits. Pack it in and push it out, sort
of speaking. For this reason the aquarium's filtration system
should be designed taking this into account.
Another concern prior to the purchase of
a rabbitfish will obviously be its potential tank mates. It
can be said that as a whole, rabbitfish are oblivious to fellow
tank mates. Obviously, being well armed with venomous spines
goes a long way in preventing harassment from other inhabitants.
However, some fish are still annoying, and will try to pester
the rabbitfish. Angelfish, surgeonfish, and butterfly fish
are the three most common tankmates that will tend to annoy
the rabbitfish. On most occasions, however, the rabbitfish
will have no problem asserting itself, and gaining a favorable
position amongst the hierarchy of your aquarium. When co-existing
amongst other rabbitfish, however, this can get tricky. In
most cases, any of the rabbitfishes noted above as schooling
adults, should not be mixed in home aquariums. However, those
rabbitfishes noted as pairing up as adults can do quite well
as paired adults in a home aquarium. For best results, individuals
should be of differing sizes, and added at the same time,
or the smaller individual added first.
Mobile invertebrates, such as shrimps and
crabs, are generally not bothered by the rabbitfish. Corals,
however, are another story. A hungry, or even curious adult
will give a "taste-test" to any number of corals.
Stony or softy, it really doesn't matter. In these instances
only two things can help solve the problem: additional feeding
or luck. In some instances, rabbitfish will relentlessly eat
prized corals. Obviously, it is best to remove the fish given
this scenario.
Compatibility
chart for Siganids:
Fish
|
Will Co-Exist
|
May Co-Exist
|
Will Not Co-Exist
|
Notes
|
Angels, Dwarf
|
X
|
|
|
Should be excellent tank mates.
|
Angels, Large
|
X
|
|
|
Should be excellent tank mates.
|
Anthias
|
X
|
|
|
Should be excellent tank mates.
|
Assessors
|
|
X
|
|
The rabbitfish may be too aggressive of a swimmer for
an Assessor species to feel comfortable.
|
Basses
|
X
|
|
|
Will likely pester until death ensues.
|
Batfish
|
X
|
|
|
Should be excellent tank mates.
|
Blennies
|
X
|
|
|
Should be excellent tank mates.
|
Boxfishes
|
X
|
|
|
Should be excellent tank mates.
|
Butterflies
|
X
|
|
|
Should be excellent tank mates.
|
Cardinals
|
X
|
|
|
Should be excellent tank mates.
|
Catfish
|
X
|
|
|
Should be excellent tank mates.
|
Comet
|
|
X
|
|
The rabbitfish may be too aggressive of a swimmer for
a Comet to feel comfortable.
|
Cowfish
|
X
|
|
|
Should be excellent tank mates.
|
Damsels
|
X
|
|
|
Should be excellent tank mates.
|
Dottybacks
|
X
|
|
|
Should be excellent tank mates.
|
Dragonets
|
X
|
|
|
Should be excellent tank mates.
|
Drums
|
X
|
|
|
Should be excellent tank mates.
|
Eels
|
X
|
|
|
Should be excellent tank mates.
|
Filefish
|
X
|
|
|
Should be excellent tank mates.
|
Frogfish
|
|
X
|
|
The rabbitfish may pester the Frogfish by mistaking
its fins as algae.
|
Goatfish
|
X
|
|
|
Should be excellent tank mates.
|
Gobies
|
|
X
|
|
Gobies will remain close to home due to the aggressive
swimming of rabbitfish.
|
Grammas
|
X
|
|
|
Should be excellent tank mates.
|
Groupers
|
X
|
|
|
Should be excellent tank mates.
|
Hamlets
|
X
|
|
|
Should be excellent tank mates.
|
Hawkfish
|
X
|
|
|
Should be excellent tank mates.
|
Jawfish
|
|
X
|
|
Jawfish should be added first, but they may remain
hidden from the presence of the rabbitfish.
|
Lionfish
|
X
|
|
|
Should be excellent tank mates.
|
Parrotfish
|
X
|
|
|
Should be excellent tank mates.
|
Pineapple Fish
|
X
|
|
|
Should be excellent tank mates.
|
Pipefish
|
|
|
X
|
Pipefish are best suited to species aquariums.
|
Puffers
|
X
|
|
|
Should be excellent tank mates.
|
Rabbitfish
|
|
X
|
|
Some rabbitfish may do well in pairs.
|
Sand Perches
|
X
|
|
|
Should be excellent tank mates.
|
Scorpionfish
|
|
X
|
|
The rabbitfish may pester the Scorpionfish by mistaking
its fins as algae.
|
Seahorses
|
|
|
X
|
Seahorses are best suited to species aquariums.
|
Snappers
|
X
|
|
|
Should be excellent tank mates.
|
Soapfishes
|
X
|
|
|
Should be excellent tank mates.
|
Soldierfish
|
X
|
|
|
Should be excellent tank mates.
|
Spinecheeks
|
X
|
|
|
Should be excellent tank mates.
|
Squirrelfish
|
X
|
|
|
Should be excellent tank mates.
|
Surgeonfish
|
X
|
|
|
Should be excellent tank mates.
|
Sweetlips
|
X
|
|
|
Should be excellent tank mates.
|
Tilefish
|
X
|
|
|
Should be excellent tank mates.
|
Toadfish
|
|
X
|
|
The rabbitfish may pester the Toadfish by mistaking
its fins as algae.
|
Triggerfish
|
|
X
|
|
Some triggers require solitary aquariums.
|
Waspfish
|
|
X
|
|
Waspfish usually require slow-feeding tank mates.
|
Wrasses
|
X
|
|
|
Should be excellent tank mates.
|
Note: While many of the fish listed are
good tank mates for Siganids, you should research
each fish individually before adding it to your aquarium.
Some of the fish mentioned are better left in the ocean, or
for advanced aquarists.
The final consideration for their proper
care would have to be aquarium size. This is no small consideration,
as most rabbitfish will reach a rather large size. The overall
large size of the fish, combined with its open water swimming
characteristics, makes this fish reminiscent of surgeonfish
with their special aquarium size requirements. As with Paracanthurus
hepatus, I find it extremely difficult to conjure up the
magical size aquarium required to maintain long-term care
for this fish family. Perhaps the only logical advice would
be to treat this family the same as you would any equally-sized
surgeonfish. For each hobbyist this minimum size will vary.
From my perspective, I hope you err on the side of caution
and provide these fish with ample amounts of room. Young juveniles
may do fine in smaller, four foot long aquariums for a short
while, but remember all Siganids have been found to reach
six to eight inches of length within their first year (Woodland,
1990).
As with all marine fish, purchase them
only after a close inspection of the fins, mouth, and tail.
Ensure there are no tears or frayed fins, and no red spots
or open sores present. Make sure the colors on the fish are
bright. Also, make sure the fish is alert and active. Finally,
ask to see the fish eat.
The drab colored species of Siganus is still going
through genetic research to determine which and how many species
there actually are. This one is possibly Siganus (S.) canaliculatus.
Photo courtesy of Eric Hall.
Meet the Species
Currently, it seems like the vast majority
of rabbitfish sold in the aquarium trade are from the subgenus
Lo. Therefore, I start with the "staple"
of the industry, Siganus (Lo) vulpinus, or more affectionately
known as the "Foxface." As one of the smaller rabbitfish,
not quite reaching 10 inches, the Foxface is known to form
permanent pair bonds once becoming an adult. These pair bonds
have been noted as being remarkably similar in size, with
less than .5cm separating the two paired adults. When chased,
these pairs will swim only a few meters before they turn around
and circle back or display a defensive position. This would
indicate a limited, but defended territory. Their limited
territory and smaller size makes the Foxface a better choice
than some of its larger, more open water cousins.
The same Siganus (Lo) unimaculatus is shown in each
of these photos. Note how drastically different each fish
appears, despite it being the same specimen. Photos by Debi
Coughlin.
A close cousin, and nearly identical in
every way, is Siganus (Lo) unimaculatus. More commonly
known as the "One-Spot Foxface," it only differs
from Siganus (Lo) vulpinus by having, well, one
spot. This spot is usually located on both sides of the fish,
although its size and shape may vary. In some instances the
spot may not exist on one side, which begs the question as
to whether Siganus (Lo) unimaculatus and Siganus
(Lo) vulpinus are actually the same species. Currently,
they are regarded as separate species.
For now, Siganus (Lo) unimaculatus is considered a
separate species.
The large, single spot on each side are the defining character.
Photo
courtesy of Greg Rothschild of Mother
Nature's Creations.
Again, a nearly identical cousin is Siganus
(Lo) uspi. The fact that it is not a common import in
the hobby probably lends to the remarkably clever common name:
Uspi Rabbitfish. The body shape and size is again nearly identical
as the two aforementioned cousins, but this one has dark brown
covering nearly two-thirds of the body. The tail and pectoral
fins remain the common yellow of a Foxface, but everything
else is brown. Like the other fish from the subgenus Lo,
when the alimentary tract was examined various seaweeds were
found to be the main staple of its diet.
A rather newly recorded Lo is Siganus
(Lo) niger. This species is reported only rarely from
the few islands it is known from around Tonga. As the name
indicates, the entire fish is dark brown, except for the pectoral
fins, which are yellow-orange. Unfortunately, this fish is
not likely to be seen within our hobby with any regularity.
The final Lo is Siganus (Lo)
magnificus, or the Magnificent Foxface. Many aquarists
consider this Foxface as the most attractive. Unfortunately,
it is also fairly rare, even from the limited areas of Thailand
and Similan Islands where it is known to inhabit. However,
this species is not necessarily impossible to get, as they
are regularly offered within the trade, for a price sometimes
five or six times that of its more common cousins. It's size
measurements, habits, and biology typically reflects that
of the entire subgenus of Lo.
Although there are twenty-two species in
the subgenus Siganus, only a handful appear in the
hobby with any regularity. Possibly the most sought after
rabbitfish of all is Siganus (Siganus) guttatus. The
leopard-like spots give rise to the common name given to it,
the Orange-Spot Rabbitfish. This is one of the larger rabbits,
reaching nearly sixteen inches in length at maturity. This
rabbitfish is particularly noted to regularly inhabit low-saline
environments. Lavina and Alcala (1974) noted the fish regularly
in 50% seawater, while Herre (1959) noted these fish riding
the tides in and out of fresh water rivers. Nonetheless, they
are also known from the fringing reefs, in full saline seawater.
In controlled studies, 101 species of algae were offered to
juvenile Siganus (Siganus) guttatus. Under laboratory
observation, the fish consumed all but 33 of these species.
A noteworthy point is the algae they didn't eat: all the calcareous
algae offered, and various algae of the Order Phaeophyceae
(kelps or brown algae)(von Westernhagen, 1974). In other words,
this fish might be the hobbyist best weapon against many of
the problem algae that face aquarists. Strangely, while all
the other Siganids are known to be diurnal, this species is
known to be active at night.
Two close cousins of Siganus (Siganus)
guttatus are Siganus (Siganus) corallinus and Siganus
(Siganus) trispilos. These two fish are nearly identical,
with expected maximum lengths around 11 inches, except Siganus
(Siganus) trispilos has three small, dark brown or black
spots across the body. Siganus (Siganus) corallinus
is missing these spots. A significant difference exists, however,
in that Siganus (Siganus) trispilos is strictly related
to feeding in and around that of thick growths of Acropora,
while Siganus (Siganus) corallinus often forms feeding
schools with other Siganids to overtake tide-flooded food
resources. An interesting side note is the structure of its
mouth, which closely resembles that of the subgenus Lo.
The next pack of obvious look-alikes is
Siganus (Siganus) puellus, Siganus (Siganus) doliatus,
Siganus (Siganus) virgatus, and Siganus (Siganus)
lineatus. Siganus (Siganus) puellus and Siganus
(Siganus) doliatus relate strongly to thickets of Acropora,
while Siganus (Siganus) lineatus can be located in
low saline or freshwater rivers (Herre, 1957), and Siganus
(Siganus) virgatus can be located in murky water - perhaps
giving reason to their shinny appearance under water. All
four species concentrate on seaweeds, though Siganus (Siganus)
puellus is known to eat sponges and Siganus (Siganus)
lineatus is known to feed on sponges and meat, such as
bivalve tissue. The size of these individuals varies from
12 inches to 15 inches.
Conclusion
Hopefully this column exposed some readers
to a new herbivore, one they had not previously considered.
The fishes collectively known as "Rabbitfish" oftentimes
make a hardier aquarium edition than those fish they are all
too often passed over for. They are not shy, and often display
a well-appreciated personality. Other times, they are camera
hogs, and simply won't get out of your way. Look out for those
spines!
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