While some hobbyists
try one Centropyge species after another only to discover
that none of them is truly reef safe, other hobbyists have
already tormented themselves by doing the same and have since
made headway in a new direction and with a new genus of Angelfish.
The beauty of Centropyge species often blinds us to
their potential to harm our corals. More often than not, once
a Centropyge is placed into the aquarium, the hobbyist
soon learns that it is not the exception to the rule. Shortly
thereafter commences the painstaking task of removing the
offending angel. Not long ago I was asked to help remove a
Centropyge ferrugata from a 900-gallon aquarium. After
two hours of fruitless labor I gave up - it wasn't my battle.
Nevertheless, it was just the reminder I needed of how much
of a pain Centropyge angelfish can be shortly before
I begin setting up my next aquarium. I simply do not need
that headache. But I can't be without my Angelfish, so I certainly
will need that "fix" at some point. And that is
why I'll be adding a pair of Genicanthus species to
my next aquarium. Perhaps you will, too, once you finish reading
about the marine fish more commonly called Swallowtail Angelfish.
Genicanthus takeuchii is the largest Swallowtail
and reaches nearly 14 inches of length in the wild.
If you are lucky enough to obtain one of these fish,
the overall tank size as well as its water temperature
are areas of concern. The Spotted Swallowtail happens
to prefer the coolest water of the genus, and aquarium
temperatures as low as 68 to the mid 70s should
be realized prior to their introduction. A male is shown
here. Photo courtesy of John Randall.
|
Meet the Family
Seven genera (possibly
soon to be nine) comprise the Family Pomacanthidae, the marine
angelfish. Centropyge has already been discussed in
a previous Reefkeeping column,
which also included discussion of the genus Paracentropyge.
The five remaining genera will undoubtedly be covered in my
column at some point, but I'm going to stay focused on Genicanthus
this month due to their reef compatibility.
Currently
Accepted Genera of Pomacanthidae:
|
Apolemichthys
|
Genicanthus
|
Centropyge
|
Holacanthus
|
Chaetodonoplus
|
Pomacanthus
|
Pygoplites
|
Soon
to be Accepted Genera of Pomacanthidae
(Pyle, pers. comm.):
|
Arusetta
|
Paracentropyge
|
Jumping into the way-back machine, Swainson (1839) was the
first to describe an angelfish he chose to separate as a new
genus, Genicanthus. In doing so he chose to recognize
the "deeply lunated" caudal fin which "extended
into filaments" as discernibly different from Holacanthus.
However, besides removing G. lamarck from the genus
Holacanthus, he also mistakenly removed H. tricolor.
Perhaps this is why the scientific community largely ignored
his naming of Genicanthus for nearly a century.
Fraser-Brunner (1933) was the next ichthyologist
to pick up on the Genicanthus name, but not until after
three additional species of Genicanthus angels were
mistakenly described as Holacanthus species. Fraser-Brunner
further differentiated Genicanthus from Holacanthus
by the "preorbital notched mesially, its hind margin
free, serrated. Teeth in both jaws short. Scales on operculum
in six to eight rows."
At this time the reader might figure that after two ichthyologists
had formally described a genus, others might have followed
suit, but this wasn't the case. Some authors (Kamohara, 1934,
1961; Herre, 1953; Yasuda and Tominaga, 1970) still chose
to recognize the Genicanthus species as Holacanthus,
and Kamohara (1934) even named Holacanthus semifasciatus,
which was later aligned with Genicanthus. As is regularly
the case, however, there was widespread disagreement. During
the same time period some authors chose to recognize Genicanthus,
namely Fowler (1934), Smith (1955), and Norman (1957) among
others. Genicanthus macclesfieldiensis, now carrying
the species name melanospilos given by Bleeker (1853),
was even named during this period of time by Chan (1965).
All the confusion was laid to rest, however, when Randall
(1975) released his revision of the genus Genicanthus.
At that time there were nine recognized species. More recently,
Pyle added a tenth species, G. takeuchii.
Pomacanthidae
|
·
Genicanthus
|
o
bellus
|
o caudovittatus
|
o
lamarck
|
o
melanospilos
|
o
personatus
|
o
semicinctus
|
o
semifasciatus
|
o
spinus
|
o
takeuchii
|
o
watanabei
|
|
Beyond the deeply lunate (crescent-shaped)
caudal fin, a few other notable characteristics are found
throughout the genus. All species are equipped with small
mouths lined with three or four rows of small setiform (bristle-like)
teeth, often with tips that have three points or cusps. The
teeth are also noted to be considerably shorter than those
of the rest of the members of the Pomacanthidae, obviously
a reflection of their feeding tactics of picking prey out
of the water column versus removing algae from encrusting
rubble. Another trait that also may reflect their feeding
habits are the mucus-secreting esophagial papillae. Michael
(2004) believes these small projections use the mucus they
secrete as protection against the tunicate's defenses which
the fish consume. However, tunicates dont have stinging
cells of any sort and while benthic tunicates may secrete
nasty toxins, the pelagic tunicates mentioned as food for
these fish are defenseless (Ruppert, et al., 2003).
Finally, similar to all members of Pomacanthidae, Swallowtail
angels do have the trademark spine which extends from their
preopercle.
|
The Blackspot angelfish, Genicanthus melanospilos,
earns its common name from the black spot located on
the male's breast. It is barely viewable in the bottom
photo located immediately prior to the pelvic fins.
The attractive looks of both the male and female and
its availability within the hobby makes it perhaps the
most popular species of the genus. Adults may reach
up to seven inches in captivity. Top photo of
the female courtesy of Ken Gosinski (Mustang), bottom
photo of the male courtesy of John Randall.
|
|
In the Wild
Photo
by Serdar Ercan.
|
As might be expected,
species distribution varies. Representatives of the genus
can be found throughout much of the Indo-Pacific region, although
geographically speaking, the species distribution is rather
spotty. Genicanthus personatus is endemic to Hawaiian
waters, while G. spinus has been collected only off
the Pitcairn Islands (though it reportedly has been seen at
other deep water locations). Another species with limited
distribution is G. watanabei which resides only within
the waters of the Pitcairn and Society Islands. Perhaps the
species with the largest distribution is G. lamarck,
which has been collected from Kenya (a single unconfirmed
individual) to Vanuatu and from Japan to the Great Barrier
Reef. All told, four species are represented in the Indo-Malaysian
hotbed of species diversity, two from the Indian Ocean and
another four from the Pacific with southern Pacific having
three species, compared to the lone species from Hawaii. Still
puzzling to ichthyologists is the apparent absence of species
from central Pacific islands.
The diurnal Swallowtail Angelfish prefers steep fore-reef
drop-offs which encompass reefs or rocky bottoms. It is unusual
to find a specimen over a sand or silt bottom or in shallow
water. Generally speaking, Swallowtail angelfish will not
be found shallower than 75 to 90 feet. The majority of species
will be found as deep as 200 feet, but Genicanthus personatus
has been recorded as deep as 400 feet and G. semifasciatus
from 650 feet. At depths allowing for observation of the fish,
the species has been observed congregating as large groups
feeding out away from the reef in the mid-water column far
above the bottom. They are planktivores, consuming copepods,
fish eggs and larvae, and polychaete larvae, although the
majority of their stomach contents was found to consist of
pelagic tunicates (Randall, 1975). They will not resist the
temptation to consume algae, however, when the situation presents
itself. True to the Angelfish roots that reside deep within
the fish, they will occasionally eat the adult polychaete
worm or dine upon sponges. This is not common, however.
|
The Wantanabe Angel, Genicanthus watanabei, is
the smallest of all Swallowtails, not quite reaching
six inches in length. The female is pictured in the
two photos on the left, the male in the right
bottom picture. Left photo courtesy of Larry (Hawkdl2);
bottom photos courtesy of John Randall.
|
|
|
Swallowtails do not form harems, small schools, or even large
schools. They are rather non-territorial to conspecifics,
yet remain within a given territory of their own. The largest
males exert their dominance over smaller males and are kings
of their domain, but do not entirely drive off smaller males.
They will remain nearby, often with an overlapping territory.
The main difference in dominance is in their mating habits.
Larger males have the opportunity to mate more frequently
than smaller males. Females rarely exert aggression nor do
they defend a territory. Instead, they move throughout the
large grouping of Swallowtails.
The courtship and mating rituals among
the sexes have been well documented. These rituals play out
during times of lackluster water movement. When the tides
bring the current, Swallowtails feed. Otherwise, males spend
the better portion of their day enticing females with a number
of different movements or fin gestures. Similar to the behavior
of Centropyge angelfish, Swallowtail males roll onto
their sides or backs in front of females, or position themselves
directly in front of the female and tremble or quiver their
caudal fin. If the male is successful in his initial attempts,
he will begin the first stage of the mating ritual. While
positioned alongside the female, the male's entire body will
vibrate or quiver excitedly. The female will then extend all
of her fins as a sign of encouragement. After a few seconds
of the male nuzzling his head near the rear of the female,
the pair separate by only a few inches, roll onto their sides,
and release their eggs and sperm. Without so much as a cigarette
afterwards, the pair go their separate ways and continue feeding.
In a previous
column, I highlighted the documentation of Centropyge
angelfish, which were previously known only as protogynous
hermaphrodites, meaning all males are the result of
a female-to-male sex change. In 2003 Sakai, et al.,
demonstrated that Centropyge angelfish have the
ability to be bi-directional hermaphrodites, i.e., a
male can revert back to a sexually functioning female.
Is it possible for Genicanthus species to be
similar?
4-11-02
Recently, a Team
RC member, Nathan Paden, has photographically documented
his Genicanthus melanospilos partake in what
appears to be a switch from male to female. The photo
above shows an adult male Blackspot Swallowtail that
was taken in early April 2002. Four months later, the
male clearly sports some indication of having both male
and female coloration (below).
8-17-02
Finally, nine full
months after the original photo, the fish (below) appears
to have taken on the coloration of an adult female Blackspot
Swallowtail. Scientifically, to make an unequivocal
confirmation of a bi-directional hermaphrodite, two
things would have to be confirmed: 1) the release of
sperm prior to the change, and 2) the release of eggs
or a redevelopment of the ovaries of the fish after
the change. Neither is available, but for purposes herein
I think we can trust the photos. Thus, it does indeed
appear that Genicanthus males may be capable
of reverting back to female.
1-11-03
|
A wonderful trait unique to the Genicanthus genus
of Pomacanthids is the sexual dichromatism that exists throughout
the genus. Males have a considerably different coloration
or pattern than females. The fish will adopt the male coloration
only after first living as a functional female for a period
of time. When the opportunity arises, most often from the
lack of a dominant male's presence, the dominant female of
the local group will become male, a process which is commonly
referred to as the fish being a protogynous hermaphrodite.
Swallowtails reportedly take up to 30 days to complete this
transformation (Michael, 2004).
|
Genicanthus spinus are not regular imports for
the marine aquarium trade. Their less than appealing
coloration doesnt make them any more sought after,
either. The Pitcairn Angelfish will barely reach eight
inches in the wild, and is another cool water species.
Photos courtesy of John Randall.
|
|
In the Home Aquarium
If the hobbyist
can acquire a healthy individual, Swallowtail angelfish can
live an extended, healthy life within the confines of an aquarium.
A few areas of concern are unique to Swallowtails in relation
to their Pomacanthid cousins. As with all marine fish, and
as I have repeatedly pointed out in previous articles, they
should be purchased only after a close inspection of their
fins, mouth, and tail. Ensure that no fins are torn or frayed,
and that no red spots or open sores are present. Make sure
the fish's colors are bright. Also, make sure the fish is
alert and active and ask to see it eat. One final consideration
for Swallowtails is their susceptibility to decompression
sickness. Due to the depth from which many of these individuals
are collected, this is the most common malady that plagues
them. If the fish are unable to swim upright or remain stable
in the water column, they most likely have a traumatized air
bladder. Bearing all these points in mind, avoid all fish
which do not pass a rigorous examination.
|
|
The Blackspot Angelfish makes for a wonderful addition
to a large home reef aquarium. Pairs, or even small
harems, when the aquarium has ample real estate, can
be successfully maintained for a number of years. Paired
fish, which interact as mates, afford the hobbyist the
opportunity to watch an interesting relationship develop.
Left photo courtesy of Ken Gosinski (Mustang); right
photo courtesy of Nathan Paden.
|
Food options are perhaps the least of the hobbyist's concerns
when keeping Swallowtails. As with any marine planktivore,
they are very easy to feed once established in the home aquarium.
Almost anything floating in the water column will get taste-tested,
making the home aquarist's job that much easier. Even so,
a proper diet must be offered. A diet rich in mysid species
shrimp will go a long way toward accomplishing this, but realistically,
most any food sold at a local fish store geared toward marine
fish will work well. Variety is the key, taking due diligence
to ensure not only that their carnivorous dietary needs are
met, but also that their marine algae requirements are fulfilled.
Because they are planktivores which feed almost constantly
in the wild, many small, frequent feedings are recommended.
Matching swallowtails with potential tank mates is an area
requiring more concern and effort than does their diet. Swallowtails
will not overtly attack the vast majority of fish, as they
are rather peaceful themselves. Care must be given, therefore,
not to confine them with fish that are outwardly more aggressive
than the Swallowtails. They can, and most certainly will,
be dominated by larger aggressors. Such aggressive fish would
include triggerfish, large angelfish, and most surgeonfish.
Likewise, thought should be given prior to introducing any
additional planktivores, like Anthias species, with
the Swallowtails. Although the angelfish will not likely bother
them, it is possible the angelfish can themselves be harassed
by the other planktivores.
The Masked Angelfish, Genicanthus personatus,
can be found only in Hawaiian waters. The cooler waters
(70 - 75 degrees) and deeper depths (100 - 400 feet)
from which they hail likely contribute to the difficulty
in acclimating this species. Pyle (1990) observed harems
consisting of up to 20 fish in a 1:5 male to female
ratio. Adults reach eight inches. The female is pictured
on the left, the male in the right photo.
Photos courtesy of John Randall.
|
Compatibility
chart for the genus Genicanthus:
Fish |
Will
Co-Exist
|
May
Co-Exist
|
Will
Not Co-Exist
|
Notes |
Angels,
Dwarf |
|
X
|
|
In
larger aquariums these fish should mix well. |
Angels,
Large |
|
|
X
|
Probably
best to avoid large angelfish unless the aquarium is similarly
large. |
Anthias |
|
X
|
|
A
planktivore that is best avoided except in large aquariums |
Assessors |
X
|
|
|
A
good choice. |
Basses |
|
|
X
|
Swallowtails
may be at risk of harassment. |
Batfish |
X
|
|
|
A
good choice. |
Blennies |
X
|
|
|
A
good choice. |
Boxfishes |
X
|
|
|
A
good choice. |
Butterflies |
X
|
|
|
A
good choice. |
Cardinals |
X
|
|
|
A
good choice. |
Catfish |
|
X
|
|
Larger
catfish can become aggressive. |
Comet |
X
|
|
|
A
good choice. |
Cowfish |
X
|
|
|
A
good choice. |
Damsels |
|
X
|
|
Probably
best to avoid most damselfish in community aquariums.
|
Dottybacks |
|
X
|
|
Larger
dottybacks may become aggressive, but the smaller species
will coexist well. |
Dragonets |
X
|
|
|
A
good choice. |
Drums |
X
|
|
|
A
good choice. |
Eels |
|
X
|
|
Smaller
eels will be fine, but avoid the large predatory species. |
Filefish |
X
|
|
|
A
good choice. |
Frogfish |
|
|
X
|
Frogfish
will consume Swallowtail angelfish if given the chance. |
Goatfish |
X
|
|
|
A
good choice. |
Gobies |
X
|
|
|
A
good choice. |
Grammas |
X
|
|
|
A
good choice. |
Groupers |
|
X
|
|
Large
groupers can consume Genicanthus species. |
Hamlets |
X
|
|
|
A
good choice. |
Hawkfish |
X
|
|
|
A
good choice. |
Jawfish |
X
|
|
|
A
good choice. |
Lionfish |
|
X
|
|
Small
lionfish are OK but the larger they get, the more likely
they are to harass or consume Swallowtail angelfish. |
Parrotfish |
X
|
|
|
A
good choice. |
Pineapple
Fish |
X
|
|
|
A
good choice. |
Pipefish |
|
|
X
|
Pipefish
are best left to their own aquarium. |
Puffers |
X
|
|
|
A
good choice. |
Rabbitfish |
X
|
|
|
A
good choice. |
Sand
Perches |
X
|
|
|
A
good choice. |
Scorpionfish |
|
X
|
|
Small
scorpionfish are OK but the larger they get the more likely
they are to harass or consume Swallowtail angelfish. |
Seahorses |
|
|
X
|
Seahorses
are best left to their own aquarium. |
Snappers |
|
|
X
|
Another
planktivore probably best avoided. |
Soapfishes |
X
|
|
|
A
good choice. |
Soldierfish |
X
|
|
|
A
good choice. |
Spinecheeks |
X
|
|
|
A
good choice. |
Squirrelfish |
X
|
|
|
A
good choice. |
Surgeonfish |
|
X
|
|
Frantic
or aggressive surgeonfish can cause concern or harassment.
|
Sweetlips |
X
|
|
|
A
good choice. |
Tilefish |
X
|
|
|
A
good choice. |
Toadfish |
|
|
X
|
Toadfish
can consume Genicanthus species. |
Triggerfish |
|
|
X
|
Most
triggerfish should be avoided. |
Waspfish |
X
|
|
|
A
good choice. |
Wrasses |
X
|
|
|
A
good choice. |
Note: While many of the fish listed
are good tank mates for members
of the genus Genicanthus, you should research each
fish individually before adding it to your aquarium. Some
of the mentioned fish are better left in the ocean or for
advanced aquarists.
|
In most
cases Genicanthus caudovittatus arrives to home
aquarists from the Red Sea, which generally increases
the price of any fish imported. Fortunately, this species
is often collected in merely 30 feet of water, thus
not adding to the already expensive cost typically associated
with deep-water dwelling species. The Red Sea Swallowtail,
also sometimes called the Zebra Swallowtail, may reach
seven inches of length in the home aquarium. A male
is seen in the top photo, and the female is on
the bottom. Photos courtesy of John Randall.
|
|
Planktivorous feeders which happen to be
smaller than the Swallowtails may themselves be at risk of
harassment. Gobies which hover mid-water column, flasher wrasses
of the genus Paracheilinus, and small tilefishes are
a few examples of such fish. Genicanthus species are
not likely to pester small fish such as gobies and blennies
if those fish are not planktivores. More than likely the angels
will not even acknowledge their presence in the aquarium.
The same can be said for most any motile invertebrate, although
the rare grounded copepod or polychaete will be snagged from
the grasps of the substrate. Sessile invertebrates are not
at risk. Since we are discussing marine angelfish, I think
the last sentence probably could be repeated: Sessile invertebrates
are not at risk. On the rare occasion that a Swallowtail
becomes curious, it is most likely to taste-test soft corals
such as Xenia or Anthelia.
A discussion about proper tankmates would be incomplete without
a word regarding housing multiple Genicanthus species
in the same aquarium. Genicanthus not only can, but
should, be kept in pairs. A lone individual will usually fare
well, but watching a pair interact is well worth the investment.
If the reefkeeper so chooses, he may obtain even more than
a pair, but should be careful to add only one male, while
all the remaining individuals must be females. Careful observation
may reveal the courting behaviors discussed earlier.
The Ornate Angelfish, Genicanthus bellus, will
stay small for Swallowtails, barely reaching seven inches
in the wild. It is not commonly found above 100 feet
depths and thus is not a regular import. The left
photo is a male, the right photo is a female.
Photos courtesy of John Randall.
|
Aquarium size is an obvious concern. Planktivorous fish are
used to having free range of the open water. Placing them
into tight quarters is a sure way to stress them and bring
any number of pathogens upon them. A single individual will
do well in a traditional four-foot long aquarium, provided
it has been aquascaped correctly. This means the fish should
have adequate hiding spots, which enable it to find areas
of quiet and darkness, yet afford the fish plenty of open
water at the front of the aquarium. Placing two or more individuals
into the same aquarium is possible in four-foot long aquariums
provided other fish are kept to a minimum. Preferably, however,
a pair will reside in a minimum six-foot long tank.
Due the depths at which Genicanthus angels are found
in the wild, an area of concern, which normally doesn't come
into play for most species, is the amount of light the aquarium
receives. These deep-water fish are not accustomed to bright
sunlight and may therefore have a prolonged or even difficult
adjustment period when moved into a brightly-lit coral dominated
aquarium. Once acclimated to the aquarium the fish will begin
to hover in front, but until that time the fish can be expected
to remain hidden in the dimly lit areas of the aquarium.
Genicanthus semicinctus wont reach eight
inches, and it likely wont reach your home aquarium,
either. The Halfbanded Angelfish has a very limited
distribution which happens to be far from typical collection
areas. Photos courtesy of John Randall.
|
|
|
Meet the Species
About half of the
species existing in the wild are available for purchase within
the marine ornamental fish trade. Limiting factors are obviously
the depth at which these fish reside coupled with their limited
geographic distribution. Of the fish that are available for
purchase, their price is naturally higher than most aquarium
fish due to the depth at which they reside and the associated
risks involved with capturing deep-water fish.
A beautiful male Blackspot Angelfish is seen here. In
the wild, males will typically claim a harem of three
to four females.
Photo courtesy of Ken Gosinski (Mustang).
|
An option frequently available to aquarists, and a hardy
choice, is Genicanthus lamarck, or Lamarck's Angelfish
as it is more commonly called within the hobby. They are large,
but certainly not the largest of the genus, reaching upwards
of nine inches in total length. Like all species of the genus,
they appreciate brief periods of turbid water.
Lamarcks angelfish, Genicanthus lamarck,
is perhaps the most common of all Swallowtail angelfish,
both in the wild and in the aquarium trade. Reaching
up to nine inches of length (not including the streamers
of some adult males), they are the second largest
species of the family. A female is displayed in the
top photo, the male in the bottom picture.
Photos courtesy of John Randall.
|
|
|
Another popular aquarium species is the Japanese Swallowtail,
Genicanthus melanospilos. Individuals of this species
will not fully reach seven inches in a home aquarium. In the
wild they are known to hover and feed with other planktivores
such as Squarespot Anthias, Pseudanthias pleurotaenia
and the tilefish, Hoplolatilus starcki. Replicating
this association in the home aquarium would make for an interesting
and beautiful display.
The last species regularly available which also generally
arrives healthy and without requiring a secured loan is
Genicanthus semifasciatus. To confuse matters, similar
to Genicanthus melanospilos, this species is also commonly
called the Japanese Swallowtail. Typical for the genus, it
will reach barely eight inches in length. Females have been
noted to begin the change to a male at four inches of length.
|
|
As the name implies the Japanese Swallowtail is fairly
common among the islands of Japan. Cooler aquarium water
temperatures, from 70 to the mid 70s, will aid
in the transition of Genicanthus semifasciatus
to captivity. Female photo above, male photo
below. Photos courtesy of John Randall.
|
Conclusion
Genicanthus
species angelfish are only starting to receive the fanfare
they deserve. Their popularity among reef aquarists is growing,
and for good reason. They are planktivores, which allows them
to be kept in aquariums filled with prized corals. In situations
where other angelfish may begin to pester or harm your corals,
Genicanthus remain completely oblivious to their presence.
Coupled with wonderful coloration and a hardy track record,
I foresee these angelfish only becoming even more popular
in years to come.
|