Many
reef fish groups have been ascribed with "colorful" common names,
that are in many cases quite descriptive. For example, there
are the hawkfishes, which perch on reef substrates, their are
the cowfishes, which have horns and big sad eyes, there are
the hogfishes, which have swine-like appetites, there are lionfish,
which have elongate fin filaments reminiscent of the mane of
their feline namesakes, and there are stonefish, which simply
look like a stone. But what about the soapfish- where does their
name come from? Although they don't look like a typical bar
of soap, they do lather like it! Almost all the soapfishes exude
a toxic skin mucous when they are distressed. A lather is formed
when a soapfish's skin is stroked, hence the common name. This
substance, which is known scientifically as grammistin, is bitter-tasting
and an effective deterrent against potential soapfish predators.
In
this article, we will take a look at two very interesting, odd
species in the soapfish tribe Diplioprionini.
Note
the characteristic sharp-snout, the elongated body and
yellow
spot on the caudal peduncle of this Arrowhead Soapfish.
Proud sponsor
of this column
Classification
and Biology
The
soapfishes belong to the family Serranidae (the groupers or
sea basses). The soapfishes make-up the two tribes Diplioprionini
and Grammistinae. These two groups include nine genera and 23
species (three genera and four species in Diplioprionini, and
eight genera and 21 species in Grammistinae). Members of the
Diplioprionini tribe have a dorsal fin that is deeply notched
or two dorsal fins. Most of their scales are also ctenoid in
form. The genus Diplioprion (tribe Diplioprionini) is
comprised of two very unique soapfishes. They are laterally
compressed, with deeper bodies than all of the other soapfishes,
and they have very long pelvic fins that extend back beyond
the front of the anal fin. Unlike most other soapfishes, these
two species are active during the day, spending much of the
diurnal hours cruising just above the substrate, or hanging
under ledges or in caves. When they hunt they adopt a head down
posture as they inspect the sea floor. One of the Diplioprion
(i.e., yellowface soapfish, D. drachi) increases its
hunting success by swimming alongside larger fishes, using them
as a mobile blind to sneak-up on its prey. I have seen the two-banded
soapfish (Diplioprion bifasciatum) following foraging
coral catfish (Plotosus lineatus). The soapfish would
pounce on small prey items flushed by the feeding catfish. The
members of the genus Diplioprion are thought to be sexually
dimorphic, with males attaining a larger size than females.
Although very different in form, the monotypic genus Belonoperca
is also a member of the tribe Diplioprionini.
Aquarium
Husbandry
The
soapfishes are durable aquarium inhabitants, but few are highly
regarded by hobbyists because of their subdued color patterns
and secretive tendencies. This is unfortunate, because all the
soapfishes exhibit interesting behavior and will usually "warm-up"
to their keeper in time. The size of the tank used to house
a soapfish will depend on the species you are interested in
keeping. Some of the smaller members of the group will do fine
in tanks as small as a standard 20 gallon, while others should
be kept in nothing less than 55 to 75 gallon aquariums.
Most
members of this group do spend the majority of the daylight
hours hiding among the aquarium decor, occasionally slinking
from one crevice to another. Therefore, it is very important
to provide them with plenty of suitable shelter sites. After
being in the tank for a while, most soapfishes will learn to
recognize their keepers as a source of food and become quite
tame. Although it may be necessary to induce feeding by offering
these fishes live food, like feeder fish and ghost shrimp, most
are easily trained to accept bite-sized pieces of fresh or frozen
seafood, frozen preparations, and frozen mysid and brine shrimp.
When they feed, some soapfishes will simply dart out from their
lair, grab the prey item, and then dash back to cover. While
others approach their prey slowly, and perform unusual swimming
motions as they make the final approach.
Although
most soapfishes will behave aggressively towards conspecifics
or congeners, they are rarely aggressive towards non-related
fish species. They are, however, very predatory and may surprise
you in what they are capable of ingesting. The biggest downside
to soapfish ownership is the potential risk they pose to their
tankmates because of their toxic body slime. If they are being
harassed by a tankmate, or the aquarist, or if they are ill,
they might secrete copious amounts of grammistin, which could
result in the death of the soapfish and any other fish in the
tank. Fortunately, this happens very rarely in the home aquarium.
The only time I have seen this occur is when a Rypticus
sp. was handled and then placed back into a tank. If you do
notice fishes kept with a soapfish breathing heavily or behaving
abnormally, remove them from the tank, and separate them from
the soapfish, immediately. When capturing a soapfish use a specimen
container as this is less stressful to the fish. The spines
on the preopercle and opercle are also susceptible to getting
tangled in an aquarium net.
Although
not all are brightly hued, the soapfishes are very interesting
to watch in the home aquarium. The attractive face of
the leaflip soapfish is shown here.
click
on image to enlarge
The
yellowhead soapfish is endemic to the Red Sea. Like
others in the family, it employs some fascinating hunting
techniques to sneak-up on its quarry.
click
on image to enlarge
The
arrowhead soapfish is a solitary species that tends
to stay
under or in caves during the day.
click
on image to enlarge
Arrowhead
Soapfish (Belonoperca chabanaudi)
This
unusual soapfish is rather rare in the aquarium trade. However,
it make a very interesting aquarium inhabitant for those hobbyists
that enjoy the unusual. As the name implies, the head comes
to a sharp point and the body is elongated. Unlike many in the
genus, this fish looks like it is built for speed. It also differs
from other soapfishes in its behavior. It spends the days hovering
in the water column, usually hanging under overhangs and in
caves or at the entrances of these structures. At night, it
moves from its diurnal shelter to feed on fishes and crustaceans.
This species is known from East Africa to Samoa, north to the
Ryukus and south to New Caledonia. I have found it to be quite
common in northeastern Papua New Guinea. It reaches a maximum
length of 15 cm (5.9 in.).
Proud
sponsor of this column
The
arrowhead soapfish is a secretive aquarium inhabitant that should
be provided with suitable microhabitat. It is best to provide
B. chabanaudi with a sizeable arch, overhang or cave
to hover under or in. Otherwise it will spend much of its time
rest on its pelvic fins on the bottom, behind aquarium decor.
Although it rarely displays interspecific aggression, it is
a voracious predator that will eat any fish or shrimp small
enough to fit in its mouth. It slowly approaches its prey by
undulating its dorsal and anal fins and then, with incredible
speed, it will swoop down and capture its quarry. The arrowhead
soapfish will consume feeder fish and live ghost shrimp, but,
unfortunately, it is not easy to switch over to non-living foods.
It may take mysid shrimp that are strategically placed in a
current so it looks like they are moving on their own. If you
are not able to switch your arrowhead soapfish to a more nutritious
diet, make sure you "gut pack" the ghost shrimp with a nutritional
food source before you feed them to your Belonoperca.
Only
one arrowhead soapfish should be kept per tank, but it can be
kept with related forms (i.e., other soapfishes, groupers).
It can be housed in a shallow or deepwater reef aquarium, however,
it may spend more time in the open in a more dimly-lit environment.
It will also eat ornamental crustaceans. Be aware that this
species is an excellent jumper and is likely to launch itself
out of an open aquarium if it is startled or being harassed
by tankmates.
Two-banded
or Barred Soapfish (Diplioprion bifasciatum)
This
is one of the more common soapfishes in the aquarium trade.
Its color can be quite variable. Most two-banded soapfish are
pale to bright yellow with a thin black band on the head that
runs through the eye, and a thick black band in the middle of
the body. Some individuals are black overall with yellow on
the median fins and yellow margins on the pelvic fins. I have
only seen the black color morph around Heron Island on the Great
Barrier Reef and it may be that this is an aggressive mimic
of the common Queensland yellowtail angelfish (Chaetodontoplus
meridithi) - this species is often referred to incorrectly
by hobbyists as the Personifer angelfish (Chaetodontoplus
personifer), which is restricted in distribution to north
western Australia. Both species are deep-bodied and the coloration
of the black morph of D. bifasciatum and this angelfish
are similar overall. The angelfish feeds on sessile invertebrates
and fish eggs, while the soapfish eats small fishes and crustaceans.
On the southern Barrier Reef, the proposed model (i.e., the
angelfish) is much more common than the mimic. For example,
of eight D. bifasciatum I observed around Heron Island,
only two exhibited the black color pattern. During this same
observation period I observed 22 C. meridithi. Rudie
Kuiter, fish expert, reports that in Java the juveniles of this
species are gray with a black head and may be a Batesian mimic
of a sympatric poison fang blenny (Meiacanthus sp.).
The
two-banded soapfish will become a very personable aquarium
resident once it fully acclimates to its new home
The
two-banded soapfish ranges from India to Papua New Guinea, north
to southern Japan and south to the Maldives and Lord Howe Island.
It reaches a maximum length of 25 cm (10 in.). This soapfish
is most common on coastal reefs, in calm lagoons, on protected
reef faces and fore reef slopes. It can be found at depths of
1 to 25 m (3.3 to 75 ft.). On rare occasions it will also enter
estuaries. Diplioprion bifasciatum is a solitary fish.
During the day it is usually observed hanging in caves or under
overhangs, or moving from one crevice to another. It feeds on
crustaceans and small fishes. The Two-banded Soapfish spawns
at dusk, with males forming temporary spawning territories on
the edge of the reef. When a female approaches a male, he will
begin to swim in a quick, exaggerated fashion in front of her.
If the female is in spawning condition, the male moves above
her with his head angled upward slightly. The pair will then
rise up into the water column until they are from 7 to 14 m
(23 to 46 ft.) above the substrate, at which time they will
rapidly turn, release their gametes, and dash back toward the
ocean floor.
The
two-banded soapfish is well-suited to captivity. It may hide
when initially introduced to its new home, but usually within
hours they will start swimming about the tank. You should make
sure you provide plenty of suitable hiding places for D.
bifasciatum. This species will eat finely chopped fresh
sea food, frozen brine shrimp, frozen mysid shrimp, frozen preparations,
and even flake food. Occasionally live guppies are necessary
to induce a feeding response in some individuals.
The
two-banded soapfish is not aggressive toward other fishes, but
they will eat any tankmate that they can swallow whole. These
fish can be kept together, rarely behaving aggressively towards
each other. They may be picked on by overly aggressive tankmates.
They may release grammistin, a toxic substance exuded from the
skin, when stressed or frightened. This can kill it and the
other fish kept with it in the aquarium.
References
Böhlke,
J.E. and C. C. G. Chaplin. 1968. Fishes of the Bahamas and
Adjacent Tropical Waters. University of Texas Press, Austin.
771 pp
Chlupaty,
P. 1985. The Two-banded Grouper. Trop. Fish Hobby. 33
(5):70-74.
Courtenay,
W.R. Jr. 1967. Atlantic fishes of the genus Rypticus
(Grammistidae). Proc. Acad. Nat. Sci. Phila. 119:241-293.
Myers,
R.F., 1999 Micronesian Reef Fishes: A Comprehensive Guide
to the Coral Reef Fishes of Micronesia, 3rd revised and expanded
edition. Coral Graphics, Barrigada, Guam. 330 pp.
