These
are good times to be a marine aquarist! I know the economy is in a
bit of a slump and we are in a long and important war against
terrorism. But even so, there are some good things happening in
the marine aquarium trade. One of the most exciting things is that
unusual fishes are showing up in the trade greater regularity! For
example, there are dottybacks, damsels and wrasses that I have
seen in aquarium stores for the first time in the last year. Many
of these are being collected in places where collecting did not
occur in the past (this is especially true for Indonesia). Members
of the genus Rhinopias have also been showing up in the
aquarium trade with greater regularity. These amazing
scorpionfishes are the subject of this article.
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The members of the genus Rhinopias
have long been considered the “Holy Grail” of aquarists who keep
rare and unusual fishes. The genus Rhinopias contains six
species (some suggest one of these is not valid) and none of these
are considered to be common. But their apparent rareness may be due
in part to their cryptic behavior, excellent camouflage and the fact
some species live in habitats that are not readily explored. The
species that comprise the genus are: the lacey or Merlet's
scorpionfish (Rhinopias
aphanes), the Easter Island scorpionfish (Rhinopias
cea), the Japanese scorpionfish (Rhinopiasargoliba), Eschmeyer's scorpionfish (Rhinopias
eschmeyeri), the weedy scorpionfish (Rhinopias
frondosa) and the strange-eyed scorpionfish (Rhinopias
xenops). All of the Rhinopias
have deep, laterally compressed bodies, eyes set high on top of
their heads and most species have dermal appendages above their
eyes, on the jaws and the body surface (the number various between
the species and even from one individual to the next).
The
Species in the Trade
There are two species that
regularly show-up in the aquarium trade: The weedy scorpionfish (Rhinopias
frondosa) and
Eschmeyer’s scorpionfish (R.
eschmeyeri). The
weedy scorpionfish is a wide-ranging species that occurs from East
Africa to the Caroline Islands, north to Japan and south to
Mauritius. Apparently, most of those being collected for the
aquarium trade are coming from Sri Lanka. This scorpaenid attains a
maximum length of 9 inches. It has been reported at depths from 10
to 297 on bottoms sandy, macroalgae, rubble and rocky substrates (Eschmeyer
et al. 1973, Myers 1989).
Eschmeyer's scorpionfish
has been reported from Mauritius to Sri Lanka (Lieske and Myers
1994), although I have seen specimens from the Philippines and Papua
New Guinea and have observed it in Indonesia. This species is
usually uniform in color and can be lilac, yellow, orange or brick
red and attains a maximum length of 7.5 inches. Rhinopias eschmeyeri is reported to occur on open sand bottoms at
depths from 7 to 132 feet (Conde 1977, Debelius 1993).
I
should point out that at least one fish expert (Rudie Kuiter) has
suggested that R. eschmeyeri is not a valid species, but a
variant of R. frondosa. One characteristic used to tell the
two species apart is the membrane between the spines and rays of the
first and second dorsal fins. In R. eschmeyeri the membrane
is incised - that is, the edge of the dorsal fins are nearly
straight. In some individuals of the Eschmeyer’s scorpionfish, the
first dorsal fin is almost sail-like. In the weedy scorpionfish the
membrane is deeply incised so the dorsal edge appears to be jagged.
Rhinopias
eschmeyeri
also exhibits a uniform body color, while R. frondosa usually
has round and oblong pale spots and blotches (these can be less
conspicuous in some individuals). In R. eschmeyeri the
supraorbital appendages are unbranched and flattened (they are
leaf-like), while those of R. frondosa are branched. It may
be these differences represent sexual dimorphism within R.
frondosa. I have seen photos of apparent pairs of Rhinopias,
where one fish was a “perfect” R. eschmeyeri and the
other fish looked more like R. frondosa. The verdict is still
out, with more study being required to determine how many Rhinopias
spp. actually exist.
The
scorpionfishes in the genus Rhinopias are highly sought
after by the collector of the rare and unusual. This is Rhinopias
aphanes, the lacey scorpionfish, which is thought to mimic
a crinoid.
The
first dorsal fin of Eschmeyer’s scorpionfish is sail-like,
with no or very reduced incisions between the dorsal spines.
The
weedy scorpionfish is the most commonly seen species in the
aquarium trade. This species often sports rings or spots on
the body, but in some individuals, like the one pictured here,
they can be indistinct.
The Rhinopias
spp. are known to shed their cuticle, or the outer epidermal layer. This
helps rid the body of algae, parasites or encrusting organisms. In some
individuals shedding can occur quite often. For example, a R.
eschmeyeri was reported to shed about every 12 days (Eschmeyer et
al. 1973). The frequency of shedding may increase if the fish is
suffering from parasitic infections. Do not freak out if the eyes of
your Rhinopias become cloudy – they sometimes do before the
fish shed. These scorpionfish may also position themselves in front of
strong water flow to facilitate the shedding process.
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These
fish rarely swim, but move about by crutching along the bottom
on their pectoral and pelvic fins. When hunting they remain
motionless and wait for their prey to approach within striking
distance or they slowly stalk their quarry. When a specimen is
very hungry and use to food presentation in the aquarium, it may
"hop" rapidly toward a prey item, rather than
approaching it slowly. When they get close enough to their prey
the Rhinopias willlunge forward and suck in its victim. Rhinopias
will also rock forward and backward in order to mimic a piece of
debris sitting on the bottom.
Keeping
them In Captivity
All
the Rhinopias readily
adapt to captivity and because of they are relatively inactive
they can be kept in smaller aquaria (Dinesen and Nash 1982, Howe
et al. 1988, personal observation). I would suggest that a
smaller Rhinopias be housed in an aquarium of at least 20
gallons, while larger adults will do fine in a standard 30
gallon tank. Although some décor is needed to help your Rhinopias
“feel at home,” do not over do it. These fishes (especially R.
eschmeyeri) often sit in repose on open sand, mud or rubble
bottoms. Because these fishes tend to spend most of their time
in the open (unlike some scorpionfishes, which are more cryptic)
they make an interesting addition to the reef aquarium.
Live
food(e.g., ghost
shrimp, mollies, guppies) will be needed to initiate feeding and
many individuals may never accept anything but live fare. You
should attempt to train your Rhinopias to take pieces of
shrimp, squid and fish off of a feeding stick. One thing you
should avoid is feeding your scorpionfish a diet consisting only
of feeder goldfish. Raw goldfish flesh contains thiaminase, an
enzyme that causes the breakdown of thiamin. If you feed your
scorpionfish a diet that consists only of goldfish, they may
become thiamin deficient, which can result in feeding cessation,
clamped fins and nervous in coordination. If you have to feed
them live food, gut pack mollies, guppies and/or ghost shrimp
with a nutritious food (e.g., Cyclop-eeze®) before you feed
them to your Rhinopias (some individual may be reluctant
to feed on live ghost shrimp).
Behavior
Hepatic lipidosis, or
fatty degeneration of the liver, has been reported in a
scorpionfish fed only fresh hake. This condition can cause liver
failure, which leads to suppression of the immune system,
hemorrhaging and anemia. Lipidosis is best avoided by giving your
scorpionfish as varied a diet as possible and by not overfeeding.
I would recommend you feed your scorpionfish to satiation twice a
week.
They can be housed with
other fish, but I would avoid keeping them with species that eat
encrusting invertebrates because they mistake the Rhinopias
as a rock covered with food! Although on some occasions these fish
may not harm your Rhinopias,
in my mind it is not worth the risk. You should also be careful
when putting them in tanks with other predatory fish. Although the
deep body and venomous spines of these fish may dissuade most
predators, smaller specimens may be eaten by larger frogfishes,
other scorpionfishes or large groupers. An Eschmeyer's
scorpionfish I was keeping met a tragic end when its head was
engulfed by a smaller striated frogfish (Antennarius
striatus). I had placed several feeder fish in the tank and
was watching these two fish stalk them. The Rhinopias
was moving around a piece of coral when the frogfish decided to
try and eat it! I quickly grabbed the frogfish by the tail and it
released the Rhinopias, but the eye of the scorpionfish was damaged, became
infected and it died several days later. I personally think that
these fishes are best kept in a species tank – that is, an
aquarium by themselves. It is not worth the risk of having you Rhinopias
harmed by a tankmate.
These
fishes are highly predatory and will eat any fish that they can
ingest. Don’t underestimate the size of a Rhinopias mouth! If
you see a Rhinopias yawn you will realize that they can eat
relatively large prey items. I had an Eschmeyer’s scorpionfish
eat an anemonefish that I thought was to deep-bodied for it to
ingest – boy, was I wrong! That said, my good friend Mitch Carl
tells me that his 5-inch Rhinopias frondosa will not eat a
fish larger than a molly. The Rhinopias will also consume
ornamental crustaceans, including shrimps and crabs.
Almost all the Rhinopias
I have kept or seen in captivity had abraded lower jaws. They
apparently swim against the plastic bag during shipping, which
results in injury to the skin on the lower jaw. In most cases,
this wound gradually heals, but it is a possible portal for
bacterial infection which can lead to death of the fish. I have
seen Rhinopias die as a result of severe bacterial
infections that manifested themselves as skin lesions on the body.
These fishes can also suffer and succumb to ich (Cryptocaryon
irritans) and coral fish disease (Amyloodiniumocellatum).
It is possible to treat them with common anti-parasitic
medications (be careful when using copper-based meds) or by
dropping the specific gravity (down to 1.012-1.014 for a couple of
weeks).
Of course, these piscine
jewels command big bucks! But if you are really in to the odd and
want to display a fish in your aquarium that will break the ice at
your neighborhood parties, then why not attempt to acquire a Rhinopias!
For
numerous Rhinopias photos and much more information on the
biology, behavior and the various species in the genus, join the
CoralRealm website (www.coralrealm.com).
This is the classic form of
the weedy scorpionfish, with conspicuous markings and long
dermal appendages. This individuals is now on exhibit at the
Omaha Henry Doorly Zoo.
The
lacey scorpionfish shows-up in the aquarium trade on rare
occasions. It always has numerous skin flaps on the head,
body and fins, antler-like growths over the eyes and dark
lines on the body.
This
beautiful weedy scorpionfish, photographed by Eric Reynolds
of Aquamarines, was collected in Sri Lanka.
Acknowledgements:
I want to thank Dennis and Eric Reynolds (Aqua Marines), Randy Walker
(The Marine Center), Jim Walters (Old Town Aquarium, Chicago) and Julian
Sprung for helping me acquire Rhinopias over the years. Mitch
Carl (Omaha Henry Doorly Zoo) and Jim Walters shared some of their
observations on Rhinopias frondosa (if your in the Omaha area,
you should go see the beauty at the Henry Doorly Zoo!). Thanks to Eric
Reynolds for supplying the photo of the orange R. frondosa.
References:
Conde, P. B. 1977.
Nouvelles observations sur les scorpaenides du genre Rhinopias
a Maruice. Rev. fr. Aquariol. 4:19-20.
Debelius,
H. 1993. Indian Ocean tropical fish guide. Aquaprint Verlags, Neu
Isenburg. 319 Pp.
Dinesen,
Z. D. and W. J. Nash. 1982. The scorpionfish, Rhinopias
aphanes Eschmeyer from Australia. Jap. J. Ich. 29:179-184.
Eschmeyer,
W. N., Y. Hirosaki and T. Abe. 1973. Two new species of the scorpionfish
genus Rhinopias, with comments
on related genera and species. Proc. Calif. Acad. Sci. 40:285-310.
Howe, J,
G. Crow and J. Herbert. 1988. The strange-eyed scorpionfish, Rhinopias
xenops. Freshwater and Marine Aquarium, 11:8-11.
Lieske, E
and R. Myers. 1994. Collins Pocket Guide. Coral reef fishes:
Indo-Pacific and Caribbean. HarperCollins Publ., London, 400 Pp.
Myers, R. F. 1989.
Micronesian Reef Fishes. Coral Graphics, Guam, Pp. 228.
