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A New Generation of Betta enisae:
or Breeding the "Metamorphosis Fish"

Copyright: the Greater City Aquarium Society, October 2001

Metamorphosis: A striking change of appearance, character, form, etc. - a transformation.

In nature, the classic example of metamorphosis is, of course, a butterfly. It starts its life as a caterpillar. Slowly, silently, and out of sight of the world, each caterpillar cell differentiates into an antennae, a thorax, or a wing that has been decorated by the paint brush of an angel. Something no less dramatic than that happened right under my nose.

This extraordinary story begins, as is most often the case, with some very ordinary circumstances. For the past two years there has been a two and one half gallon aquarium unobtrusively holding the end spot in a row of similarly sized tanks along the top shelf of the hutch in my kitchen. It has been the home of a pair of Betta enisae; a mouthbrooding anabantoid native to Borneo. These fish were drab and unremarkable. For a very long time I didn't even realize there were two fish in this tank. It was a rare event to see even one of them. They liked to wedge themselves behind and/or under the triangular-shaped sponge filter in the rear left hand corner. Many an observer saw nothing but an empty tank.

Three Questions

Before I plunge into my story I want to answer some questions that you may be asking yourselves. First, "what is an anabantoid?" An anabantoid is a fish which has adapted to its oxygen-poor environment by developing a labyrinth organ. This organ is an auxiliary to the gills. It allows the fish to extract oxygen from the air as well as the water.

Second, "what is a mouthbrooder?" A mouthbrooder is a fish which lays eggs (as opposed to a livebearer which gives birth to viable fry). What sets it apart from other egg-laying fishes is that after the eggs are laid, one of the parents (in the case of Betta enisae, it is the male), "carries" or "holds" the fertilized eggs within its mouth, usually for several days. This provides the eggs with an extraordinarily protective environment, and also makes for small families (at least by fish standards). After the eggs hatch, the fry emerge, curious and even hungrier than their dad, who hasn't eaten the entire time he has been brooding them.

This behavior is not unique to anabantoids. Other species, notably some of the cichlids, are also mouthbrooders. Among fish who mouthbrood, it is more common for the female to perform the chore of brooding the eggs.

Third and last, "where in the world is Borneo?" Borneo is part of the Greater Sunda Islands of Indonesia. It is neighbored on the south by Java, on the west by Sumatra, on the northwest by Vietnam, on the northeast by the Philippine Islands, and on the east by Sulawesi.

NOW - back to our adventure!

Here's Lookin At Ya

The Betta enisae are regularly fed adult brine shrimp. One day, at feeding time, Al saw a "brine shrimp" with eyes looking out at him. You guessed it! Either it took these fish two years to reach sexual maturity, or they had been waiting for the heat wave of 2001. This was a Sunday.

Small Fry

We moved the parents to another two and one half gallon tank in the same row, with a Java Fern, a columnar-shape sponge filter, and something they hadn't had before - a cave! (It looks kind of like a water-logged hollow tree that was abandoned by the Keebler Elves!) This cave was very much to their liking, and they immediately moved in. They didn't seem to know or care that we could now look in on them.

Some time on Thursday, we discovered a clutch of "small fry," that is, a second spawning. These fish were clearly smaller than the first bunch.

Second Sunday

We were spending a lot of time observing and tending both "families" when the metamorphosis of the title occurred. Both adults were swimming out in the open, and displaying their brilliant spawning colors. They were astonishing not only for their beauty, but because we had never seen both of them swimming together without a trace of timidity. They were proud to show their true colors. The fact that we were close by, and so was our camera, did not spook them at all. Au contraire! They weren't exactly showing off, but they were doing what comes naturally, and didn't care who was watching. This was the second Sunday. What followed were several hours of one of the most fascinating experiences in my ten years of fish keeping.

Say "Ahhh"

The pair circled around and around each other. As the circle closed into an embrace, and the female was squeezed ever so gently in just the right spot, an egg or two could be seen cradled in the slightly cupped anal fin of the male, where it was surely being fertilized. It was rapidly picked up in the mouth of the female. Remember, it is the male who carries the eggs.

The female would spit an egg out, and then grab it back - or, so I thought. The male's repeated attempts to retrieve an egg during this game of catch always appeared to go unrewarded. I watched this many dozens of times, and I would have said that the female was so fast that the male never caught a single egg. Well, his mouth was quicker than my eye. After a while, it became clear that his buccal cavity (that is, the upper throat area) was expanding, and that he had, indeed, succeeded in grabbing an egg here and there until he was holding virtually all of them. Eventually, both fish retired to the cave, where a different kind of metamorphosis took place.

Statistically Speaking

Let me backtrack a little, and give you some statistics on the original environment of the adults. You already know that the tank had a volume of two and one half gallons, and a triangular-shaped sponge filter. This is the filter of choice for these fish because the water remains relatively calm. It had a bare bottom, and there were several Java Ferns (Microsorium pteropus) floating freely. There was no heater in the tank. Even in the winter, it would stay as warm as 84F. It received indirect lighting from the room and a nearby window. The pH measured in at 6.8 (slightly acidic). Both the GH (general hardness) and CH (carbonate hardness) tested to be extremely soft, with less than one degree of hardness.

This tank was TIGHTLY COVERED. If they can fit through a crevice, they will. Even feeding time is a "jumping hazard." Dried foods were not readily accepted, and their regular feedings consisted of live foods; adult brine shrimp and blackworms. More often than not, the brine shrimp were doused in liquid vitamins.

We gave the tank a 50% water change every two weeks. The only special treatment this tank received was the addition of black water extract to our Bronx tap water (which is neutral and soft). Black water extract helps to simulate the soft, acidic water in areas where rainwater is combined with decaying plant material.

Comparatively Speaking

In the past, Al and I have observed the spawning behavior of the Siamese Fighting Fish (Betta splendens), and two aspects of the behavior of the Betta enisae stand out in contrast. When the Siamese Fighters are spawning, there are torn fins, missing scales, bloody lips, and a female, although badly battered, which will predate her own eggs, eating them right out of the bubblenest.

Betta enisae are most notable for the peaceful nature of their relationship. They are gentle, almost tender, in their encounters. Neither are wounded. There is, of course, no way to tell if they eat some of the eggs during their exchanges, but we observed no predation of the fry. A possible exception could be that they may eat any weak or deformed offspring, as there was absolutely no culling for us to do.

Fast Food

When your fish spawn three times in eight days, you suddenly find yourself with a lot of hungry mouths to feed. Where to begin? We fed the following foods to the fry, hoping that there was something for every size of mouth: 1) Liquifry for egg layers, 2) newly hatched brine shrimp and 3) microworms. Actually, the fry that have grown the fastest are the few that remain in the tank with the parents. We have seen them nibbling on the large blackworms that we feed to the adults.

Cheek To Cheek

This pair of fish exhibit a behavior which can safely be described as rare, and quite possibly borders on unique. As they co-habit their hollow log, they spend many hours at a time in physical contact with each other. Their bodies are touching!

This is not part of the posturing, embracing, or manipulating of eggs that takes place during spawning. This is how they spend much, if not most, of their time. This was probably taking place behind and/or under the sponge filter in the other tank, but we had not observed it.

21st Century Photography

We took between 450 and 500 photographs of the events of "Second Sunday." We used a digital camera, which captures images, not on film, but on "SmartMedia." These are very small "disks" which measure one and one half inches by one and three quarter inches. The photos can be read directly by a computer where they can be sized, cropped, e-mailed, and, yes, even printed!

The length of a battery charge on the camera would not exceed an hour of continuous use. Our photo session lasted several hours. It just so happened that this aquarium was within cord length of a power strip, so we had the camera plugged in the entire time.

We used a "bipod" to stabilize the camera. This was nothing more hi-tech than a tripod with only two of its feet standing on the bottom ledge of the hutch, approximately one inch above the floor.

As I snapped photo after photo and filled each disk, Al "emptied" it onto a Zip disk (another media for computer data storage), returning the clean ones to me. We were working at the highest resolution our camera supported. This means that we were getting the fewest number of shots per disk, with the highest amount of detail.

Then came the "culling" process. We scanned through the photos, deleting the ones that were not up to Modern Aquarium standards. I was afraid there wouldn't be much left when we got done, but after the first cut, we still had 50 photos to work with.

Tales of Transformation

If a butterfly was a mouthbrooder, it would open its mouth and a swarm of tiny butterfly fry would come fluttering out. If a caterpillar was a fish, it would emerge from its cocoon as a Betta enisae!

Sometimes change is subtle and silent, and sometimes it is bold and blaring. Sometimes we are the transformers, and sometimes we are the transformed. Always, we must be open to the adventure of metamorphosis.

Pairing Off

Adult B. enisae pair.  Female is on top, male is on bottom

B. enisae pair peeking out of their "cave."  The male is on the lower left,
the female on the upper right.

The Embrace

Egg Play

Look carefully and you'll see a small white spot between the two fish.  This is an egg
being tossed by the female (right) to the male (left), a process that was repeated many times.

Male with obviously swollen buccal cavity holding eggs.


New Websters Dictionary and Thesaurus of the English Language, Lexicon Publications, Inc., 1992

Aqualog: All Labyrinths by Frank Schafer, Verlag A. C. S., 1997

Baensch Aquarium Atlas, Volume 1 by Dr. Rüdiger Riehl and Hans A. Baensch, Tetra Press, 1991.

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