Guest Blogger: Joelle Montes

The following guest post was voted best in the class for an undergraduate assignment on fish adaptation from Humboldt State University’s Fall 2017 Fish Conservation and Management course taught by Dr. Andre Buchheister. The assignment required students to find a peer-reviewed article on a fascinating fish adaptation or species and to communicate the scientific information in a blog format to a general audience. 

One of the best-selling fish in aquariums, carnivals, and pet stores nationwide- probably because of their flowy aesthetic and bright colors- is Betta splendens. This fish, known as the “Siamese fighting fish,” acquired its name because of the fierce territorial behavior of males; they will duel any fish that is in their space – especially if it is a fellow male Betta. The fight can be so intense that it sometimes results in a death of one of the fish. This type of gruesome behavior might be the last thing you expect from such a majestic looking fish.

 A Peaceful Betta?

But, what if I were to tell you that there is a fish out there – a part of the same family, Osphronemidae – that is equally as mesmerizing but lives a more peaceful lifestyle? That’s right, B. splendens has a chill cousin! Introducing the well-mannered Betta imbellis. This “peaceful Betta” is sometimes referred to as a “crescent Betta” as their rounded caudal fin is outlined with red, making it appear as a crescent shape.

Where Siamese fighting fish competes for territory, the peaceful Betta doesn’t mind having company around. In fact, B. imbellis is quite humble, only showing its most striking colors when ready to mate. Perhaps, it is their lack of color (compared to that of B. splendens) or their small size (about 50-60 mm) that contributes to their lack of notoriety.

Air Breathing

Though peaceful Bettas may have different temperaments, sizes, and colors than Siamese fighting fish, they do share a special adaptation. Both species have “labyrinth organs” that function like lungs in terrestrial animals. This means you and B. imbellis have something in common: the ability to breathe air! This adaptation comes in handy considering that a Betta’s natural habitat is the murky, stagnant, oxygen-deprived waters of lakes, streams, and shallow ponds of Malaysia and Thailand (Khoo, 2007).

B. imbellis can use their labyrinth organs while jumping several inches out of water to catch insects, or simply to get a breath of fresh air! It is important to note that air breathing comes with drawbacks, too. It exposes Bettas to an entirely new group of predators to fear: birds and humans (Jonna, 2003). But, they have ways to avoid these new predators; the go-to move for B. imbellis in threatening situations is to hide beneath dense areas of aquatic vegetation. Here, just below the surface, this peaceful Betta is safe from both birds and humans.

Bubble Nests

Having labyrinth organs does not limit them to just breathing air, though. It also helps with a great nesting technique. The peaceful Betta, like his popular cousin, is a “bubble nest” builder. To do this, a B. imbellis male briefly sticks his head out of water to take a big gulp of air and returns underwater to blow tiny air-filled mucous bubbles at the water’s surface. Floating, the eggs of this bubble nest have access to the richest oxygen. Often times, this nest will be made under leaves for the sake of protection from predators. With the bubbles being so tightly packed together, this serves as a perfect nest for the offspring they hope to have!

After the nest is completed to the size of his liking, B. imbellis patiently waits near it for a female to take interest in him. Nest size is completely dependent on the male’s preference; it is likely that he will take into account how much space he has and how much time and effort he is willing to put into it. In fact, the quality of a bubble nest indicates the health of a male to a female. If a female crescent Betta is interested, she will display striking, bright colors as she approaches him. The male will flare up to represent his acceptance of her as his mate. The purpose of flaring up is to appear larger to other fish that pose a threat or to show off his size to a potential mate. He does this by turning his gill covers outward and extending his branchiostegal membranes beyond his gill cavity. The two then meet under the bubble nest where the male grasps the female and turns her over on her back. The male will then lay on top of her with his body in the shape of an arc or upside down “U” (Vierke, 1996). Once this is done, the female releases her eggs at the same time that the male releases sperm to fertilize the eggs. The male quickly catches them in his mouth and takes them to the bubble nest where he will take care of them until they become fry, old enough to fend for themselves. Until they are of age, this father fish will protect and maintain the nest by replacing bubbles that might have broken down over time. When these baby Bettas go their separate ways, they spend some time gaining bulk by feasting on shrimp, fish, and insects in and out of water (Jonna, 2003). If they are lucky, they will repeat the cycle their mother and father started.

A fascinating fish

Indeed, Betta imbellis is a pretty cool fish. Their adaptation of labyrinth organs have allowed them to live a lifestyle uncommon to most fish, a lifestyle that not only assists them in air and water, but enables the fathers to be strong, gentle caretakers. With this sense of purpose and lack in aggressive behavior, it is no wonder that they are known as the peaceful Betta. Though they do not get as much attention as the Siamese fighting fish, maybe one day the peaceful Betta will be recognized for all that they are and not be overshadowed by its cousin!

About the author

Hello, my name is Joelle Montes and I am a Fisheries Biology Major at Humboldt State University. From early on in my life, I took on swimming as a sport. Oh, how I loved being in the water! Growing up, my family struggled financially which led to moving around a lot. I never had the opportunity to live near the coast or any beach. I remember the first time I went to a lake- that day changed my life. It was amazing to me that the whole time I had been living my life, those fish had been living theirs. As a kid, my interest for life underwater sparked. And when I finally got to experience the beach, I knew that this was something I wanted to be a part of. I have been unsure along the way because of my past with financial stability scared me into only exploring careers that would keep that part of my life secure. When I discovered Humboldt and the university’s fisheries program, I knew that I had to stay true to who I was. Today, I look at our world and I know that I made no mistake choosing to educate myself on the organisms I plan to spend my life protecting!

References

Vierke, J. 1996. Betta imbellis: Something Special.

Tropical Fish Hobbyist 44(6): 16-28.

Jonna, R. Jamil. 2003. “Osphronemidae (Gouramies).” Animal Diversity Web, University of Michigan: Museum of Zoology, animaldiversity.org/accounts/Osphronemidae/.

Khoo, Sock Yee. 2007. “All About Aquarium Fish.” Peaceful Betta Imbellis Fish Compatibility, www.allabout-aquariumfish.com/2009/12/peaceful-betta-imbellis-fish.html.

For other Humboldt State student posts, please see:

• DANANANANANANANA BAT RAY by Angela Schmidt
• FROM REEF BANK TO FISH TANK: HOW THE AQUARIUM TRADE CAN IMPACT CORAL REEF CONSERVATION by Josh Cahill