Betta fish
Betta splendens: the splendid fighter
There have been several fish over the course of my fishkeeping journey that left an indelible mark. There was Tembo, the glorious goldfish; Jimba, the most coveted Cory catafish in my PhD study population (Jimba’s milkshake brought all the boy fish to the aquarium yard, so to speak); and Buddy, my beloved betta fish from childhood. Here in the uncivilized United States, betta fish are often called Siamese fighting fish, because there’s nothing the US likes more than injecting smidges of racism into something totally innocuous. Bettas have a long human history – they have been extensively bred since the 18th century – and they are among the most diversely and elaborately ornamented domesticated fish. Native to Thailand, their beauty and fascinating behavior has inspired aquarists and scientists the whole world around. In fact, bettas were among the first fish to be studied by early behavioral researchers, having a crucial role in developing fundamental concepts of this interesting branch of biology since the 1930s. Buddy was a red betta fish, and he lived on my dresser for three happy years. Let’s dive into the fascinating biology that Buddy so elegantly represented.
The wild variety of the male betta
Like many species, the betta fish exhibit sexual dimorphism, which is when females and males have different physical traits (humans are sexually dimorphic too!). Domesticated strains are like peacocks, and the male is all kitted out with brightly colored, flamboyant fins while the female is dressed more sensibly – I guess this is where the human analogy ends.
As fine a bubble nest as we've ever seen
The betta fish, however, does not follow all of the stereotypes. Like many fishes, bettas are devoted parents, but in a twist of the usual script, it’s the male that does the heavy lifting of raising baby fish. He starts by constructing a bubble nest, which will serve as his babies’ first home. Here they hatch and get a little experience being fish while their dad stands guard.
One of the most pernicious myths about the betta fish is that it can live in a tiny bowl without filtration. This is not the case, and it’s cruel to keep betta fish this way. Betta fish need a proper aquarium and a filter just like any aquarium fish. There is a reason that this myth persists, however, and it’s the unique way Betta fish adapted to the low oxygen canals, floodplains, and rice paddies of Thailand and the surrounding countries. Betta fish have a fascinating organ that most fish don’t have, and it’s called the labyrinth organ. Let’s take a look:
The labyrinth organ is basically a lung, if a lung were made from gills (instead of the swim bladder, which is what human lungs evolved from). The first gill arch expands and lots of blood vessels appear, with the result that betta fish (and their relatives) can breathe oxygen from the air. This is why they can survive for short periods in the tiny little cups in pet stores, and why wild betta fish can survive in puddles with little water flow.
Of course, I can’t write an article about betta fish without mentioning the real reason they’re so famous: the ‘fighting fish’ part of their US name is not without justification. Males are famously territorial, which is an issue in fish tanks, which are generally too small for more than one male to establish a territory. This is why male bettas should generally be kept apart, as they will fight quite aggressively: the operculum (the cover over the gills) flares out like that scary little dinosaur from Jurassic Park, and biting and chasing can be relentless. Male bettas get so worked up about warding off rivals that they’ll attack their own reflections! Buddy would do this, and I would sometimes put the lights low to give him a break from trying to chase away… himself. Males will seldom fight to the death, however, even in inhumane, illegal gambling contests where males are pitted together. Betta fish are more sensible than they seem, and many species have ways of avoiding needless violence – there aren’t Band-Aids or hospitals in the wild, after all. The trick is that contests are highly ritualized and start with low levels of actual aggression… it is all about convincing the other that one is the bigger, stronger, prettier betta without actually ‘taking the gloves off’! Much like men insulting each other in a bar. And in most cases, these displays of one’s own formidability suffice to resolve a given conflict. These rituals actually follow a set order of escalation, the reason why early behavioral biologists were so fascinated by these creatures. Bettas in nature will rarely have to take ‘their business outside’.
Of all of the betta fish’s splendid characteristics, however, the one that fascinate me most is their intelligence. Females are generally peaceful, but groups of females establish dominance hierarchies very much like mammals and birds. Sociality in betta fish in general is quite rich and complex – male bettas may seek to oust other males, but they reliably recognize and then turn on the charm for females. And they remember past opponents and the outcome of their interactions and behave accordingly: like a winner or a loser. Bettas are also excellent learners – I taught Buddy to bite my finger through the aquarium (I called it ‘playing pat-a-cake’).
In the case of the splendid betta fish, the bright colors of domestication have drawn our attention to the fascinating evolution and ecology of this much-loved fish. There’s so much more to betta fish than the flashiness that meets the eye, so check out the links below if you’d like to learn more.
2) http://www.scienceasia.org/2009.35.n1/scias35_8.pdf
3) https://www.sciencedirect.com/science/article/pii/S0376635705002378?casa_token=N6qUHNV_dHQAAAAA:UtPmpTb-5012Zntn9hayj9UFLKN6b59KrkCCa4bTcIUJT2kEpIk3JUxVhsvvWBEEs_tcAqTLLYY