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May 11, 2005

Cichlid Intelligence & Diversity

My father has always populated his aquarium with cichlids - African ones. They're fascinating creatures, and to date there are more than 1300 known species, making up more than 5% of all species of vertebrates. Much smarter than your average fish, these guys show some really interesting behavior, especially when you take into account their generally small size. Most aquarium fish are boring, but when you see a tank of cichlids, you can tell they've got significant cognitive abilities just by the way they react to you.
For example, most fish do not respond to much outside the tank, but wiggle your fingers in front of a cichlid tank and you'll have everyone's attention and interest. Here are some of the other interesting behaviors of cichlids:

• Unlike most fishes, both parents care for their young. Some even lay their eggs in abandoned snail shells and then guard the entrance.
• They're highly predatory. They often live together in flocks or tribes of like species, in the same environment. They are not hospitable to other fish, including other cichlids of different species.
• They're often ambush predators - yet omnivorous
• They're big diggers and excavators
• They often express timidity and dominance through color - a pale fish is a stressed or submissive fish, and a bright fish is an aggressive or dominant fish
• They're extremely territorial
• They express themselves with specific movements for fighting and flirting
• Sometimes when a male loses his territory, he loses his bright coloring. However, sometimes he goes into hiding, turns on the color signals of dominance, and pretends that he's still dominant for several more weeks, in hopes of attracting mates before they figure it out

I guess there is a huge problem with non-indigenous species of fish populating lakes and rivers throughout the world and messing with fragile ecosystems. Sometimes this is purposeful introduction and sometimes it's accidental. One cichlid that's been introduced a lot is the Tilapia - which you may have been seeing on the menu lately as part of the white fish healthy food push of many fast food restaurants. Scientists are still speculating on why there are so much diversity of species within the Cichlid family. The diversification seems to happen over an extraordinarily short period of time. Is the adaptability of cichlids going to cause even more serious problems to the environment as they spread into new ecosystems?

Ironically, as prolific as these fishes are, my father never seems to be able to keep more than one alive in a tank at a time. He originally named his cichlid Beast, and he's on at least Beast III at this point. Either they fight each other to death or they dig under rocks and then die in cave-ins.

The cichlids, a family of tropical freshwater fish, have evolved an astonishing array of forms in Africa. Their diversity is perhaps most impressive in the Great Lakes of East Africa, where a handful of colonizing fish species have multiplied over thousands of years into many hundreds of species found nowhere else in the world.

...

The study team found that cichlids found today in rivers such as the Congo, Zambezi, Okavango, and Limpopo originated from a massive lake that dried up some 2,000 years ago. Known as Lake Makgadikgadi, it once covered an area larger than Switzerland and was centered north of the Kalahari Desert in present-day Botswana.

...

"The high rates of speciation [evolution of new species] observed in these African cichlids are almost beyond belief, but the evidence is clear," he added.

More at: National Geographic News: Lost African Lake Spawned Fish Diversity "Beyond Belief"

Posted by sorsha at May 11, 2005 9:15 PM