Think Bomb

Sunday, January 21, 2007

So What's so Cool About Puffers?

Well, aside from being cute and frisky little creatures, green spotted puffer fish are actually a subject of much research these days. The green spotted pufferfish, Tetraodon nigroviridis, has a genome of 350 megabases, about an 8th the size of the human genome and the smallest genome known of all vertebrates. That’s not to say they have less genes, but rather they have less space between the genes. They have very small introns—the regions of genes which are not used to code proteins. In humans and other vertebrates, the entire gene, introns included, is transcribed into mRNA; then the introns are spliced out by the cell machinery before translation (protein creation) begins. Some introns have unknown functions, but others exist so that alternative splicing—cutting the mRNA in different ways to create different proteins—can take place. Puffer fish not only have fewer and smaller introns, but they also have less DNA in between genes. One example is transposable elements, moveable genetic sequences that may have arisen due to interaction with viruses. These make up 45% of the sequence of the human genome, while green spotted puffers only contain about 3.8% transposable elements in their genomes. Scientists are now asking why puffers did not develop long non-coding regions like most vertebrates, and what sort of cell machinery exists to prevent their coming about. Basically, how do these little guys keep their DNA so tidy?

For more info. on the compact genome of Tetraodon nigroviridis, check out this cool site:

Puffer pic:

Tank Keeping

Brackish water has proven to be quite a challenge for this fish lover. Some of the hardier fish-—like the scat-—will soar through fluctuations in water chemistry with little difficulty, but my personal favorite fish, the green spotted puffer, is far more sensitive. These little cuties don't have scales, but delicate skin, and they also don't have gill guards. This makes them susceptible to a myriad of diseases, and at the same time sensitive to medication. They are also very particular about water chemistry, and making that perfect combination of salt water and fresh water conditions known as brackish requires some clever tricks when all the products sold at the pet store are for fresh or salt water aquariums only. One interesting trick I've leaned is to increase pH with the use of baking soda. You probably remember all the grade school experiments where you mixed vinegar (acetic acid) with baking soda (bicarbonate) inside a paper mache volcano to see it erupt in a glorious acid/base neutralization reaction. The base from that reaction, baking soda, works wonderfully to increase the pH of the tank. Puffers like fairly alkaline conditions near a pH of 8, and the filtered water I use is closer to 7. Although marine salt can be used instead of aquarium salt to pick up the pH, it also contains some minerals that are unnecessary and possibly harmful to the puffers. A touch of baking soda added with the aquarium salt seems to do the trick just as well.

Thursday, January 04, 2007


Recently I set up an aquarium for my apartment. It’s a 25 gallon filled with a slightly exotic combination of salt and fresh water called “brackish” water. Anything with a salt content between 0.5% and 30% is considered brackish, and is found naturally in estuaries as well as some swamps, seas, and lakes. Many of the aquarium fish sold for brackish tanks come from mangrove swaps, an interesting tidal habitat where the roots of the mangrove trees protrude throughout the water.

I chose brackish instead of any other because you can find some of the most interesting fish in this type of habitat. My favorite, the green spotted puffer fish (Tetraodon nigroviridis), is very lively and playful. They’re fun to watch because of their brilliant green color and their endless antics—mine does loop-d-loops and is curious about anything new in the tank. They seem to be pretty much always hungry though and will eat anything in a shell, so keeping snails, crabs, or shrimps in the tank is a hopeless venture.

Another fish with a big personality is the green spotted scat (Scatphagus argus). Also green with spots and also endlessly hungry, these fish will go crazy for most anything you put in the tank. Their scientific name is Scatphagus, meaning "eater of feces," so it's no surprise that they'll go for about anything edible in the tanks. I like to stick a piece of cucumber slice on a post, so that it half floats in the water. The scat will feed off of it, looking like a boxer with a punching bag, swooping in and out as it bites at the cucumber.

Although I don’t yet have either, monos (Monodactylus sebae) and archer fish (Toxotes jaculatrix) are also brackish tank favorites. Both archers and monos come from mangrove swamps. In nature, archer fish spit down their prey (insects) from overhanging leaves. Monos are flat, sliver, and diamond shaped. Although tempting, they would get much to large for my 25 gallon tank.

Many hardier fish will also acclimate to brackish water. I currently have a pleco which are normally fresh water fish. He is quite the ready cleaner and will suck the algae off of the glass and fake plants.

Puffer picture: