Tag Archives: zebrafish

Danio year 2009: Danio quagga

In March last year, our PhD student Te Yu Liao and I were able to collect along the Myanmar border with India, in tributaries to the Chindwin River. Our intended stops were Kalaymyo and Tamu, but we also tried stopping at streams along the road. It was very dry at the time, and even large rivers reduced to small streams.

Stopping by one of these streams, in the heart of a large village, we seined a pool with some vegetation. And in there was a zebrafish! Zebrafish in Myanmar, in the Ayeyarwaddy drainage. No way. It had to be something new, and as we have learned from Meinken, all danios are striped anyway. The fish went into formalin, and the chase for the next specimen commenced.

The stream

After one more hour, still not one more specimen of this schooling species, but hundreds of Danio albolineatus, and we were called to inspection by the local authorities, so we had to move on. Indeed, we were in a hurry between Kalaymyo and Tamu to arrive at our destination before dark, not only because of likely shortage of accommodation in Tamu, but also because we were given only one day of permanence in Tamu and would need to spend time with local authorities to explain our presence. But hand on heart, you can’t leave a new species like that? Well, we moved on convinced we would find more specimens in some other place. Unfortunately it did not turn out so. We left Tamu with four more specimens from the market, where they hid in heaps of plenty of other little fish, dead to the bone, and with the total of five we eventually left Myanmar. Myanmar markets have large fish, but also large quantities of very small ones, used to prepare a special fish paste, ngapi. In the early morning there is thus plenty of fresh fish in the market and saves on collecting in the wild, with the caveat that fresh fish from the stream preserve better.

So, we were back with only formalin preserved specimens, and in the present times that is bad, because DNA sequencing is in the vogue, and generally a useful tool to check on phylogenetic relationships, and because formalin denatures DNA. Some of us can still do systematics without DNA, however, and that we did. The striped danio turned out not very similar to zebrafish at all, except in the general colour pattern. It is rather related to the spotted species, Danio kyathit from the neighbouring upper Ayeyarwaddy drainage and with one specimen recorded from the uppermost Chindwin.

The mammal: Equus quagga.

We named our striped danio Danio quagga. Quagga is the species or subspecies epithet of one of the zebras, so that within the genus of the zebrafish there should be at least one species with a name associating to zebras. We didn’t call it Danio zebra just not to confuse things for the zebrafish people (and perhaps, in the end, ourselves). (But wouldn’t it have been fun?)

The fish: Danio quagga, holotype.

See above what it looks like, now that the holotype has been dead for a while. Exciting as it was to encounter another zebrafish in the wild, I am not convinced that this will become an ornamental fish hit. Our comparisons suggest that it is most close to Danio kyathit, which hasn’t outcompeted the leopard danio in the hobby. It is also somewhat larger than a normal Danio rerio, requiring more swimming space (the holotype was the only one in 50 m of stream …). And, of course, why would we need another striped danio in our tanks. Seems we have exhausted danios as ornamental fish? But there is of course more to a fish than populating an aquarium. We are gradually building a phylogenetic history of danios, and then it is just great to find a sister-species pair, a split branch on the tree, rather than having single branches of uniques. Now we will move on to connect D. quagga and D. kyathit to the rest of the tree.
If you want to read the original description, you can download an Open Access copy, which you can share with families and friends as much as you like. Just click on the reference below. It’s magic!

Reference
Kullander, S.O., T.Y. Liao & F. Fang. 2009. Danio quagga, a new species of striped danio from western Myanmar (Teleostei: Cyprinidae). Ichthyological Exploration of Freshwaters, 20: 193-199. Open Access PDF


Image credits:
Map from the NRM Ichthyology Collection online database, using Google Maps
Danio quagga and stream: Sven O kullander, CC-BY-NC
Equus quagga: Muhammad Mahdi Karim, from Wikimedia Commons, GNU FDL 1.2

Similar images

Has it not happened that you use Google search to search for images of say Danio rerio (a well-known fish). You get 16 900 hits. Unfortunately it is all too impossible to find a fish on many of those photos, because Google finds pages with the text Danio rerio having an image. And it takes time to browse through 16 900 images. This kind of image search is useful for finding the unexpected, such as anatomical drawings, phylogenetic trees, and people working on zebrafish, and definitely worth trying now and then. Without the image filter, you get 1 510 000 hits for Danio rerio, and that is just too much to browse in the hope of finding an image of the fish.

Google Labs now have a new tool under development that looks promising. It is called Similar Images, and uses some kind of image pattern recognition. What you do hear is that you specify a search for images as usual, e.g., Danio rerio, get the same result (but 16 500), but some images have the link “similar images”. Click one of those, and you get a subset of the 16 500, and on succeeding searches using the same method, you get down to 300-500 look-alike images, and most likely you have exactly what you want within reach.

This might be a tool for matching photos of unidentified fish specimens, and could also be helpful to check fish identifications on the web. Maybe could be used for other things than fish? Seems to work well with Paris Hilton (a well-known human), but for what …?

Danio rerio from Wikimedia (c) Free use

Danio rerio from Wikipedia © Free use

Zebrafish in spirits

Zebrafish (Danio rerio) are probably the most important fish for understanding humans. They are small fish, 2-3 cm long and native to India, Bangladesh, and Pakistan. Most conspicuous about them is the contrasted coloration with alternating blue and white horizontal stripes, even extending onto the caudal fin. That means they are horizontal where zebras are vertical. Otherwise there are no similarities 🙂

Zebrafish occur in many places in India, in the north in the Indus, Ganga, and Brahmaputra as well as in Kerala in the south, but appear uniform in color pattern and other morphology. They live in schools in different habitats, and are often collected in large numbers. As aquarium fish they are hardy, easy to breed, and prolific.

The distinctive colour pattern, which can be genetically altered, ease of keeping, and the fast generation time contribute to zebrafish status as a so-called model organism, which developmental biologists use to study the development and inheritance of various structures. Recently also, zebrafish researchers have been helped by improved understanding of the systematics of the group of fishes to which zebrafish belong, so that structures can be studied comparatively in closely related species.

Here is a dead zebrafish in alcohol from Assam, India. Not very colourful, but useful for taxonomic studies.

I just spent two days writing a description of a new species that I and my student Te Yu Liao collected last year (about this time) in Myanmar. There are many species of fishes closely related to the zebrafish. Thirteen species have been named in the genus Danio, and at least ten more species remain to be described. Most fascinating among the zebrafish relatives, is the leopard danio, which turned up in aquarium circles in Czechoslovakia in the 1960s and was described as a new species with the name Brachydanio frankei. This form, with small dark spots all over the body and fins, has never been found in the wild. It is probably a mutant of zebrafish, differing only in the irregular colour pattern. The genus, however, includes species that are spotted for real.

I will come back to fish species that only exist in the aquarium trade later. Let us round off the day with some zebrafish entertainment.

If you need just an overview of zebrafish, with the basic data, try Fishbase.

Wikipedia insists on being very technical about zebrafish

These developing zebrafish embryos are just irresistible:

The Wolfgang Driever Lab at the University of Freiburg has still images so you can track all the details at different stages. Click the image (from their website) to enter the zebrafish anatomy:

And then there is an enthusiasts’s website with images of various zebrafish-like species, Pete Cottle’s Danios and Devarios.