Thursday, June 12, 2014

Barcoding snakeheads

Snakeheads are freshwater fishes with the ability to breath atmospheric air through some chambers that are located behind their gills.The group is split into the two genera Channa (native to Asia) and Parachanna (native to tropical Africa). Some snakeheads are small fish with a body length of 15 cm, but most of them grow much larger (up to 2 m). All Channa and Parachanna are fish-eating thrust predators with pretty sharp teeth. I can attest to that as I got bitten by a blotched snakehead (Channa maculata) once. It was painful, a bit bloody, but the most remarkable thing was that it was just a juvenile probably not larger than 10 cm. Adults of this species have been reported to grow as large as 1.5 m.

The smaller snakehead species and juveniles of some larger species are available to hobbyists through the aquarium fish trade. Especially some of the juveniles of larger species are very colorful which makes them a target for many hobbyists but there lies the problem. One day the fish outgrows any regular tank and the owner is looking for ways to get rid of it. Unfortunately most just bring the animals to a nearby pond or lake to release them and because of this, introductions far beyond native ranges have occurred. 

Some species are already established in North America while others have been captured from natural waters of the United States and more recently Canada without evidence of reproduction and likely represent released aquarium fishes. In addition to that snakeheads at or near sexual maturity are being sold alive in ethnic food markets as several species are highly valued as food fishes within parts of their native ranges.

Here a little video about snakeheads. It is already seven years old and exaggerating but that has become rather common in networks such as National Geographic or Discovery. Nevertheless, it shows why these fish are so successful once introduced.

And why am I talking about snakeheads today? Well, we just published a paper on DNA Barcoding of snakeheads and it is time for some self-promotion:

The objectives of this study were to assemble a library of DNA Barcode sequences derived from expert identified reference specimens in order to determine the identity and aid invasion pathway analysis of the non-indigenous species found in North America using DNA Barcodes. Sequences were obtained from 121 tissue samples representing 25 species and combined with public records from GenBank for a total of 36 putative species, which then partitioned into 49 discrete haplogroups. Multiple divergent clusters were observed within C. gachua, C. marulius, C. punctata and C. striata suggesting the potential presence of cryptic species diversity within these lineages.

Any utilization of DNA Barcoding needs a reference library and the establishment of one for snakeheads was our primary goal. During the process we discovered some cryptic diversity in some species and the next step will be to look closer into this and describe new species where appropriate. However, species listings such as FishBase and Catalog of Fishes currently list about 38 species for Channa and Parachanna which means that we covered most of them with our work. All species that are currently listed as introduced or potentially invasive species are covered.

The barcode data from this work could also inform the development of species-specific PCR primer and probe sets for the detection of environmental DNA for some of the known invasive species. This would greatly help conservation management with the detection of non-native and potentially invasive species without the need to catch any specimens.

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