DNA monitors trade in marine fish species


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Using a method similar to the genetic fingerprinting used to convict criminals, a team of scientists at the Canadian Centre for DNA Barcoding have applied molecular techniques to assess and catalogue the marine fish species entering the ornamental trade in Canada.

Over a three year period, importers sent all dead on arrival specimens to a laboratory for identification, resulting in 1638 individuals from 391 traded species.

The researchers demonstrated that 98% of these species could be distinguished from one another. Genetic variation was found to be 26 times greater between species, than within species. Species generally formed unique and cohesive units, which were clearly separated.

However, there were exceptions to this observation, such as three species of Skunk clownfish (Amphiprion akallopisos, A. perideraion and A. sandaracinos), as well as the Yellow and Scopas tangs (Zebrasoma flavescens and Z. scopas), which could not be separated by the DNA testing used.

To explain this phenomenon, the authors hypothesised that the Skunk clowns may be hybridising with one another, as they are found together in many locations.

The two tang species were believed either to have evolved very recently, meaning less time for changes in the genetic code to build up, or that they could actually comprise two colour variations of the same species.

Another surprising find was that several fishes were found to comprise what appear to be cryptic species complexes.

There were multiple genetically and geographically isolated lineages found within the fairy basslet (Pseudanthias squamipinnis), False lemon peel angel (Centropyge heraldi), Blue devil damsel (Chrysiptera cyanea), Starck s damsel (C. starcki), and two species of sleeper goby (Valenciennea puellaris and V. wardii).

The status of these as new species would have to be confirmed with further collections.

Although DNA data have been used for biological identification purposes for many years, it is only recently that the DNA barcoding technique has aimed to ambitiously catalogue the planet s biodiversity using the same standardised region of the mitochondrial genome.

This technology has many useful applications to society, such as the rapid identification of invasive, or economically important pest species, and the monitoring of activities such as illegal shark finning or mislabelling of food products.

The authors believe their study will assist in reef conservation efforts, by allowing regulatory agencies to quickly and effectively manage their marine resources using a publicly accessible DNA database.

Despite these advantages, the DNA barcoding initiative remains controversial among many in the scientific community, who believe this high profile project is an inferior shortcut to thorough taxonomic research, and will ultimately divert resources from the recruitment of experts, trained in the often time consuming traditional methods of identification and classification.

Supplementary information, including photos of all specimens is also publicly available at http://www.barcodinglife.org.

Steinke D, Zemlak TS, Hebert PDN (2009) Barcoding Nemo: DNA-Based Identifications for the Ornamental Fish Trade. PLoS ONE 4(7): e6300. doi:10.1371/journal.pone.0006300