Thursday, September 13, 2012

Larva Thursday (1)

One of the many promising applications of DNA Barcoding was always the ability to assign larval stages of animals to their adult form. There are many groups where the larval forms are distressingly uniform in appearance and the young don't look at all like the adults. It is no surprise that a significant number of researchers who are interested in larval identification have tested DNA Barcoding and its value for their work. Therefore, I will use every Thursday in the weeks to come to present their research and how DNA Barcoding has changed their workflow.

Zu cristatus  (Credit: Allan D. Connell)
Our first episode of the series "Larva Thursday" will be on fish - maybe not a surprise to readers that know me a bit better as this is a group of animals close to my heart :-)

Unfortunately not many fish larvae do resemble juveniles and adults in basic form, and, even more helpful for the identifier, in the number of fin spines and rays and myomeres, which represent commonly used traits. More often they are transparent, very small, and, while they are alive, look just like tiny slivers of glass with eyes. Therefore, identification to species or genus is very often only possible for real taxonomic experts who perhaps spend a good time of the their life to look at larvae and describing their appearance. There are indeed quite a few monumental books out there with drawings and keys to the regional ichthyofauna but frankly the average non-taxonomist won't use them very often. More accessible are online keys and listings with images of alive animals and when researchers also went through the lengths to confirm their identifications by matching larval DNA Barcodes to adult ones I personally find that very appealing. 

Of the various websites documenting fish larvae I picked two that utilized DNA Barcoding results to confirm assignments and even discover new species.

Malacoctenus gilli (Credit: Ben Victor)
One is a guide to the larval reef fishes of the Caribbean. As most sites this is not a complete list yet but as it's owner Ben Victor states himself, "there is no reason in the age of the internet not to have a work in progress made generally accessible". Quite a few families, genera and species are already represented by short descriptions, lots of photos, and explanations of key characters. Many have been barcoded and are available as references on BOLD and GenBank. While Ben travels the Caribbean (and other places) to dive and collect larvae, one of his colleagues, Allan Connell, collects fish eggs almost every day in his "backyard" (Indian Ocean) close to Durban, South Africa. He hatches the eggs, rears the larvae and documents every stage with images and measurements. Species assignments are made morphological were possible but more and more by using DNA Barcoding because he actively helps building a reference library of DNA Barcodes of adult fishes in South African waters. All his data are publicly available through his website

Both researchers do something exceptional. They are sharing their findings openly prior to any formal publication. It would be great if many of us could follow their lead.

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