Thursday, June 25, 2015

Antarctic sponges

Sponges constitute an important component of marine ecosystems in the waters around Antarctica. As filter feeders that rely on food particles suspended in the water passing through complex networks of canals lined with flagellated cells, they provide protected niches for many other organisms.
Some 350 sponge species have been described from the seas around Antarctica, many of which occur nowhere else. This high proportion of endemic species most likely is a reflection o the isolation of the continent, which separated from Gondwana around 140 million years ago. Progressive cooling of the climate, together with the development of the Antarctic Circumpolar Current, set up effective barriers to dispersion, and stimulated ecological specialization.

A team of researchers from Germany and New Zealand has now carried out the first comprehensive molecular genetic survey of sponge diversity in Antarctic waters, using DNA Barcoding. The colleagues found out that Antarctic sponges are a surprisingly diverse group. In fact, the degree of species richness found in the waters around the coldest continent is comparable to that found in tropical sponge communities. Their analyses also supports the idea that Antarctic sponges developed as a largely isolated population, descendants from a small number of ancestral forms that evolved in the waters off Gondwana prior to the break-up of the supercontinent. Some species of Antarctic sponges are known to be widespread on the continental coasts, but very little is known about the genetic relationships between them.

In spite of their considerable ecological significance, Antarctic sponges have never before been investigated with modern molecular methods, which permit rapid and unambiguous species identification and yield insights into the evolution of the group. 

Our results make it possible to create a library of DNA barcodes, which can be used for comparative investigations of the group. We can determine, for instance, whether an ostensibly circumpolar species actually represents a single species or a collection of diverse local forms. Such information is of great significance for the conservation and management of the marine resources in the seas around this unique landmass, which is acutely threatened by global climate change.

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