The smaller side of Arctic life

Two Russian scientists have set out to document what they say are among the most undervalued creatures in the Arctic.

Shell-bearing microgastropods (snails no larger than five millimetres) have a variety of diets and lifestyles and perform many functions in marine ecosystems, says ecologist Ivan Nekhaev, from St Petersburg State University.

They provide a range of information that can inform responses to the region’s two biggest problems – climate change and environmental pollution – yet we don’t know as much as we should about them.

There are 66 known species in four sub-classes, Nekhaev says, but half of them have only had the external appearance of the shell studied. Important details of the internal structure and sequence of genes, traditionally used in the classification of animals, remain unknown.

Part of that is no doubt because studying these animals is not easy.

“Imagine a two-millimetre mollusc in front of you. From it, you need to extract its reproductive system, which is… tenths of a millimetre,” Nekhaev says. “This is a very delicate, laborious and meticulous work.”

He and colleague Ekaterina Krol appear up for the task, however. They’ve summarised and analysed known information on the species composition and lifestyle of these animals in the eastern sector of the Arctic and described two species, with two others being worked on.

Their work to date is set out in a paper in the journal Systematics and Biodiversity.

“Starting from the 18th century, snails were classified according to their shell: each species was believed to have its own shape,” Nekhaev says. “Later molluscs began to be dissected and only at the current stage scientists have started studying their DNA. These studies have shown inconsistency in the classification by shell.”

That can cause problems if, for example, a microgastropod found in the north, that was thought to be from the south, in fact isn’t.

“Despite the formal resemblance, the physiology and requirements for living conditions of these animals can vary significantly. The shape of the shell of some species is typical of the more southern areas.

“When they are found, it is often written that this is due to climate change. Such publications raise information noise, which makes it difficult to capture real changes in ecosystems.”

To date 51 of the 66 species have been found in the Barents Sea, between Russia and Norway, but as few as 10-20 in other seas of the eastern Arctic and nine in the deep-water Arctic basin.

However, an analysis of the similarity of species composition in different regions has also revealed a connection between the distribution of species complexes and hydrological conditions.