The work published in the prestigious journal Frontiers in Ecology and Evolution aimed to understand the impact of glacial cycles on the diversity patterns and genetic structure of Laevilacunaria antarctica.

A territory in very dry, cold conditions and with areas of water mostly turned into ice. This was the so-called “Last Glacial Maximum” recorded approximately 20,000 years ago, and considered the time of maximum extension of ice sheets on the planet. An excellent example pointed out from Valdivia by Claudio González-Wevar, PhD in Science with a major in Ecology and Evolutionary Biology, allows the study of genetic patterns and the impact of polar events on the Antarctic mollusk known as Laevilacunaria antarctica.

“As a consequence of the Last Glacial Maximum, species were isolated in refuges, causing the so-called population fragmentation, along with the formation of many complexes of cryptic species,” warns González-Wevar. As a result of this extreme scenario, a part of the Antarctic biodiversity survived these glaciations, although benthic marine organisms, that is, those that live on the sea floor, would have been the most affected by the advance and retreat of the ice.

This is indicated by a recent study published in the prestigious journal Frontiers in Ecology and Evolution, which analyzed the patterns of diversity and genetic structure of the small Antarctic snail Laevilacunaria antarctica throughout its distribution in the South Shetland Islands, Antarctic Peninsula and South Georgia Islands. The results suggest that the population of the small Antarctic snail located in South Georgia shows very marked genetic differences with the rest of the populations of the South Shetland Islands and the Antarctic Peninsula: “This means that the populations of this mollusk—which does not exceed the 20 millimeters—have evolved independently for at least a million years,” says González-Wevar, an academic at the Faculty of Sciences of the Austral University of Chile (UACh) and researcher at the IDEAL Center and the BASE Institute.

The scientist highlights the characteristics of Laevilacunaria antarctica as an amazing Antarctic sea snail: “It is incredible in many ways, but the main one is that it would have had the ability to survive the coldest moments of the Quaternary glacial cycles and subsequently re-colonize much of of the Antarctic Peninsula and the South Shetland Islands.

“By studying in detail the growth of Laevilacunaria antarctica, the researcher explains that this species is characterized by not having free-living larval stages, that is, the females deposit masses of eggs from which juveniles emerge, which later become snails. adults, therefore, have what is called a “low dispersion potential.” How do they manage to extend their presence to other polar regions? Apparently through seaweed, the research postulates.

“The re-colonization capacity of this species, in a large area of the Antarctic continent, would probably be associated with the close relationship it maintains with macroalgae,” says González-Wevar. “In this way, the so-called rafting on macroalgae – which are part of the Antarctic seabed – would be a transcendental mechanism in the biology of the species and would explain the high genetic homogeneity detected in the Antarctic Peninsula and the South Shetland Islands, an area covering thousands of square kilometers.”

To take samples of the species in the challenging Antarctic territory, with sub-zero temperatures and sometimes hurricane-force winds, Dr. Claudio González-Wevar had to move to the coastal edges of the frozen continent, the so-called intertidal: “Thus, we access ice-free areas, we carried out a visual search that requires a lot of time and caution, to finally find the snails, collect some specimens, and then return to Chile and carry out their analysis in the laboratory,” warns the researcher..

It is usually possible to identify the Antarctic sea snail Laevilacunaria antarctica in rocks or algae of the Antarctic intertidal. Its brown color allows for almost perfect camouflage, despite its black antennae and shell that radiate blue flashes, which in every movement imitate elegant velvet clothing, details the scientific team. Due to its small size, its collection is highly complex, and only through tweezers and sampling tubes is it possible to transport it to the laboratories in the Los Ríos region.

The research team made up of scientists from Chile, France and New Zealand, emphasizes that the marked divergence between the populations of the species Laevilacunaria antarctica in the Antarctic Peninsula and South Georgia is evidence that these populations have evolved independently during at least a million years. Furthermore, it is possible that the Antarctic Peninsula/South Shetland Islands populations and the Georgian populations are different species. This hypothesis will be tested in future studies including morphological and radular analyses. Furthermore, the species would have seen its population sizes greatly affected by the advance and retreat of the ice during the glaciations.