The Antarctic waters are not simply an aquatic desert but deem with life. Almost every season, researchers find new and previously unknown species in the depths of the ocean and their bizarre shapes astonish both scientists and common people alike. In addition, the not widely known sea spider seems to exist in a higher number than previously assumed. It is probable that these eight-legged aquatic animals have once spread from Antarctica to adjacent waters and from there conquered the world’s oceans according to marine biologists. The scientists have published their findings in the magazine “Royal Society Open Science. Until now, it had been hypothesized that several species of sea spider had moved to Antarctic waters instead of developing there.

Sea spiders are an independent group of marine organisms not really related to spiders. However, they possess eight legs and an elongated body, which gives them a spider-like look. Foto: Claudia Arango, Queensland University
Sea spiders are an independent group of marine organisms not really related to spiders. However, they possess eight legs and an elongated body, which gives them a spider-like look. Foto: Claudia Arango, Queensland University

It is pitch dark and icy cold – but still, the place is abundant with life and a fascinating biodiversity. Scientists from Germany, Australia, and the USA reveal the secrets of aquatic Antarctica now. Among them is a researcher from the University of Duisburg-Essen. The scientists have examined more than 500 giant sea spiders (or pycnogonids) which are considered abundant in the Southern Ocean. The results, published in the magazine “Royal Society Open Science), now show that some of the species had developed in the Antarctic and from there had settled in other oceans. This is in contrast to the current believe that they da moved to the Antarctic several times.

Prof. Florian Leese from the University of Duisburg-Essen is heading the working group „Aquatic Ecosystem Research“ within the Faculty of Biology. His main interest is the origin, the expansion and the adaption strategies of aquatic organisms, i.e. sea spiders in the Antarctic.
Prof. Florian Leese from the University of Duisburg-Essen is heading the working group „Aquatic Ecosystem Research“ within the Faculty of Biology. His main interest is the origin, the expansion and the adaption strategies of aquatic organisms, i.e. sea spiders in the Antarctic.

For a long time, the icy waters of the Southern Ocean had been considered low on species and more like a desert. However, several expeditions over the last 30 years were able to prove that theory wrong. “Especially the Antarctic continental shelf is home to several different species of pcynogonids nowhere else found on this planet, so-called endemites”, says Prof. Florian Leese from the faculty of biology at the University of Duisburg-Essen. The sea spiders are hard to distinguish by appearance. Therefore, a definite classification is only possible by genetic analysis.

The biodiversity of the Southern Ocean is remarkable. Pictures from various regions often show unknown species of organisms and emphasize the diversity of the Antarctic.
The biodiversity of the Southern Ocean is remarkable. Pictures from various regions often show unknown species of organisms and emphasize the diversity of the Antarctic.

The genetic data hints to an explosive development of new species during the ice ages of the last five million years. This result was obtained by analyzing a certain gene of Colossendeis megalonyx, the giant sea spider. The scientists examined more than 500 specimen of this 25 cm large, bizarre animal that had been caught with trawling nets. On the one hand, the results point to the Antarctic as a center of species development, from where the eight-legged animals settled in other oceans. On the other hand, it is apparent that the animals were able to withstand the massive and extensive glaciation periods in situ and did not resettle from the South American continental slopes. Twenty genetically distinctive lines had been identified via one mitochondrial gene. “Their nucleoid DNA tells us, however, that they are not 20 different species, but have a genetic exchange and thus have merged again with each other”, said Leese. “Thus, we expect five to seven different species of sea spiders.”

The researchers had spent ten years to investigate this biodiversity hotspot. By this, they were able to construct one of the largest data sets on molecular diversity. In a next step, the scientists would like to investigate the mechanisms of speciation via high-resolution gene analysis and other tools.

Source: University of Duisburg-Essen, www.uni-due.de