On Liljeborgia fissicornis (M. Sars, 1858) and three related new species from Scandinavia, with a hypothesis on the origin of the group fissicornis

Abstract

The large and common Scandinavian amphipod Liljeborgia fissicornis (M. Sars) is split into four species: the deep-water L. caliginis sp. nov. and L. charybdis sp. nov., and the shallow-water L. fissicornis and L. ossiani sp. nov. The poorly known species L. polosi Barnard and Karaman, recorded from the deep Canadian Basin of the Arctic Ocean, is considered as belonging to the same group. All those northern species are completely devoid of eyes, while similar species from the Antarctic and sub-Antarctic continental shelf do have eyes. It is hypothesized that the group fissicornis, which is specific to cold waters, derives from ancestors living on the continental shelf of the Southern Ocean. These ancestors would have adapted to deep-sea environments, losing their eyes completely. Then they would have migrated northwards through the cold abyss, and reached the cold but shallow waters of the Arctic/sub-Arctic continental shelf, without redeveloping visual organs.

Keywords:

• Liljeborgia
• Amphipoda
• Atlantic
• Arctic
• deep-sea

Acknowledgements

This paper has been written in the framework of an “Action 1” research project “Evolution of biodiversity patterns in shelf and abyssal liljeborgiid amphipods from the Polar Oceans and surrounding Seas” of the first author, funded by the Federal Belgian Science Policy. We are deeply indebted to Hilde C. Trannum (Norwegian Institute for Water Research, Oslo) for the gift of specimens collected during the cruise “Barentshavet 02”, and to Egor Vinogradov (Severtsov Institute of Ecology and Evolution RAS, Moscow) for the gift of the specimens now designed as the types of L. charybdis sp. nov. and for helping us to sort out the problem of the stations of Kamenskaya (1980).