Vulnerability in Antarctic limpets: ready for an invasion of shell-crushing predators?

The establishment of non-indigenous species in the Antarctic, an ecosystem isolated for millions of years, could dramatically alter its unique and endemic biota. In coastal waters, calcified species (e.g., echinoderms, gastropods, bivalves) of benthic communities will be particularly vulnerable to shell-crushing (i.e., durophagous) predators such as crabs. The magnitude of changes in the community structure of shallow Antarctic waters potentially produced by such non-indigenous predators will depend on the innate vulnerability of these species (e.g., shell characteristics) and their potential to respond to novel threats (e.g., behavior, shell thickening). This study aims to evaluate the potential interaction between shell-crushing predators and the limpet Nacella concinna , an endemic Antarctic species and one of the most abundant and conspicuous gastropods in intertidal and shallow subtidal zones of the Antarctic. First, we showed that the king crab Lithodes santolla, a representative species of a group of crabs likely to invade Antarctic waters, was able to break the shell of N. concinna and consume it in the laboratory. We then assessed the shell-breaking force of N. concinna living in four Antarctic habitats (two intertidal and two subtidal) and found wide variation in this trait. Finally, we examined shell-breaking force of a subantarctic congener, N. deurata, which naturally coexists with shell-crushing predators in its native range, and found its shell-breaking force to be similar to the strongest populations of the Antarctic species. Taking into account the crushing claw force of crabs and their high consumption rate of limpets, N. concinna will be highly vulnerable to this kind of durophagous predators and may have limited reaction norms for increasing any inducible defenses such as the thickening and hardening of the shell or changes in their behavior in the face of the almost inevitable invasion of shell-crushing predators into the Antarctic marine ecosystem.