Assessment of the capacity of Halicarcinus planatus larva to reach the South Shetland Islands through passive dispersal

In the last 50 years, the anthropogenic activity and atmospheric temperature in the West Antarctic Peninsula have increased constantly, and consequently have facilitated the establishment of exotic species. Different populations of alien plant and insect species have been already recorded in the terrestrial Antarctic (e.g.Poa annua, Juncus bufoniusand Eretmoptera murphyi). In contrast, no alien marine species have been reported until now in Antarctic seawater, with the exception of a single ovigerous female of Halicarcinus pla-natusfound in the shallow waters of Deception Island in 2010 and reported in the scientific literature in 2015. Halicarcinus planatusis a small brachyuran crab living in shallow habitats, distributed in the southern South-America and in Sub-Antarctic islands (i.e. Prince Edward and Marion Islands, Crozet and Kerguelen Islands, Falkland Islandsand New Zealand). In the Sub-Antarctic islands, H. planatusis usually the unique crab species present in the shallow ecosystems. This species is able to live in cold Sub-Antarctic water mainly be-cause of its capacity to down-regulate Magnesium concentration ([Mg2+]) in the hemolymph below seawater concentration. Because of these physiological characteristics, together with a high potential of dispersal through a 45 to 60 days larva, H. planatushas beenhistorically considered as a potential invasor ofAntarctic shallow ecosystems.Here, the ability of H. planatuslarvae to be transported by water current from Sub-Antarctic to An-tarctic is evaluated through the Lagrangian particles approach and model-estimated ocean circulation. Model parameters were defined by the species characteristics (i.e. behavior, habitat preference and reproductive stra-tegy) and ecophysiology lab experiments. The survival rates of H. planatuswere measured for extreme tempe-ratures (between -1.8 and 5°C for adults and at 1, 2 and 5°C for larvae) and for salinity between 4 and 32 PSU (for only adults). Results showed that H. planatuscould survive at temperature above 1°C and salinity above 18 PSU. So that, larvae could reach Antarctic waters during summer, when temperatures are above 0°C.A possible larvae transport is from Diego Ramirez Island; it’s the last island from South America that in addi-tion is located very near of polar front and where H. planatuscan be found.Financial support: FONDECYT 1161358, Centro Fondap-IDEAL 15150003, INACH DG_14_17, FONDECYT 1160877, PIA CONICYT ACT172065. The collaborative Belgian BRAIN project: Refugia and ecosystem tolerance in the Southern Ocean (RECTO).

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