larvae remain near the seabed during this time but become pelagic for up to 6 months as brachiolaria larvae which allows them to disperse widely. They then return to the seabed, undergo metamorphosis and develop into juvenile sea star. Research Odontaster validus does not attack members of its own species but can attack sea star of other species. This seems to be due to chemoreceptors which can identify conspecifics by their odour. Sea star often converge on food sources and a study was undertaken to examine how they do this. It was found that food-deprived individual Odontaster validus could distinguish between the odours emitted by satiated and by starved sea star of the same species. They were strongly attracted to the former and took little notice of the latter. Odontaster validus is much less sensitive to higher water temperatures than the other Antarctic marine species on which it feeds which mostly find temperatures above 3 °C lethal. Even when not killed at higher temperatures, many organisms cease to feed, may remain immobile or fail to reproduce and others started metabolising anaerobically. A study was undertaken to examine the implications of this for the Antarctic marine environment if water temperatures rise as a result of global warming. Another research study examined the parameters required for successful fertilisation of the eggs of Odontaster validus compared to similar temperate water sea stars. It was found that a density of sperm of 105 sperm per millilitre was sufficient to cause a high proportion of eggs to be fertilised and that this was at least ten times the density required by comparable species in less harsh environments. The sperm still retained a minimal fertilisation ability after 24 hours but had a narrow tolerance to variations in water temperature. References Odontasteridae Fauna of the Atlantic Ocean Fauna of the Southern Ocean Animals described in 1906