Southern Ocean
Molluscs, urchins, squid and sponges

Many aquatic molluscs are present in Antarctica. Bivalves such as Adamussium colbecki move around on the seafloor, while others such as Laternula elliptica live in burrows filtering the water above.

There are around 70 cephalopod species in the Southern Ocean, the largest of which is the colossal squid (Mesonychoteuthis hamiltoni), which at up to 14 metres (46 ft) is among the largest invertebrate in the world. Squid makes up most of the diet of some animals, such as grey-headed albatrosses and sperm whales, and the warty squid (Moroteuthis ingens) is one of the subantarctic's most preyed upon species by vertebrates.

The sea urchin genus Abatus burrow through the sediment eating the nutrients they find in it. Two species of salps are common in Antarctic waters: Salpa thompsoni and Ihlea racovitzai. Salpa thompsoni is found in ice-free areas, whereas Ihlea racovitzai is found in the high-latitude areas near ice. Due to their low nutritional value, they are normally only eaten by fish, with larger animals such as birds and marine mammals only eating them when other food is scarce.

Antarctic sponges are long-lived and sensitive to environmental changes due to the specificity of the symbiotic microbial communities within them. As a result, they function as indicators of environmental health.
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