Six, seven, or eight arms radiate from a large central disc. Despite its name, the seven-armed sea star can have anywhere from six to eight arms. The arms are thick and tapering. They are covered in short spines. The colour ranges from brown to grey to orange. Darker mottling is often present. Variation is the norm. Symmetry is flexible. The appearance is unpredictable. The reef provides the background. The star provides the contrast. Mussel beds are its hunting ground. The seven-armed sea star is a voracious predator. It feeds on mussels, barnacles, and other shellfish. It climbs onto the shells of its prey. It attaches its tube feet to the two halves. Then it pulls. Slowly. Steadily. Until the shell opens a crack. The sea star everts its stomach through its mouth. It pushes the stomach into the shell. Digestive enzymes liquefy the prey. The sea star absorbs the liquid. Digestion is external. Consumption is internal. The process is efficient. The mussel does not escape. One of the largest sea stars in New Zealand waters, it can reach thirty centimetres across. The disc is thick and fleshy. The arms are muscular. When it moves, it crawls on hundreds of tube feet. Each one is tipped with a suction cup. The movement is slow but inexorable. A mussel cannot escape once a seven-armed sea star has decided to eat it. Persistence is the strategy. Speed is irrelevant. The outcome is certain. Rough, spiny skin protects it from predators. The spines are short and sharp. They are embedded in a leathery skin. Large fish and octopus will eat sea stars. But the spines make the seven-armed sea star difficult to swallow. It is not invulnerable. But it is well defended. Armour replaces speed. Defence is structural. Survival is passive. The shell holds. The predator retreats. Rocky reefs and harbours provide its preferred habitat. The seven-armed sea star lives from the low tide mark down to fifty metres depth. It occurs on mussel beds, on rocky bottoms, and among the pilings of wharves. It is common throughout New Zealand. From Northland to Stewart Island. It is one of the most frequently encountered large sea stars in the subtidal zone. Distribution is broad. Adaptation is general. Tolerance is high. Reproduction occurs in winter. The seven-armed sea star releases eggs and sperm into the water. Fertilisation occurs there. The larvae drift in the plankton for several weeks. They settle to the bottom. They are tiny at first. Barely visible. But they grow quickly in the food-rich waters of the reef. Growth is rapid. Survival is chance. The next generation arrives. The cycle continues. Climate change may affect it indirectly. Ocean acidification makes it harder for mussels and barnacles to build their shells. If the prey declines, the predator may decline with it. For now, the seven-armed sea star remains common. A large, spiny predator on the reef. Pulling open mussels with inexorable patience. Resilience is tested. Limits are unknown. The future is uncertain. The present is stable. No one told it otherwise. It carries on. The rock stays cold. The water stays dark. The arm extends. The cycle repeats. It is a quiet victory. No fanfare accompanies it. No celebration marks it. The sea star simply exists. It continues its work. It maintains its watch. And that seems to be enough.