A serrated blade extends forward between its eyes. This rostrum, the nose spine, gives the jack-knife prawn its name. It resembles a folding knife, a jack-knife, with teeth along the edge. The serrations are not for cutting. They are sensory structures. They help the prawn detect prey in the soft sediment of the seafloor. Function overrides form. Sensation is key. Between two hundred and six hundred metres depth, it lives. The jack-knife prawn inhabits deep continental slopes and seamounts. It prefers sandy and muddy bottoms with stable temperatures. In New Zealand waters, it is most common on the Chatham Rise. It also occurs off the west coast of the South Island. It is found in the Pacific and Indian Oceans. Distribution is global. Presence is local. Depth defines existence. Burrowing is its daytime occupation. The prawn uses its rostrum to dig into the sediment. It clears a path. It senses what lies ahead. It buries itself in the mud. It hides from predators that hunt by sight. Only its antennae and the tip of its rostrum remain exposed. They monitor the water for danger. Concealment is total. Exposure is risk. Survival depends on staying hidden. At night, it emerges. The jack-knife prawn rises from the sediment. It begins to hunt. It feeds on small crustaceans, worms, and zooplankton. It uses its long, slender legs to pick prey from the water column and from the seafloor. Its body is pale pinkish-brown. This provides camouflage against the muddy bottom. Visibility is low. Predation is reduced. The hunt is quiet. Like all prawns, it swims backwards. Rapid flicks of its tail propel it away from danger. The tail fan is broad and muscular. It provides powerful thrust. When threatened, it flexes its abdomen. It shoots backward. It disappears into a cloud of sediment. The escape is fast. But it is also costly. The prawn cannot sustain it for long. Energy is finite. Conservation is necessary. Moulting is regular and risky. The prawn sheds its old exoskeleton. It inflates a new, soft one. It hides in the sediment until the new shell hardens. The old shell is eaten or breaks down. The prawn grows quickly. It reaches adult size within a year. It lives for only three to five years. Time is short. Growth is rapid. Survival is brief. No one targets it. The jack-knife prawn is not commercially fished in New Zealand. It is caught occasionally as bycatch in deep-sea trawl fisheries for hoki and oreo. The bycatch is not large. The species is not considered threatened. Its distinctive rostrum makes it easy to identify. But it is otherwise unremarkable. A pale prawn in the dark water. Value is low. Interest is minimal. Most of the deep sea is mud. Flat, featureless, grey mud. It stretches for hundreds of kilometres. But that mud is full of life. If you know where to look. The jack-knife prawn is one of the creatures that has adapted to this environment. It uses its serrated rostrum to sense its way through the dark. It feeds on the small animals that live in the sediment. It is not a glamorous life. But it is a successful one. The prawn has been doing it for millions of years. No one told it otherwise.