Ocean covers two-thirds of the surface of the Earth to a depth of four kilometres. It is by far the largest ecosystem. Study of the deep ocean started at the end of the 19th century, though much more recently in Australia.
Since the 1980s, marine biologists at the museum have been building collections from the deep sea off the coast of south-eastern Australia to explore the evolutionary history of this extraordinary environment. The sea floor and mid-water has been sampled from oceanographic ships using dredges, trawls and grabs. The continental slope and sea mounts are of special interest and have revealed a diverse fauna of fishes, crabs, lobsters, molluscs, corals, sponges and many other things.
It is likely that the majority of species in the ocean’s deep mid-water produce biological light. Contrary to what might be expected, this assists many to escape notice, helping protect them from becoming a meal for marauding predators. Among the best adapted are the deep-sea hatchet fish, whose downward-directed photophores completely cover the underside of their very compressed bodies. The light they produce matches the dim light coming from above and obscures their profile when seen from below.
Many species of the deep-sea floor have long, thin legs and are larger than their shallow-water cousins. The Giant Sea Spider, with a leg span of 500 millimetres, is an example, adapted to walk gently on the soft mud covering the ocean floor.
The museum’s deep-sea collections are of global significance because they contain species found nowhere else and are not replicated in other museums.