The abyss, the deep water off Australia, has given up some of its secrets.

A team of 40 international scientists, including those from Museums Victoria and the CSIRO, have just returned from an expedition on the research vessel Investigator looking at the dark, crushing environment 4000m below the surface.

More than one-third of the spineless critters and some of the fishes found during this voyage are new to science.

The finds include worms that live in whale skulls, a red coffinfish with a fishing rod on its head, giant anemone-sucking sea spiders, a blob fish, a shortarse feelerfish, flesh-eating crustaceans, a cookie cutter shark with teeth arranged like the serrated edge of a steak knife and a herd of sea pigs.

The one-month voyage of the Investigator visited seven Commonwealth marine reserves from the Freycinet Peninsula off eastern Tasmania to the Coral Sea off central Queensland.

“The abyss is the largest and deepest habitat on the planet, covering half the world’s oceans and one-third of Australia’s territory, but it remains the most unexplored environment on Earth,” says Dr Tim O’Hara, Museums Victoria’s senior curator of Marine Invertebrates.

“We know that abyssal animals have been around for at least 40 million years, but until recently only a handful of samples had been collected from Australia’s abyss.”

At these depths it is so dark that creatures often have no eyes or produce their own light through bioluminescence. Food is scarce and animals are often small and move slowly.

The researchers used multi-beam sonar to map the structure of the seafloor, and cameras, nets and sleds to sample habitats at 2500 and 4000 metre depths.

In the deepest parts of the ocean it takes seven hours to lower and raise the equipment from the seafloor.

The journey rediscovered the “faceless” fish, a deep sea fish with no-visible eyes and a mouth on the underside of its head.

With no eyes and a Mona Lisa smile, the “faceless” fish had the crew baffled when it was brought up from 4km below the surface.

However, John Pogonoski, of the CSIRO’s Australian National Fish Collection, found it while flicking through the pages of the scientific literature aboard.

It turns out the species was first collected in the northern Coral Sea more than 140 years ago during the Voyage of HMS Challenger, the world’s first round-the-world oceanographic expedition.

“Australia’s deep-sea environment is larger in size than the mainland, and until now, almost nothing was known about life on the abyssal plain,” says Dr O’Hara.

“We’re really excited about the discoveries that we’ve made and are thrilled that we can now share them with the Australian and international public.”

Here are some of the finds:

Blob fish

This fish collected from a depth of 2.5km off New South Wales, has soft watery flesh and is an ambush predator that lies very still on the bottom waiting for unsuspecting prey to pass by.

Cookie cutter shark

A bioluminescent shark with its neatly arranged serrated teeth inhabits the oceanic twilight zone in depths to 1000 metres. It preys on big fishes, whales, dolphins and the occasional unfortunate swimmer, latching onto them before gouging out cookie-sized chunks of flesh.

Faceless fish

Rediscovered in Australian waters after more than 140 years.

Dragonfish

Gelatinous cusk eel

Red coffinfish

This mysterious deep sea coffinfish belongs to the anglerfish group. It attracts unsuspecting prey using a fishing rod tipped with a fluffy bait on top of its head.

Tripod fish

Often called spiderfishes, these sit high off the seafloor on their stilt-like fins. To feed, they face into the current, extending their elongated pectoral fins forward to feel their prey drifting by.

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