ANIMAL SPECIES:Numbfish, Hypnos monopterygium (Shaw & Nodder 1795)
The Numbfish is well known to divers. The fish often hides under the sand from where it can deliver a powerful electric shock to anyone who touches it.
Alternative Name/s
NumbrayIdentification
The Numbfish is shaped like two discs. The head and pectoral fins form a large disc, while a second smaller disc is formed by the pelvic fins. Located on the second disc are two small dorsal fins, immediately followed by a similar-looking caudal fin.
The species can vary from grey or light brown through to black.
Size range
It grows to at 60 cm in length but is uncommon over 40 cm.Distribution
The Numbfish is endemic to Australian waters. It is recorded from southern Queensland, around the south of the country and north to the north-western coast of Western Australia. It is rare in Victoria and absent from Tasmania.
Distribution by collection data
Biomaps map of Numbfish specimens in the Australian Museum collection.
Habitat
The species is found on sand and mud bottoms in shallow bays and estuaries, but is also known to depths over 200 m. When seen by divers it is usually buried in the sediment where a telltale rounded depression gives away its presence.
Behaviour and adaptations
Feeding and Diet
The Numbfish can deliver powerful electric shocks with an electric organ located in each pectoral fin. This organ is used to shock crabs, worms and fishes, which make up the Numbfish's diet.
To swallow relatively large prey whole, the Numbfish is able to greatly expand its mouth.
Craig Henderson, who was the Unit Supervisor of Taronga Zoo Aquarium until its closure in 1992 made the following comments: "I undertook a captive management study of Hypnos monopterygium as the Aquarium had never previously been successful in keeping them in captivity. We found that the rays would only feed on fish (only whole fish initially) that were presented to them on a plastic stick which was 'swum' past their nose. They rays required a soft substrate such as sand or fine shellgrit to bury into. Their attack of the prey was incredibly fast, without any warning, and was always accompanied by an electrical discharge. The prey item (including very large fish) would be swallowed head first, whole, very quickly before the animal would re-bury itself."
Sean McMahon stated that: "On the weekend I was talking to a family friend who does a lot of beach fishing. He said that in the last ten years he has found a few dead numbfish washed up on the beach. There is a large estuary near Taree (northern NSW) that opens to the sea. He said that once he found a numbfish that had just washed in and was very fat so he cut it open. Inside was a small penguin that had not been digested! He said that he found another numbfish with a penguin in it a few years later as well! I have read the e-mails concerning the 'rat in the numbfish' so I thought this may be of some interest to you."
Other behaviours and adaptations
The electric organs of the torpedo rays (family Torpedinidae) can deliver strong electric shocks (50 amps, with peak of pulses sometimes exceeding 1 kilowatt).
Classification
- Species:
- monopterygium
- Genus:
- Hypnos
- Family:
- Hypnidae
- Order:
- Torpediniformes
- Class:
- Chondrichthyes
- Subphylum:
- Vertebrata
- Phylum:
- Chordata
- Kingdom:
- Animalia
References
- Edgar, G.J. 1997. Australian Marine Life: the plants and animals of temperate waters. Reed Books. Pp. 544.
- Hoar, W.W. & D.J. Randall. 1971. Fish Physiology. Sensory systems and electric organs. Academic Press. Volume V. Pp 347.
- Last, P.R. in Gomon, M.F., Glover, C.J.M. & R.H. Kuiter (Eds). 1994. The Fishes of Australia's South Coast. State Print, Adelaide. Pp. 992.
- Hutchins, B. & R. Swainston. 1986. Sea Fishes of Southern Australia. Complete Field Guide for Anglers and Divers. Swainston Publishing. Pp. 180.
- Kuiter, R.H. 1996. Guide to Sea Fishes of Australia. New Holland. Pp. 433.
- Kuiter, R.H. 2000. Coastal Fishes of South-eastern Australia. Gary Allen. Pp. 437.
- Last, PR & J.D. Stevens. 1994 Sharks and Rays of Australia. CSIRO. Pp. 513.
- Randall, J.E., Allen, G.R. & R.C. Steene. 1997. Fishes of the Great Barrier Reef and Coral Sea. Crawford House Press. Pp. 557.
Would you like to add a comment?
Sign up to add comments and find out more about the other benefits you can enjoy.
Would you like to add a tag?
Sign up to add tags and find out more about the other benefits you can enjoy.
A Numbfish partially buried in the sand View full size
Erik Schlögl
© Erik Schlögl
Numbfish, Hypnos monopterygium View full size
Erik Schlögl
© Erik Schlögl
A Numbfish at Shiprock, Port Hacking View full size
Erik Schlögl
© Erik Schlögl
Numbfish with its terminal meal View full size
Lynda Clarke
© Lynda Clarke
Numbfish buried in sand View full size
Erik Schlögl
© Erik Schlögl
A Numbfish on the beach at Greenpatch View full size
Alex Booth
© Alex Booth
A Numbfish on the beach View full size
Alex Booth
© Alex Booth
Rat protruding from Numbfish's gut View full size
Cilla Johnstone
© Cilla Johnstone
A gilled leech beside the nostril of a Numbfish View full size
Erik Schlögl
© Erik Schlögl
Support us
Your support will have a real impact.
Online Shop
Great gifts.
Australian Museum Members
Join today.
Australian Museum Business Services
Professional consulting.
Museum as a Venue
Unique spaces.
Media Resources
Contact Publicity.