www.ntnews.com.au Saturday, January 18, 2014. NT NEWS. 47

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NTNE-WS-DA-TE:18-JGE:47 CO-LO-R: C-M Y-K

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And you thought youwere afraid of change

The elephant shark gets its moniker from a trunk-like snout with which it rummages for crustaceans on the ocean floor

A PREHISTORIC fish that in-habits the waters off southernAustralia and New Zealandevolves even slower thanthe coelacanth, a famous ‘‘liv-ing fossil’’ whose DNA hasbarely changed over hun-dreds of millions of years,scientists say.

The genome of the elephantshark ‘‘is evolving signifi-cantly slower than other ver-tebrates, including the coela-canth’’, they reported in thejournal Nature.

Known by its Latin name asCallorhinchus milii, the el-ephant shark gets its monikerfrom a trunk-like snout withwhich it rummages for crus-taceans on the ocean floor atdepths of about 200 metres.

Despite its name, the crea-ture is not a shark.

Strictly speaking, it is a chi-maera, a small group of fishthat diverged from sharks,rays and skates, called elas-mobranchs, about 420 millionyears ago.

Both groups are ver-

tebrates whose skeleton ismade of cartilage. They splitfrom bony vertebrates about450 million years ago.

Comparing the genomes ofthe elephant shark with thatof humans and other ver-tebrates, the study found thatthe genetic code of C. milii isextremely compact, being lessthan a third that of humans.

Its genome, they found, hasevolved even less than that ofthe coelacanth — a rare fishfound off South Africa thatis such a success in its habitatniche that it has hardlyhad to change over nearly400 million years.

The genome could hold in-sights into how bones are for-med, which could help thefight against the bone diseaseosteoporosis.

Elephant sharks, also cal-led Australian ghost sharks,grow to about 120cm inlength. The fish is occasion-ally netted as by-catch bycommercial trawlers but isnot considered endangered.