August 5, 2005
Australia seeks to breed test-tube sharks
By Michael Perry
SYDNEY (Reuters) - The endangered gray nurse shark is its
own worst enemy -- its young eat each other in the womb -- so
Australian scientists have a radical rescue plan to
artificially inseminate and breed the ocean predator in
docile marine creatures, and despite it being declared
endangered in 1984 and its habitat protected, it could become
extinct along Australia's east coast within 20 years,
In a process called intrauterine cannibalism, gray nurse
embryo pups develop a jaw and razor-sharp teeth very early in
their development and cannibalize siblings in the womb.
The sharks have two wombs in which a dominant pup will
consume its siblings, leaving only two surviving pups every two
years when the shark breeds.
"It is not breeding quickly enough. It is being caught out
in the wild and it is not recovering from the fishing pressures
on the east coast," said Melbourne Aquarium curator Nick Kirby.
Nicknamed the "labrador of the sea" due to its docile
nature, gray nurse numbers plunged after being wrongfully
blamed for many attacks on swimmers off Sydney beaches and it
was brutally hunted until the 1960s.
Their plight has now become critical.
Breeding programs have been used to conserve the endangered
cod trout in Australia, the Mexican gray wolf and Californian
condor, but scientists here say this will be the first attempt
at shark breeding.
Melbourne Aquarium this month artificially inseminated
Lonnie, an 8-1/2-foot-long seven-gill shark with the sperm from
a male tank mate.
It will take several months to see the first signs of any
pregnancy, but if successful the insemination technique could
be used on the critically endangered gray nurse.
"We are using our seven gill shark as a surrogate species
because they are more common and easier to work with than
risking the gray nurse shark," Kirby told Reuters.
A common problem trying to breed sharks in aquariums is
their reluctance to mate. No seven gill sharks have been born
in captivity in Australia and only eight gray nurse pups have
been born in Australian aquariums in the past decade.
To inseminate Lonnie, scientists had to first use
ultrasound to determine the female shark was ovulating and then
sedate a seven-gill male shark, named Gonzo, and internally
massage its guts to stimulate the production of sperm, which
was then injected into Lonnie's reproductive tract.
"We expect in two or three months to do an ultrasound to
check the embryos and eggs development," said Kirby. "After
fertilization we are talking a year for pups to be born and
with seven gills there could be 60 or more pups."
Artificially inseminating gray nurse sharks will not avoid
intrauterine cannibalism, so marine scientists at the New South
Wales (NSW) state fisheries department have come up with a
radical plan to breed the embryo sharks in individual test
"Once the embryos have developed to a certain size they
actually have a fully functional set of jaws and teeth, then
they swim around and cannibalize their siblings," said
fisheries marine biologist Nick Otway.
"We have to bypass this cannibalistic phase. Once the
animal gets through that stage it fends for itself. It just
swims around the womb eating, we just have to feed it," Otway
With only one embryo pup surviving in each womb, the female
shark then produces unfertilized eggs for it to feed on until
it grows to about 3 feet in length and is born. Each pup
consumes an estimated 17,000 pea-sized unfertilized eggs.
Scientists plan to harvest embryos from pregnant female
gray nurse sharks in the wild, then raise them in specially
built artificial uteri in fisheries laboratories.
The A$250,000 (US$189,400) government funded shark
test-tube plan has a 10-year timeframe as scientists must first
learn how to create an artificial shark uterus and develop
artificial uterine fluids and artificial eggs to feed the shark
Once built, the artificial uteri will be tested with
embryos from nonaggressive sharks so as not to risk gray nurse
Scientists will then develop the surgical procedures to
harvest embryos from female sharks in the wild and insert the
embryos into the artificial uteri.
Gray nurse (Carchatias taurus) numbers are declining
worldwide, with populations off South Africa, the U.S. east
coast, South America, Japan and New Zealand.
HOW TO INSEMINATE A SHARK? VERY CAREFULLY
Otway believes current tagging techniques to keep track of
gray nurse sharks will be used to help harvest embryos.
Identity tags will tell scientists which female sharks are
likely to be pregnant, they will then be caught in a plastic
float and ultrasound checked to confirm pregnancy.
If they are pregnant they will be lifted into a tank
onboard a ship and flipped onto their backs, which causes tonic
immobility, or catalepsy, just as it does in chickens, enabling
embryos to be either flushed out or extracted with forceps.
Unlike other sharks which must be constantly moving forward
to force oxygen-enriched sea water through their gills, gray
nurse sharks can pump the water through gills enabling them to
remain stationary. This will help scientists keep them in a
fixed position while extracting embryos, and if necessary, to
administer a sedative over their gills.
Once inserted into the artificial wombs the embryos will be
fed artificial shark eggs until they reach birth size and then
released into the wild.
"If we do not do this the animal is going down the gurgler
(drain)," said Otway. "This animal will not survive on the east
coast of Australia unless we can do this."