230
thousand
Approximate number of described
marine species
1 – 1. 4
million
estimated total
number of
marine species
Marine census
count continues
most species diversity seen
in waters by Japan, Australia
By Susan Milius
A 10-year, 2,700-scientist effort to find
and record marine life estimates that
roughly 80 percent of sea species remain
undiscovered.
The international Census of Marine
Life has so far described 1,200 new species, with more on the way. Census scientists have also tallied an average of
10,000 known marine species in each of
25 important ocean regions.
Based on the ease with which scientists are still finding new species,
researchers suggest that much of the
oceans’ diversity remains unknown.
“There is a lot more to do, but most of
the big stuff is known,” says Ron O’Dor of
Dalhousie University in Halifax, Canada,
the senior scientist for the census.
Big stuff, however, such as species of whales or turtles or sea lions,
barely amounts to a drop in the oceanic bucket. Census data indicate that
crustaceans are the largest chunk of
known marine creatures, including
crabs, shrimp and the unsung but ecologically crucial krill.
Formal census efforts will come to an
end in October 2010 when researchers
unveil their final results. But a first set of
papers on regional efforts was published
in PLoS ONE on August 2.
Australian and Japanese ocean waters,
each with about 33,000 known species,
top the list for highest diversity among
the 25 regions surveyed. The Gulf of Mexico, examined before the 2010 oil spill,
ranked in the top five with 15,374 species.
(The other two high-scoring zones: China
with 22,365 and the Mediterranean
with 16,848.)
Other areas with lower totals, such as
the waters off South Korea, were rich in
species for their seabed area.
Census scientists also ranked the big-
gest threats to sea life. Overharvesting
tops the list, O’Dor says, with fisheries
such as cod collapsing dramatically in
recent decades. Next come habitat
destruction from coastal development,
pollution and other human activities.
Climate change presents a major chal-
lenge too, with associated perils of
altered seawater chemistry.
Marsupial family tree gets new root
New genetic analysis traces group’s origins to South America
A marine-life census has discovered
more than 1,200 species, including this
crustacean found near Antarctica.
By Gwyneth Dickey
The kangaroo’s twisted marsupial
family tree is now in order, thanks to
jumping genes. Genetic evidence shows
that a South American ancestor gave rise
to all Australian marsupials, and that the
South American opossums were the earliest group to branch off from the other
six marsupial clans.
Distinctive for raising their live-born
young in protective pouches, marsupials all trace back to a common ancestor
that split from other mammals about 130
million years ago. But fossil and genetic
evidence conflict about which subsequent marsupial species evolved first,
and where.
Jumping genes provide new clues for
solving the puzzle. These strands of DNA
make copies of themselves to reinsert
randomly in the genome — the entire set
of genes in a cell’s nucleus. Gene-jump-ing is rare, and each jump is unlikely to
happen again. So if two species share a
jumping gene, they probably inherited
it from a common ancestor.
Maria Nilsson and colleagues at West-
fälische Wilhelms Universität Münster
in Germany compared jumping genes in
the seven main branches of marsupials.
In the July PLoS Biology, the team pres-
ents a new marsupial family tree with
slightly different familial relationships
than other research had predicted.
