A marine snail has a shell that is remarkably 
well adapted for diffusing the light that it emits 
to ward off predators.

Stimulating Hinea brasiliana snails (pictured 
left), by tapping them or placing them in contact 
with potential predators, causes them to emit a 
blue-green light from defined areas of their body, 
report Dimitri Deheyn and Nerida Wilson of 
the Scripps Institution of Oceanography in San 
Diego, California. The shell directly transmits 

most wavelengths of light, with the exception of 
blue-green ones. These are instead spread by the 
shell from the limited production regions of the 
snail’s body over a much larger area (right).

The shell produced brighter and larger areas 
of diffused light than a commercial diffuser. 
Such shells allow snails to produce visible and 
extensive bioluminescent signals from their 
protected position inside the shell.
Proc. R. Soc. B doi:10.1098/rspb.2010.2203 (2010)

Z o o l o g y

Snail shells spread light around

E C o l o g y

Hotter climate, 
altered breeding
As Earth warms, amphibians 
are shifting their breeding 
times at unprecedented rates. 

Four out of ten amphibian 
species studied at a South 
Carolina wetland either 
delayed or advanced their 
breeding — depending on 
their breeding season — by 
15.3–76.4 days over a 30-year 
period. For two of the species, 
Ambystoma opacum and 
Eurycea quadridigitata, 
this coincided with a 1.2 °C 
increase in overnight air 
temperature during their pre-
breeding and breeding periods. 

Brian Todd at the University 
of California, Davis, and 
his team say that the altered 
breeding times, which 
range from 5.9 to 37.2 days 
per decade, are among the 
greatest rates of change seen 
in ecological life-cycle events. 
The changes could affect 
the dynamics of the larger 
amphibian larval community, 
including resource availability 
and predation rates.
Proc. R. Soc. B doi:10.1098/
rspb.2010.1768 (2010)

A N T H R o P o l o g y

DNA from across 
the ocean 
A handful of Icelanders may 
be descendents of a Native 
American woman ferried to 
the island hundreds of years 

M A T E R I A l S  S C I E N C E

Magnetic gel 
delivers drugs
Drugs and cells can be 
delivered on demand by a 
porous material engineered 
to compress in response to an 
applied magnetic field.

David Mooney at Harvard 
University in Cambridge, 

Massachusetts, and his team 
prepared an alginate-based 
gel with micrometre-sized 
pores, and paramagnetic iron 
nanoparticles embedded 
throughout. On exposure 
to a magnetic field, the 
nanoparticles put the squeeze 
on the ferrogel. The authors 
used this to release a drug 
payload in in vitro experiments 
and, by implanting the gel into 

mice, for localized release of 
dye-stained stem cells. 

With a reversible volume 
reduction of more than 70% 
(pictured), such ferrogels 
may also find applications 
as actuators and sensors in 
biomedical applications.
Proc. Natl Acad. Sci. USA  
doi:10.1073/pnas.1007862108 
(2010)

before Christopher Columbus 
reached the New World. 

In a tiny proportion of the 
country’s residents, DNA 
sequences from cell organelles 
called mitochondria (mtDNA) 
resemble those of some Native 
Americans. Unlike nuclear 
DNA, mtDNA is inherited 
only from the mother. 

Sigríður Sunna 
Ebenesersdóttir at deCODE 
Genetics in Reykjavík and her 
colleagues traced the sequence 
variants back to four Icelanders 
born in the early 1700s. 
However, genetic differences 
between them suggest that the 
mtDNA derived from a woman 
who arrived in Iceland much 
earlier — possibly around 

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ReseaRch highlights Selections from the  scientific literature

© 20  Macmillan Publishers Limited. All rights reserved10



 Nature.com
For the latest research published by 
Nature visit:
www.nature.com/latestresearch

N E U R o S C I E N C E

Better memory with less microRNA
Learning and memory in mice seem to 
be enhanced by the loss of small RNA 
molecules called microRNAs (miRNAs) in 
the brain.

Witold Konopka at the German Cancer Research Center in 
Heidelberg and his colleagues deactivated the gene for Dicer, 
a key enzyme in miRNA synthesis, in forebrain neurons of 
adult mice. Twelve weeks later, the mice showed improved 
learning and memory in a behavioural test. This was mirrored 
by increased numbers of a type of dendritic spine in mutant 
neurons that is associated with learning. After 20 weeks, 
however, some of the neurons had degenerated, confirming 
the importance of microRNAs for neuronal survival. 
J. Neurosci. 30, 14835–14842 (2010)

✪ HigHly read
on jneurosci.org
in November

commuNity
choice

The most viewed 
papers in science

C A N C E R

Tumours aided by 
immune cells
Zebrafish cells with the 
propensity to give rise to 
tumours behave similarly to 
wounded tissue, and call for 
assistance from the immune 
system. So say Paul Martin 
at the University of Bristol, 
UK, and his colleagues, who 
imaged the interactions 

g l A C I o l o g y

Imaging grooves 
from glaciers
Developments in radar 
technology have allowed 
geoscientists to ‘see through’ 
a Greenland glacier and 
construct three-dimensional 
topographic maps of its bed.

Kenneth Jezek of Ohio 
State University in Columbus 
and his team used high-
resolution radar tomography 
and synthetic-aperture radar 
data to measure ice thickness 
in a region of the Jakobshavn 
Glacier. They found that as the 
glacier slides over its bed, it 
cuts large-scale ridge–groove 
features into the bedrock that 
are similar to landforms found 
on deglaciated terrain. The 
orientation and dimensions 
of the grooves suggest that 
the glacier has been flowing 
persistently in the same 
direction. 

Understanding past glacier 
movement and bedrock 
geomorphology helps 
researchers to forecast climate-
driven changes in the seaward 
flux of ice sheets.
Geophys. Res. Lett. doi:10.1029/ 
2010GL045519 (2010)

P A l A E o A N T H R o P o l o g y

Neanderthal 
family tree
Neanderthals living 49,000 
years ago may have abided in 
small clans banded together by 
their male kin.

Carles Lalueza-Fox at 
Pompeu Fabra University in 
Barcelona, Spain, Antonio 
Rosas at the National Museum 
of Natural Sciences in Madrid 
and their colleagues analysed 
the remains of 12 Neanderthals. 
They sequenced certain regions 
of the mitochondrial DNA 
extracted from fragments of 
bones and teeth.

The results showed that the 
group’s three adult males were 
close relatives, but the three 
adult females were not. The 
authors further inferred that 
an infant and two juveniles 
were offspring of two of the 
adult females. The team 
suggests that the individuals 
represent a social unit based 
on patrilocality, in which 
individuals live with the adult 
male’s family. 
Proc. Natl Acad. Sci. USA  
doi:10.1073/pnas.1011553108 
(2010)

D E V E l o P M E N T A l  B I o l o g y

Immune system 
emerges in layers
The human immune system 
develops in waves, the first 
of which begins even before 
birth. Fetal and adult T cells 
originate from different stem-
cell populations, allowing the 
fetal immune system to better 
tolerate foreign antigens — 
namely the mother’s. 

Joseph McCune at the 
University of California, San 
Francisco, and his colleagues 
compared human fetal blood 
stem cells and T cells with those 
of adults. After implantation in 
mice that permit human blood-
cell maturation, fetal stem cells 
were more likely than adult 
ones to develop into regulatory 
T cells. These suppress immune 
activity, enhancing tolerance to 
antigens. 

Fetal stem cells and T cells 
also had different gene-
expression profiles from the 
adult versions of these cells. 
Statistical analysis revealed that 
developmental stage accounted 
for most of these differences. 
Science 330, 1695–1699 (2010)

V I S I o N  S C I E N C E

Man or woman? 
Depends on view
Whether a face looks like that 
of a man or a woman depends 
on the part of the retina on 
which the image lands.  

the time the Vikings started 
exploring the Americas in 
about ad 1000. Because Native 
American populations were 
decimated after the arrival of 
the Europeans, the lineage may 
be missing from contemporary 
populations. DNA analysis of 
the remains of ancient Native 
Americans could provide a 
more definitive link.
Am. J. Phys. Anthropol. 144, 
92–99 (2011)

between the cells in real time. 
The authors expressed a 

cancer-associated mutant form 
of the Ras protein in zebrafish 
(Danio rerio). Because 
zebrafish larvae are translucent, 
the team was able to visualize 
fluorescently labelled immune 
cells as they responded to the 
transformed cells. 

Cells expressing mutant Ras, 
and their healthy neighbours, 
released hydrogen peroxide, 
attracting immune cells called 
neutrophils and macrophages, 
which tethered themselves to 
the transformed cells. Blocking 
hydrogen peroxide synthesis 
— and so the recruitment of 
the immune cells — slowed the 
proliferation of transformed 
cells, suggesting that early 
immune responses may 
support tumour development. 
PLoS Biol. 18, e1000562 (2010)

may have varying responses; 
these are averaged out by a 
larger image, which stimulates 
a greater number of cells.
Curr. Biol. 20, 2112–2116 (2010)

Eleven volunteers were asked 
to identify the gender of a series 
of faces (pictured) presented in 
one of eight possible visual-
field locations relative to a 
central point. Arash Afraz at 
the Massachusetts Institute of 
Technology in Cambridge and 
his co-workers found that two 
identical faces were perceived 
to be of different gender if they 
were presented simultaneously 
in specific, different locations. 
Volunteers’ responses became 
more consistent across the 
visual field as the images grew 
in size. 

The researchers think that 
the perceptual variation may 
result from the small size of 
the stimuli relative to that of 
the receptive field. The small 
number of brain cells analysing 
the images at any given location 

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ReseaRch highlights this week

© 20  Macmillan Publishers Limited. All rights reserved10


	Anthropology: DNA from across the ocean