28 November 2020 | New Scientist | 11Animal behaviour Biodiversity
Michael Marshall Donna Lu
A MICROSCOPIC worm that has
been studied by biologists for
decades has been hiding a secret:
it can make milk to feed its young,
and it does so in a way that supports
the idea that ageing is programmed
by evolution, rather than simply
being an accident.
The nematode worm
Caenorhabditis elegans is used
in many biological studies every
year, but David Gems at University
College London and his colleagues
are the first to investigate why
the worms, some of which are
egg-laying hermaphrodites, leave
smears of brown liquid in their wake
after depositing eggs. The liquid
came out of the worms’ vulvas, the
orifice through which they lay eggs,
and contains yolk protein.
Experiments showed that the
offspring consumed the liquid and
grew better as a result. Gems and
his colleagues say it serves the
same function as mammalian
milk. They propose calling it
“yolk milk” (bioRxiv, doi.org/fjx8).
“We had no idea that C. elegans,
has this primitive form of lactation,”
says Marina Ezcurra at the
University of Kent in Canterbury, UK.
True milk is unique to mammals.
However, other animals, from
spiders to pigeons, secrete
nutritious liquids for their young.
The C. elegans milk production
was triggered by a biochemical
pathway called the insulin-like
signalling pathway, which is known
to promote ageing in many species.
Gems and his colleagues argue
that, after laying hundreds of eggs
in a few days, C. elegans adults
sacrifice themselves by breaking
down their bodies to make yolk milk.
The implication, they say, is that this
form of ageing has been favoured
by evolution because it allows
parents to support their young.
“What this paper is saying
is: ageing has a biological
purpose,” says Ezcurra. ❚
Tiny worm makes
milk to feed its
offspring
THE meat of several protected
African animals has been
illegally imported into and sold
in Belgium. Sophie Gombeer
at the Royal Belgian Institute
of Natural Sciences and her
colleagues have identified
wild animal meat, known as
bushmeat, being sold in several
markets in Brussels.
They identified the meat of
three species listed as protected
according to CITES, the
Convention on International
Trade in Endangered Species
of Wild Fauna and Flora: the
red-tailed monkey, De Brazza’s
monkey and a species of small
antelope called the blue duiker.
Under European Union law,
importing wild meat products
is illegal without specific
authorisation.
In 2017 and 2018, the research
team visited five vendors and
purchased a total of 15 pieces
of bushmeat. According to the
vendors, the meat originated
from the Democratic Republic
of the Congo. It wasn’t directly
advertised, but was available
on request at €40 per kilogram.
The team used DNA
sequencing to identifythe species that the meat came
from. In addition to the three
CITES-listed species, the team
identified meat from species
including the greater cane rat
and domestic cattle, which had
been sold as African buffalo
(Biodiversity and Conservation,
doi.org/fjx7).The researchers had heard
anecdotal reports of bushmeat
being imported into Brussels,
but existing research was scant.
“Because there is no [existing]
data, it’s easy to ignore the
problem,” says Gombeer.
To better understand
the drivers of bushmeat
consumption, the team spoke
to expatriates from seven
African countries who had been
living in Belgium for the past
10 years. Of the 16 interviewees,
15 said they often imported
African food items, including
bushmeat, primarily driven
by a desire to stay connected
to their countries of origin.In certain regions with
tropical forests, wild animals
are hunted as a source of
protein, particularly when meat
from domesticated animals is
unavailable or unaffordable.
“It’s very much a practice
that’s just embedded in
everyday life,” says Liana Chua
at Brunel University London,
who has studied wildlife hunting
in Borneo. A challenge for
conservationists when trying to
reduce wild meat hunting, she
says, is to take into account the
social and nutritional role that
hunting plays in people’s lives.
Local and Indigenous people
living in and around forest
areas should have the right to
continue traditional practices
and hunt sustainably, says Julia
Fa at Manchester Metropolitan
University in the UK.
“You have to make the
distinction between eating wild
meats really to survive... and the
market that has grown in the
past decade in big cities where
there are alternative proteins
available and it’s more of a
delicacy,” says Gombeer.
She suggests that stricter
enforcement of meat
importation laws could help
reduce sales, while Fa favours
social campaigns in Brussels
to reduce demand.
“There shouldn’t be any
consumption of wild meat
in urban centres,” says Fa.
She estimates that 5 million
metric tonnes of mammal
meat is hunted and extracted
from the Congo basin each
year – a rate two to three times
higher than hunted animal
populations can sustainably
support. ❚Illegal bushmeat found
for sale in Belgium
GEMMA^ DILULLO/ALAMYMeat from a red-tailed
monkey has been sold
in Belgium€
Cost per kilogram of bushmeat
on sale in Brussels, Belgium