3 August 2019 | New Scientist | 17Sexual reproduction Technology
Michael Marshall Donna Lu
FEMALE Tripedalia cystophora
box jellyfish are stung from the
inside by packets of sperm. The
tiny stinging structures may boost
reproduction by anchoring sperm
cells in the body of females.
Unlike most jellyfish,
T. cystophora copulates, which
means the eggs are fertilised
inside the female, rather than out
in the water. Anders Garm and
Sandra Helmark at the University
of Copenhagen in Denmark have
now shown that T. cystophora
sperm are unusual in that they come
in packages equipped with stinging
structures called cnidocytes.
The sperm cnidocytes shouldn’t
hurt the female, says Garm.
“They are of a type without the
penetrating arrow and without
poison.” Instead, they seem to
anchor the sperm inside the female
during fertilisation (Journal of
Morphology, doi.org/c8vc).
This finding follows on from a
2015 study in which Garm and his
colleagues looked at the only other
box jellyfish known to copulate:
Copula sivickisi. Not only do the
sperm packages of this species also
have cnidocytes, but the female sex
glands carry them too.
Garm says this may be because,
after fertilisation, C. sivickisi
releases embryos to develop
outside the body. The stinging
cells may help protect these from
predators. In contrast, female
T. cystophora keep their fertilised
eggs inside their bodies until they
have developed. This means the
fertilised eggs don’t need to be
armed with protective cnidocytes.
The species differ in that
T. cystophora only mates rarely, so
females take more care of each set
of offspring. In contrast, C. sivickisi
is more prolific, rapidly releasing
a set of fertilised eggs and mating
again within days. “The two
strategies each have their
advantages,” says Garm. ❚
Jellyfish sperm with
stingers that fire
inside females
EXAMS can make the heart race
for even the most well-prepared
candidate, but a simple
smartwatch app could help
alleviate the stress. The app
produces a slow, soothing
tapping that seems to help
people perform better in
situations filled with anxiety.
Jean Costa and his
colleagues at Cornell University
in New York created an app
that reacts to people’s heart
rates by producing a slow, light
tapping on the inner wrist
of a smartwatch wearer.
They tested the app, called
BoostMeUp, on 72 college
students who were given
two maths exams under
pressure, and found that slow
taps reduced anxiety and
improved test performance.Other studies have suggested
that techniques like meditation
can reduce stress, which apps
like Headspace and Calm try
to help with. “But in many
situations we need something
in the moment,” says Costa.
During a practice maths test,
the team used smartwatches to
measure the students’ baseline
heart rates. In subsequent tests,
the watch gave half of the people
a wrist tapping that was 30 per
cent faster than their baseline
heart rate, while the other half
received tapping that was 30 per
cent slower than their baseline.
After all the tests, participants
filled out questionnaires to
assess their levels of anxiety.
Those who were given faster
taps reported higher levels
of anxiety compared with
the slow-tapping group. The
fast-tapping group also did
worse on the test of 36 questions,
answering 0.58 more questionsincorrectly on average
compared with when they had
no feedback. The slow-feedback
group answered 1.75 more
questions correctly when the
tapping was on (Proceedings of
the ACM on Interactive, Mobile,
Wearable and Ubiquitous
Technologies, doi.org/c8vb).Karin Petrini at the University
of Bath, UK, thinks improving
cognitive performance like this
is exciting, but isn’t convinced
that the results are conclusive.
There was only a small
reduction in anxiety for the
slow-tapping group, but a
greater improvement in
cognitive performance. This
calls into question whether the
improvement was linked to
changes in anxiety, says Petrini.
Costa says the app may be
hard for students to use in
real exams, where technology
such as mobile phones and
smartwatches are banned. But
he says it could be useful during
a job interview or while public
speaking, for example.
Another approach, tested
by Asma Ghandeharioun at
the Massachusetts Institute of
Technology and her colleagues,
plays breathing sounds slightly
slower than someone is
breathing. Her team found this
made people breathe deeper
and slower, which has been
shown to reduce blood pressure.
Other apps have been trialled
as a way to track students’
mental health, such as
StudentLife, which uses a
smartphone to monitor social
interaction, physical activity
and sleep patterns. ❚Soothing smartwatch app
improves exam results
ZINKEVYCH/GETTYA smartwatch app
seems to keep you
calmer during exams1.
People using an app got this
many extra exam questions rightAll the latest on gadgets and wearables
More on tech to improve everyday life at
newscientist.com/article-topic/wearables/