B eedi g
scheme
to
p oduce
backc oss
males
a d
(b)
possible
i he ita ce
patte s
of
self-sac ificial
mati g
t aits.
C edit:
Biology
Lette s
(2026)
Male
Aust alia
edback
spide s
pe fo m
a
ac obatic
some sault
du i g
mati g
that
se ds
thei
abdome
di ectly
towa d
the
female’s
fa gs.
Scie tists
have
ow
fou d
that
this
deadly
self-sac ifice
behavio
comes
f om
a
su p isi gly
simple
ge etic
egio .I
a
study
led
by
Ka dele
Özgü
Uludağ
a d
published
i
Biology
Lette s,
esea che s
fou d
that
although
the
moveme t
is
physically
complex,
the
male’s
te de cy
to
th ow
itself
towa d
the
female’s
jaws
is
co t olled
by
a
si gle
ge e
egio
o
the
X
ch omosome.The
discove y
challe ges
the
lo g-held
idea
that
complex
physical
a d
behavio al
t aits
must
always
depe d
o
ma y
i te acti g
ge es.
Self-sac ifice
b i gs
ep oductive
be efits
The
Aust alia
edback
spide
(Lat odectus
hasselti),
a
close
elative
of
the
No th
Ame ica
black
widow,
is
well
k ow
fo
ext eme
sexual
ca ibalism.Du i g
mati g,
the
male
pe fo ms
a
ac obatic
some sault
a d
places
its
vul e able
abdome
di ectly
ove
the
female’s
mouthpa ts.
The
male
is
ofte
eate ,
but
this
appa e t
self-sac ifice
has
a
evolutio a y
be efit.
It
ca
exte d
mati g
a d
i c ease
the
umbe
of
offsp i g
the
male
fathe s.Some
male
edbacks
also
have
a othe
physical
t ait
called
abdomi al
a owi g
du i g
mati g.
This
a owi g
makes
it
ha de
fo
the
female
to
bite
the
abdome
ight
away.
It
delays
the
male’s
death
lo g
e ough
fo
him
to
complete
a
seco d
t a sfe
of
spe m.To
u de sta d
how
these
diffe e t
t aits
a e
i he ited,
esea che s
studied
a
closely
elated
species
f om
New
Zeala d,
the
katipo
spide
(Lat odectus
katipo).
Katipo
males
do
ot
pe fo m
the
self-sac ifici g
some sault
o
develop
abdomi al
a owi g,
a d
katipo
females
do
ot
eat
males
du i g
mati g.Whe
edback
males
mate
with
katipo
females,
howeve ,
the
males
still
pe fo m
thei
usual
some sault,
eve
though
the
females
do
ot
attack
them.As
the
esea che s
explai ,
this
behavio
suggests
that
both
the
male
some sault
a d
female
ca ibalism
i
edbacks
have
a
ge etic
basis.
Hyb id
b eedi g
eveals
a
ch omosome
li k
To
u de sta d
how
these
mati g
t aits
a e
i he ited,
the
esea che s
ca ied
out
co t olled
b eedi g
expe ime ts
betwee
Aust alia
edbacks
a d
New
Zeala d
katipos.The
fi st-ge e atio
hyb id
males
did
ot
pe fo m
the
some sault
at
all.
This
showed
that
the
ge etic
t ait
behi d
the
behavio
is
ecessive.The
esea che s
the
b ed
hyb id
females
back
with
pu eb ed
males
f om
both
species.
They
aised
a d
filmed
104
male
offsp i g
du i g
live
mati g
t ials.By
eco di g
which
males
pe fo med
the
some sault,
developed
abdomi al
a owi g,
o
showed
both
t aits,
the
esea che s
we e
able
to
study
how
the
t aits
we e
passed
f om
pa e ts
to
offsp i g.The
esults
matched
the
patte
expected
f om
a
si gle
ge e
o
ge etic
egio
located
o
the
X
ch omosome.
The
two
t aits
a e
i he ited
sepa ately
The
b eedi g
expe ime t
also
showed
that
the
some sault
a d
abdomi al
a owi g
a e
ot
co t olled
by
the
same
ge etic
package.About
half
of
the
backc ossed
male
offsp i g
showed
o ly
o e
of
the
two
t aits.
This
showed
that
the
t aits
ca
sepa ate
a d
a e
i he ited
i depe de tly.U like
the
some sault,
abdomi al
a owi g
did
ot
follow
a
simple
X-li ked
o
si gle-ge e
patte .
This
suggests
that
the
physical
t ait
is
co t olled
by
seve al
ge es
a d
may
also
be
i flue ced
by
e vi o me tal
facto s.The
esea che s
co cluded
that
the
two
mati g
t aits
a e
ot
closely
li ked
to
o e
“supe ge e.”
Because
the
t aits
sepa ated
so
ofte ,
they
must
be
co t olled
by
two
u li ked
ge etic
egio s.
These
egio s
could
be
fa
apa t
o
the
same
ch omosome
o
located
o
diffe e t
ch omosomes.
Rapid
evolutio
ac oss
the
Tasma
Sea
Ge etic
evide ce
suggests
that
Aust alia
edbacks
a d
New
Zeala d
katipo
spide s
split
f om
a
commo
a cesto
about
100,000
yea s
ago.
I
evolutio a y
te ms,
this
is
a
ve y
sho t
pe iod.Sex
ch omosomes
ca
evolve
faste
tha
othe
ch omosomes
because
they
have
smalle
effective
populatio s.
This
may
help
explai
how
such
majo
diffe e ces
i
mati g
behavio
developed
i
a
elatively
sho t
time.The
esea che s
suggest
that
the
male
self-sac ifici g
behavio
was
lost
i
most
othe
Lat odectus
species
a d
late
appea ed
agai
i
Aust alia
L.
hasselti.
They
p opose
that
New
Zeala d
was
colo ized
by
edbacks
f om
Aust alia,
afte
which
L.
katipo
evolved
a d
lost
the
ext eme
mati g
t aits.The
study
shows
that
eve
highly
complex
behavio s
ca
have
a
simple
ge etic
fou datio .
The
esea che s
say
that
futu e
ge etic
studies
of
the
two
species
a d
thei
hyb ids
could
ide tify
the
specific
ge es
espo sible
fo
thei
ve y
diffe e t
mati g
behavio s.
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