<s>
Double	B-Algorithm
cones	I-Algorithm
(	O
DCs	O
)	O
,	O
known	O
as	O
twin	B-Algorithm
cones	I-Algorithm
when	O
the	O
two	O
members	O
are	O
the	O
same	O
,	O
are	O
two	O
cone	O
cells	O
(	O
colour	O
detecting	O
photoreceptors	O
)	O
joined	O
together	O
that	O
may	O
also	O
be	O
coupled	O
optically/electrically	O
.	O
</s>
<s>
They	O
are	O
the	O
most	O
common	O
type	O
of	O
cone	O
cells	O
in	O
fish	O
,	O
reptiles	B-Language
,	O
birds	O
,	O
and	O
monotremes	O
such	O
as	O
the	O
platypus	B-Operating_System
and	O
are	O
present	O
in	O
most	O
vertebrates	O
,	O
though	O
they	O
have	O
been	O
noted	O
as	O
absent	O
in	O
most	O
placental	O
mammals	O
(	O
including	O
humans	O
)	O
,	O
elasmobranches	O
and	O
catfish	B-Application
.	O
</s>
<s>
There	O
are	O
many	O
gap	O
junctions	O
between	O
the	O
cells	O
of	O
fish	O
double	B-Algorithm
cones	I-Algorithm
.	O
</s>
<s>
Some	O
double	B-Algorithm
cones	I-Algorithm
have	O
members	O
with	O
same	O
opsin	O
(	O
twin	B-Algorithm
cones	I-Algorithm
)	O
,	O
while	O
others	O
have	O
members	O
with	O
different	O
cone	O
types	O
(	O
members	O
have	O
a	O
different	O
spectral	O
sensitivity	O
)	O
.	O
</s>
<s>
Behavioural	O
research	O
on	O
the	O
reef	O
dwelling	O
triggerfish	O
Rhinecanthus	O
aculeatus	O
has	O
provided	O
evidence	O
that	O
individual	O
members	O
of	O
double	B-Algorithm
cones	I-Algorithm
can	O
act	O
as	O
independent	O
channels	O
of	O
colour	O
information	O
.	O
</s>
<s>
In	O
a	O
book	O
about	O
vision	O
in	O
fishes	O
,	O
James	O
Bowmaker	O
writes	O
that	O
double	B-Algorithm
cones	I-Algorithm
tend	O
to	O
be	O
sensitive	O
to	O
longer	O
wavelengths	O
of	O
light	O
than	O
single	O
cones	O
.	O
</s>
<s>
He	O
also	O
states	O
that	O
the	O
single	O
cones	O
are	O
usually	O
smaller	O
than	O
the	O
individual	O
members	O
of	O
the	O
double	B-Algorithm
cones	I-Algorithm
.	O
</s>
