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hunting. Some Australian frogs synthesize the
alkaloids that are irritants, hallucinogenic, con-
vulsants, nerve poisoning and vasoconstrictors,
so they are severely affecting humans. Poisonous
mushrooms, which contain many kinds of toxins,
are often looking like the edible ones and taste
good. For example, an edible chanterelle looks
like a poisonous Jack-o-lantern.
Magnetic fields act upon the unpaired electrons
and affect the sensitivity of a bird's retina (Stapput,
Güntürkün, Hoffmann, Wiltschko, & Wiltschko,
2010).
Sight and Camouflage
Some fish show their colorful parts of fins only
to their mates and hide them in other times while
trying to stay invisible. Many mammals such as
polar bears or foxes change their color according
to the season so they are almost invisible from a
distance. Many birds have colorful feathers on
their sides only, so the predators cannot see them
from above.
Chameleons, which have stereoscopic vision
and depth perception can see in both visible and
ultraviolet light. They can change their skin color;
in three layers below their transparent outer skin
they have the chromatophores - cells containing
pigments (yellow, red, blue, or white) in their
cytoplasm, and melanophores with a pigment
melanin controlling how much light is reflected,
which sets the intensity of each color. Prairie dogs
use a dichromatic color vision. The common toad
has golden irises and horizontal slit-like pupils, the
red-eye tree frog has vertical slit pupils, the poison
dart frog has dark irises, the fire-bellied toad has
triangular pupils and the tomato frog has circular
ones. The irises of the southern frog are patterned
so as to blend in with the surrounding camouflaged
skin (Beltz, 2009; Mattison, C., 2007).
Cuttlefish - the mollusk of the order Sepia,
one of the most intelligent invertebrates, release
brown pigment from its siphon when it is alarmed.
The pupils of their eyes have a W shape. They do
not see colors; they can perceive light polarization
and contrast. The sensor cells (foveae) in their
retina look forward and backward. According to
Mäthger, Barbosa, Miner, & Hanlon (2005), the
eyes focus by shifting the position of the entire
lens with respect to the retina, instead of reshap-
ing the lens as in mammals. Unlike the vertebrate
eye, there is no blind spot because the optic
Senses Related to Electricity
and Magnetism
An electric eel that is often over 6 feet long is
capable of generating electric shocks up to 600
volts and use them for self-defense and hunting.
They can stun the prey by producing either a low
voltage or high voltage electric charges in two pairs
of electric organs made of electrocytes - muscle-
like cells. Electric eel can also use electrolocation
by emitting electrical signals.
Many kinds of animals can detect the direction
of the Earth's magnetic field and use this infor-
mation for orientation and navigation. Those are
turtles, spiny lobsters, newts (including salaman-
ders), and birds (Lohman, Lohmann, & Putman,
2007). Also earthworms can feel magnetic field.
The directional 'compass' information extracted
from the Earth's field provides the animals with
positional 'map' information. It helps navigate;
for example, small birds pied flycatchers navigate
along the migratory pathways possibly using sev-
eral magnetic navigational strategies in different
parts of their journey. The tied to vision magnetic
sense in the birds such as European robins, Aus-
tralian silvereyes, homing pigeons, and domestic
chickens allows them to sense the direction of the
Earth's magnetic field and navigate when other
landmarks are obscured. The magnetic compass
orientation of birds is light dependent, in particular
on blue-green wavelengths. The compass lies in
the right eye of the robin. For example, if their
right eye was blocked, they headed in random
directions. Thanks to special molecules in their
retinas, birds like robins can 'see' magnetic fields.
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