By Dr J Floor Anthoni (2003)
Do you know which marine creatures belong to these
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The eye is the most wonderful part of our bodies. Interestingly, it
was already fully developed hundreds of millions of years ago, reason why
most creatures have very good eyesight, and their eyes are similar to ours.
The eyes of the more primitive creatures, such as reptiles and birds, are
very noticeably different from ours. Even those of cats, which are mammals
just like us, differ because they have different pupils.
Considering that all reptiles, amphibians, birds and mammals originally
stemmed from fishes in the ocean, it is surprising that fish eyes are so
well developed, and that they are so similar to ours. But fish have larger
eyes, in order to see better in the darkness of the sea. The fishes found
in depths of 100-200m have indeed very large eyes, which you can admire
in the fish shop. But even at the depths visited by divers, the light has
diminished to only a fraction of its intensity above water. The eyes of
the sea creatures living there, thus had to adapt to low light conditions,
which means that their eyes are comparatively larger than those of land
If we try to see with our eyes submerged, we'll notice that everything
looks blurred. That is because the lens of our eye is a water lens, which
works only because there is air outside our eyes. In the water it does
not work very well. So fish eyes have a different substance as their lens,
and it is highly curved. Because the outside of our eyes needs to be moistened
frequently, we have eye lids. These also allow us to close our eyes. But
fish lack such a mechanism. It is therefore surprising that they are able
to keep their eyes so clean, and free from attack by the likes of sea lice.
Some fish have indeed very beautiful eyes.
This john dory (Zeus faber) was photographed by night. It
is a hunter who depends entirely on its eyesight. Flat as a plate, he can
make himself invisible by simply looking at you. Because he swims by vibrating
his fins, it seems as if he does not move at all. But his biggest surprise
lies in the final attack, in which he extends his mouth suddenly far forward.
Notice his very curved eye lens.
f017712: A john dory has turned itself flat on its side and
changed its colours to resemble an innocent stone. However, its prey,
young jack mackerels, seen in the top right corner, have recognised him,
keeping their distance.
this john dory died in a trawl net, the pressure of which caused internal
bleeding. His extremely extendable mouth is shown by pulling it outward.
The close-up of his eye shows further internal bleeding.
porcupine fish (Allomycterus jaculiferus) are very endearing because
of their large, beautiful eyes. These fish have a bulky shape, while they
swim with the two fins near their tails, which makes them rather slow.
But they have excellent defences, being poisonous to eat, and being able
to inflate themselves with water. Their prickles also help a little.
porcupine fish have very good frontal vision, as this photo shows, but
they are also able to roll their eyes backward for a complete rear view.
Notice how each eye has an outer lens and also a very curved inner lens.
Many fish have dark circles around their eye balls, which helps to prevent
The Lord Howe coralfish (Amphichaetodon howensis) is one of many
whose skin patterns run through their eyes by way of disruptive coloration.
This fish is found only in a very restricted range in the subtropical South
Pacific. Once mature, it finds a partner, and the two stay loyal to each
other until one dies.
Like other coral fishes, it finds food in between the complicated
structures of coral. Having a pointed snout then serves to advantage. With
its eyes set very close to its mouth, it can even find those creatures
that have camouflaged themselves well. Notice how its breast fins have
become small, and that its belly fins have taken some of their function.
Young snappers (Pagrus auratus) have beautiful shiny pink bodies,
covered in blue spots. Their fins also look blue when the light falls on
it from the right angle (from above and behind). Above their eyes they
carry a bright iridescent blue spot. Notice how these spots disappear as
they grow older (see right).
f030211: This large snapper has no fear of divers because
it lives in a marine reserve where it is fully protected. Divers respect
these fish which are often older than expected. This snapper is about twenty
f030119: a large snapper of about 30 years old.
f031709: The black spotted grouper (Epinephelus damelii)
which can still be found in the remote Kermadec Islands, grows very large
and very old, up to four times the weight of an adult person, and over
100 years. They are intelligent fishes, and a joy to encounter. Once they
know you, they love to be played with and to be stroked. This one is a
large female. On the back of its eyeballs, the grouper has a number of
smaller fake eyes, see right-hand enlargement. It is not known why.
f031613: White-lip is the large male grouper, seen here nuzzling
up to a snorkeldiver. Look at his size! He has a harem of five females
who stay with him. But earlier in life, he too, was a female. These fish
change sex later in life when it suits them.
f031742: a snorkeldiver descends from the surface to meet
White-lip, the large black spotted grouper. Such moments are awe-inspiring.
the northern scorpionfish (Scorpaena cardinalis) hunts by sitting
still and waiting until a hapless victim comes close to its mouth. Then
it lurches forward, while opening its cavernous mouth. This movement also
sucks the victim inside.
f030522: Scorpionfishes are so well camouflaged that they
are hard to see.
The jock stewart (Helicolenus percoides) or sea perch lives in the
cooler waters of New Zealand, where the northern scorpionfish is no longer
the grey moray eel (Gymnothorax nubilus) has rather small eyes for
its size. Moray eels hide among crevices by day, in order to hunt by night.
But this moray is active by day, and can be found enjoying itself while
looking for food.
The yellow moray eel (Gymnothorax prasinus) is larger than the grey
moray, but not as outgoing. However, when extended a human hand, it comes
out of its hole to sniff and nuzzle it, which is rather daunting, considering
its impressive sharp teeth.
a young bigeye (Pempheris adspersa) shows why it is named this way.
Bigeyes are nocturnal fish that hide by daylight and come out at night.
This makes many people think they are uncommon. Bigeyes have a peculiar
way of swimming. They hang motionless in the water, in order to be able
to observe the slightest movement around themselves. Then they suddenly
dart forward, not to pursue their prey but to skilfully intercept it.
f022713: A diver enters the hold of a shipwreck where thousands
of bigeyes are hiding from the daylight. Blinded by the light and attempting
to dodge the divers, they nervously swim around in this dark cavern, which
is home to them. Yet they do not dare to swim outside. Near hideouts like
this, one often finds large scorpionfish waiting till a bigeye makes a
mistake. Like many other small fishes this bigeye is endemic to New Zealand.
f029324: The crested blenny (Parablennius lacticlavius)
is no larger than your finger, and usually much smaller. But unlike other
small fishes, it grows old, and as can be expected of old creatures, it
grows wiser as well. Here it is waiting inside a narrow hole in the rock,
for its visitors. Larger fish visit him because of his sharp little teeth
which enable him to prise sea lice from their skins.
a side-on photo like this is difficult to obtain, because these fish are
very cautious. Notice how its breast fins have developed into fingers,
with which it can firmly hold onto rocks in wave-washed conditions.
the blue-eyed triplefin (Notoclinops segmentatus), also called the
red-banded triplefin, shows just how extravagant the colouring can be in
small fishes like triplefins. The name triplefin comes from the three fins
they carry on their backs.
the specctacled triplefin (Ruanoho whero) has dark eyes and a band
in between, joining them up like having 'shades' on. With these eyes it
obtains a very clear perception of its environment.
Small fishes like these do not spread easily across oceans,
and both shown here are home to New Zealand only (endemic).
the seahorse (Hippocampus abdominalis has a long snout with a very
small mouth at its end. It can turn its eyes independently to look all
around or to focus on prey in front of it. Its large gill cover behind
its eyes, allows it to suck water in with a loud snap. At the same time
it jerks its snout upward. With these two movements it efficiently catches
free swimming shrimps and crustaceans hiding on the bottom and on plant
leaves. Its large eyes allows it to see the slightest movement.
f003929: A seahorse holds on to a sunken twig in order to
resist the fierce current in this current channel of an estuary. Estuaries
are rich in food, particularly in small organisms creeping over the sandy
bottom. When the tidal currents stop, the seahorse makes long excursions
over the sand flats, but returns to his favourite hang-out before the current
f021623: a male seahorse in the tangling environment surrounding
a commercial wharf. The human-made mess gives the seahorse many items to
hang on to.
this baby sand flounder has covered itself expertly with sand, leaving
its bulbous eyes free to look out. Flounders are very hard to find this
f007802: a sand flounder (Rhombosolea plebea) swims
freely over the sandy bottom, relying on its camouflage to protect it.
Not only do these fish cloak themselves with sand when settling down, but
they can also change the colour and patterns on their skins to match that
of the bottom.
An eagle ray (Myliobatus tenuicaudatus) has burrowed itself in the
sand, while at the same time digging up a deeply hidden clam. With its
very strong bony jaws it then cracks the clam to remove its flesh. Rays
do not use their eyes for catching prey, and these are less developed as
f021005: An eagle ray flies over the sand in search of food.
Notice its blunt head and antenna-like tail with a little fin on it. Stingrays
have adapted to living on the bottom by becoming flat-bodied. Related to
sharks, which also have cartilageous skeletons, the rays have enlarged
their breast fins into wings, with which they fly like birds. The fins
on the rear of their bodies are pelvic fins.
A sand octopus (Octopus gibsi) has come out of its deep den in the
sand to have a better view of the photographer. These animals are related
to sea slugs, but their eyes are sharp and inquisitive. Here the octopus
has closed its eyelids as it squints in the photographer's modelling light.
It sleeps with its eyelids closed.
f022605: a large female sand octopus is guarding her eggs
inside her burrow in the sand underneath a large rock. Octopus mature in
two years, mate and the female lays her eggs in strings hanging from the
ceiling of her burrow. From that moment on she stops eating, never leaving
her nest. By the time the eggs hatch, she dies to make room for her offspring.
Male octopus live a little longer and may mate several times.
stalk-eyed mudcrab (Hemiplax hertipes) carries its blue eyes on
stalks, by way of periscope, in order to be able to spy its surroundings
while submerged under the sand. Here he is seen in a defying stance, defending
its territory, or just soaking up the last sun rays of the day.
Here the stalk-eyed mudcrab is seen feeding on a morsel it
found hidden under the sand. Like most crabs, mud crabs have taste sensors
on their legs, and taste the bottom while walking around. This crab is
not common on mud flats, but prefers a sandy bottom amongst the eelgrass.
The mantis shrimp (Squilla sp.) is one of the most amazing shrimps
on earth. Constructed like a swiss army knife, it bristles with all kinds
of utensils: boxing gloves, catching claws, brushes, trowels, spades, knives
and more. It has the most amazing eyes ever evolved, since each side consists
of two grooved domes, within which two eyes move independently. The grooves
run perpendicular to each other, bottom and top, which allows the animal
to see depth with stunning accuracy.
f006130: the mantis shrimp is half-round in shape and very
flexible, being able to turn around inside its snug round burrow. It constructs
such burrows in rather loose sand, by cementing the tunnel with 'spit'
using its brushes and then trowelling it smooth with its trowels. It can
swim forward and backward with ease, using its flat tail fins as ailerons.
In captivity it is a most endearing animal to observe,
always active, always inquisitive.
A bottlenose dolphin (Tursiops truncatus) swims by, really close.
From a distance it has already observed the photographer's acoustical image,
but now it is catching a glimpse with its eyes. Because dolphins have such
excellent echolocation, their eyesight is rather poor.
f011708: We will never know what dolphins see, because most
of their perception consists of images, reflected by loud clicks. Nonetheless,
they are often seen poking their heads out of the sea, to look around ('spy-hopping'),
and each dolphin has enough visual markings to tell it apart from others.
Compare these two dolphins for instance.
The bottlenose dolphin can swim large distances without
food, reason why it is found in many oceans.
The splendid hawkfish lives in turbulent water where it holds itself steady
with the fingers on its breast fins. Its white-red-green colours make it
look splendid indeed. However, in natural light, the colour red becomes
This detailed photo shows a peculiarity of the family of
hawkfishes: they have brushes at the ends of their dorsal spines. It is
not known what these are for, but they look cute. Although very colourful
on these photos, the splendid hawkfish is very difficult to spot in its
natural surroundings. Very little is known about it.