FISH
1 Coelacanth NYTimes Apr. 18, 1995 B6
By
MALCOLM W BROWNE
Unless decisive steps are
swiftly taken to curb human predation, the coelacanth, a very rare fish once
thought to have accompanied the
dinosaurs into extinction, will truly die
out, a team of German zoologists reports.
This gloomy assessment by
Dr Hans Fricke and his colleagues at the Max Planck Institute for Behavioral
Physiology in Seewiesen follows their latest annual
census of coelacanths living off the coast of
It is possible, Dr, Fricke
says, that this alarming decline is the result of a natural population
fluctuation or an emigration of coelacanths away from the survey area, but it
seems much likelier that has descended aboard submersibles into the
coelacanths’ habitat. Through thick
viewing ports, the team photographs, studies and counts the coelacanths in
their submarine caves, which, although close to shore, lie at a depth or about
650 feet. Coelacanths are nocturnal animals, hunting at night for
bottom-dwelling prey at depths up in 2,300 feet and resting during the day in
their caves. Since individual coelacanths have distinctive markings, scientists
can identify and track them year after year.
Although a handful of the
big fish have been found in waters off the coast of
The main problem
threatening the survival of the coelacanth (Latimeria chalumnae) is that it lives in a coastal
area heavily fished by Comorans for other species of
fish used as food and sources of oil. Although the five-foot coelacanths have
little or no commercial value, they occasionally grab the hooks intended for
other fish and are hauled to the surface. Under a new
Both European government
agencies and the Comoran Government have tried to
halt the accidental landing of coelacanths.
One measure was the mooring of “fish attractors,’ long, brightly
colored plastic streamers, from buoys anchored farther from shore than the coelacanth
habitats. The attractors only lure ordinary fish and apparently do not appeal
to coelacanths.
But the attractors were
anchored so far from shore that fishermen found it inconvenient to paddle their
canoes to the designated area. To rectify this, international agencies helped
local fishermen buy outboard motors for their canoes. But by last December, Dr. Fricke said, most
of the motors had broken down and the fishermen were again working the
coelacanth zone.
In their Nature paper, the
scientists from the Max Planck Institute group propose a new approach. They
suggest replacing the fish attractors, mooring them close to shore but at a
depth well above the coelacanth habitat. They also suggest installing a
submarine television camera in front of one of the coelacanth caves with
continuous live video displayed at an information center to be built for
fishermen in one of the local villages.
“Frankly. I doubt at this point
that the beast can survive, but we have to try something,” Dr. Fricke said.
Coelacanths are members of a very ancient suborder of fishes called
crossopterygians, or ‘fringe-finned’ fish. Although fossil crossopterygian
fishes are common in sedimentary rock dated between 350 million and 60 million
years old, they were long thought to have
died out shortly after the end of the Mesozoic era, the age of
dinosaurs. But in 1936, paleontologists
were stunned to learn hat fishermen off the coast of
Since then about 200 coelacanths
have been caught, but none has survived capture for more than a few hours. The
fish are almost always injured by fishhooks, and since they have strong jaws
armed with dagger sharp teeth, fishermen generally club them to avoid dangerous
bites. It is also believed that hauling the fish up from great depths may cause
injurious pressure changes in their bodies.
Until last year when the Comoros Government banned
the export of coelacanth specimens or tissue, Scientists around the world were
supplied with enough carcass material to study these fish extensively. Some
scientists believe that modern coelacanths, which have fins below their bodies
somewhat resembling legs in shape and movement, are
close relatives of the line of fishes that gave rise to the first vertebrates
to walk on land. This would mean that the ancestors of modern coelacanths were
also the ancestors of human beings.
Another
group of scientists believe, however, that land terapods
(four-legged creatures) descended from a very different line, the
lungfish.
Whatever
the case, naturalists, biologists and paleontologists agree that every effort
should be made to save the only species of crossopterygian
known in have survived to the present day, the coelacanth.
“Everybody feels sorry about extinctions,” Dr.
Fricke said. “But they have become so common a lot of us just don’t pay much
attention anymore. The coelacanth is something special, however. It’s a remarkable fish, a window into the
distant past and a treasure of nature. If we
let him die out it will be a tragedy”
~
II
Fishy Sex-Uncovering the
The public has had an unusual number of sex
stories to mull over of late. Scarcely a week goes by without a report of
another politician’s scandalous sexual foray or a gossip column piece on some
stars in vitro fertilization.
But for science buffs with an appetite for bizarre
sex yarns, new findings on the antics of fish may prove more satisfying.
For starters, that
grouper you dined on at the beach this summer had probably undergone a complete
sex change. What’s more, studies suggest that
a few species of fish living In and around coral reefs
reverse gender as many as 10 times. Some species have two kinds of males—the
family man and the run-around. Yet others, such as the common bluehead wrasse, reverse sex , and
have two very different types of males.
Why this prurient
interest in piscine sex? Scientists hope that investigating what goes on in the
brains and bodies of these mutable creatures may help uncover some of the
mysteries of human sexuality.
Sex-changing fish are
known as successive hermaphrodites—each fish can make either testes or ovaries
and produce either eggs or sperm. The simultaneous hermaphrodite, however,
comes equipped with both testes and ovaries. These fish would have to check
both the male and female boxes on a personal questionnaire.
One species of sea bass,
Serrunus torrugarum, releases
eggs during about half of Its 14 or so daily spawns and contributes sperm for
the other half. It can switch from providing sperm to releasing eggs within 30
seconds.
S. torrugarum develops more female gonadal tissue as it grows bigger, causing it to release
more eggs and fewer sperm. The fish’s spawning behavior remains the same,
however. lts increased egg production may boost reproductive
success, since almost all eggs get fertilized but not all sperm find eggs
Other simultaneous
hermaphrodites develop more male tissue as they grow. These fish eventually
change sex completely, however, becoming successive hermaphrodites. Scientists
have studied more than 100 species of successive hermaphrodites but suspect
that many more exist. Most of the
species found so far reside in shallow ocean waters.
In the most common type
of sex reversal, females mature, reproduce, and then become males. Their
ovaries disappear entirely (or almost entirely, they grow testes, and their
hormonal systems switch. Many fish also change color. They act like males,
which in some species includes protecting their nests, behaving aggressively,
and courting females. Less commonly, some species change from male to female.
Either way, sex reversal
is a very dramatic change in almost all aspects of the life of the fish.
Most fish undertake the
change only once. For many species. It occurs in response to an altered
social environment, as when a dominant male dies
or leaves his social group and one of the females becomes male and takes his
place. Changing sex can take as little as 4 days. What keeps fish from doing it
more often remains unclear. Some researchers suggest that the dominant male’s
aggression inhibits sex change in subordinates. Others argue that it’s much
more complicated than that.
Some females, for
example, won’t become male if their group includes fewer than two to five
other females. The benefits of changing sex may not outweigh the costs when so
few females exist for males to mate with.
If, as ecologists think,
a fish’s primary goal is to reproduce as often as possible, then becoming a
male makes a lot of sense. Females often outnumber males, so males get a good
rate of return on their mating efforts.
But becoming a female
has benefits too. Anemone fish live in small groups. Only the largest female
and male reproduce and the female outweighs the male.
If this female dies or leaves, her mate becomes a female the largest juvenile
fish in the group becomes male and mates with the new female Douglas Shapiro at
EMU explains in The Differences Between
the Sexes (1994, Cambridge U Press.)
Despite its advantages, acquiring a new sexual
identity takes a toll on fish. During the process. they cant reproduce, yet they probably expend a lot of
energy and don't defend themselves well..
Some fish dont stop with one sex change. Scientists have identified
at least three species of reefdwelling fish that
change sex several times: Paragobiodon echinocepfiahss, Cirrhauchzhss auit-us. and Tnnrnru okincuuxse.
No doubt other fish perform the same trick.
However, scientists know of no other vertebrate that undergoes multiple sex
changes. Only one other vertebrate, an African frog, can reverse its gender.
Earlier
laboratory studies revealed that the female T
okinwae, a tiny Japanese goby, becomes male in
response to the departure of a dominant male. But such males revert back to
female when a larger male comes on the scene. The frequency of gender changes
depends on the stability of the social system.
The researchers wondered
whether all these adjustments left the fish behaving and looking different from
female males or females. In a new study it was found that fish going for round
two as a male or a female look just like fish that have never entered the ring.
Two scientists, Grober
and Sunobe induced females to become males, males to
become females, and females to become male and then female again—all by
swapping their companions. The fish completed a single gender change its as few as 4 days.
Unlike many other sex-changing species, T. okinauiae always carry with them a remnant of the opposite sex’s gonad.
“The {gonad} cells are already there (and) can
probably generate rapid changes in hormones.” Grober
speculates. Scientists don’t know whether the other two fish that reverse
their sex more than once retain such cells.
In just those few days, the fish’s gonads, genital
papilia (a flap of skin sensitive to steroid
hormones), brain cells, and other
anatomical parts changed. The fish’s sex hormones adjusted, the authors assume,
but they are only now examining them.
The scientists knew that the number and size of
cells that produce peptldes important to reproduction
differ in male and female bluehead wrasse, one-time
sex reversals. So they examined cells in T oknawae that produce arginine vasotocin (AVT) neuropeptides,
which regulate reproductive behavior in many vertebrates, to see whether they
changed.
The cells enlarged when males became females and
shrank when females became males. When these males went back to being females,
the cells enlarged again, Grober and Sunobe find. The total number of cells didn’t vary
Behavior also served as a good indicator of the fishs
current sexual status, Grober says. Males, even those
new to the job, behaved aggressively, defended their nests and performed a
traditional courtship dance.
A trained eye couldn’t
miss the differences between the males and the females, he contends. it’s like walking into a singles bar. Is there any issue as
to who is a male and who is a female? Absolutely not.”
Sometimes, there a even a clear distinction between the males. Take the saddleback wrasse, Thaksssoma duperrey. Like
salmon and many other species, it has
two types of males. They vary in size and take very different approaches to life,
including mating.
Grober and his
colleagues are finding clear differences in their brains is
well. In one section of the brain, the larger male has many more cells that
produce AVT than the smaller males or females do.
Among vertebrates, almost no other animals except
certain fish species have two distinct classes of males, and no vertebrates
are known to have two types of females, says Andrew H. Bass of
Over the years, Bass has compiled a detailed
picture of the two versions of male midshipman fish living off the West Coast
of the
The type I male midshipman takes longer to mature,
which gives him time to grow bigger and develop a stronger vocal system for
courting. Type II males put their energy into becoming sexually mature and
developing their gonads, which make up 9 percent of their body weight. Type I
males’ gonads account for a mere 1 percent of their weight. The two males also
have different types of testosterone, Bass explains.
Type I fish build and guard their nests,
activities type II males never bother with. The nest builders also hum to
attract females and grunt in defense of their home. Type II fellows avoid the
courtship, trying instead to invade their neighbors
nests to mate with the females.
Midshipman males may
resemble comical stereotypes of some human males, but marine scientists say
that fish and people actually have enough in common to make the study of fish
worthwhile.
Research on fish may shed light on how environment
and stress inhibit human reproduction and on the role of the brain in human
sexual orientation, scientists say. Fish also emphasize the inflexible nature of most other vertebrates’ sexuality, Grober says.
“The speed of (sex changes in fish}the diversity
of body systems involved, and their reversibility are remarkable, relative to
the rigid nature of these characteristics in most vertebrates,” Grober and Sunobe contend.
All of this sexual variation and gender gymnastics
helps fish to reproduce more successfully, scientists suspect. But maybe
another benefit exists. Maybe. having
walked in each othe~s shoes. male and female fish get along
better.
Would the battle of
the sexes never have begun if humans had more fishlike qualities?
OCTOBER21. 1995
SCIENCE NEWS.
VOL.148
267
III White
Sharks can Jump
By Elia, J. Swift
Surfer Magazine
And Other Fun Facts about Your Worst Nightmare
The
white shark does not give up its secrets
easily.
For decades, scientists have filmed, followed and
tagged the sharks; jabbed them with instruments; fed them radio transmitters;
and witnessed hundreds of attacks. But even scientists who have spent their
careers in pursuit of whites say the sharks remain shrouded in the darkness of
the sea—until they erupt in fearsome violence.
To better understand this elusive predator, 70 of
the world’s leading white shark experts gathered this March in Bodega Bay,
north of San Francisco, to present their latest research. It was the largest
such gathering ever held, and the information shared by the scientists is
changing our understanding of the white. "I think we can put an end to the
mythos that this is a simple beast that just eats, swims and makes babies,’
said Leonard Compagno, director of the Shark Research
Center In Cape Town, South Africa. “It Is an animal
far more complex than that.’
The white shark, researchers say, is one of the
most efficient predators in the world—far more deadly than a land tiger—with a
kill ratio of 80 percent or higher per attack. Behavioral studies show whites
are sophisticated ‘ambush killers’ who stalk their prey, hiding over dark rock
shelves until an animal swims by. Often they will kill seals and let them drift
away from rookeries before eating them—in private, so to speak—so as not to
alarm other seals. Unlike most of their cousins, whites are daytime predators,
whose eyes are among the most highly developed ever found in sharks.
They are not fat, slow fish, as some have
speculated, but are extremely fast on the attack and able to ‘rocket’ through
the water. Scientists have seen them chase down uninjured sea lions in pursuits
more than 100 yards long.
The
more that is known about the white, the more fascinating it becomes. But what is not known is as impressive as
what is known.
Scientists at the conference offered detailed maps
of the shark’s brain, nervous system and body, plus extraordinarily complex
mathematical equations to estimate populations, behavior, growth rates and
appetites. They argued for hours over the significance of one shark splashing
water on another, debated at length about the effects of sun, moon and tides on
predation. They showed endless hours of photos and slow-motion films of
whites attacking—after three days, enough to make any surfer seriously queasy.
But although experts from
all of the major white-shark regions—the U.S., Australia, Africa, Europe, South
America and Japan—were there, no one could offer more than guesses on some of
the most basic questions about the animal. For instance, none of the scientists
could say with certainty just now many whites there are in any given area.
Guesses range from colonies in the tens off
One thing is certain: No
other sea animals prey upon a full-grown great white. Whites do die of
unnatural causes. Aside from getting caught In fishing
nets and hunted by men, they seem to have a propensity for choking to death by
eating too large a chunk, at least judging from several choked whites that have
washed ashore in
Some
questions about the white’s reproductive pattern have been answered in recent
years, but the picture they paint only serves to make the shark scarier than
ever. According to Harold Pratt, a federal fisheries biologist from
The first pregnant female was found in 1987 by
Japanese researchers who recovered a l7-foot white
that had drowned in a fishing net. Inside the female they discovered 10 full-term, 4-foot long embryos—the first confirmation that
whites give live birth. Here’s the eerie part: The babies’ stomachs were filled
with tiny teeth, leading some to speculate that the young whites practice
inner-uterine cannibalism. In other words, the unborn whites swim
in the womb, eating each other until only a handful of the strongest survive. The white is a predator and hunter even
before birth, according to some scientists. (Other scientists at the conference
speculated the fish had simply discarded and swallowed teeth as they developed
in the womb. Like much in the white shark world, the debate remains unsettled.)
What scientists do know is that off
“All of the abalone divers
agree that the population has grown. They are seeing more every year. .” said
Peter Klimiey. a biologist
who heads a white shark research project centered on the
What they and other
scientists have found is changing some of the myths surrounding the shark’s
behavior. It was once thought that whites were clumsy killers who often missed
their targets. One prominent scientist even suggested were
so slow that an Olympic swimmer could give them a race. But the latest research
indicates great whites are built for speed, equipped with a tail and muscle
structure shared by some of the some of the fastest fish in the sea.
In the
What that means is you’ll never out paddle one,
even on a longboard.
Forget it!. But that really doesn’t matter
because chances are
you’ll never see it coming.. According to attack profiles, whites are devious
killers who use their natural coloring to creep within a few feet of prey that
never suspect death is watching end waiting.
The great white stalks Its game much like tiger
might by swimming along the edges of the reef, typically near a drop-off, “They
sight their prey and then come up from underneath and usually behind with a
great explosion.
Unlike many research programs, the Farailon group does not entice the sharks with baited traps
or feeding targets. All of the data is based upon natural predation patterns.
The attacks were usually announced only by a huge splash and spreading blood
slick. “There is usually a thunderous splash up to 5 meters high, and then the
sea lion appears not devoured, but with a large bite taken out.” Klimiey said. “In not one case did we see the shark or sea
lion before the attack. A large percentage of the seals and sea lions are
beheaded.”
Klimley has painstakingly plotted
and graphed every attack. His team studies water clarity, weather, temperature,
time of day, wind direction, lunar phase and a dozen other factors in hopes the
date will reveal patterns of behavior to unlock the secrets of the white. What
they found is that wind, air temperature, clear or
foggy weather, swell direction, lunar phase and water clarity have no significant
influence.
Other factors were more consistent. “The higher
the swells the more attacks there were,” said biologist Peter Pyle, a member of
the Farailon group. “Also, If there was a period of
higher upwelling (marked by strong winds) the day before, we saw more attacks.”
Typically, the white will slowly swim into an area
of game, near rocks or beaches where sea mammals gather, and glide along the
edge of a reef—right where surfers like to hang out. The sharks have been known
to sit almost motionless among the rocks, their dark skin blending in with the
reefs, watching their targets before exploding into an attack.
Its only a matter of time until more surfers are hit,” said Dr.
Robert Lea, a biologist with the California Department of Fish and Game who
records shark attacks. 1n fact, I can’t believe more people haven’t been hit.”
One reason more surfers haven’t been killed is
that whites aren’t particularly interested in people. Statistical studies and
field observations indicate whites are regularly in the same area as surfers
and divers, but rarely attack.
If whites wanted to feed on surfers, it would be
so easy that few people would surf or dive north of
Leo Demski, a
The eyes of a great white---described by attack
survivors as solid black orbs the size of silver dollars, contain a
sophisticated array of silvery nerve cords attached to the brain. The nerves
are so large that Demski initially assumed they were
muscle. Nobody knows how far they can see.
But while the eyes look extraordinary, the brain itse!f is small arid only moderately
developed compared with other sharks. “It is quite a disappointment for such a
star,” Demski said. “Basically, it has a small
brain, big nose and warm eyes."
But he would not call the fish dumb. “Being at the
top of the food chain, they don’t need the more highly developed nerve
clusters other species have developed to avoid predation," -Demskl said.
Despite the painstaking data, hundreds of
videotapes and scores of scientific papers, the great white remains an
unpredictable predator. For every dozen attacks that follow a pattern, there is
an incident of bizarre behavior creating maddening fluctuations in the
statistics. After hitting scores of marine mammals and ignoring other targets
in a display of discriminating prey selections, the sharks suddenly will skew
the date by eating cardboard boxes, birds, boats and surfers.
“The
sharks can discriminate very well. They have amazing sensory abiilty," said Harold Pratt, a federal fisheries biologist
from
IV When Fish Bite
BY
FRANK STEPHENSON
Sea
Frontiers
Fish have been catching and eating things longer
than the swiftest, most terrifying predator that ever roamed the earth. Yet
they are such commonplace animals—wherever there’s water you’ll likely find
them— that it’s easy to understand why they’re often taken for granted. But to
scientists with a passion to learn how earth’s incredible web of life came into
being, few organisms that have ever existed come close to offering as rich a
field of evolutionary evidence as fish.
If anything stands out about the 425-million-year-old
history of fish. Wainwright says. it’s that the forces
of evolution have been stupefyingly creative,
Scientists figure there are at least 23.000 species alive today, a figure that
easily makes them the most common vertebrate on earth. And among themselves,
fish are so confoundingly varied that fish
taxonomists are to be pitied. To complicate matters even more, consider
nature’s bizarre packaging: there are fish with and without jaws: with and
without bony skeletons: fish whose entire bodies are encased in rock-hard
“boxes:” fish with no teeth and others with fangs. There are fish that look
like snakes (eels): like doormats (flounders and rays). like
boxcars with fins (whale sharks).
Perhaps not surprisingly, such gaudily
diverse morphology begets a wide range of behavior. Like most wild animals,
fish really don’t have much to do in their lives but elude predators.,breed, and eat. But in practicing such basic survival
habits, fish demonstrate an astonishing latitude in
skill and finicky behavior.
What fish eat has been a matter of supreme
interest to humans ever since the invention of the fish hook by Stone Age
man. Given that three quarters of
earth’s surface is drowned by their domain, fish have a menu before them like
no other living creature. There are vegetarian fish: fish that plow bottom sediments
for worms and such: gigantic fish that eat only microscopic plants: fish that
can eat fish bigger than they are: parasitic fish who
live off their hosts’ good fortune.
A motley bunch of trencher-men to be sure,
but how and why fish eat the things they do have been more interesting
questions among scientists who’ve ever taken a serious look at the way fish
feed.
Judging by the collection of skeletalized
fish heads in his office, Wainwnght clearly is among
this group. He’s a specialist in piecing together the evolutionary history of
feeding behavior in fishes. As arcane as that may sound, such work falls into a
classic line of research dating to Darwin, whose evolutionary theories sprang
from his observations on the eating habits of Galapagos finches. Just as
“People have always had this intuition that you
can figure out what a fish does for its living just by looking at its mouth,”
says Wainwright. It’s little wonder that fishes’ heads are by far the most
interesting part of their anatomy—they have little option but to use their
mouths to do what most animals can do easily with claws, paws, or hands.
Seemingly, the animals have tried to make up for being limbless by evolving
what clearly are the most complex mouth and feeding assemblages found in the
vertebrate world. The task is more complicated because fish live in a medium
that is 900 times as dense as air and 80 times as viscous. The result is a
morphological tour de force.’ the
head of’ an average fish contains as many as two dozen separate bones, and up
to three times that many muscles and ligaments, says Wairtwnght.
“Compare that to a typical mammal, such as man,
with a head that has only one moving part, the jaw. When fish
feed. nearly all of these dozens of parts move
in concert.”
Most fish that prey on highly mobile food—such as
other fish—rely on speed, cunning, or ingest their food with sucking action
that can be downright explosive— with prey literally vanishing in the blink of
an eye. Fish accomplish such feats by creating powerful vacuums inside their
mouths, springing them open like hydraulic traps in the presence of food,
Wainwright explained.
Since 1993, Wainwright’s work has centered on an
odd order called Terraodontiformes. Descended from a line of
coral-dwelling species that arose 40 million years ago, modern “tetradonts” have no close relatives among living fish.
Examples include triggertish, cowfish, puffers,
filefish, and the ocean sunfish, Mola mola.
“If ever there was a group of related animals
where it’s obvious there’s been a lot of evolutionary changes, it’s the tetradonts,” Wainwright says.
Even a
glance at photos of tetradont specimens reveals sharp
contrasts in the fishes’ overall looks. Triggerfish.,
noted for dagger-like dorsal spines and tough, leathery hides, bear
considerable likeness to their filefish cousins, but hardly any to cowfish,
which get their name from two “horns” protruding from their bony
foreheads. Cowfish.,and their cousin trunk-fish, are akin to swimming
rocks, with skins quite literally made of solid bone.
Puffers, and their close cousins, the porcupinefish and the burrfish—both
of whom bristle with gristle-like spines— are improbable relatives, too. With
perhaps the lone exception of the swell shark, these fish are the only fish
capable of expanding the size of their bodies, surely among the most creative
self-defense mechanisms in all of nature.
And then there is the sunfish, best
represented by the genus Mola. Looking for all the world like
earless, swimming heads, these tail-less wonders spend their entire lives
wandering the tropical seas, often basking their ponderous bodies—which can
weigh up to a ton—at the surface. Mid-ocean sailors reportedly have mistaken
large specimens for submerged life-rafts. Such profound diversity in body
shapes within any single group of related animals is extraordinary. The highly
variegated tetradont family tree is rooted by two
striking characteristics common to all members, Wainwright says. First, all of
them are missing gill covers, flaps of flesh and bone that flank the heads of
most fish, practically a standard-issue item in fishdom
for protecting the animals’ delicate breathing organs. Tetradonts'
gills, on the other hand, are almost entirely concealed by skin or bone, with only
a slit or small hole appearing where rows of gills should be.
But it’s the second distinction that intrigues
Wainwright. It’s the way tetradonts use their mouths
when foraging for food, for eating, and—in the bizarre case of the puffers—for
blowing themselves up. When frightened, puffers madly gulp water to the point
where they could pass for softballs—even basketballs—with fins. Out of the
water, the fish can do the same trick with air, inflating themselves to
comical proportions in an instant.
Almost
all fish are noted for their talents at “spitting out” undesirable items (e.g. fish hooks),
a behavior Wainwright says is more accurately described as “coughing.”
Snail-and other mollusk-munching species are experts at ejecting showers of
shell fragments.
Tetradonts are superb “coughers.” says Wainwright, but where
some of them really shine is in their abilities to blow water, a specialty
which he believes may be unique to the group whose members all have rather
small, flute-like mouths imminently suited to the task. Triggerfish.
for example, can fire jets of water powerful enough to
overturn large sand dollars and even small rocks.
Using an evolutionary history of the tetradont family worked out by others in the 1970s.
Wainwright noted that while all the family members “cough,” as do most fish
only the more advanced forms can do much else. For example, “blowing” behavior
shows up in the triggerfish, a species that appeared sometime after the earlier
triplespines. The strange ability to inflate shows up
only in the puffers, among the latest arrivals.
The phylogeny clearly suggests a link between all
behaviors, but what physiological evidence was there to prove it?
First, Wainwright had to
establish whether there was anything unusual about how the mouths or heads of
various tetradonts are constructed that allow for
such remarkable latitude in behavior. After a detailed comparison of skeletal
and muscular tissue collected from the fishes’ skulls and jaws, he found that
in the main, tetradonts share the same skull bones,
muscles, and ligaments of most bony fish.
But between species he discovered
striking differences in how these same parts looked and often how they were
linked together. Wainwright not only found wide variation in length, thickness,
and definition of muscles, for example, but also in where some of the same muscles
tied together bones in the head and mouth.
The study turned up no different parts—just different sizes and shapes of
the same parts, which were often connected to each other in different
ways. Perhaps, then, the fish were using
their modified muscles in different ways to take advantage of modified
skeletons to produce different “mouth action”— coughing, blowing, inflation.
Perhaps. To answer the question,
Wainwright collected electrical impulses recorded directly from the living,
muscle-bound heads of the various species while they did all three things. Such
delicate work involves implanting fine-wire electrodes in the fishes’ heads and
jaws.
Analysis of the data revealed a surprising find:
all of the fish were using the same patterns of muscle contraction, whether
they were coughing, blowing, or blowing themselves up.
Interestingly, despite
having highly diversified capabilities, with exquisite control of their varied
muscles.
Wainwright realized that the tetradonts were using a
pattern of muscle contraction that apparently governed not only their own
curious feeding behavior but that of other, entirely unrelated species.
“Here we were looking at animals possessing great
freedom of movement in their heads, perhaps greater than most fish, and yet
they were relying on the same, primitive motor patterns to feed.”
Triggerfish didn’t acquire their spewing talents
by evolving different ways to use their jaw muscles—they evolved differently
shaped bones and muscles instead. The signal to “blow" sent by the
triggerfish's brain to muscles in its mouth is the same signal that might
prompt a puffer to inflate.
“When you apply the same
muscle contraction patterns to different sets of mouth parts, you get different
responses,” Wainwright says. An analogy might be two car engines, both of which
run off the same fuel, applied the same way, but with internal parts configured
differently. Pressing the accelerator effects both
engines, but performance can—and most likely will be—quite different between
the two.
Wainwright had to conclude that for some reason,
the forces of evolution left the basic motor functions that dictate how fish
eat comparatively untouched. Instead of
changing the way feeding muscles are used, evolution has instead had a field
day changing how such muscles look, as well as the bones and ligaments
associated with them.
Apparently,
in trying to make a fish a better feeder or a more successful predator, by
tweaking the way its nerves stimulate its muscles, evolution hit a dead end,
with the neuromuscular system finally reaching a point where it became as efficient
as it was ever going to get. The path to advances in feeding capability thus
lay in radically changing the size and shape of the mouth. Further advances lay
in reshaping the entire body and improving the ability to swim.
Wainwright
says such a finding is surprising, since there’s no apparent reason why evolution
shouldn’t be able to crank out brand new motor patterns— neurological codes so
fundamentally stamped into the brain that they amount to involuntary
reflexes—to drive new or greatly remodeled bones and muscles. After all, a
general trend in evolution is that neurological systems become more complex the
farther up the ladder an organism gets.
“But that’s just not the way it works.” says
Wainwright. “It’s basically a story of new behaviors arising from an ancient
set of motor patterns.” Wainwright’s research offers yet another commentary on
the fundamental curiosities of evolution. As a dynamic system that literally
feeds on change, on occasion evolution finds it prudent to quit fidgeting with
things and leave them as they are—as though following the handyman’s dictum:
“if it ain’t broke.,don’t fix
it.”
adapted
,wth permission
from
V An Amazon
Adventure--Candiru
Can their be a fish that is more feared than a shark? The
Amazonian fish, the Candiru, will be introduced and
explained why the fish is so feared. Three different issues related to the Candiru fish will be explained; its characteristics, its
bad habit, and the cures for the incident which the fish causes.
The Candiru is a fish that is not widely known, but has
interesting characteristics. Also called the Carnero
fish, the Candiru is a very small breed of catfish.
The fish's length is one to two inches (Topping Family Publishers, World Wide
Web) or 40 to 60 millimeters Mike Hagen,
World Wide Web). Only being four to six millimeters wide, (Mike Hagen, World
Wide Web ) helps the bad habit the fish has. The Candiru is a parasitic fish which is completely transparent
(Topping Family Publishers, World Wide Web), which makes it almost impossible
to see. Despite the transparent look of the fish it is very spiny and its bones
are very sharp. The fish only lives in the Amazon and
The Candiru fish does have an odd and painful instinctual
habit. However, this habit is completely human insinuated. Blood and urine
attract the fish to humans (Mike Hagen, World Wide Web ),
so never swim nude in these Amazonian rivers or urinate in the water. If this
is done, while the person is urinating, the Candiru
will swim up the person's open urethra, man or women. At first, their is a small tickle felt by the person, almost a sexual
tickle (Topping Family Publishers, World Wide Web). After the Candiru is in a comfortable position, it raises its spine,
stabbing the inner surface of the urethra and causing outrageous pain (Topping
Family Publishers and Mike Hagen, World Wide Web). However, that is only the
beginning of the problem. Once the spine is lodged into the urethra, the fish
will never leave. Women are more likely to have this event happen to them than
men because they have a larger opening. However, more cases of this incident
have been reported by men than women. This behavior of the Candiru
is a very easily avoided.
Though this
incident causes extreme pain, their are ways to make
the pain stop. Unfortunately, they are either amputation of the organ or death
(Topping Family Publishers, World Wide Web). However, these are not the only
options to cure this incident. If the person is able to afford it, the person
may have very expensive surgery to take out or kill the fish. The two plants
used to do this are the Xaqua plant and the Buitach Apple Mike Hagen, World Wide Web). These
plants are inserted up the urethra and let alone to do the job at hand. The Buitach Apple kills the fish and dissolves it like an
effervescent tablet
Mike Hagen, World Wide Web). If the surgery cannot be performed
or afforded, their are always the first two
options.
In summary,
the Candiru Fish's habit of climbing into a urinating
urethra shows why is the most feared fish in all the
Amazon. Though its characteristics are not like those of the shark or other
dangerous fish, this small parasitic catch can cause just as much pain. The
cures do exist, but amputation and death are the only quick ways for the pain
to stop. These options are probably most often taken because of the intense
non-stop pain. So, one might think twice before making vacation plans to the
Amazon and
Bibliography
Hagen, Mike. "Candiru
Urethra" (http://www.best.com/- debunk/animals/candiru_urethra.html)
(12/15/96)
Topping Family Publishers. "Text Bohica
Candiru" (http://text_bohica_candiru/fish/fish3./html)
(12/15/96)
by Peter Ambrose (1996)
Don't Pee In The Pool
If you
happen to be vacationing in
The Candiru (Vaudellia cirrhosa)
This
catfish is a member of the Trichomycteridae family,
the parasitic catfishes. It is a small, slender fish that is 2.5-6.0cm long and
up to 3.5mm thick. Parasitic by nature, it lives on the blood of host animals.
It is not particular, it will just as soon snack on
human blood as it will its normal meal, fish blood. Don't be fooled by its
slender body either. It can expand considerably when gorging itself on its
victim's blood.
Candiru enter the gill chamber of their host fish and feed
on their blood. This is achieved using "its mouth as a sucking apparatus
and rasping with the long teeth in the middle part of its upper jaw." This
species doesn't limit its diet only to fish, however. They also have a taste
for human blood, which is acquired in a most unpleasant way. (Unpleasant
for the human bather that is.) The candiru
sometimes enters the urogenital openings of human
bathers in search of a meal. Especially if the bather happens
to urinate while in the water. Hence the above warning - don't pee in
the pool. The flow of urine gives the candiru a
distinct path to follow to locate its next meal, just as the flow of water
leaving a fish's gills does. Protection affords itself only in the form of
tight-fitting clothes. Natives are even known to wear coconut shell guards over
their private parts to prevent this very unwelcome visitor.
Just how
unwelcome is it, you may ask. Well, after forcing its
way as far inside its chosen crevice as it can (remember how slender they are), it then locks itself in place using spines located on the
gill covers. Not only does this cause excrutiating
pain, it also may cause massive bleeding leaving you open to infection. But
wait - that's not even the worst. You still have to figure out how to remove
this intruder. Most often surgery is the only solution. Surgery you know where.
Ouch.
So next
time you are swimming, remember to take Mom's advice...
Don't
Pee In The Pool!
from the March 1973
article of Urology, pages 265-267 Candiru: Urinophilic Catfish Its
Gift to Urology John R. Herman, M.D.
In the
early 1900s many strange and florid tales arose in that rich source of
extravaganzas, the
(snip) In 1836 Poeppig, after a long journey through the country, wrote of
a plant known as the Xagua.
The fresh
juice of Xagua is rightfully claimed to be the surest
means of killing and getting rid of these two-inch long little fishes which
slip into the outer opening of the bodies of careless bathers and bring about
the most dreadful accidents.
Gudger, of the
Use of
"Cod Pieces" Gudger evaluated reports of penetration of the human
urethra, including those of a U.S. Naval surgeon who stated that he had
performed surgical procedures on three such patients, doing a suprapubic cystostomy on one to
remove the fish. He concluded that the candiru does
penetrate the human urethra, offering further circumstantial evidence, such as
the various "cod pieces" or penis protectors worn by the men when
they entered the infested water of the Amazon. The women also wore pudendal covers for this purpose. (snip)
In 1941
Vinton and Stickler(6) wrote that "there is no
doubt that the creatures actually exist." These fishes are known by the
"collective name carnero." The authors
quote from a letter by Dr. H.H. Rusby, a pharmacognosist, "as to the attacks of carnero on men and women, the records are established.
Feather-bed explorers and theoretical researchers have disputed the facts, but
the evidence is abundant and confirmed." Their article also gives
first-hand accounts of the fish. The authors also seem to feel that reported
losses of penes are more likely due to piranha than
to surgical intervention for removal of candiru.
Treatment
Most important to urologists as well as to the unhappy victims is obtaining
relief after an attack. Because the fish spreads its gill covers in trying to
get oxygen, the sharp spinous processes on the ends
of the opercula engage the urethral wall making extraction from the urethra
almost impossible or at least most traumatic. The green fruit of the jagua tree, Genipa
(discussion about using buitach for
dissolving kidney stones, rather than the bones of candiru) The buitach apple
tissue contains large quantities of apparently usable citric acid, thus calcium
is dissolved. Amazonians appear to have been aware of this long before the era
of modern medicine, providing another example of a folk-remedy having a valid
scientific basis.
COELACANTH
1. What is the COELACANTH and why is it
considered unique?
2. What are the two theories for terripods concerning the COELACANTH and lung fish?
3. What use are
COELACANTH?
4. What might be some reasons for their population drop?
5. What has man done to protect them? Is it working?
6. Where is the COELACANTH found?
7. What has happened to their population?
8. What is the major characteristic in
crossopterygians in their skull?
9. What might the fat deposit dorsal to the
abdominal organs represent?
10. Describe the attachment of the fins.
11. What did rhipidistians
have to survive on land?
12. To what family do coelacanths belong?
13. What is the average size of a Coelacanth?
14. When had coelacanths been thought to have
gone extinct?
15. When did man find a living coelacanth and
where?
20.
Fish
1. How often do some reef fish reverse gender?
2. What are sex-changing fish known as?
3. Describe how sea bass (S. tortugarum) spawn?
4. What is the most common type of sex reversal?
5. Some fish only change once. What causes this to occur?
6. Name 3 species of reef fish that change sex
several times?
7.
Do fish change appearance when they go
back to the one sex each time?
8. Which fish has two types of males? How are they different? What about type I & II?
9. How can one determine the sex of a
fish...like the males?
10. How is this sex reversing a benefit?
18
SHARK
STORY "WHITE SHARKS CAN
JUMP"
1.
WHAT IS THE GREAT WHITE SHARK'S KILL RATIO PER ATTACK?
2.
DO GREAT WHITE SHARKS STALK THEIR PREY BEFORE ATTACKING?
3. WHEN DO GREAT WHITE SHARKS FEED?
4. WHEN WAS THE FIRST PREGNANT GREAT WHITE SHARK
CAUGHT FOR STUDY?
5. WHAT WAS THE LARGEST DOCUMENTED GREAT WHITE
SHARK CAUGHT?
6. CAN ANY OTHER SEA ANIMALS PREY ON A GREAT
WHITE SHARK?
7. WHAT ARE THREE UNNATURAL WAYS GREAT WHITE
SHARKS CAN DIE?
8. HOW BIG ARE THE EYES OF THE GREAT WHITE?
9. CAN SHARKS DISCRIMINATE BETWEEN CARDBOARD
BOXES, BOATS, AND SURFERS?
10. COULD AN OLYMPIC SWIMMER OUTSWIM A GREAT
WHITE SHARK?
21.
When fish bite reading
name.........................................................................pd...........
1. What acivities do fish partake in?
2. List the menus of
fish?
3. What is the symmetry
of a fish related to?
4. Who are the tetradants?
5. Who are the tetradonts closest relatives to modern day fish?
6. What characteristics
are common to all of these fish?
7. What is the genus of the sunish...describe
this fish?
8. Wha
would our term for spitting out a hook called?
9. What types of mouth
activities can these fish exhibit?
10. What different muscle pattern do the fish
demonstrate for the different mouth actions?
11. What part of the triggerfish evolved to use
their jaw muscles?
12. How successful was evolution in bringing
about changes in the way the nerves stimulate muscles?
13.
Describe the adaptations of the mouthparts in these fish in relation to muscle development and bone
development?
5.
Ciguatera Poisoning Questions:
____1.In
paragraph 4, the idea that seaweeds and the dinoflagellates
are mixed up in the water column….is considered (A) fact (B) Opinion
____2. The estimated loss of $10 million annualy in the seafood industry is considered (A) Fact (B) Opinion
Put
the following stages of the evolution of toxicity into order.
____3. Only large eels and snappers and groupers
are toxic (A) 1st
(B) 2nd (C) 3rd (D) 4th
____4 . Almost all reef fish are toxic (A) 1st (B) 2nd (C) 3rd
(D) 4th
____5. Herbivorous fish become toxic (A) 1st (B) 2nd
(C) 3rd (D) 4th
____6
Carnivorous fish become toxic
(A) 1st (B) 2nd
(C) 3rd (D) 4th
____7. The
main idea of this reading is
(A)
Ciguatera can move up the food chain without killing fish but being passed on
to other animals.(B) Attempts to grow G. toxicus in the
lab have been disappointing because lab-cultured organisms produce less toxin
than those in natural surroundings(C) thousands of people living in tropical
regions of the world are affected by ciguatera poisoning caused by eating
fish.(D) Symptoms of Ciguatera
poisoning may include headache, nausea, vomiting, abdominal cramps, etc., and
even death.
6. An
Amazon Adventure—Candiru
1. What is the main idea of the “Article”?
2. What scientific principle(s) are
illustrated in the “article”?
a)
____________________________________________________
b)
____________________________________________________
c)
____________________________________________________
3. What are 5 facts stated in the “article”?
a)
_____________________________________________________
b)
_____________________________________________________
c)
_____________________________________________________
d)______________________________________________________
e)______________________________________________________
4. What is the conclusion of the “article”?