- [20:02 06/05/2005] <@Craig> Goooooood evening everyone! Welcome
to Live! Fishchat!
- [20:02 06/05/2005] <@Craig> Tonight's speaker is one of our
very own, Russ! He will be speaking on Sensory Systems, this being
- [20:02 06/05/2005] <@craig> Russ, when ever you are ready!
- [20:03 06/05/2005] <+russ> Thanks
- [20:04 06/05/2005] <+russ> Good evening folks. Thank you once
more for an opportunity to ramble about fish, ah.......stuff. Fish
physiology is still not an all-inclusive subject and scientists are
continuing to discover and re-discover new aspects of this.
- [20:04 06/05/2005] <+russ> Because this type subject matter
can get rather deep and utterly boring, I have condensed this presentation
tonight in the hope I can present this in a easy and understanding
manner. This presentation had to be divided into two parts. ( I have
a Part 3 tucked away for the future)
- [20:05 06/05/2005] <+russ> Part 1 of fish sensory systems
covered the use of two sensory systems; Photoreceptors, which utilize
light energy into nervous impulses for sight, and Mechanoreceptors,
which convert the movements of water into electrical impulses responsible
for balance and hearing and the actions of the lateral line.
- [20:06 06/05/2005] <+russ> Rather than briefly going over
what was previously covered in Part 1, I've provided a link you can
explore that goes into a little greater detail than the original presentation.
Or, you can refer to the subject in the past presentation section
of the moderated chats.
- [20:07 06/05/2005] <+russ> Here is the link:
- [20:07 06/05/2005] <+russ> http://www.badmanstropicalfish.com/message_board/messages/27480/31265.html?1106194051
- [20:07 06/05/2005] <+russ> Tonight I'll concentrate on Chemoreptoin.-
Olfaction and Taste
- [20:08 06/05/2005] <+russ> While sometimes it is sometimes
difficult for us to determine whether a particular reaction in our
fishes was caused by olfaction or taste, scientist know that fish
do have distinct olfactory and taste organs that are very similar
in their morphology to terrestrial vertebrates. The main difference
in fishes is that very rarely does the olfactory organ open to the
- [20:08 06/05/2005] <+russ> The basic function of olfaction
in fishes is for detecting substances at a distance. The basic importance
(in most fishes) of the taste organ(s) could be considered a 'contact
sense' for testing the palatability of something.
- [20:09 06/05/2005] <+russ> OLFACTION:
- [20:09 06/05/2005] <+russ> In most fishes, these organs are
far more sensitive than taste organs, thus making them more important
for sensing dilute quantities of substances at a distance. Like terrestrial
critters, these organs are positioned in relative locations of the
fish's head or snout
- [20:10 06/05/2005] <+russ> There are variations in the actual
development with some fishes having only a single median nostril with
just one opening. (Lampreys and Hagfish are an example). Sharks and
Rays have paired olfactory organs located on the ventral side of the
- [20:11 06/05/2005] <+russ> But, most fishes have paired organs
located on the snout above the mouth. These have a separate inlet
and outlet for water that is passed through the organ in three ways:
(1) breathing movements that compress an olfactory pouch and force
water in and out of a single opening in conjunction with the respiratory
- [20:11 06/05/2005] <+russ> (2) cilia, or breathing movements,
or both, of the fish cause water to circulate through the anterior
opening and out the posterior opening,......(3) water is deflected
in and out of the organ by the fish's movement through the water.
- [20:12 06/05/2005] <+russ> The shape of this organ (sac) varies
from species and are in three basic shapes:.....round, which is associated
with fishes that are primarily sight feeders. .........oblong, associated
with fishes that use both sight and olfaction to locate food. ........and
elongate, which is generally associated with fishes that have poor
vision, but a highly developed sense of smell.
- [20:12 06/05/2005] <+russ> (How this organ works....in a nutshell):
- [20:15 06/05/2005] <+russ> What has been observed is that
substances with similar molecular configurations have similar odors.
Ancillary to this theory, molecules with intermediate shapes produce
intermediate odor sensations by 'fitting', and stimulating different
receptor sites, accounting for why relatively few different types
of receptor sites could be responsible for many odor sensations
- [20:16 06/05/2005] <+russ> Electro physiological and behavioral
tests have shown that fishes have a wide range of sensitivity between
different organic materials. Fishes with highly sensitive olfactory
organs are considered 'macrosmatic' and those fishes with less highly
developed systems are considered 'microsmatic'. Examples of macrosmatic
fish are minnows, trout, and the American Eel.
- [20:17 06/05/2005] <+russ> Because they are building blocks
for protein, various amino acids have been studied in relation to
their effect on the olfactory systems of fishes, and what combinations
might prove as a attractant to fishes. Valine and lysine proved to
be very good attractants although in other tests, different species
did prefer different amino acids. In lab tests, other pure substances
that evoked a feeding response were ammonia, lactic ac
- [20:18 06/05/2005] <+russ> Natural food extracts (earthworms,
clams, shrimp, fish, various plant and algae) elicit degrees of feeding
responses in various species of fish. This would indicate a specific
combination of amino acids in foods that form an 'odor profile' which
is recognized by species of fish. These differences in attractants
of certain amino acids may be one of the reasons that fish raised
on a particular food resist changing to a ne
- [20:19 06/05/2005] <+russ> From a previous presentation on
Non-growth In Fishes, we learned how various stesses and immune responses
affect fishes. Chemoreceptors can shut down fully, or to varying degrees,
when a fish is ill or injured in order to conserve only the most vital
system organs and corresponding brain sensations. This is one of the
reasons for a fish not to eat when sick or injured.
- [20:20 06/05/2005] <+russ> Scientists have also explored the
crowding factor and how they relate to chemorecption in regards to
the retardation of growth, reproduction, and depressed heart rates.
Sampling of species that were tested : Zebra Danios, goldfish, carp/koi,
and Blue Gourami.
- [20:21 06/05/2005] <+russ> The majority of the heart rate-inhibiting
factor for goldfish and carp was extracted from water with chloroform
and was in the neutral lipid fraction. And it has been suggested that
the factors inhibiting heart-rate, growth, and reproduction are either
very closely related or the same substance.
- [20:22 06/05/2005] <+russ> A fright reaction, in which a fish
stops feeding, concentrate, then seek cover or flee when a member
of their species has been injured, was first reported in 1938. Since
then, it has also been reported for many species and has been associated
- [20:22 06/05/2005] <+russ> The fright reaction was initiated
by a substance called 'Schreckstoff' in German, given off by the injured
skin of fishes. Although the chemical makeup of this compound is not
quite known, from observations, it is believed the substance is produced
by specialized epidermal cells that do not open to the surface and
only release the fright substance when the skin is broken or injured.
- [20:23 06/05/2005] <+russ> Fishes killed without injury to
the skin did not elicit this response. Tests and observations have
also shown that this reaction can be induced by skin extracts across
species, but the intensity of the response was greater in related
- [20:24 06/05/2005] <+russ> Fishes that do show this fright
response can react to very low concentrations of the skin extracts.
Species of Cyprinidae tested, reacted to concentrations that were
in the parts per trillion.
- [20:24 06/05/2005] <+russ> TASTE BUDS/RECEPTORS:
- [20:25 06/05/2005] <+russ> In most fishes, taste is a contact
sport when it comes to playing with their food; used primarily as
the final screening process to accept or reject a food morsel. The
sensitivity of taste receptors in some fish, such as the catfishes,
are very sensitive. Test have also suggested that many fishes respond
to a wide variety of tastes.
- [20:26 06/05/2005] <+russ> In addition to their location in
the mouth of a fish, taste receptors can also be located in the pharynx,
on gill rakers and gill arches, and widely scattered over the outer
surface of a fish's body. Catfishes have thousands of external taste
buds on their bodies with dense concentrations on their barbels.
- [20:26 06/05/2005] <+russ> It has been estimated that a Yellow
Bullhead of approx. 10 inches in length, has about 175,000 taste buds
on it's external body surface, and an additional 20,000 in it's mouth
and throat. In comparison, the average human tongue contains about
10,000 taste buds.
- [20:28 06/05/2005] <+russ> I believe that taste buds may be
affected to varying degrees of impairment when a fish employs various
immune responses, such as accelerated mucus production during a external
parasitic attack. With the generation of excess mucus, many taste
bud ends could be covered by thicker coats of mucus or damaged from
resulting lesions of infection.
- [20:29 06/05/2005] <+russ> As indicated, electro physiological
and behavior-response tests, indicate fishes respond to a wide variety
of tastes. Tests have shown that taste buds located on the palatal
organ of carp respond to acetic acid, sucrose dextrose, levulose,
glycine, quinine, NaCl, human saliva, carbon dioxide, and a extract
from the papae of silkworm. For many substances, the sense of taste
in fishes is more sensitive that it is in humans.
- [20:30 06/05/2005] <+russ> Some thresholds were also established
in tests. The thresholds for sucrose and salt in species of minnows
are reported to be 2 x 10(-5) M and 4 x 10(-5) M, respectively where
M stands for molar. These values are approx 512 and 184 times lower
than those reported for humans. The threshold value for fructose is
approx. 2,500 times lower than that of humans.
- [20:31 06/05/2005] <+russ> Sorry, I couldn't get my keyboard
to disply those figures correctly
- [20:32 06/05/2005] <+russ> In catfishes, taste is so sensitive,
that it is also utilized to detect substances at a distance. Tests
have shown that catfishes can use their sense of taste to located
food up to 25 times their body length. Like olfaction, taste receptors
in catfish and other fishes are very sensitive to certain amino acids
and combinations of amino acids.
- [20:33 06/05/2005] <+russ> The taste sensation begins when
fish are some distance from their food, intensifies as they get closer,
and is the strongest when the food is ingested (or as Alton Brown
would say, 'good eats')
- [20:34 06/05/2005] <+russ> I was going to talk about migration
and imprinting in a manner of some detail, but will elect to attempt
to answer questions anyone may have on this when the floor is open
- [20:35 06/05/2005] <+russ> Hopefully, with this information
(as condensed as possible) and a review of Part 1, you can get a better
idea of how fish stay 'in-tuned' with their surroundings. Much of
this information should be very familiar with the microbiologists
and physiologists board members. I have a presentation on the respiration
of fishes lined up for the future if anyone is interested.
- [20:35 06/05/2005] <@craig> Thank you Russ!
- [20:35 06/05/2005] <+russ> That is about it. Thank you. JP,
you can wake up now! :-)
- [20:35 06/05/2005] <@JP> Well done, Russ. :-D
- [20:36 06/05/2005] <@JP> Bite me. ;-)
- [20:36 06/05/2005] <@craig> Any qualms about me just opening
the floor and letting the free for all begin?
- [20:36 06/05/2005] <+russ> I'll try to keep track:-)
- [20:36 06/05/2005] <@craig> Let him have it folks.. :-D
- [20:36 06/05/2005] <@JP> Floor is open. Talk away. :-D
- [20:37 06/05/2005] <Karen> Thanks Russ!
- [20:38 06/05/2005] <@craig> Come on now folks, someone has
to have a question to stump Russ with.. :-D
- [20:38 06/05/2005] <+russ> OMG! I did put everyone to sleep:-D
- [20:38 06/05/2005] <Karen> didn't put me to sleep! I'ms till
- [20:38 06/05/2005] <Karen> I'm
- [20:38 06/05/2005] <Karen> still
- [20:38 06/05/2005] <@JP> Nah, they're still amazed about the
wealth of info. :-D No need to ask questions. ;-)
- [20:39 06/05/2005] <@craig> There is a lot to digest there..
- [20:39 06/05/2005] <+russ> I did go a little faster than I've
done in the past
- [20:40 06/05/2005] <@craig> Only hacked one sentence off too,
very proud of you. ;-)
- [20:40 06/05/2005] <@JP> Was happy when you finally picked
a color. ;-)
- [20:41 06/05/2005] <+russ> Oh oh. Which sentence was that?
- [20:41 06/05/2005] <@JP> The one you hacked off.
- [20:42 06/05/2005] <+russ> Probably the one that was the key
to the whole presentation
- [20:42 06/05/2005] <@JP> "These differences in attractants
of certain amino acids may be one of the reasons that fish raised
on a particular food resist changing to a ne..."
- [20:42 06/05/2005] <@craig> Thanks JP :-D
- [20:42 06/05/2005] <+russ> new food
- [20:42 06/05/2005] <@JP> :-D
- [20:43 06/05/2005] <+russ> or new diet, to be a little more
- [20:43 06/05/2005] <@JP> We strive for perfection around here,
you should know that.
- [20:43 06/05/2005] <Karen> now it makes scense:)
- [20:43 06/05/2005] <Karen> sense
- [20:43 06/05/2005] <Karen> i'm tired tonight--can't spell
- [20:44 06/05/2005] <+russ> either can my keyboard
- [20:44 06/05/2005] <@JP> We're used to that.
- [20:44 06/05/2005] * @JP glances at Russ.
- [20:44 06/05/2005] <@craig> Karen, don't worry about typos,
we edit this before it hits the masses. ;-D
- [20:44 06/05/2005] <@JP> There's no "we" in Craig.
- [20:44 06/05/2005] <@craig> Of course, Russ, does make me
work a bit more.. (Damn smart quotes..)
- [20:45 06/05/2005] <+russ> Just as JP mentioned.......
- [20:45 06/05/2005] <Karen> well I can always remember that
Russ gave my first fishchat
- [20:45 06/05/2005] <+russ> Surely you must have a question?
- [20:48 06/05/2005] <Karen> about the size of the olfaction....
what catagory would most livebearers fall under? (sorry all my thoughts
are based on guppies:))
- [20:50 06/05/2005] <+russ> Karen, you mean, what shape, or
- [20:51 06/05/2005] <+russ> I would actually have to clasify
livebearers as 'microsmatic'
- [20:52 06/05/2005] <+russ> They feed all over the tank and
are not very dependent onexternal delivery assistance.
- [20:52 06/05/2005] <Karen> sorry--i was reading the link you
- [20:53 06/05/2005] <Karen> I was actually asking whether they
were oblong, elongate, or round
- [20:53 06/05/2005] <+russ> I forgot which one went into more
detail. The link or the prior chat.
- [20:55 06/05/2005] <+russ> On the livebears you asked about;
is my best guess. I don't have a ready reference for that one at the
- [20:57 06/05/2005] <Karen> thanks
- [20:57 06/05/2005] <Karen> i'll try to google it for more
- [20:58 06/05/2005] <+russ> Livebearers are generalized grazers,
so they don't have to rely heavily on just one or two senses, but
utilze all(as most other s also), such as vision
- [20:59 06/05/2005] <Karen> "grazers" as in they
just nibble at stuff all day?
- [21:00 06/05/2005] <+russ> Basically, yes. All over the tank
and water surface
- [21:01 06/05/2005] <Karen> that fits my livebearers!
- [21:01 06/05/2005] <Karen> They'll try anything--whether edible
or not. :)
- [21:02 06/05/2005] <+russ> Of all the various livebearers
I've ever raised, owned,, or otherwise, they almost all had one thing
in common as far as eating
- [21:03 06/05/2005] <+russ> they all seemed to play with their
- [21:04 06/05/2005] <+russ> 90% of those guys would grab a
morsel, then spit it out several times before accepting or rejecting
- [21:05 06/05/2005] <Karen> that's exactly what mine do.
- [21:05 06/05/2005] <Karen> their mother needs to teach them
some manners :D
- [21:05 06/05/2005] <+russ> 90% of those livebearers would
tend to accept it directly from the surface though.
- [21:05 06/05/2005] <Karen> (don't play with your food!)
- [21:06 06/05/2005] <+russ> That is another reason why I think
livebears are microsmatic. They need to 'taste' it up close and personal:-D
- [21:08 06/05/2005] <Karen> they don't seem like their senses
are too developed, (kinda dum) so I think taht you're probably right.
- [21:10 06/05/2005] <+russ> Craig, think we should move to
the other side?
- [21:10 06/05/2005] <@JP> Does anyone else have something to
add or ask?
- [21:10 06/05/2005] <+russ> Karen, it looks like you are the
only one with questions tonight:-)
- [21:10 06/05/2005] <@craig> Yes, lets close up shop..