How do Angelfish How do Angelfish Sense their Sense their

World?World?A Presentation for The A Presentation for The

Angelfish Society Angelfish Society

March 16, 2008 MeetingMarch 16, 2008 Meeting

By Tamar StephensBy Tamar Stephens

Have you ever Have you ever wondered…?wondered…?

If you live in the water, is it better to be If you live in the water, is it better to be warm blooded or cold blooded?warm blooded or cold blooded?

Do angelfish have ears?Do angelfish have ears? What is the lateral line? What is the lateral line? Do angelfish see color?Do angelfish see color? Do angelfish have noses?Do angelfish have noses?

This presentation will give you an This presentation will give you an overview of how angelfish sense the overview of how angelfish sense the world around them.world around them.

If you feel cold…If you feel cold…

If you feel cold, your body If you feel cold, your body responds by producing more responds by producing more heat to keep the body heat to keep the body temperature at a fairly temperature at a fairly constant temperature right constant temperature right around 98.6°F.around 98.6°F.

If you regulate your If you regulate your temperature internally, you temperature internally, you are what we call an are what we call an “endotherm” – or warm-“endotherm” – or warm-blooded.blooded.

If an angelfish feels cold…If an angelfish feels cold…

If an angelfish feels colder surroundings, If an angelfish feels colder surroundings, its body does not generate heat to keep it its body does not generate heat to keep it warm. Instead its body temperature will warm. Instead its body temperature will drop to the surrounding temperature.drop to the surrounding temperature.

Angelfish are “ectotherms.” (Huh? Angelfish are “ectotherms.” (Huh? What’s an ectotherm?)What’s an ectotherm?)

If the body temperature is regulated by If the body temperature is regulated by the surrounding environment a creature is the surrounding environment a creature is an “ectotherm” – more familiarly called an “ectotherm” – more familiarly called cold blooded.. cold blooded..

It doesn’t take much energy It doesn’t take much energy to heat air!to heat air!

Your body stays very close to Your body stays very close to 98.6°F regardless of the 98.6°F regardless of the surrounding temperature. surrounding temperature.

If you stand in 70°F air, it doesn’t If you stand in 70°F air, it doesn’t take much to heat the air that is take much to heat the air that is close to your body. With a light close to your body. With a light jacket to capture a thin layer of jacket to capture a thin layer of air, you can be comfortable in a air, you can be comfortable in a wide range of temperatures. wide range of temperatures.

A polar bear’s coat allows it to A polar bear’s coat allows it to maintain its body heat in maintain its body heat in temperatures down to -50°F and temperatures down to -50°F and colder!colder!

Is it better to be warm Is it better to be warm blooded or cold blooded if blooded or cold blooded if

you live in the water?you live in the water? It takes a lot more energy to heat water than air. If It takes a lot more energy to heat water than air. If

you jump into cold water, you lose body heat very you jump into cold water, you lose body heat very rapidly. rapidly.

Most creatures that live in the water have their body Most creatures that live in the water have their body temperature regulated by the surrounding water. It temperature regulated by the surrounding water. It takes tremendous energy to generate the heat to takes tremendous energy to generate the heat to warm up the water or to maintain a body warm up the water or to maintain a body temperature higher than the surrounding water! So temperature higher than the surrounding water! So except for large marine mammals and a few types of except for large marine mammals and a few types of large fish, water-dwelling animals are adapted to large fish, water-dwelling animals are adapted to adjust to their environment’s temperature.adjust to their environment’s temperature.

One consequence is that most fish live in a fairly One consequence is that most fish live in a fairly small temperature range. Angelfish generally do small temperature range. Angelfish generally do best between about 75 to 85 degrees F, and they best between about 75 to 85 degrees F, and they don’t do well with sudden temperature changes!don’t do well with sudden temperature changes!

Do angelfish have ears?Do angelfish have ears?

Well, yes they do!Well, yes they do!

You won’t see their ears, because You won’t see their ears, because angelfish do not have external ears. angelfish do not have external ears. Their ears are internal!Their ears are internal!

Sound travels very well through Sound travels very well through water – much better than through water – much better than through air.air.

Sound vibrations in the water will Sound vibrations in the water will transmit through the fish’s body to transmit through the fish’s body to the ear.the ear.

Ear structureEar structure

The upper section of the ear (called the pars The upper section of the ear (called the pars superior) has three semicircular canals that superior) has three semicircular canals that give fish its sense of balance. The canals are give fish its sense of balance. The canals are filled with fluid and have sensory hairs that filled with fluid and have sensory hairs that are stimulated by rotational motion of the are stimulated by rotational motion of the fluid.fluid.

The lower section (called the utriculus) The lower section (called the utriculus) senses sound. Vibrations of the utriculus senses sound. Vibrations of the utriculus stimulate surrounding hair cells to vibrate, a stimulate surrounding hair cells to vibrate, a lot like our ears. lot like our ears.

Fish ear structure Fish ear structure

Pars superior – sense of balance.

Utriculus – sense of sound

Figure is a diagram of a gourami inner ear. Source: http://www.life.umd.edu/biology/popperlab/background/index.htm

What is the lateral line?What is the lateral line?

Have you ever noticed a Have you ever noticed a curved row of dots on your curved row of dots on your

angelfish?angelfish?

Yellow arrow points to the lateral line.

(Photo is of a black crossover female, courtesy of Gil Repetto)

Here’s another exampleHere’s another example

(Wild angelfish photo from Bob Barone)

Lateral

Line

And one moreAnd one more

(Photo from phenotype library. Sorry, name of contributor not known.)

Lateral line

The lateral line is sort of a The lateral line is sort of a cross between hearing and cross between hearing and

feeling.feeling. The lateral line consists of a series of The lateral line consists of a series of

fluid-filled ducts that sense pressure fluid-filled ducts that sense pressure or vibrations. As the ducts are or vibrations. As the ducts are stimulated in sequence, the stimulated in sequence, the angelfish can sense the direction of angelfish can sense the direction of the stimulus. This allows it to sense the stimulus. This allows it to sense the motion of another fish and the the motion of another fish and the direction from which it is coming. direction from which it is coming.

Do angelfish see color?Do angelfish see color?

Photo of leopard male from Gil Repetto

Vision in fishVision in fish

Sorry, I don’t have information specific to Sorry, I don’t have information specific to angelfish. So this is general information angelfish. So this is general information about fish vision. about fish vision.

Fish in general have a good sense of vision, Fish in general have a good sense of vision, on a par with human vision. on a par with human vision.

Many fish can see color. Many fish can see color. A fish’s eyes are different from ours. We A fish’s eyes are different from ours. We

have a convex lens. A fish’s lens is spherical. have a convex lens. A fish’s lens is spherical. The spherical shape has a higher refractive The spherical shape has a higher refractive index, which enables them to see better index, which enables them to see better under water. under water.

They focus by moving the lens in and out, They focus by moving the lens in and out, instead of changing its shape like we do. instead of changing its shape like we do.

But do angelfish see color? But do angelfish see color?

Anecdotal evidence that Anecdotal evidence that angelfish see colorangelfish see color

I read on a forum some time ago someone I read on a forum some time ago someone describing letting her fish select which kind of describing letting her fish select which kind of food they wanted. She would hold up the food they wanted. She would hold up the different containers, each a different color, and different containers, each a different color, and the angelfish would gather by the food the angelfish would gather by the food container that they selected.container that they selected.

I have observed my fish act startled if they see I have observed my fish act startled if they see me appear in new clothing in a color they me appear in new clothing in a color they aren’t accustomed to seeing me in. aren’t accustomed to seeing me in.

So, based on these anecdotal bits of So, based on these anecdotal bits of information, I think angelfish do see color. information, I think angelfish do see color. (Maybe in a future presentation we can look at (Maybe in a future presentation we can look at how researchers investigate the ability of fish how researchers investigate the ability of fish to distinguish colors – and you can do a study to distinguish colors – and you can do a study on color vision in angelfish!)on color vision in angelfish!)

Do Angelfish have noses?Do Angelfish have noses?

Fish in general have a a well-developed Fish in general have a a well-developed sense of smell.sense of smell.

They don’t have noses, but they do They don’t have noses, but they do have two nostrils - “olfactory rosettes” - have two nostrils - “olfactory rosettes” - one on each side of the head. They are one on each side of the head. They are not connected to the throat as in not connected to the throat as in humans. They are not obvious in humans. They are not obvious in angelfish to the casual observer. angelfish to the casual observer.

(Sorry, no photos. You would need a (Sorry, no photos. You would need a good close up photo to see the nostrils.)good close up photo to see the nostrils.)

Do they have a sense of Do they have a sense of taste?taste?

Yes!Yes! Fish have taste buds on their lips, Fish have taste buds on their lips,

tongue and mouth.tongue and mouth.

““Feeler” FinsFeeler” Fins

Every now and then someone new to Every now and then someone new to angelfish will ask a question on a angelfish will ask a question on a forum about the “feeler” fins. Of forum about the “feeler” fins. Of course, those of us who are more course, those of us who are more experienced know these are more experienced know these are more properly called “ventral” fins, or properly called “ventral” fins, or ventrals for short.ventrals for short.

But there is a nugget of truth to in But there is a nugget of truth to in referring to them as “feeler” fins. referring to them as “feeler” fins.

Ventral fins allow the Ventral fins allow the angelfish to “feel” things angelfish to “feel” things

below them.below them.

Angelfish can feel Angelfish can feel the contours of the the contours of the bottom of their bottom of their environment (pond, environment (pond, river, aquarium) as river, aquarium) as the tips of the the tips of the ventrals brush ventrals brush against sediments, against sediments, rocks, or vegetation. rocks, or vegetation. This can be very This can be very useful in the dark.useful in the dark.

Photo from phenotype library. Contributor not known.

The EndThe End

I hope you enjoyed this presentation!I hope you enjoyed this presentation!

Now back to the meeting chat room Now back to the meeting chat room for discussion!for discussion!