Lecture 22. October 29, 2008. Vision, smell and taste. Friday is review. Review questions will be...

Lecture 22. October 29, 2008. Vision, smell and taste.

Friday is review.

Review questions will be posted by the end of the day.

Monday is test #2.

light

inner limiting membrane

nerves

rods

cones

pigment epithelium

night day

rodscones

Terrestrial vision is adapted to light traveling through air. Aquatic visionis adapted to light bending in water (refractive index). When light hits a terrestrial eye, it bends as it enters the cornea & inner parts of eye (in liquid).In fish, this doesn’t happen because everything is already in water.

Both shorter wavelengths & longer wavelengths are reduced with depth.

Lighting environment changes with depth.

UV filtered (below 300nm) inozone.

IR filtered in atmosphere.At sea level, big range in wavelengths (320-1100nm)

IR quickly filtered in water.UV & blue filtered somewhattoo.

In deep waters, narrow rangeof light -- 480-520 nm.

Deep sea fishrods in 480-520nmrange.

Coastal fish in 490-510 nm range.

FW fish 500 - 540 nmrange.

Crater Lake - very clear water

“normal” lake water with somealgae

swamp water w/tannins - “tea” colored

Properties of Terrestrial Vertebrates.

Humans have 3 cone types (blue – 437nm, green – 533 nm, red 564 nm).

Some monkeys only have 2 cones.

Most birds have 4 cones – one of which is UV- sensitive.

0

0.2

0.4

0.6

0.8

1

350 400 450 500 550 600 650 700 750

wavelength

absorbance

Bluefin killifish have 5 cones!

Fuller et al. 2003. J Comparative Physiology A

blue reduv violet yellow0.0

0.1

0.2

0.3

0.4

0.5

rela

tive

cone

fre

quen

cy

swampspring

Breeding Scheme

r/b r/r y/by/y

Fuller et al. 2005. Journal of Evolutionary Biology

opsins - cone pigment

UV blue redviolet yellow0.0

0.5

cleartea

0.4

0.3

0.2

0.1

rela

tive

opsi

n ex

pres

sion

Large effects of environment!

Blue species - top

Red species - bottom

intermediates Range in colors of males.

Lighting environment differs with depth. Light spectrumis red-shifted in deeper water .

Blue males in shallower water and red males in deeper water.

Red males in habitats with higher proportion of red light.

Two different types of red cone photopigment.

The blue males are more likely to have the blue shifted cone type (P). The red males are more likely to have the red shifted cone type (H).

Assumption is that differences in vision affect differences female mating preferences and isolation between the two types.

Cichlid story put together.

1. Males differ in color patterns and they differ in the depths at which they are found.

2. Deeper water is red-shifted and this is where red males are found.Shallower water is blue-shifted and this is where the blue males are found.

3. Red males are more likely to possess the red-shifted red cone. Blue males are more likely to possess blue-shifted red cone. Note the animals don’t differ in the blue or red cones.

4. The assumption is that differences in lighting environment are “driving” reproductive isolation.

5. Another study has shown that eutrophication (making the water turbid and algae-filled) has led to increased levels of hybridization between species.

6. Details need to be worked out, but the lighting environment is critical for some aspects of reproductive isolation.

Chemoreception

• Olfactory organsOlfactory organs– nares nares (blind sacks) with(blind sacks) with

»rosettesrosettes

• Taste organsTaste organs– taste buds taste buds (all parts of body)(all parts of body)

»barbelsbarbels

Olfactory organs

Taste Organs

Taste buds

Taste Organs

Taste buds

Review Questions - Vision:

1. List 2 ways that vision differs between terrestrial vertebrates versus fish.Specifically, how do fish differ from terrestrial vertebrates in how they move their lenses? How do terrestrial vertebrates differ from fish in how they focus imageson their retinas?

2. How does the lighting environment differ between shallow water versus thatat 250m down in the ocean? How do rod pigments reflect theses differences?

3. How does the lighting environment differ between clear water versus lake waterversus swamp water? How does bluefin killifish differ between clear water versusswamp water? Is this variation environmental or genetic or both? What is the evidence for each source of variation?

4. Bluefin killifish have 5 cone cell types. Humans have 3. What does this meanfor differences in the visual experience between humans and bluefin killifish?

5. Even for fish with only 3 cone cell types, what does it mean if the lambda-max value for a species differs from ours? What is the lambda-max value?

6. What evidence is there that differences in the sensory system environment are related to speciation in cichlids?

Review Questions (cont’d.)

7. Explain how the placement of nares differs between Actinopterygiians, lungfish, Coelacanth, and tetrapods.

8. How does smell and taste differ? In terms of detection on the body? In terms of sensitivity?

9. How do salmon make their way back to their natal streams?