Lecture 22. October 29, 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 rods cones

Terrestrial vision is adapted to light traveling through air. Aquatic vision is 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) in ozone. IR filtered in atmosphere. At sea level, big range in wavelengths ( nm) IR quickly filtered in water. UV & blue filtered somewhat too. In deep waters, narrow range of light nm.

Deep sea fish rods in nm range. Coastal fish in nm range. FW fish nm range.

Crater Lake - very clear water “normal” lake water with some algae 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.

Bluefin killifish have 5 cones!

Fuller et al J Comparative Physiology A blue red uvviolet yellow relative cone frequency swamp spring

Breeding Scheme r/br/ry/by/y

Fuller et al Journal of Evolutionary Biology opsins - cone pigment UVblueredvioletyellow clear tea relative opsin expression Large effects of environment!

Blue species - top Red species - bottom intermediates Range in colors of males. Lighting environment differs with depth. Light spectrum is 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 (blind sacks) with »rosettes Taste organsTaste organs –taste buds (all parts of body) »barbels

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 images on their retinas? 2. How does the lighting environment differ between shallow water versus that at 250m down in the ocean? How do rod pigments reflect theses differences? 3. How does the lighting environment differ between clear water versus lake water versus swamp water? How does bluefin killifish differ between clear water versus swamp 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 mean for 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?