Lecture 21. October 27, 2008. Electroreception & other senses.

open circles show lateral line system. black dots show ampullae of Lorenzini

Electro-Reception HO#52

1) Be able to draw the ampulla in the semi-circular canal and label the following parts: endolymph, hair cells, sensory hairs, cupula.How do fish detect their own movement in water via the ampulla? 2) Be able to draw the otoliths and how they connect to the hair cells via the sensory hairs. 2b) Why do fish need otoliths to detect sound? How do hair cells detect sound? 3) How do the Webberian apparatus and the extended swimbladder increase the sensitivity of fish to sound? How do they stimulate the otoliths? Which fish have a Webberian apparatus? Which fish have an extended swimbladder? 4) Draw out a neuromast and label the following parts: hair cells, cupula, sensory hairs. How do neuromasts provide information on the direction of water flow? Where on the fish can neuromasts be located? Which fish have neuromasts in pores as opposed to on the body surface? 5) Why do fish orient their lateral lines so that they “are out of the way” of their pectoral fins? 6) Which fish have electroreception? How do ampullary and tuberous organs detect electric signals? How and why does the canal of the ampullary organ differ between freshwater and saltwater species? What types of abiotic and biotic signals can animals detect with electroreception? 7) Why does self-stimulation occur with electric signals?

inner limiting membrane light inner limiting membrane nerves rods cones pigment epithelium

night day rods cones

Terrestrial vision is adapted to light traveling through air 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. Both shorter wavelengths & longer wavelengths are reduced with depth.

UV filtered (below 300nm) in ozone. IR filtered in atmosphere. At sea level, big range in wavelengths (320-1100nm) IR quickly filtered in water. UV & blue filtered somewhat too. In deep waters, narrow range of light -- 480-520 nm.

Deep sea fish rods in 480-520nm range. Coastal fish in 490- 510 nm range. FW fish 500 - 540 nm

Crater Lake - very clear water “normal” lake water with some algae swamp water w/ tannins - “tea” colored

examples of water color

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!

relative cone frequency Fuller et al. 2003. J Comparative Physiology A blue red uv violet yellow 0.0 0.1 0.2 0.3 0.4 0.5 relative cone frequency swamp spring

Breeding Scheme r/b r/r y/y y/b greenhouse set-up

Large effects of environment! Fuller et al. 2005. Journal of Evolutionary Biology Large effects of environment! UV blue red violet yellow 0.0 0.5 clear tea 0.4 0.3 0.2 0.1 relative opsin expression opsins - cone pigment

Chemoreception Olfactory organs nares (blind sacks) with rosettes Taste organs taste buds (all parts of body) barbels

Olfactory organs

Rosettes

Nares anterior naris posterior naris

Taste Organs Taste buds HO#57

Taste Organs Taste buds HO#57

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?