lecture 21. october 27, 2008. electroreception & other senses

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?

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!

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

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 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?