L 21 Eyes and Vision

Question 1

What are 5 major features of the eye?

Answer 1

1. anterior chamber -filled with aqueous humor
2. iris
3. lens
4. posterior chamber containing vitreous humor
5. retina - contains light sensitive cells

Question 2

What is the anterior chamber filled with?

Answer 2

aqueous humor

Question 3

What is the retina like in the eye?

Answer 3

a multi layered network of light sensitive cells

Question 4

What does the suspendsory ligament do?

Answer 4

It helps hold up the lens

Question 5

Where the vascularized choroid layer located and what does it do?

Answer 5

It is located between the retina and scleroid coat.

it functions to nourish the retina and serves to absorb stray light or in some species, reflect light back through the retina

Question 6

Where is the chroid body prominent? What does if function as?

Answer 6

Prominent in the choroid layer and functions to provide a high partial pressure of oxygen to the retina

Question 7

What are nictitating membranes?

Answer 7

eyelids of certain sharks

Question 8

How is the max field of view achieved in fishes?

Answer 8

placement of the lens so that it bulges through the opening of the pupil and nearly touches the cornea.

So the lens can gather light from entire hemisphere

Question 9

Refraction and image formation depends entirely on what? and why?

Answer 9

it depends on the lens, and the index of refraction of cornea is about the same as the water

Question 10

What does myopic mean?

Answer 10

near sighted

Question 11

What are lamprey’s sight like and what happens when the cornea is flattened?

Answer 11

It pushes the lens inward, closer to the retina and bring more distant objects into focus.

So lampreys are myopic

Question 12

What does the corneal muscle do?

Answer 12

inserts on the outer transparent covering of the eye and flattens the cornea when it contracts

Question 13

What does hyperopic mean?

Answer 13

far sighted

Question 14

What does the protractor muscles do?

Answer 14

located on the naterior part of the choroid layer and pulls the lens outwards, away from retina and closer to cornea

Question 15

What are the eye muscles and sight like in elasmobranches?

Answer 15

Smooth muscle fibers , protractor muscles, far sighted.

Question 16

What kind of visision does hammerheads have?

Answer 16

• wide range of vision, they may see what’s ahead, up, down and behind.
• their eye separation gives them binocular vision and depth perception

Question 17

How do hammerheads make up for their blind spots?

Answer 17

• Sensors in the head helps them detect electrical fields emitted by other fishes
• placement of nostrils near eye means enhanced stereo smell

Question 18

If the lens are spherical and the retina is an ellipsoid shape, what effect is achieved? Also what type of fish is this present in?

Answer 18

• oresent in teleosts
• effect achieved is distant objects lateral to the fish are in focus but close objects are not.

anteriorly, near objcets in binocular field are better in focus than more distant objects.

Question 19

What does the retractor muscle/lentis do?

Answer 19

moves lens backwards, and allows distant vision in the anterior field

Question 20

Teleosts are thought to be myopic and hyperopic where?

Answer 20

myopic anteriorly

hyperopic laterally

Question 21

In general, where are retractor muscles/lentis most developed?

Answer 21

In wide open spaces, they have well developed retractor lentis.

Most freshwater teleosts living in habitats where most objects are close by have less well developed muscles.

Question 22

What are six different ways to adapt to the light or dark?

Answer 22

1. Distance- swim toward of away light
2. PIgment in the cornea/lens that acts as a filter
3. Contractile irises that control amnt of light that enters the eye
4. Pupillary operculum that expand and cut off most of light reaching the pupil
5. Nictitating membranes- some sharks have it, it’s mostly developed in tetrapods. It may be drawn across the eye to reduce excessive illumination.
6. Movement of pigment and visual cells

Question 23

How does melanin work under bright illumination?

Answer 23

Melanin moves towards visual cells, and movement of the outer segments of rods into pigmented area where they are shielded from light

Question 24

What wavelengths do deep sea species absorb with their rod pigments?

Answer 24

Short wavelengths, about 470 to 490 mm

Question 25

What wavelength do marine fishes living at intermediate depth see?

Answer 25

460 - 540 nm

Question 26

What wavelengths do freshwater fishes living near the bottom see in?

Answer 26

530 - 620 nm

long wavelength match the spectral quality of the light fairly well

Question 27

What’s the difference between cone pigments in freshwater fishes living in shallow aters and deeper living forms?

Answer 27

Freshwater fishes have 3 cone pigments

They absorb around 430 nm

deeper living forms have two cones

three cones covers a wider range of the spectrum

Question 28

What does UV sensitivity correlate with?

Answer 28

living near the surface

Question 29

what’s interesting with UV light and its absorption by the water?

Answer 29

It’s present at any intensity only in the srface layers

Question 30

What spectrum does the deep sea fishes see in? What family is it present in?

Answer 30

They may see in the red spectrum, and it is the family Stomiidae.