Fish Sensory Systems

Chapters 14 & 15

Basic Eye Components

• light enters through cornea & pupil

• most fish can’t control the amount of light entering by constricting the pupil

• spherical lens is highly refractive

• retractor lentis contracts/relaxes to focus by moving the lens toward/away from the retina

Mudskippers

• can blink

• have flatter lens

• curved cornea adapted to lower light refraction in air

Rod and Cone Cells in Fish Eyes

• found in the retina

  • photoreceptor, light-sensitive cells of the eye containing opsins

• rod cells detect light intensity

• cone cells provide color vision

Silver Spinyfish

• 2 cone opsins

• 38 rod opsins (the most of any vertebrate)

• Rhodopsin-1 absorbs maximally at the most blue-shifted wavelength of any vertebrate (444 nm)

Monochromatic Vision

• single type of cone cell with single type of pigment

  • perceive light intensity but not color

Trichromatic Vision

three different cones that detect certain wavelengths

Tetrachromatic Vision

Four different cone types

Damselfish

• can see UV patterns

• UV-reflective facial patterns in some species

Hagfish

eyespot (cannot form images)

Anableps

• four-eyed fish

• single lens divided into two regions (dorsal and ventral)

• helpful for feeding on flying insect & aquatic prey

Barreleye

• unique tubular eyes point directly upwards

• can see faint outline of prey items sinking from above

• secondary lens & retina produce unfocused images

Chemoreception

• chemoreceptors located in the mouth, barbels, or surface of the body

• gills have chemoreceptor for detecting O₂ , CO₂ , and NH₄⁺

Olfactory System

• water enters nasal cavity through the anterior nares

  • leaves out the posterior nares

• forward motion, hydraulic pumping, or beating cilia bring water into nasal cavity

• Olfactory Epithelium (OE) is arranged into a series of folded, petal-like lamallae called a nasal rosette