OEB 130 Lecture 15+16 (Sensory Systems)

Midterm 2

What do fish need to sense, and how do they do it?

• Light

• Water movement, both velocity and pressure

• Smell and taste

• Body position/balance

Light: eyes

Water movement, both velocity and pressure: lateral line and individual neuromast sensors

Smell and taste: olfactory system (“nose”) and mouth (and body) taste buds

Body position/balance: inner ear semicircular canals and otoliths (ear stones)

Vision: main challenges

1. water density (bends light differently to air)

2. water high absorptive capacity - 10% or more lost in first meter of clear lake water

3. Water absorbs long wavelengths (low frequency) light more readily than short wavelengths

red vs blue in water

red drops out in shallow water blue penetrates to greatest depths

Ciliary muscle

in humans — muscle (oval in shape) changes the shape of the lens

fundamental idea of how we see

Light enters the eye and strikes the retina

What is refractive index? what is fish’s refractive index?

light bending ability of 1.65

fish vs human lens

Fish lens fixed

human lens flexible

Retractor muscles

muscles in fish that move the whole fish eye lens

Argentiniformes

A procanthopterygii

• Contains Opisthoproctidae: “marine smelts” and “barreleye fishes”

Opisthoproctidae

the barrel eye fish

• possibly adapted to eat crumps out of Siphonophores, but avoids stinging with eyes inside head

Siphonophores

colonial organisms in the ocean with stinging cells to capture prey, usually copepods, small crustaceans, and small fish.

• Almost all species are bioluminescent.

Shark eye adaptations

1. Nictitating membrane —closes over eyes for protection

2. Tapetum lucidum – reflects light back toward the retina, to amplify vision

What does the presence of cones suggest in fish?

presence of cones suggests color vision in most fishes.

Rods are predominately in what type of fish?

predominate in deep-sea fishes

• detect light intensity (brightness) → used for night vision, no color, low detail

problem of parallax

parallax refers to the apparent shift in the position of an object when viewed from two different points (in and out of water)

How do fish overcome parallax?

2 retinas and an oval lens in each eye

• oval shaped to account for refractive index of water/air

Anableps

the “four-eyed fish”

• specialized eyes to overcome parallex

What is the olfactory rosette? What does it include?

nasal smelling system of fish which includes

• plates of sensory epithelium

• walls of nasal capsule

• Incurrent vs excurrent nares

Incurrent vs excurrent nares

Entrance vs exit of olfactory rosette

olfaction rosette

Olfaction evolution

the change from both openings external in ray-finned fishes, to one or more openings internal in sarcopterygian “fishes

chemical sensing system aka

chemosensation

chemosensation includes? How are they different?

Olfaction (smell) and Gustation (taste)

• Both are part of the chemical sensing system (chemosensation), but involve different cranial nerves

how do fish tastebuds differ

taste buds located all over the body

The lateral line senses water flow:

-- surface sensors detect velocity

-- canal sensors detect pressure differences

Lateral lines contain:

pore to canal

and Trunk canal

Surface velocity sensors

Lateral line canal structure

Flow sensing is based

Flow sensing is based on neuromasts which contain multiple sensory hair cells

superficial vs canal neuromast

schematic of velocity vs pressure sensors on fish

The tail of rays is a hydrodynamic antenna means that

tails can sense pressure and velocity

Balance relies on:

the inner ear and otoliths

• is used for balance, and senses head/body position and acceleration

Inner ear of a teleost fish contains

1. three looping hollow canals

2. three “ear stones” = otoliths inside three sacks

three looping hollow canals

anterior vertical canal, posterior vertical canal, horizontal canal

three “ear stones” = otoliths inside three sacks

sagitta, lapillus, asteriscus are otoliths that sit inside three sacs

The three semi-circular canals allow fish

to sense acceleration of the body

The three sacks and ear stones allow fish

to sense position and orientation of their body

The macula:

The macula is a sensory membrane w/ haircells underneath the otolithic membrane

How do otoliths help detect head position?

3 Electric fish general classification

1. Strong generation of electric fields: to stun prey or defend against predators

2. Weak/active electroreception: they sense distortion of electric fields that they generate themselves and use these to actively sense their environment

3. Passive electroreception: sense ambient electric fields (from the earth or other organisms): they don’t generate electric fields

Strongly electric fish (generate) examples + clade

• electric “eel” - otocephela catfish

• torpedo rays - Batoid/chondrichtys

• stargazer - acanthomorpha

Passively electric (only sense)

• all chondrichthys

• basal ray-finned fish: bichirs, paddlefish, sturgeon

• lungfish, coelocanth

• platypus; amphibians

Weakly electric fish

• skates

• elephant fish - osteoglossamorphs

• “knifefish” fish - otocephela

Electric field produced by

modified muscle cells (electrocytes) —> electroplaques

Electrocytes are disc shaped and stacked in columns called

electroplaques

Why are electric currents efficient in water

Great efficiency of electric currents in water due to the water’s density and salt content

What is electrosense used for?

prey detection, navigation, and communication, but has been modified for defensive purposes and feeding in several species

2 teleost groups with the most “electric” fish species

osteoglossomorphs + otocephela

Where are strongly vs weakly distributed in the world?

Otocephela phylogeny. What orders are electric?

Electric rays and electric eels ____ evolved capability of generating strong electric fields

Independently evolved capability

where is the electric organ on a catfish?

Kalmijn, A. (1971). The electric sense of sharks and rays

• passive sense of electric fields for feeding

• preference of electric field over chopped up fish

Sharks detecte electric signals throug

Ampullae of Lorenzini

Sachs vs hunters organ in electric eel

Ampullary Organ

Recepter opening

Jelly in canal

Sensory cell of ampullary organ

Nerve

Kalmijn, A. (1987) blurb

Where is the electric organ usually located

In the tail

how does electroreception work

local increase in current density = an "electrical bright spot" on the skin

how do fish sense their own electric fields (electroreception)

with tuberous organ receptors (bud-shaped swellings under the skin)

Electrosensory Image Formation (an object near and far)

2 types of electric production

Wave - Ostariophysi

Pulse - Osteoglossomorph

How do species deal with Intraspecific communication

Intraspecific communication can result in a JAR: Jamming Avoidance Response

• change pitch slighty to avoid confusion

Sound travels rapidly in water. How much faster?

5x faster than air

Harder to determine the directionality of sounds in water

facts

Hearing in Otocephela

Amplification of sound by air-filled organs (swimbladder)

Hearing in fish is primarily by the otoliths

“near-field” hearing

lateral line can detect low frequency sounds that are close to the body, where the sound generates water displacement which activates the neuromasts

“far-field” hearing

otoliths detect stimuli which are pressure waves with little water displacement

• when these pressure waves hit the otoliths, they cause motion of the denser otolith over the hair cell bed

What does the inner ear do? Where is it located?

used for balance, and senses head/body position and acceleration

• Located inside the neurocranium

Beyond head position, what else does the otolith detect

SOUND!

How do fish produce sound?

1. Stridulation: rubbing of structures together

2. Drumming: producing vibrations of the swimbladder with specialized muscle

3. Clap front or pharyngeal jaws together to make sounds

What do you know about magnetic reception (who, how, what for)?

• few ray finned fish (like tuna) can detect earth strength magnetic fields

• Mechanism unknown

• used for locating long distance migration routes for feeding and reproduction

Magnetic reception conditioning studies found that

fish alter their heart rate in response to an electric field