Week 10: Sensory Systems

mechanicalelectrical

electrical signalsmuscleheartgill..

low frequency ACaction potentials 0.1 to 50 Hz

electricalexternal stimulus

behavior

electrosensory systems

environmental linkhighly selective

external stimulus

(filtered)

no energytransduction

electric signal

sensory neuron

Auditory

= Gustatory

smell

sight electric

movementhearing

taste

visual chemicalmechanicalelectrical

6 senses

~ SW signals ~FW signals prey detection prey detection

communication navigation/communication

low frequency high frequency

2 types of electroreceptorsno cilia

(-)

seawater (+ + +)

(+)

[fish] 1/3 < [saltwater environment]

hypo-osmotic [less]

low potential

(-)

freshwater (+)

(+ + +)

hyper-osmotic [more]

[fish] 3x > [freshwater environment]

high potential

(- - -)

~ SW signals ~FW signals prey detection prey detection

communication navigation/communication

low frequency high frequency

2 types of electroreceptorsno cilia

(-)

Biology of Fishes Week 4 Character Summary jaws paired fins lobed fins skeleton scales Lungs spiracles intestine urea electroreception Lamprey (La)

cartilage

spiral

Chondrichthyes (Ch) X X cartilage placoid X spiral X X

Osteichthyes Sarcopterygii Lungfish (Lu)

X

X

X

cartilage

cosmoid

1–2 v

spiral

X

Coelacanth (Co)

X X X cartilage bone

cosmoid spiral X X

Actinopterygii Bichir (Bi)

X

X

X*

cartilage bone

ganoid

2 v

X

spiral

Sturgeon/ Paddlefish (S/P)

X X cartilage bone

ganoid scutes

X spiral X

Gar (G)

X X bone ganoid 1 d spiral

Bowfin (Bo)

X X bone elasmoid 1 d spiral vestigial

X

Early Teleosts (T)

X X bone elasmoid cycloid

x x x

X=present in all; x=present in some v=ventral; d=dorsal *independently arose

Cladogram Exercise: Using the character summary above, build a cladogram below for the Osteichthyes incorporating the characters as they appear from left to right. Use the initials given for each fish group and have Chondrichthyes be the outgroup.

electrosensory cells

~ SW prey detection

electric signals:

muscle activityAC current

woundingDC current

low frequency0.1 to 50 Hz

Chondrichthyes

“weak” electric fishes

Electrogenic fishes

all skates =

generate

receive

communication

generates 2.5 Hz mean electrical pulse frequency

receives 2.0 to 3.0 Hzpeak electrical pulse sensitivity

electrical organsmyogenic = from muscle

clearnose skate (Raja eglanteria)

Sarcopterygii: coelacanth

rostral electroreceptors

Actinopterygii: paddlefishes and sturgeonNA, Asia

Clupeomorpha: Engraulidae (sardines and anchovies)

~ SW signals ~FW signals prey detection prey detection

communication navigation/communication

low frequency high frequency

2 types of electrosensory cells

Osteoglossomorpha

freshwater (not in Europe)bony tongueleft oriented intestine

African electricfishes

exception

“weak” electric fishes

Electrogenic fishes

generatereceive

apical membrane(0) mVto (–x) mV

sensitivity to µV

0 to 250/s continuousbasement membrane(0) mVto (–2x) mV

Ca+

electric current

columns of electric cellselectrocytesstacks of columnselectroplaques

output: frequency, field shape, wave form, timing, pattern

behavior: navigation, species recognition, predation, courtship, territorial defense

sturgeon bowfin salmon

minnow catfish elephantfishcerebellum enlargement

receptor system

OsteoglossiformesGymnarchidaeAfrica

Gymnotiformesknifefishes~60 to 100 sp.

sister group to Siluriformes

no dorsal, pelvic finsextended anal fin

South American electricfishes

S. America

SA knifefishes

electric knifefish ghost knifefishmyogenic = from muscle neurogenic = from nervous tissue

nocturnal

female frequency > male

dominant male < submissive

personal ~10-15 Hz differenceto avoid “jamming”

“weak” electric fishes

Jamming Avoidance Response = JAR

South American knifefish are weak electric fish

African knifefish are not electric...