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Ichthyology > Senses > Flashcards

Senses Flashcards

1
Q

Fish senses (6)

A

sight, smell, taste, touch, sound, electroreception

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2
Q

sight

A

10s m

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3
Q

lateral line

A

roughly 100 m

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4
Q

smell

A

100s m

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5
Q

hearing

A

kms

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6
Q

taste

A

v short distance

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7
Q

electroreception

A

cms

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8
Q

UV and Visible Spectrum

A

light is not transmitted uniformly through water

light reduced by absorption + scattering

intensity declines with depth

shorter wavelengths transmitted better so red light absorbed first, blue/green absorbed last

pigments in water also affects absorption

oceanic blue/green (470-480), coastal (500-530nm) freshwater (550-560)

blue light reaches furthest depths, UV reaches shortest depths

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9
Q

Fish eye

A

similar to vertebrate eye, but lens = solid

retractor lentis muscle used to move lens

photoreceptor cells on retina

choroid provide O2 to retina

position of falciform process -> provides O2 to retractor lentis muscle

parts: dermal layer, scleral layer, cornea, iris, retractor lentis muclse, lens, suspensory ligament, retina, position of falciform process, choroid, optic nerve

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10
Q

Control of light entering eye

A

Elasmobranchs + few teleosts have contractile irises (react v. slowly)

other mechanisms:
- pigments in cornea
- operculum
- nictitating membrane

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11
Q

Retina - rod + cone cells: diurnal feeders, lower light inhabitants, nocturnal + mesopelagic fish

A
  • rod cells = more sensitive to low light
  • cone cells = detail + colour vision
  • diurnal (daytime) feeders have high cone:rod ratio
  • lower light inhabitants have twin cones (2 or more cells linked to 1 nerve ganglion to amplify signal)
  • nocturnal and mesopelagic fish = more rods than cones, oftne w/ many rods per ganglion
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12
Q

retina - choroid

A
  • high O2 consumption
  • backed by nutritive choroid
  • choroid has choroid gland (a rete mirabile) to maintain high O2 levels in retina
  • Elasmobranchs + some teleosts have a Tapetum lucidum = layer of reflecting guanine platelets behind the retina
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13
Q

mesopelagic (deep sea) fish

A
  • large eyes
  • retinas w/ high density of rods
  • large pupils + lenses
  • adapted to blue/green 470-480nm (chryopsin)
  • often tubular, fixed eyes
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14
Q

Tubular eye

A

allows small fish to have large lens

lens capture light -> bigger lens = more sensitive

one direction, not mobile

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15
Q

advantages of tubular eyes

A

allow smaller fish to possess larger lenses

good binocular vision but in one direction only - main axes of eye are nearer parallel than in normal eyes

some tubular eyes have vertical axes to see prey silhouetted above

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16
Q

disadvantage of tubular eyes

A
  • fixed so can only view straight ahead - ability to view in other direction = sacrificed
  • peripheral retina = too near lens for adequate focal length so poor focus
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17
Q

chemical senses - olfaction

A

nostrils in fish = not respiratory

pits lines w/ sensitive, olfactory epithelium folded + convoluted into rosette

usually 1 pair of connected nares (openings) each side of the head

flow through is either:
- forward motion of the fish
- ciliary action
- muscular pumping

18
Q

use of olfaction

A
  1. food location
  2. migration (salmon use olfactory memory of natal river)
  3. presence of predators
  4. alarm substance (e.g. cypriniformes)
  5. social beh - i. recognition of opposite sex, ii. stimulation of courtship beh
19
Q

gustation (taste)

A

similar to olfaction but separate system of taste buds

elasmobranchs - confined to mouth + pharynx

teleosts - all over but mainly palate, lips, barbels + lower part of head

react to: bitter, sweet, salt, sour, amino acids, carbon dioxide

v. sensitive + used in food selection, especially where olfaction is used in food location

20
Q

Acoustico-lateralis system

A

ear + lateral line system

both use hair cells = sensitive mechanoreceptors

hair cells found in:
- lateral line in fishes + amphibians
- organ of hearing in all vertebrates

21
Q

single hair cell

A

??? on recording

22
Q

lateral line system

A

kinocilium + stereocilis of several hair cells embedded in gelatinous cupula

hair cells respond to deformation of cupula caused by water movement (vibration)

whole organ = neuromast

hair cells = v sensitive, so not on outside of fish, instead in canals
detection of water motion

23
Q

where are neuromasts found?

A

in canals on head + canals extending along side of body (lateral line)

24
Q

neuromasts in canals

A

canals connected to surrounding water through pores

source vibration obtained by comparing responses of diff neuromasts along lateral line

displacement of <2nm can be detected - movement up to 30 m away

prone to near-field effects (noise) from fishes own body, hence in canal + often displaces away from fins

25
Q

functions of lateral line

A

prey detection

awareness of currents (rhenotaxis)

avoiding obstacles/predators

schooling

26
Q

Acoustico part (ears)

A

inner ear consists of a membraneous sac w/ 3 semicircular canals + bony chambers, in either side of head

used for: positioning w/ respect to gravity (static equilibrium) angular acceleration (dynamic equilibrium) hearing

pars superior (3 semi-circular canals + utriculus)
pars inferior (2 more bony chambers)
sacculus
lagena

utriculus, sacculus, lagena = chambers

27
Q

inner ear

A

semi-circular canals contain a fluid called endolymph

components: anterior vertical canal, posterior vertical canal, horizontal canal, ampullae
+ ampullary organ

Ampullae contain hair cells on ridges which project into lumen of ampulla + respond to movement of endolymph (dynamic equilibrium)

detect motion in three directions via canals

28
Q

Otoliths

A

bony otoliths (particularly lapillus) measure fishes reference to gravity (static equilibrium)

each otolith lies on bed of hair cells called a macula

29
Q

Otoliths responding to sound (pressure) waves

A

esp sagitta

more dense than surrounding fish tissue, so respond more slowly to pressure waves, triggering the hair cells

swimbladder can magnify sound waves

many fish have evolved connection between ‘ears’ + swimbladder

Clupeids (herring family) have a canal

Ostariophysi (carps & catfish) have chain of modified vertebrae

Weberian ossicles - 4 bones either side of head

30
Q

Otoliths reflect…

A

…seasonality in growth of fish

summer growth = dense “opaque” zone

winter growth = less dense “hyaline” zone

one pair of rings = 1 year’s growth

31
Q

Elasmobranchs

A

not bony fish, so NO calcareous otoliths, just sand particles in mucus jelly

do same job for fish

can’t age them

32
Q

how many spp of fish produce sound

A

800

33
Q

Electricity in fish - 4 main uses

A
  • electrogenic fish create electric fish
  • electroreceptive fish can detect electric fields

4 main ways fish use electricity:
1. navigation - create electric fields around themselves to navigate, this is esp useful in turbid/murky waters
2. hunting - detection of microvolts generated by small muscle contractions; some (e.g. electric eels) can stun prey
3. defence - stunning or killing of potential predators; hypopomid electric fish produce broad frequency electric fields to precent detection by electroreceptive fish
4. communication - electrical signals can be sent to warn males + during courtship w/ females

33
Q

Electroreceptive fish

A

Ampullary (tonic) receptors

Ampullae of Lorenzini found in all elasmobranchs + some teleosts (some catfish, sturgeons, paddle fish, lungfish)

sensory cells sensitive to electrical stimulus of low frequency 0.05-8Hz, as well as mechanical stimulation + changes in salinity + temp

34
Q

location of ampullae of Lorenzini

A

around head of sharks, all over body of catfish + on pectoral ‘wings’ of ray

35
Q

prey detection

A

cells constantly receptive to low frequency stimulus from weak action potentials of muscle + nerve fibres in prey animals

36
Q

Phasic receptors

A
  • some fish have Tuberous or Phasic receptors cells - show brief response to high frequency stimulus
  • found in electric fishes, such as gymnotids (knife fishes) mormyrids (elephant-nose fish)
  • similar to Ampullae of Lorenzini but no ‘apparent’ canal to surface
37
Q

difference between tonic and phasic receptors

A

adaptation to use
- Tonic (ampullary) receptors used to detect prey
- phasic receptors to register high frequency discharge from electric organs in other fish

38
Q

electric organs

A
  • stacks of modified muscle or nerve cells used just to generate electricity
  • action potentials between individual plates = small, 0.1-0.15 volts, but in series, as in a battery, are additive + can generate many volts

Electrophorus electric eel

Malapterus electric catfish

Have thousands of plates, takes up 40% of fish volume generates >500 volts

39
Q

Functions of electric organs

A

protection:
- danger to anyone handling such fish, protection wearing required

stunning prey

electro-location of prey + position
- requires generating an electric field + identifying distortions in field by phasic receptors generated by surrounding objects

40
Q

Electro-location

A

need to avoid creating own distortions in electric field, necessary to remain rigid + swim using just fins running length to body

most live in murky freshwater (eyes aren’t much use). seawater loses discharge rapidly + thought to just use for intraspecific signalling

BUT Torpedo electric rays generates >50 volts

41
Q

magnetoreception

A
  • electric current = induced in any conductor moving through a magnetic field
  • seawater (but not freshwater) = sufficiently good conductor for elasmobranchs (at least) to use their Ampullae of Lorenzini to detect the Earth’s magnetic field

Ichthyology (10 decks)

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