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Hilary Term 1 > The Biology of Fish II > Flashcards

The Biology of Fish II Flashcards

1
Q

List some constraints of aquatic existence

A
  • bones, scales and skin
  • respiration (obtaining oxygen)
  • buoyancy and depth regulation
  • ion exchange (maintaining stable internal environment within body)
  • heat exchange (regulating body temperature)
  • reproduction
  • feeding
  • dense medium for movement
  • navigation through complex, volumetric
    environments
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2
Q

Describe the basics of the Chondrichthyes

A
  • cartilaginous fishes
  • Elasmobranchii (sharks and rays)
  • Holocephalii (deep-sea chimaeras
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3
Q

Give an Elasmobranchii

A

Cetorhinus maximus

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4
Q

Give a Holocephalii

A

Hydrolagus colliei

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5
Q

Describe the basics of the Osteichthyes

A
  • bony fishes
  • Actinopterygii (ray fins, including teleosts)
  • Sarcopterygii (lobe fins, including lungfish)
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6
Q

Give an Actinopterygii

A

Pristella maxillaris

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7
Q

Give a Sarcopterygii

A

Protopterus aethiopicus

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8
Q

Describe fish bones

A
  • bony skeletal elements start off as cartilage then become calcified and vascularised
  • ossification of dermal elements: scales become bony.
  • become thinner and more mobile.
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9
Q

In Osteichthyes, skeleton + scales … of total weight

A

c. 20%

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10
Q

In Chondrichthyes, skeleton + scales … of total weight

A

c. 12%

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11
Q

Describe early Osteichthyes

A
  • thick leathery skin
  • thick interlocking ganoid scales
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12
Q

ganoin

A

≈ enamel

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13
Q

Describe teleost skin

A
  • thin
  • bony dermal scales are thin and flexible
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14
Q

Describe teleost scales

A
  • primitive teleosts have cycloid scales which grow in annuli
  • advanced teleosts (esp. fast swimmers) have ctenoid scales with drag-reducing trailing edges
  • serrated edge opposite edge that attaches to the skin
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15
Q

annuli

A

annual growth rings

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16
Q

Describe teleost reflective skin

A
  • many teleosts appear silvery due to reflective layers in the skin, under the scales
  • reflectors are guanine/tissue sandwiches of at least 5 layers
  • light reflected from the outer and inner faces of the guanine layers interferes constructively
  • reflectances may exceed 90%
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17
Q

Give a silvery teleost

A

Gyropelecus: hatchet fish

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18
Q

Give some reflective teleosts

A
  • Neon tetra
  • Goldfish
  • Endler guppies
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19
Q

Describe the Chondrichthyes

A

cartilaginous skeletal elements are not vascularised

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20
Q

Describe the skeleton of sharks

A
  • uses varying degrees of calcification
  • jaws may be heavily calcified and thus are rigid
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21
Q

Describe the skeleton of skate fin rays

A
  • may be totally uncalcified
  • remain flexible
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22
Q

Describe shark skin

A
  • thick and leathery
  • crossed helices of collagen fibres
  • provides a tough support for the pavement of scales and, in the mouth, for the teeth
  • placoid scales (e.g. Whale shark)
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23
Q

Describe placoid scales

A
  • aka dermal denticles
  • same structure as a tooth
  • three layers: an outer layer of vitro-dentine, dentine, and a pulp cavity
  • do not get larger as the fish grows
  • the fish grows more scales.
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24
Q

vitro-dentine

A

an enamel

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25
Q

How does shark skin reduce drag?

A
  • water flows in under the fronts of the scales and out along the ridges on the outside of the scales
  • spaces under the scales and their surface sculpturing vary along the body and fins, reflecting differences in the flow conditions
    -creates micro-turbulence over the skin surface
  • reduces overall drag by c. 10%
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26
Q

Describe Osteichthyes respiration

A
  • teleost gills enclosed in opercular cavities
  • water is pumped in through the mouth and out through the gills
  • pumping action of mouth and opercular cavities creates positive pressure across gills
  • respiratory current is only slightly interrupted during each pumping cycle
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27
Q

Describe the mechanics of Osteichthyes inspiration

A
  • mouth open
  • opercular valve closed
  • opercular chamber expanding
  • negative pressure
  • water sucked into the pharynx by lowering the floor of the mouth
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28
Q

Describe the mechanics of Osteichthyes expiration

A
  • mouth closed
  • opercular valve open
  • buccal chamber contracting
  • positive pressure
  • water forced through gills by raising the floor of the mouth
  • back flow prevented by buccal flap valve
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29
Q

Describe counter-current exchange

A
  • blood flows through lamellae
  • H2O from mouth flows between lamellae
  • maximises exchange gradient across flow
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30
Q

Describe the gill lamella

A
  • blood flows in thin flat spaces
  • walls of which are held together by pillar cells
  • blood-water distance varies with the fish’s lifestyle
  • 10μm in sluggish tench
  • 0.6μm in tuna
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31
Q

Describe Scomber

A
  • mackerel
  • high activity
  • 0.73 oxygen consumption
  • 31 secondary gill lamellae
  • 1160 gill area
  • 14.8 oxygen capacity
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32
Q

oxygen consumption

A

ml O2//g.h

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33
Q

secondary gill lamellae

A

mm-1 of primary gill lamellae

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34
Q

gill area

A

mm2 / gm of body mass

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35
Q

oxygen capacity

A

14.8

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36
Q

Describe Stenotomus

A
  • porgy
  • intermediate activity
  • 0.17 oxygen consumption
  • 26 secondary gill lamellae
  • 506 gill area
  • 7.3 oxygen capacity
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37
Q

Describe Opsanus

A
  • toadfish
  • sluggish activity
  • 0.11 oxygen consumption
  • 11 secondary gill lamellae
  • 197 gill area
  • 6.2 oxygen capacity
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38
Q

Describe perpetual swimmers

A
  • some fish have reduced or lost ability to pump water across gills
  • create respiratory current by swimming with their mouths open
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39
Q

List some perpetual swimmers

A

certain sharks, tunas, swordfish

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40
Q

Describe fish in low oxygen conditions

A
  • supplement oxygen from gills with oxygen from air
  • air breathing evolved independently many times
  • a number of derived teleosts have accessory structures to obtain O2 from air
  • lungfish (Sarcoptergyii) have true lungs
41
Q

Describe the accessory structures of the low oxygen actinoptergyii

A
  • large lips extended just above surface
  • internal structures into which air is gulped
42
Q

Describe Bettas

A
  • tropical Asia
  • labyrinths
  • air sucked into mouth and transferred to labyrinth where gas exchange occurs
43
Q

labyrinths

A

vascularised chambers in rear of head called

44
Q

Describe Betta bubble nests

A
  • male Betta gulp air and construct bubbles with saliva (contains adhesive proteins)
  • once female Betta lays eggs, male will pick them up in his mouth and put them in his bubble nest
  • guards the eggs until they hatch
45
Q

Describe fry in Bettas

A
  • specialised attachment cells that run from their heads to their anterior trunks
  • keeps them from falling out of the nest
46
Q

Describe mudskippers

A
  • Periophthalmus cantonensis
  • cutaneous air breathing
  • enlarged gill chambers where they retain a bubble of air
  • digging burrows
47
Q

Describe cutaneous air breathing

A
  • breathing through skin, mouth mucosa and pharynx
  • only possible when skin is wet
48
Q

Describe Sarcopterygii in low oxygen conditions

A
  • true lungs in obligate air breathers originate from gut during development
  • e.g. Australian lungfish (Neoceratodus forsteri)
49
Q

Describe Actinopterygians buoyancy

A
  • teleost swim-bladder is a gas-filled diverticulum of the gut that regulates buoyancy
  • fish can adjust gas volume to obtain neutral buoyancy or ascend and descend
50
Q

Give an example of a teleost

A

Astyanax fasciatus

51
Q

Describe Physostomes

A
  • in more primitive condition, swim-bladder opens into the gut via a duct
  • gas can swallowed or burped out
  • e.g. in sturgeon or carp
52
Q

Describe Physoclists

A
  • in the more derived condition, swim bladder volume is regulated by uptake or secretion of O2 from a gas gland on the ventral wall of the bladder
53
Q

rete mirabilis

A

= lactate exchanger

54
Q

Describe the first stage to how Physoclists fill the swim bladder

A
  • gas gland is fed by a “rete” in which blood vessels entering divide and form a meshwork close to the blood vessels leaving
  • lactate is pumped from the outgoing vessels into the incoming vessels.
  • pH at the gas gland is lowered to c. 6.3, liberating O2 from the blood
  • only takes 0.05s for pH lowering to cause gas release
  • recovery takes c.15s
  • blood stays in the exchanger for c.2s, which allows O2 release on the way in
  • too brief for re-uptake on the way out
  • once in, gas is retained by the bladder wall
    -100x less permeable than tissues
55
Q

Describe teleosts and pH

A
  • oxygen-carrying capacity of teleost blood is highly dependent on its pH and CO2 content
  • if the pH is lowered from 7 to 6.3. the blood can only hold half as much O2
  • The Root effect
56
Q

Describe the second stage to how Physoclists fill the swim bladder

A
  • oxygenated blood enters the swim-bladder
  • amount of O2 liberated or taken up can be controlled by the fish
57
Q

Describe bladder wall permeability in teleosts

A
  • contains layers of large-area 0.02μm thick guanine plates
  • flexible
  • solid-phase
  • gas-impermeable
58
Q

Describe the Root effect

A

asymmetrical

59
Q

Summarise the Root effect

A
  • oxygen is high
  • lactate is actively transported from areas of low to high anteriorly
  • lactate flows in direction of blood flow
  • pH lowers
  • O2 capacity low
  • O2 enters swim bladder
  • lactate flows back
60
Q

How can pressure be used to determine depth?

A
  • varies linearly with depth
  • fish use rate in change in swim-bladder volume to determine depth
61
Q

Describe Chondrichthyes buoyancy

A
  • no swim bladders
62
Q

When wouldn’t you need a swim bladder?

A

if you’re a Benthic bottom-dweller

63
Q

Give an example of a Benthic bottom-dweller

A
  • skates
  • Dipturus laevis
64
Q

Give an example of a Chondrichthyes

A

D. laevis

65
Q

Describe buoyancy in sharks

A
  • vast liver
  • dynamic lift
66
Q

Describe the basking shark

A
  • 2 tonne
  • 7m long
  • close to neutrally buoyant
67
Q

Squalene

A

hydrocarbon derived from the food

68
Q

Describe the use of the liver for buoyancy in sharks

A
  • up to 25% of body weight
  • rich in squalene
  • sea water density is 1025 kg/m3
  • shark body density is 1060 kg/m3
  • squalene density is 860 kg/m3
  • such a heavy buoyancy organ has considerable inertia, slowing turning
  • large volume increases the frontal area and hence the hydrodynamic drag of the shark
69
Q

Describe dynamic lift in sharks

A
  • many fast-swimming pelagic sharks
  • frontal area is smaller
  • swimming is cheaper
  • if they stop, they sink
70
Q

Describe skates

A
  • relatively small livers
  • heavier than water
71
Q

Describe osmotic and ionic regulation in teleosts

A
  • most teleosts are hypotonic to seawater but hypertonic to freshwater
  • skin is fairly impermeable
  • gills are v. permeable
72
Q

What do teleosts do in the sea?

A
  • salts excreted by specialised glands the gills (to prevent diffusion in)
  • water leaves osmotically
  • drink
  • pass little urine (conserve water)
  • secrete excess NaCl at the gills
73
Q

What do teleosts do in freshwater?

A
  • salts absorbed by the gills (to counteract diffusion out)
  • water enters osmotically
  • does not drink
  • get some salts from their food
  • pass copious dilute urine from the kidneys
74
Q

Describe freshwater teleosts

A

10% increase in salinity between body fluids and freshwater

75
Q

Describe marine teleosts

A

20% decrease in salinity of body fluids relative to seawater

76
Q

Describe osmotic and ionic regulation in the Chondrichthyes

A
  • approximately isotonic with sea water
  • blood contains urea and tri-methylamine oxide
  • hydrogen bonds are broken by urea solutions
  • proteins of Chondrichthyes specialised
  • effect is reduced by TMAO
  • NaCl diffuses in at the gills
  • excreted by the rectal glands
77
Q

Where do Chondrichthyes obtain urea from?

A
  • proteinaceous diet
  • all are carnivores
78
Q

Describe fresh water sharks

A
  • tend to have reduced blood ionic and urea concentrations
  • e.g. in Lake Nicaragua
79
Q

TMAO

A

tri-methylamine oxide

80
Q

Describe fish heat exchange

A
  • blood is cooled to ambient temperature in the gills
  • muscles’ blood supply along the mid-line
  • cold blood passing inwards exchanges heat with the outgoing blood from the centre of the myotomes
81
Q

What do fishes warm muscles require?

A
  • large bodies to minimise losses due to conduction
  • heat exchanger system in the thickness of the body
82
Q

Describe fish deep temp

A

29 to ambient 19

83
Q

Describe heat exchange in tuna (and some sharks)

A

muscles are supplied by vessels
running just under the skin.

84
Q

Describe teleost reproduction

A
  • majority use external fertilisation
  • congregate
  • make fertilisation pits, nests
  • elaborate courtship
85
Q

Describe Lebistes reproduction

A
  • guppies
  • fertilise internally
  • viviparity
86
Q

Describe freshwater fish reproduction

A
  • eggs tend to be 1 to 5mm diameter
  • produced in hundreds or thousands
87
Q

Describe marine fish reproduction

A
  • 1 to 2mm diameter
  • produced in large numbers:
  • sea provides a rich alternative planktonic niche for fish larvae
  • larval development lasting a few weeks is common.
88
Q

Describe the sardine

A
  • up to 18 cm long
  • 10,000 to 50,000 eggs
  • 7mm larva
89
Q

Describe sunfish

A
  • up to 3 m long
  • 100 to 500 million eggs
  • 25 mm larva
90
Q

Describe shark reproduction

A
  • all Chondrichthyes have internal fertilisation
  • sperm is transferred to the female’s oviduct along one of the male’s pelvic claspers
  • male wrapped around female with left clasper inserted into cloaca
  • elaborate courtship
  • e.g. dogfish
91
Q

Describe the Piranha

A
  • Actinopterygian
  • subfamily Serrasalminae
  • omnivore
92
Q

Describe the swordfish

A
  • Actinopterygian
  • family Xiphiidae
  • predator
93
Q

Describe the cichlid Pseudotropheus crabro

A
  • Actinopterygian
  • feeds on parasites from a catfish
94
Q

Describe the dwarf pygmy goby

A
  • Actinopterygian
  • 1cm
  • Pandaka pygmaea
  • feeds on plankton
95
Q

Describe feeding in Chondrichthyes

A
  • large body size
  • mostly marine
  • few species
  • predatory life is common
  • e.g. Great white shark, Carcharodon carcharias
96
Q

Give a Chondrichthyan filter feeder

A

Whale shark, Rhincodon typus

97
Q

Describe Great White Shark

A
  • C. carcharias
  • > 7 m
  • eats prey in large chunks
98
Q

Describe Cretaceous shark fossils

A
  • teeth over 12cm
  • sharks must have been over 15m
  • Carcharodon appeared in the Cretaceous but was even bigger

Hilary Term 1 (61 decks)

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