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VERTEBRATES > Fishes: Chondrichthyes > Flashcards

Fishes: Chondrichthyes Flashcards

1
Q

Gnathostomes (jawed verts) main features

A
  • Duplication of hox gene complex (4 hox gene clusters)
  • 2 olfactory bulbs
  • Centrum
  • Properly formed vertebrate
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2
Q

Placoderms

A
  • Extinct species
  • Name means plate skin - covered in plates
  • Variety of body forms and sizes >8m
  • Marine and freshwater
  • Teeth but not replaced
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3
Q

Placoderm reproduction

A
  • Viviparity - gave birth to live young (embryos found in female bodies - fossils)
  • Internal fertilisation - claspers behind pelvic fin.
  • Clasper found in scottish fossil - first evidence of copulation (385 mya)
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4
Q

Acanthodians (spiny sharks)

A
  • Stem/basal chondrichthyans (cartilaginous fish)
  • Extinct
  • Toothless or tooth whorl (also seen in cartilaginous fish)
  • Mainly marine, also freshwater
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5
Q

Placoderm heart

A
  • Gogo fossil - two chambered heart, heart is getting more complex
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6
Q

Chondrichthyes?

A

Cartilaginous fish

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7
Q

Chondrichthyes - cartilaginous fish

A
  • 400 mya
  • Mineralised cartilage - allows for buoyancy and flexibility
  • Most have hyostylic jaw suspension.
  • Internal fertilisation
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8
Q

How do chondrichthyes maintain buoyancy?

A
  • lipid-filled liver aids buoyancy - benthic shark would have low lipid levels, active sharks would have more lipid for more buoyancy.
  • High blood urea concentration - also aids buoyancy
  • Mineralised cartilage aids buoyancy
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9
Q

Hyostylic jaw suspension

Chondrichthyes

A
  • Held in place at the back by the hyomandibular arch and by ligaments at the front.
  • Jaw has independence from the skull
  • Jaw held together with ligaments
  • Able to drop upper jaw down and protrude it forward
  • Allows jaw flexibility
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10
Q

2 groups of Chondrichthyes

A
  1. Holocephalans
  2. Elasmobranchs
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11
Q

Holocephalans

Chondrichthyes

A
  • Ratfish
  • Rabbit fish
  • Chimaera
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12
Q

Elasmobranchs

Chondrichthyes

A
  • Sharks
  • Skates
  • Rays
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13
Q

Holocephalans structure

A
  • Holostylic jaw (upper jaw fused to the skull)
  • Have large pectoral fins
  • Whip like tail
  • 4 gill slits
  • Tooth plates - crushing
  • Mechanoreceptors and electroreceptors
  • Have a spine that can produce venom on dorsal fin
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14
Q

Holocephalans reproduction

A
  • Oviparous (lay eggs after internal fertilisation)
  • Males have head clasper - used as an attachment device in mating
  • Modified pelvic fin with clasper
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15
Q

Sharks are further divided into?

Chondrichthyes - Elasmobranchs

A
  • Galeomorphs (anal fin)
  • Squalomorphs (no anal fin)
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16
Q

Galeomorphs (anal fin) examples

Chondrichthyes - Elasmobranchs - sharks

A
  • Great whites, hammer heads, whale sharks, thresher shark
  • Large active predators
  • Whale shark - not predator (filter feeder)
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17
Q

Squalomorphs

Chondrichthyes - Elasmobranchs - sharks

A
  • Smaller
  • No anal fin
  • E.g. spiny dogfish
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18
Q

Batoidea features

Elasmobranchs - Batoidea - skates and rays

A
  • Dorso-ventrally compressed
  • Have a spiracle in dorsal side
  • Mouth and gills slits on ventral side
  • Water drawn in through gills slits and out through mouth and gills (how they feed.
  • Many are benthic
  • Manta ray is a filter feeder using cephalic fins to direct water in through mouth
  • Jaw is protrusible, teeth are flat plates (sexual dimorphism - teeth become sharp (for latching) depending on reproductive season.)
  • Some produce electric currents (predation and communication)
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19
Q

Shark examples: Cookie cutter shark

A

Small but takes many bite chunks out of prey

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20
Q

Examples of sharks: Hammerhead

A

Theories for the use of the hammerhead. Improve sensitivity of receptors? Binocular vision (accurate perception of depth, distance)? ← binocular vision newest theory

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21
Q

Cartilaginous fish

A
  • Teeth
  • Liver (25% body mass)
  • Paired fins
  • Short intestine with high surface area
  • Spiral valve in intestine
  • Tail is heterocercal - asymmetrical - gives them lift when swimming
22
Q

What are Batoidea

A

Skates and Rays

23
Q

Placoid scales

Chondrichthyes

A
  • Denticles (tooth-like structures found on surface of skin)
  • Sharks
  • Shape and arrangement is species specific
  • Allow for a smoother flow of water of the skin
  • Pulp cavity - Dentine middle - Enameloid outer layer.
24
Q

How are placoid scales modified in skates and rays?

A
  • Single placoid scale modified to barb in sting rays.
  • Many small placoid scales along dorsal line of skates (reduced into small nobbly protrusions)
25
Q

How do dog fish embryos use their placoid scales?

A

Use them to tear and manipulate food by rubbing the food across their back in the opposite direction of the scales

26
Q

Skates and Ray reproduction

A
  • ray (viviparous)
  • Skate (oviparous)
27
Q

How to electric rays stun their prey?

A

Use electrical currents of around 200v to stun prey

28
Q

Diversity in Ray feeding behaviours

A
  • Manta rays are filter feeders
  • Electric ray kills prey
29
Q

What is the name of Chondrichthyes Teeth structure?

A

Tooth Whorl

30
Q

Where in the jaw does the tooth whorl sit?

A

Teeth form within skin - tooth whorl rests on jaw

31
Q

What is the condrichthyes tooth whorl ?

A

Teeth are continuously being replaced (in a conveyer belt fashion)

32
Q

Condrichthyes Tooth whorl shapes

A
  • Shapes vary depending on species
  • Shapes and size vary depending on where they are in the mouth
  • Different shapes maximise damage to prey
33
Q

Some chondrichthyes kill mammal prey by exsanguination, what does this mean?

A
  • Cause max damage and blood loss to the mammal
  • Weaken prey so they can feed on it (bleed to death)
34
Q

How did Megaladon feeding habits effect baleen whale size?

A

It has been suggested that megaladons would would feed on baleen whales and keep their size reduced. Acting as a cap

35
Q

How do chondrichthyes detect their prey?

Chondrichthyes sensory systems

A
  • Mechanoreceptors: detect vibrations
  • Chemoreceptors: Acute sense of smell
  • Electroreceptors: detect electrical pulses of prey
  • Visual: allow site in low light
36
Q

Mechanoreceptors

Chondrichthyes sensory systems

A
  • Neuromast organs
  • Detect vibrations from prey in the water
  • Found along lateral line
37
Q

Chemoreceptors

Chondrichthyes sensory systems

A
  • Olfactory organs
  • acute sense of smell
  • They will turn to the side (nostril) that detects the cue first and follow that direction.
38
Q

Electroreceptors

Chondrichthyes sensory systems

A
  • Ampullary organs
  • Organs found in the head of sharks
  • Found in pectoral fins of rays
  • Found on the Rostrum of holocephalans
  • Electrical charges going round preys body will be detected by these organs
39
Q

Vision

Chondrichthyes sensory systems

A
  • Well developed eyes for low light intensities
  • Rod rich retina: Cells with crystals of guanine behind retina.
  • Shines light off retina (almost like a wall of mirrors behind eye)
  • Tapetum lucidum
40
Q

What is tapetum lucidum?

A
  • Rod rich retina
  • Cells with crystals of guanine behind retina
  • allows good vision in low light
41
Q

What is the sequence of events in predation of chondrichthyes?

A
  • Olfaction or mechanoreception
  • Vision - prey detection
  • Attack - electroreception (eyelids cover eyes for protection - rely soley on electroreception as can’t see).
42
Q

What is different about brain size and itelligence of chondrichthyes

A
  • Brain size is proportionally heavier than brains of other fishes
  • Similar brain to body mass ratios to some tetrapods
  • Manta rays have shown mirror self recognition (some debate over this).
43
Q

What are pelvic claspers and what are they used for?

Chondrichthyes reproduciton

A
  • Pelvic claspers (associated with pelvic fins)
  • Aids in internal fertilisation.
  • Claspers have hooks and other attachment devices that ensure claspers stay in place
  • A way of maintainting attachment to female during reproduction
44
Q

How is sperm released?

Chondrichthyes reproduciton

A

Via siphon sacs

45
Q

what are some male adaptations for maintaining attachment to the female during mating

Chondrichthyes reproduciton

A
  • Males bite onto females
  • In some smaller species the male wraps arounf the female
  • Some ray species get sharper teeth during maring season to latch onto female
46
Q

How have females adapted to males biting them during copulation?

A

Females have thickened skin in areas where males latch on.

47
Q

Different Breeding systems within chondrichthyes

Oviparous

A
  • Oviparous (egg laying).
  • Water can flow through egg cases (respiration).
  • Egg case contain tentril that attach to rocks etc. (e.g. mermaid purse)
  • Nutrients from yolk
48
Q

Different breeding systems within chondrichthyes

Ovoviviparity

A
  • Ovoviviparity - retain eggs in oviduct until hatching (lecithotrophy).
  • Give birth to live young.
  • Nutrients from egg yolk.
49
Q

Different breeding systems within chondrichyes

Viviparity

A
  • Vivipary - nutrition comes from yolk and female (matrotrophy).
  • Some females secrete substances (uterine fluid).
  • Some ovulate to feed young or cannibalism (embryos eat each other (survival of the fittest).
  • Some have yolk sac placenta (placentotrophic viviparity)
  • Once born no parental care.
50
Q

Why are chondrichthyes threatened and why is this a conservation issue?

A
  • Long gestation period and long lived means generational development is slow
  • Invest a lot in reproduction and takes many years to reach sexual maturity.
  • Don’t reproduce every year.
  • Apex predators - consequences for the food chain if they decline
51
Q

What is a hunting adaptation of great white sharks?

A

Approach prey with sun behind them so the prey cant see them

52
Q

Greenland shark life and sexual maturity

A

Thought to live for 400 years and reach sexual maturity at 150 years old

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