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VERTEBRATE EVOL > Rise of Chondrichthyans > Flashcards

Rise of Chondrichthyans Flashcards

1
Q

chondrichthyans: aka and how they came to be

A
  • sharks
  • rays
  • chimaeras
  • appearance of jaws and paired fins: diverse predatory and locomotor specialisations
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2
Q

chondrichthyans: list 5 major characteristics which differentiate them from teleosts (bony fish)

A
  • cartilaginous skeleton
  • placoid scales
  • lipid-filled liver
  • spiral valve intestine
  • high blood urea
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3
Q

chondrichthyans: cartiliaginous skeleton

A
  • low weight = increased buoyancy
  • less energetically costly (vs bone)
  • strong and far more flexible
  • cartilage not neccessarily weaker than bone as calcified cartilage extremely strong (multiple layers, int struts)
  • in jaws of rays, sharks which crush molluscs
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4
Q

chondrichthyans: placoid scales and eg.

A
  • aka dermal denticles
  • homologous w vert teeth (composed: dentine, ‘enamel’)
  • central pulp cavity w blood v, dentine layer covered w enamel-like substance (vitrodentine)
  • like chainmail, good protection and flexibility
  • reduce hydrodynamic drag
  • possibly reduce parasites
    eg. pat shark used as sandpaper
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5
Q

chondrichthyans: teeth and eg.

A
  • modified placoid scales
  • highly variable due to ecological niche (prey they feed on)
  • benthic sharks, rays: teeth fused forming crushing plates (feed on crustaceans etc.)
  • most species replace teeth every 2wks (most common fossil)
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6
Q

chondrichthyans: lipid filled liver

A
  • as chondrichthyans lack swim bladders, compensate by liver filled w squalene (buoyant oil)
  • size liver varies, benthic smaller, pelagic species bigger
  • eg. great white liver (18% of body vol)
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7
Q

chondrichthyans: spiral valve intestine vs teleosts

A
  • increase SA for digestion, absorption of food
  • small size makes room for liver, and embryos (females)
  • vs teleosts long digestive sys coil around body cavity
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8
Q

chondrichthyans: high urea conc. in blood

A
  • osmoregulation: big issue, loss of water due to high salt content in sea water
  • reabsorb urea keep body fluids similar conc. to seawater
  • gains water via osmosis
  • salt excreting gland w small influx salt
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9
Q

evolution of chondrichthyans: when diverged and features and eg.

A
  • 450mya diverged from bony fish
  • ancient ≠ primitive
  • extant species evolved around same time as humans
  • eg. some teeth in silurian and ordovocian time, but definite first appearance in early Devonian
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10
Q

Paleozoic radiation: Silurian time- Holocephali features and name 2 groups

A
  • first split from lineage of ancestors of sharks and rays during Silurian
  • earliest fossil: mid Devonian
  • Holocephalimorpha
  • Paraselachimorpha
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11
Q

Holocephali: holocephalimorpha

A
  • incl order containing mordern chimaeras (chimaeriformes)

- have holostylic jaw (upper jaw fused to skull)

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12
Q

Holocephali: paraselachimorpha

A
  • contains ~6 orders restricted to later paleozoic

- look like sharks, w shark-like teeth

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13
Q

Paleozoic radiation: early Devonian time- elasmobranchii features

A
  • all chondrichthyan fishes that aren’t chimaeras part of group called elasmobranchii (stem elasmobranchs)
  • generally shark-like but distinct: terminal mouth (mouth front of head/snout)
  • dorsal spines before their 2 dorsal fins
  • multicusped teeth, lil root dev
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14
Q

stem elasmobranchs: cladoselache features

A
  • terminal mouth

- dorsal spines

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15
Q

stem elasmobranchs: eugeneodontiformes

A
  • spiral jaw/ tooth whorl
  • where teeth replaced by new teeth
  • modern have alot of tooth whorls
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16
Q

stem elasmobranchs: symmoriiformes

A
  • single dorsal fin
  • shoulder spines (modified 1st dorsal fin)
  • shoulder spines possible role in courtship
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17
Q

Paleozoic radiation: Devonian time- elasmobranchs: damocles serratus sig

A
  • symmoniformes
  • sexual dimorphism
  • males: large shoulder spines, females non
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18
Q

Paleozoic radiation: Devonian time- elasmobranchs: falcatus falcatus sig

A
  • also symmoniformes

- fossil found shoulder spines used for courtship (female grasping spine)

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19
Q

Paleozoic radiation: Devonian time- elasmobranchs: xenacanthus sig

A
  • similar to cladoselache
  • bottom dwelling freshwater species
  • robust fins, elongated eel-like body
  • heavily calcified skeleton
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20
Q

early Mesozoic radiation: hybodonta list changes (3) and eg.

A
  • heterodonts

- distinguished by changes to dentition, jaws, fins

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21
Q

early Mesozoic radiation: hybodonta- heterodont dentition

A
  • different shaped teeth for diff parts of jaw
  • ant: pointed for piercing, slicing
  • post: blunt for crushing hard bodied prey
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22
Q

early Mesozoic radiation: hybodonta- fins and eg. ceratotrichia, heterocercal

A
  • fins w basal cartilage
  • ceratotrichia (flexible fin rays of keratin-like protein, support fin)
  • heterocercal caudal fin (reduction of lower lobe, upper large lrger and helped w forward/upward thrust)
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23
Q

early Mesozoic radiation: hybodonta- amphystilic jaw

A
  • upper jaw attached to skull by several points articulation
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24
Q

extant chondrichtyans: spp. and branches into

A
  • ~1200 species

holocephali (aka chimaeras): ~51 spp

elasmobranchs

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25
Q

extant chondrichtyans: elasmobranchs branch into: and spp

A
  • sharks
  • batoidea
    ~516 spp
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26
Q

extant chondrichtyans: sharks branches into

A
  • sharks/ flatsharks
  • galeomorphi (superorder)
  • squalomorphi (superorder)
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27
Q

extant chondrichtyans: sharks- galeomorphi list 4 orders

A
  • modern sharks
  • heterodontiformes
  • lamniformes
  • carcharhiniformes
  • orectolobiformes
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28
Q

extant chondrichtyans: Galeomorphi sharks- heterodontiformes eg

A
  • bullhead
  • port jackson
  • crested horns
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29
Q

extant chondrichtyans: Galeomorphi sharks- lamniformes eg

A
  • mackerel
  • great white
  • goblin
  • megamouth
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30
Q

extant chondrichtyans: Galeomorphi sharks- carcharhiniformes eg

A
  • ground sharks:
  • catshark
  • swell shark
  • requiem (tiger, blacktip, reef)
31
Q

extant chondrichtyans: Galeomorphi sharks- orectolobiformes eg

A
  • carpet sharks:

- wobbegongs

32
Q

extant chondrichtyans: Squalomorphi sharks- lack

A
  • no anal fins
33
Q

extant chondrichtyans: Galeomorphi sharks- eg

A
  • deep sea sharks:
  • sleeper
  • lantern
  • dogfish
34
Q

extant chondrichtyans: batoidea (superorder)- list 4 orders

A
  • myliobatiformes
  • rajiformes
  • torpediniformes
  • rhinopristiformes
35
Q

extant chondrichtyans: batoidea- myliobatiformes eg

A
  • stingray
  • eagle ray
  • devil ray
36
Q

extant chondrichtyans: batoidea- rajiformes eg

A
  • skates
37
Q

extant chondrichtyans: batoidea- torpediniformes eg

A
  • electric rays
38
Q

extant chondrichtyans: batoidea- rhinopristiformes

A
  • shovelnose ray

- sawfishes

39
Q

name smallest and largest shark: and size

A
  • dwarf lantern (20cm)

- whale (18m)

40
Q

Holocephali: aka and features

A
  • aka elephantfish, ratfish
  • 4 gill slits covered by operculum
  • upper jaws holostylic (fused to cranium)
  • probosci: covered in lateral line, electromagnetic receptors
  • cephalic clasper/ tentaculum (grab females pec fin during mating)
  • some: poison glands at base of spine, in front of dorsal fin
  • separate anal, urogenital openings
41
Q

galeomorphi + squalomorphi: features

A
  • galeomorphi: modern sharks
  • squalomorphi: deepwater sharks
  • mostly cylindrical (benthic slightly flattened)
  • most 5 gill slits, some 6-7 (not covered like chimaeras)
  • mouth under snout
  • most species pelagic
42
Q

batoidea: features

A
  • batoids r flattened sharks (dorsoventrally)
  • gills, mouth, nares on ventral surface
  • eyes, spiracles on dorsal side
  • pectoral fins enlarged/fused to sides of head
  • stingray 1/4 of batoidea, 1/3 of batoids
43
Q

batoidea: ray w barb tail

A
  • myliobatiformes
44
Q

batoidea: benthic, bentho-pelagic and pelagic rays eg.

A
  • most batoids (benthic)
  • eagle ray (bentho-pelagic)
  • manta ray (pelagic)
45
Q

skates vs rays: physical diff

A

skates:
- 2 dorsal fins on tail
- pelvic fins hav 2 lobes (1st lobe: locomotion)

46
Q

skates vs rays: which orders from baitodea’s 4 orders

A

skate: rajiformes
rays: myliobatiformes, torpediniformes, rhinopristiformes

47
Q

skates vs rays: reproduction

A
  • w all elasmobranchs: internal fertilisation
    skates: oviparous (lay eggs, lil/no dev in mother)
    rays: ovoviviparous (egg dev in mother, no placenta), viviparous (live birth)
48
Q

cladogram: cartilaginous fish what (3) features arise when separated from bony fish?

A
  • placoid scales
  • pelvic claspers
  • cartilaginous skeleton
49
Q

cladogram: what features arise- (1) cartilaginous fish branching into holocephali

A

gill openings covered by soft tissue

50
Q

cladogram: what features arise- (1) holocephali branched into extant chimaeras

A

holostylic jaw (jaw fused to cranium)

51
Q

cladogram: what features arise- (1) further cart fish stem branched into EXTINCT elasmobranchs

A

gill openings separated and uncovered

52
Q

cladogram: what features arise- (1) on stem branched into EXTINCT hybodonts

A

tribasal fin

53
Q

cladogram: what features arise- (1) extant elasmobranchs

A

mouth move from terminal -> subterminal =giving rise to modern sharks

54
Q

cladogram: what features arise- (1) stem to skates and rays

A

dorsoventral flattening

- rise of skates and rays

55
Q

chondrichthyan senses: olfaction features

A
  • first sense chondr. generally use
  • nares on snout
  • highly dev olfactory bulbs
  • 4x better than us
  • good long distances, not well directed
56
Q

chondrichthyan senses: lateral line features

A
  • sense shared btw chond. and bony fish
  • sensitive to vibrations in water
  • immediate info of location of prey
  • second sense after olfaction
57
Q

chondrichthyan senses: vision features

A
  • once close to stimulus, dom smell as 1º mode detection

- good at detecting contrast, but depends on lifestyle many colourblind

58
Q

chondrichthyan senses: vision- eg. tapetum lucidum

A
  • in eye group of shiny crystals of guanine (act like mirrors)
  • reflect light back thrugh retina
  • increase chance of photons to be absorbed
  • 4x better than cat retinas
59
Q

chondrichthyan senses: vision- eg. eye protection (3) features

A
  • nicitating membrane: eyelid only seen in Carcarhiniformes
  • eye rolling: eg. great whites roll eyes back to protect pupil when feeding
  • eye retraction: many rays pull eyes into skull
60
Q

chondrichthyan senses: electroreception features

A
  • ampullae of Lorenzini (AOL)
  • AOL tiny pores w gelatinous substance conducting electrical fields
  • generally used in v low visibility o just before bite
  • benthic species like rays: use sense as ‘metal detector’ when finding prey in sand
  • rays hav no. of pore on their back, detecting above and behind them
61
Q

chondrichthyan senses: hearing

A
  • thought most sensitive to freq below 100 Hz and up to 1000 Hz
  • much less than humans
62
Q

chondrichthyan senses: reproduction

A
  • sexually dimorphic: male claspers (modified pelvic fins)
  • claspers grow during ontogeny, considered sexually mature when flly calcified
  • shark sex aggressive: males bite to grasp females
  • females hav dev thicker skin
63
Q

chondrichthyan senses: reproduction- oviparous, oviviviparous, viviparous

A
  • ovi: egg laying
  • ovo: egg hatches within mother
  • vivi: live birth
  • some spp evol true placenta, evolved separately from mammals
64
Q

chondrichthyan senses: reproduction-k-selected strategy vs r-selected

A

K: sharks

  • slow growth rate
  • late onset of maturity
  • long gestational period (months)
  • few, well dev young at a time

R: bony fish

  • produce many ‘cheap’ offspring
  • 2-11mil eggs laid by atlantic cod/yr, sexually mature after 2yrs
65
Q

chondrichthyan senses: reproduction- eg. grey nurse sharks

A
  • only every 2 yrs
  • give birth 1-2 pups due to intrauterine cannibalism
  • biggest, strongest shark eats other developing embryos
66
Q

convergent evolution: eg.

A
  • analogous structure developed eg. saw-like rostrum w pointy teeth of batoid and shark spp, diverged 210mya
67
Q

chondrichthyes research: where and what can be learned

A
  • 1000s caught each yr, ‘flake’ or ‘boneless fish’ in Aus

dead sharks can learn:

  • biology
  • age
  • diet
  • movement
  • reproduction
  • behaviour
68
Q

elasmobranch research: how

A
  • logistically difficult to do research in ocean on highly mobile spp like sharks
  • tagging and tracking
69
Q

elasmobranch research: benefits/cons of tracking and tagging

A
  • removes need of direct observation
  • collect oceanographic data also
  • expensive, time consuming
70
Q

acoustic tagging: features

A
  • acoustic telemetry 1 method
  • transmitter/tag affixed to animal and receivers (stationary) set in areas of interest
  • when tagged animal in range, receivers record date, time, location, which individual
  • can link data w many receivers to track movement in area
71
Q

acoustic tagging: IMOS national receiver network

A
  • database w multiple receivers all over Aus uploads location and data recorded
  • 170+ installations
    ~9500 receivers
    ~7500 active transmitters
  • millions of detections a yr
72
Q

acoustic tracking: eg port jackson sharks

A
  • usually breed in jervis bay during winter
  • tracked in cape barren island (TAS)
  • sharks return to same bay to breed every yr, same reef in bay = site attachment and good memory
73
Q

acoustic tracking: eg. smooth stingrays

A
  • study home ranges and influence of certain activities
  • SE NSW, tourist attraction to hand feed
  • higher intensity food provisioning, more restrictive home range of rays
  • control: core use range=30km2
  • moderate: 3km2
  • high: 0.6m2
74
Q

cognition and behaviour: elasmobranchs research

A
  • although studied v long time, no credit to intelligence

- can recognise, categorise objects, learn assoc btw stimulus + outcome (eg. boat=food), count, learn from others

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