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VERTEBRATE EVOL > Rise of Chondrichthyans > Flashcards

Rise of Chondrichthyans Flashcards

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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
extant chondrichtyans: elasmobranchs branch into: and spp
- sharks - batoidea ~516 spp
26
extant chondrichtyans: sharks branches into
- sharks/ flatsharks - galeomorphi (superorder) - squalomorphi (superorder)
27
extant chondrichtyans: sharks- galeomorphi list 4 orders
- modern sharks - heterodontiformes - lamniformes - carcharhiniformes - orectolobiformes
28
extant chondrichtyans: Galeomorphi sharks- heterodontiformes eg
- bullhead - port jackson - crested horns
29
extant chondrichtyans: Galeomorphi sharks- lamniformes eg
- mackerel - great white - goblin - megamouth
30
extant chondrichtyans: Galeomorphi sharks- carcharhiniformes eg
- ground sharks: - catshark - swell shark - requiem (tiger, blacktip, reef)
31
extant chondrichtyans: Galeomorphi sharks- orectolobiformes eg
- carpet sharks: | - wobbegongs
32
extant chondrichtyans: Squalomorphi sharks- lack
- no anal fins
33
extant chondrichtyans: Galeomorphi sharks- eg
- deep sea sharks: - sleeper - lantern - dogfish
34
extant chondrichtyans: batoidea (superorder)- list 4 orders
- myliobatiformes - rajiformes - torpediniformes - rhinopristiformes
35
extant chondrichtyans: batoidea- myliobatiformes eg
- stingray - eagle ray - devil ray
36
extant chondrichtyans: batoidea- rajiformes eg
- skates
37
extant chondrichtyans: batoidea- torpediniformes eg
- electric rays
38
extant chondrichtyans: batoidea- rhinopristiformes
- shovelnose ray | - sawfishes
39
name smallest and largest shark: and size
- dwarf lantern (20cm) | - whale (18m)
40
Holocephali: aka and features
- 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
galeomorphi + squalomorphi: features
- 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
batoidea: features
- 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
batoidea: ray w barb tail
- myliobatiformes
44
batoidea: benthic, bentho-pelagic and pelagic rays eg.
- most batoids (benthic) - eagle ray (bentho-pelagic) - manta ray (pelagic)
45
skates vs rays: physical diff
skates: - 2 dorsal fins on tail - pelvic fins hav 2 lobes (1st lobe: locomotion)
46
skates vs rays: which orders from baitodea's 4 orders
skate: rajiformes rays: myliobatiformes, torpediniformes, rhinopristiformes
47
skates vs rays: reproduction
- 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
cladogram: cartilaginous fish what (3) features arise when separated from bony fish?
- placoid scales - pelvic claspers - cartilaginous skeleton
49
cladogram: what features arise- (1) cartilaginous fish branching into holocephali
gill openings covered by soft tissue
50
cladogram: what features arise- (1) holocephali branched into extant chimaeras
holostylic jaw (jaw fused to cranium)
51
cladogram: what features arise- (1) further cart fish stem branched into EXTINCT elasmobranchs
gill openings separated and uncovered
52
cladogram: what features arise- (1) on stem branched into EXTINCT hybodonts
tribasal fin
53
cladogram: what features arise- (1) extant elasmobranchs
mouth move from terminal -> subterminal =giving rise to modern sharks
54
cladogram: what features arise- (1) stem to skates and rays
dorsoventral flattening | - rise of skates and rays
55
chondrichthyan senses: olfaction features
- first sense chondr. generally use - nares on snout - highly dev olfactory bulbs - 4x better than us - good long distances, not well directed
56
chondrichthyan senses: lateral line features
- sense shared btw chond. and bony fish - sensitive to vibrations in water - immediate info of location of prey - second sense after olfaction
57
chondrichthyan senses: vision features
- once close to stimulus, dom smell as 1º mode detection | - good at detecting contrast, but depends on lifestyle many colourblind
58
chondrichthyan senses: vision- eg. tapetum lucidum
- 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
chondrichthyan senses: vision- eg. eye protection (3) features
- 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
chondrichthyan senses: electroreception features
- 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
chondrichthyan senses: hearing
- thought most sensitive to freq below 100 Hz and up to 1000 Hz - much less than humans
62
chondrichthyan senses: reproduction
- 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
chondrichthyan senses: reproduction- oviparous, oviviviparous, viviparous
- ovi: egg laying - ovo: egg hatches within mother - vivi: live birth - some spp evol true placenta, evolved separately from mammals
64
chondrichthyan senses: reproduction-k-selected strategy vs r-selected
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
chondrichthyan senses: reproduction- eg. grey nurse sharks
- only every 2 yrs - give birth 1-2 pups due to intrauterine cannibalism - biggest, strongest shark eats other developing embryos
66
convergent evolution: eg.
- analogous structure developed eg. saw-like rostrum w pointy teeth of batoid and shark spp, diverged 210mya
67
chondrichthyes research: where and what can be learned
- 1000s caught each yr, 'flake' or 'boneless fish' in Aus dead sharks can learn: - biology - age - diet - movement - reproduction - behaviour
68
elasmobranch research: how
- logistically difficult to do research in ocean on highly mobile spp like sharks - tagging and tracking
69
elasmobranch research: benefits/cons of tracking and tagging
- removes need of direct observation - collect oceanographic data also - expensive, time consuming
70
acoustic tagging: features
- 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
acoustic tagging: IMOS national receiver network
- 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
acoustic tracking: eg port jackson sharks
- 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
acoustic tracking: eg. smooth stingrays
- 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
cognition and behaviour: elasmobranchs research
- 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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