Rise of Chondrichthyans Flashcards
chondrichthyans: aka and how they came to be
- sharks
- rays
- chimaeras
- appearance of jaws and paired fins: diverse predatory and locomotor specialisations
chondrichthyans: list 5 major characteristics which differentiate them from teleosts (bony fish)
- cartilaginous skeleton
- placoid scales
- lipid-filled liver
- spiral valve intestine
- high blood urea
chondrichthyans: cartiliaginous skeleton
- 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
chondrichthyans: placoid scales and eg.
- 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
chondrichthyans: teeth and eg.
- 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)
chondrichthyans: lipid filled liver
- 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)
chondrichthyans: spiral valve intestine vs teleosts
- 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
chondrichthyans: high urea conc. in blood
- 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
evolution of chondrichthyans: when diverged and features and eg.
- 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
Paleozoic radiation: Silurian time- Holocephali features and name 2 groups
- first split from lineage of ancestors of sharks and rays during Silurian
- earliest fossil: mid Devonian
- Holocephalimorpha
- Paraselachimorpha
Holocephali: holocephalimorpha
- incl order containing mordern chimaeras (chimaeriformes)
- have holostylic jaw (upper jaw fused to skull)
Holocephali: paraselachimorpha
- contains ~6 orders restricted to later paleozoic
- look like sharks, w shark-like teeth
Paleozoic radiation: early Devonian time- elasmobranchii features
- 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
stem elasmobranchs: cladoselache features
- terminal mouth
- dorsal spines
stem elasmobranchs: eugeneodontiformes
- spiral jaw/ tooth whorl
- where teeth replaced by new teeth
- modern have alot of tooth whorls
stem elasmobranchs: symmoriiformes
- single dorsal fin
- shoulder spines (modified 1st dorsal fin)
- shoulder spines possible role in courtship
Paleozoic radiation: Devonian time- elasmobranchs: damocles serratus sig
- symmoniformes
- sexual dimorphism
- males: large shoulder spines, females non
Paleozoic radiation: Devonian time- elasmobranchs: falcatus falcatus sig
- also symmoniformes
- fossil found shoulder spines used for courtship (female grasping spine)
Paleozoic radiation: Devonian time- elasmobranchs: xenacanthus sig
- similar to cladoselache
- bottom dwelling freshwater species
- robust fins, elongated eel-like body
- heavily calcified skeleton
early Mesozoic radiation: hybodonta list changes (3) and eg.
- heterodonts
- distinguished by changes to dentition, jaws, fins
early Mesozoic radiation: hybodonta- heterodont dentition
- different shaped teeth for diff parts of jaw
- ant: pointed for piercing, slicing
- post: blunt for crushing hard bodied prey
early Mesozoic radiation: hybodonta- fins and eg. ceratotrichia, heterocercal
- 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)
early Mesozoic radiation: hybodonta- amphystilic jaw
- upper jaw attached to skull by several points articulation
extant chondrichtyans: spp. and branches into
- ~1200 species
holocephali (aka chimaeras): ~51 spp
elasmobranchs
extant chondrichtyans: elasmobranchs branch into: and spp
- sharks
- batoidea
~516 spp
extant chondrichtyans: sharks branches into
- sharks/ flatsharks
- galeomorphi (superorder)
- squalomorphi (superorder)
extant chondrichtyans: sharks- galeomorphi list 4 orders
- modern sharks
- heterodontiformes
- lamniformes
- carcharhiniformes
- orectolobiformes
extant chondrichtyans: Galeomorphi sharks- heterodontiformes eg
- bullhead
- port jackson
- crested horns
extant chondrichtyans: Galeomorphi sharks- lamniformes eg
- mackerel
- great white
- goblin
- megamouth
extant chondrichtyans: Galeomorphi sharks- carcharhiniformes eg
- ground sharks:
- catshark
- swell shark
- requiem (tiger, blacktip, reef)
extant chondrichtyans: Galeomorphi sharks- orectolobiformes eg
- carpet sharks:
- wobbegongs
extant chondrichtyans: Squalomorphi sharks- lack
- no anal fins
extant chondrichtyans: Galeomorphi sharks- eg
- deep sea sharks:
- sleeper
- lantern
- dogfish
extant chondrichtyans: batoidea (superorder)- list 4 orders
- myliobatiformes
- rajiformes
- torpediniformes
- rhinopristiformes
extant chondrichtyans: batoidea- myliobatiformes eg
- stingray
- eagle ray
- devil ray
extant chondrichtyans: batoidea- rajiformes eg
- skates
extant chondrichtyans: batoidea- torpediniformes eg
- electric rays
extant chondrichtyans: batoidea- rhinopristiformes
- shovelnose ray
- sawfishes
name smallest and largest shark: and size
- dwarf lantern (20cm)
- whale (18m)
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
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
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
batoidea: ray w barb tail
- myliobatiformes
batoidea: benthic, bentho-pelagic and pelagic rays eg.
- most batoids (benthic)
- eagle ray (bentho-pelagic)
- manta ray (pelagic)
skates vs rays: physical diff
skates:
- 2 dorsal fins on tail
- pelvic fins hav 2 lobes (1st lobe: locomotion)
skates vs rays: which orders from baitodea’s 4 orders
skate: rajiformes
rays: myliobatiformes, torpediniformes, rhinopristiformes
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)
cladogram: cartilaginous fish what (3) features arise when separated from bony fish?
- placoid scales
- pelvic claspers
- cartilaginous skeleton
cladogram: what features arise- (1) cartilaginous fish branching into holocephali
gill openings covered by soft tissue
cladogram: what features arise- (1) holocephali branched into extant chimaeras
holostylic jaw (jaw fused to cranium)
cladogram: what features arise- (1) further cart fish stem branched into EXTINCT elasmobranchs
gill openings separated and uncovered
cladogram: what features arise- (1) on stem branched into EXTINCT hybodonts
tribasal fin
cladogram: what features arise- (1) extant elasmobranchs
mouth move from terminal -> subterminal =giving rise to modern sharks
cladogram: what features arise- (1) stem to skates and rays
dorsoventral flattening
- rise of skates and rays
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
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
chondrichthyan senses: vision features
- once close to stimulus, dom smell as 1º mode detection
- good at detecting contrast, but depends on lifestyle many colourblind
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
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
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
chondrichthyan senses: hearing
- thought most sensitive to freq below 100 Hz and up to 1000 Hz
- much less than humans
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
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
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
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
convergent evolution: eg.
- analogous structure developed eg. saw-like rostrum w pointy teeth of batoid and shark spp, diverged 210mya
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
elasmobranch research: how
- logistically difficult to do research in ocean on highly mobile spp like sharks
- tagging and tracking
elasmobranch research: benefits/cons of tracking and tagging
- removes need of direct observation
- collect oceanographic data also
- expensive, time consuming
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
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
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
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
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
