Jawless-jawed and life in the water Flashcards
evidence early vert evolution occurred in marine env:
- earliest fossils found in marine deposits
- all non-vert chordates and deuterostome phyla are marine
odontodes: features and eg
- first appearance of mineralised tissue
- teeth-like structures that form in dermal layer of skin and overlaid w epidermis
- eg. catfish have odontodes assoc w mouth
odontodes: function
- mineral storage
- protection
- improved electroreception
early vert: vert w mineralised bone find
480-500mya
early vert: soft bodies vert found
520mya
early vert: fish-like creatures features and lacking
- lack rays
- complex myomeres
world wide dist of ostracoderms and gnathostomes by:
400mya
extinct placoderms more closely related to living jawed/jawless fish:
- jawed fish
myxiniformes: hagfish- features
- eel-like scavengers
- produces copious slime
- 1-15 gill openings (species dependent)
- lack true vert
- simple kidneys
- single semi-circular canal
- single terminal nasal opening
- horny plates of keratin (vs mineralised) in mouth
- horny teeth on mm tongue can be extruded
- degenerate eyes
- 6 tentacles
- large blood sinuses, low BP
- 3 chambered heart
- accessory hearts in liver and tail
- heart is ANEURAL
myxiniformes: hagfish- reproduction and embryonic dev
- almost unknown
peteromyzontiformes: lamprey- features
- intermediate btw hagfish and gnathostomes (anatomy wise)
- 2 semicircular canals: body orientation and momentum
- heart inn by vagus nn (like gnathostomes)
- active ion transport across skin
- well dev kidneys: good control of hydrostatic pressure
- useful for anadromous lifestyle (migration)
- 7 pairs gills: pump water through mouth, out gills
- but when attached to prey, ventilate back/forth through gills
- large eyes, well dev pineal gland (close to nasal opening)
- teeth keratinised
- oral gland secretes anti-coagulant so feed on hosts uninterrupted
- super rich diet, simple digestive tract
peteromyzontiformes: lamprey- unique features
- single nasal opening connects to pituitary (hypophysis)
- unknown function
peteromyzontiformes: lamprey- lifestyle
- most adults live in sea, some in lakes as fish parasites
- migrate to freshwater to spawn
- females builds nest in stream riffle, male wraps and fertilises eggs depositing into nest
- 2 wks hatch into amoceotes larvae (burrow into soil and filter feed)
- this stage up to 3 yrs
- metamorphose into adults, drift downstream to sea
- adults live to 2 yrs
peteromyzontiformes: lamprey- name phases
- spawning
- larval
- transforming
- parasitic
why important to study jawless fish in regards to early evol of vert:
- fossil record not helpful
- but can’t assume rep ancestral vert (highly specialised niches: scavenger and parasite)
- hagfish eg. CNS reflects but others like eye loss most likely derived/ hard to interpret
condonts: elements
- small mineralised teeth-like fossils
- og thought to belong to invert
- but assigned to true vert when discovered fossilised impressions
condonts: features
- clear myomeres (V shaped)
- well defined heads
- large eyes
- fins w fin rays
- entire clade extinct 200mya
condonts: current phylogeny places them
- btw lamprey and gnathostomes
ostracoderms: features
- paraphyletic group
- encased in dermal bone, well dev brains
- all had central dorsal fin, some had true pectoral fins w assoc girdles and skeletal fin supports
ostracoderms: more closer to living jawed/jawless fish
- closer related to jawed vert
ostracoderms: extinction
- some say emergence of gnathostomes pushed ostracoderms to extinction (lived side by side for 50mya)
- also coincides w mass invert extinctions
- suggest catastrophic shift in env conditions
gnathostome: dev of jaws
- probs started out as support for improved respiration vs. eating
- once evolved, predation possibility and opened new niches
gnathostome: main obv distinctions btw jawed/jawless
- jaws w teeth
- paired pectoral and pelvic fins
- duplication of HOX genes
gnathostome: other key innovations- jawless to jawed
- jointed branchial arches
- hypobranchial mm
- 2 nares
- first gill slit: spiracle
- 3 semicircular canals
- conus arteriosus (controls blood flow)
- horizontal septum dividing epaxial and hypaxial mm
- vert w centra and ribs
jaws and teeth: features
- most likely evolved separately
- teeth came from denticles already existing in some shape/form as seen on todays shark skin
- placoderms (earliest jawed vert had jaw, no teeth)
jaws and teeth: seen in shark
- ancestral situation where teeth form in skin
- rest on jaw bone
- new teeth roll forward in a whorl to replace old teeth
jaws and teeth: bony fish and tetrapods (incl ancestral and modern eg.)
- teeth embedded into jawbone
- ancestral form: like pleurodont where teeth set in shelf on inner side of jawbone
- also seen in modern amphibians
jaws and teeth: acrodont teeth and eg.
- teeth fastened to top of ridge, absence of socket
- most common in teleosts
jaws and teeth: thecodont teeth and eg.
- teeth fastened in sockets and held in place by ligs
- most common mammals
hypobranchial mm: features
- assoc w existing branchiomeric mm
- allows animals form strong suction action
- for ventilating gills
- also suck in prey
vertebra: features- ancestral gnathostomes
- dev more complex vert through time
- ossified dorsal arches, protect nn cord (neural arch),
- matching pair on ventral side (hemal arch)
vertebra: features- tetrapods
- notochord more less replaced by series of well dev vert acting as scaffolding for axial mm
vertebra: features- recent gnathostomes
- vertebral centrum/and or central elements which ribs articulate
vertebra: features- mammals
- all sorts of spines
- interlocking processes unlike ancestral vert
ribs: features and assoc parts
- gnathostome invention
- offer further scaffolding upon axial mm: better locomotion
- axial mm clearly arranged into ep/hypaxial segments divided by horizontal septum
- middle of mm pack, lateral line collects vibration info (sent to ear)
- 3rd semicircular canal allow movement and orientation in 3D space
soft tissue: ostracoderm
- well dev brain
- cerebellum
- olfactory tracts
- lack 3rd semicircular canal
soft tissue: gnathostomes
- evolved myelin sheaths
- increase efficiency of NS
- 3 semicircular canals
- conus arteriosus in heart: elastic reservoir to maintain uni-directional high pressure pumping sys
- specialised duct connecting gonads to cloaca, for sperm/egg
fins: features
- guidance sys in 3D
- unpaired fins of midline: control roll and yaw
- pectoral, pelvic fins: control pitch, and breaks
- caudal fin: increase SA of tail, more thrust
fins: tribasal
- connection from pectoral fins (in sharks)
- three elements of fin articulating w girdle
gills: ancestral og
- ancestral vert had both int/ext arches
- alternatively lost in cyclostomes and gnathostomes
- morphological changes due to changing timing of dev genes
gills: transition btw gills and jaw
- likely gill arches evolved to enhance fill ventilation
- changes co-opted to perform new functions as jaws
gills: features
- once produce powerful suction for gill ventilation, easy for using to forage
- first arch must be articulated so open/close mouth
- hyper/branchial mm dev to help power opening/closing -added stress so arch stronger, second gill recruited for structural support
jaws: features and name arches
- vert jaw derived from branchial arches historically assoc w gills
- 1st gill arch: mandibular arch
- 2nd: hyoid arch (supports 1st)
- those post arches: support gills
- most vert no hole btw 1st/2nd, some present as spherical in sharks/fish
devonian gnathostomes: list 4 jawed vert (and whether extinct or not)
still exists:
- sharks,
- bony fish
extinct:
- placoderms
- acanthodians
devonian gnathostomes: ostracoderms important features
- large and diverse group
- paraphyletic
- grouped based on morphology
- some more primitive/ more recently derived taxa in group
devonian gnathostomes: acanthodians (spiny sharks)
- traditionally grouped w bony fish, molecular evidence suggests not group at all
devonian gnathostomes: placoderms- features
- covered in bony plates, typically ant end
- distinct set head plates linked via joint to rest of body: head can move independently
- endoskeleton mineralised on edges only (perichondral) vs bony fish complete ossification (endochondral)
- during Devonian times, dom and most diverse vert
- some 8m length
- majority wiped out by later Devonian event
placoderms: teeth, soft features, reproduction
- most lacked true teeth, modified dermal plates projecting from jawbones
- later species evolved true teeth
- not much known about soft bits, evidence in Aus:
- myomeres weakly W shaped, lack clear distinctions btw epaxial and hypaxial sections
- some: internal fertilisation, modified anal fins resembling male sharks
- also may had embryos inside specimen
acanthodians: features
- named after strong spines assoc w fins
- probs not single clade, dist all over gnathostome heritage
- most diverse during Devonian period in freshwater (started out as marine group)
- fusiform caudal fin suggest midwater taxa
- some species 2+ paired fins: pectoral, anal
- wide diversity of lifestyles, some w teeth also had whorls similar to sharks
water living: features and facts
- gravity insig in water vs. huge effect on terrestial vert
- low viscosity of air: wind resistence neglible, but in water good hydrodynamics is vital
- 800x denser than air
- 55x more viscous than air
- 40x less O2
- water conducts heat 25x faster than air
oxygen:
- much harder to extract from water
- need to pass over gills w high SA
- by buccal pumping, ram ventilation
- blood vessels in gills arranged to max uptake:
- deoxy blood flows one direction, fully oxy water opp direction
- counter current= O2 diffusion gradient maximised from water to blood
buoyancy: features and eg.
- fish effectively made of water, neutral buoyant (no effort to maintain position in water column)
- bony fish: swim bladder on doral side wedged btw vert column/ peritoneal cavity (body vol- 5% marine teleosts, 7% freshwater teleosts)
buoyancy: adjust position in water column- primitive and more derived fish
- to swim up/down water column, need to adjust pressure
- primitive fish: valve connecting stomach to burp air out/ gulp air and force back in
- more derived fish: changes in vol by secreting gas from blood v into/out of swim bladder
buoyancy: define physosomous fish and eg.
- have link btw swim bladder and gut
- more primitive fish
- eg. trout
buoyancy: rete mirabile
- despite diff of primitive/more derived fish
- both have this aka gas gland
- enable excretion of O2 into swim bladder even at incredible depths
- coz pressure in deep sea, rete mirabile have to be v long to overcome gradient
buoyancy: define physoclistous fish
- no connection btw swim bladder and gut
- more derived fish
fish sense: name important properties in water (3)
- light/ colour
- mechanical disturbance
- chemical cues
fish sense: light and eg.
- water rapidly absorbs light
- red hardly penetrates, most colours lost in first 100m of water
- only blue light persists afterwards
- surface fish nearly all tetrachromatic, spherical lens coz refractive index of water
- other fish, vision waste so depend on other senses
fish sense: mechanical disturbance
- works v well underwater
- most bony fish has well dev lateral line
- neuromasts detect displacement of water
- also hav typical vert internal ear, for orientation and hearing
fish sense: chemical cues
- spread nicely underwater
- already in solution
- many fish sense chemicals 1 part/ billion
electroreception: why and define electrocytes and eg.
- also works well as water conducts electricity
- electrosensitivity likely ancient vert trait
- some fish: electrocytes (modified mm cells) generate electricity to stun prey, communicate or navigate
- eg. weak electric fishes
electroreception: sharks
- network (ampullae of Lorenzini) on head
- hone electrical discharge from mm and nn activity of prey
- also picks up earths magnetic field
electroreception: echidna and platypus
- pre good electrosensitivity for foraging
- may evolved independently
water and ions: features, waste and eg.
- srs issue for all vert esp aquatic ones to control ions
- skin highly permeable (not equally to everything)
- vert control water/ion balance by actively/passively passing molecules from inside/outside vice versa
- also deal w waste (ammonia) toxic product of protein decay
- kidneys play huge role in both
kidneys: nephron
- fundamental unit is nephron
- millions in kidney producing urine
- extracts foreign substances and waste products from blood
- control salt and water balance
nephron: glomerulus
- structure unique to vert
- arteriole under pressure leaks ultrafiltrate into bowmans capsule
osmoregulation: hagfish
- don’t achieve iron conc. diff from env =isotonic to sea water
- other vert hav lower salt conc.
- salt move into marine vert
- water tries to leave
- cartilaginous fish counteract by having high urea lvls in blood
- opp for freshwater fish
osmoregulation: define stenhaline
- fish that remain in either salt/fresh water entire lives
- thus fixed physiology
osmoregulation: define euryhaline
- move btw fresh/salt water
- more complicated physiology
osmoregulation: marine teleost and eg.
- keep as much water as possible, excrete excess ions
- marine teleosts drink alot of seawater and pump ions across stomach into blood to encourage water follow
- gills pump Cl- out and Na follows
- small glomeruli, lack distal convoluted tubule
- produce lil but highly conc. urine
osmoregulation: Coelacanths and eg.
- sharks
- high urea to prevent salt in, like coelacanths
- water actively flows across gill membranes
- sharks don’t need to drink
- plenty of water, glomeruli large, great filtration rates
- ions follow water across gills but unlike marine teleosts, membranes relatively impermeable to ions
- excess salt secreted by rectal gland
osmoregulation: freshwater teleosts and amphibians
- salt tries to escape, water coming in
- teleosts reasonably impermeable skin
- huge water across gills to breathe
- both amphibians and fish produce huge vol urine, kidneys overtime to extract excess water from blood
- nephrons actively pump ions back into bloodstream from ultrafiltrate
- fish also hav Cl- ion pumps in gills to actively move Cl from water to blood
- causes diffusion grad and Na travels across passively
nitrogenous waste- teleosts: waste product
ammonia
nitrogenous waste- teleosts: excrete where
skin, gills, urine
nitrogenous waste- teleosts: cost
low
nitrogenous waste- teleosts: toxicity
high
nitrogenous waste- teleosts: water conservation
low
nitrogenous waste- mammals: waste product
urea
nitrogenous waste- mammals: excrete where
urine
nitrogenous waste- mammals: cost
med
nitrogenous waste- mammals: toxicity
med
nitrogenous waste- mammals: water conservation
med
nitrogenous waste- reptiles (birds): waste product
uric acid
nitrogenous waste- reptiles (birds): excrete where
urine
nitrogenous waste- reptiles (birds): cost
high
nitrogenous waste- reptiles (birds): toxicity
low
nitrogenous waste- reptiles (birds): water conservation
high
