BIOL 322 Part II Flashcards
volume of a cylinder
pi r^2 L
a solid under tension, over time
will not continue to extend over time
mesoglea under tension over time
will continue to extend over time
cross latticed fibres stress-strain curve
J-shaped
two-anchor crawling
alternatively push and pull against 2 anchors
two anchors used for 2 anchor crawling
- penetration anchor
2. terminal anchor
penetration anchor
- posterior
- contract circular muscles to push anterior end of body forward
example organisms that use 2-anchor crawling
leech
caterpillar
bivalve 2-anchor burrowing, penetration anchor
- adductor muscles relaxed
- shell valves open
- push against sediment
- circular muscles contract
- foot elongated, pushing deeper
bivalve 2-anchor burrowing, terminal anchor
- shell valves close
- sediment loosened up
- terminal end of foot extends laterally (anchor)
- longitudinal muscle contract, pulling against anchor
- shell and body move down
multi-anchor crawling
- eg. earthworm
- fat metameres push against sediment
- thin metameres push against anchor
- can be many penetration anchors at once, ‘move’ down body like a wave
- train of muscle contraction and relaxation
terminal anchor
- anterior
- pull on this anchor by contracting ventral lon`gitudinal muscles to bring posterior up
aids in gastropod movement
mucus
Mucus gliding
- mucus is glue and lubricant depending on force
- push foot against mucus to anchor
- lift A end of foot, slide while pressing the rest of foot
- put A part of food down
- lift next segment..
testing banana slug mucus
dynamic hexometer?
- 2 metal discs on a pole that rotate relative to each other w/ mucus btw discs
- constant rate of strain
- stop, strain, stop, intervals of 1s
- record stress mucus undergoes
results of banana slug mucus test
- if strain is low enough mucus acts like glue
- hit yield point and it starts acting like a liquid/ lubricant
mucus production cost, gastropod
7-26% of energy budget
gastropod mucus functions
- chemical cues
- foraging routes
- defense
- temporary adhesion
- useful to predators
gastropod mucus, chemical cues
locate conspecifics
-ex. mating
gastropod mucus, foraging
adhesive trap
-ex. microalgae
gastropod mucus defense
- chemical defense
- ex. stop anemone nematocyst discharge (nudibranch)
gastropod mucus adhesion
epiphragm of periwinkle snail
epiphragm
- temporary structure that protects against
- adhesion dessication in intertidal
- predation
- similar functions as operculum
gastropod mucus, predators
a trail to their prey
before shedding an exoskeleton
a new exoskeleton begins secretion
arthropod exoskeleton number of layers
3
layers of arthropod exoskeleton
- epicuticle
- exocuticle
- endocuticle
epicuticle
lipids, waxes
-impermeable to water
cuticle material
- scleratized chiton
- crosslinked protein
stages of molting
- cuticle begins to separate from epithelium
- cells proliferate, animal enlarging
- inactive chitonase secreted into space btw epidermis and cuticle
- new exosk. secreted
- chitonase activated
- old endocuticle digested
- ecdysis
ecdysis
molting
how is ecdysis (final stage) facilitated
-exo/endo cuticle are fractured along planes of weakness
first layer of new exoskeleton secreted
epicuticle
-VIP to protect new exosk. from chitonase
once new exosk. is secreted and ecdysis has occurred
- pump up fluids under new exosk. while soft
- make space to grow
- before cross linking
- release fluid once sclerotized
pre-formed breakage planes
- where exoskeleton will split for animal to crawl out
- where carapace meets abdomen
how to get large distal appendages out of narrow basal part of appendage in ecdysis
- break down muscle myofilaments
- up to 60% of proposes muscle
- loss of proteins (actin)
- not water, not myocytes
- only chelae, not walking legs
myocytes
-whole muscle fibres
pre-moult intermoult thin:thick myofilament ratio, crustacean cheliped ecdysis
pre-moult: 6 thin: 1 thick
inter moult: 9 thin: 1 thick
how do arthropods move in newly formed unscleretized skeleton
switching skeletons
- rigid skeleton
- hydrostatic skeleton
testing crab hydrostatic skeleton
- string around propodus to transducer - measure movement
- pressure gauge penetrates soft exoskeleton at carpus/merus joint - measure pressure of joint fluid
results of crab hydrostatic skeleton experiment
- movement of joint corresponds w/ spike in hemolymph pressure
- after hardening no spike in hemolymph pressure
flexural stiffness of soft-hard material
soft - low
paper - low but higher
hard - high
tensile strength of soft -> hard materials
soft: medium
paper: highest
hard: medium
hydrostat container must be
-deformable but resistant to tension
movement during soft exosk. stage requires change to
how levers achieve flexural stiffness
pre-molt flexural stiffness
-high material stiffness
post-molt flexural stiffness
internal fluid pressure
hydrostatic skeleton internal fluid, arthropods intermoult
hemolymph
chemical signal between same species
pheromones
chemical signal btw different species that causes change in behaviour beneficial to producer
Allomones
sessile marine invert. allomones
- secondary metabolites
- protect against predators and environment
- unpallatable
- toxic
example of secondary metabolite forming organisms
- porifera
- cnideria
- bryozoa
- ascidiacea
chemical signal between different species that causes a change of behaviour beneficial to receiver
Kairomones
why defensive allomones important for sessile organisms
-cant limit search of pursuit phases of predator
allomones may provide defense against
- predators (in subjugation phase)
- space competitors
- settling larvae of other species
- pathogens
study of Porifera secondary metabolites
- Caribbean sponges
- novel 2º metab.
- put metabolite in tasty agar tablets
- feed to fish in lab
primary metabolite
formed in metabolic pathway
Caribbean sponges w/ novel 2º metabolite
Ectyplasia ferox
Erylus formosus
Caribbean sponges novel 2º metabolite
- triterpene glycoside
- formoside
- unpalatable or toxic
secondary metabolite
not formed directly in metabolic pathway
study of Porifera secondary metabolites, stage 2
- anchored supports w/ ‘clothesline’ in ocean
- dangle phytogel strips w/ squid paste and metabolite
- monitor, weigh strips
other formoside use
-inhibit settlement of larvae
results of study of Porifera secondary metabolites
- in lab find pellets rejected
- field study: eaten, but only about half as much as control
formoside settlement experiment
- field study
- suspend phytogel + formicide in dishes
- quantify % cover of fouling organisms on surface of gel
results of formoside settlement experiment
- control 40% covered
- treated less than 10% covered
- p = 0.0016
formoside overgrowth experiment
- tablet w/ 1 large depression in middle, 4 smaller at corners
- fix aggressive space competitive sponge in middle
- formiside in 2 corners
- suspend in ocean
- allow sponge to grow
results of formoside overgrowth experiment
control: 20% coverage
treated: 5%
minimal criteria to show allomone is adaptation
- isolated chemical deters predator in palatable food
- effective at native concentration
- effective against sympatric predators
- appropriate anatomical distribution
- survival after attack
- isolated chemical deters predator in palatable food, allomone adaptation
reduce confounding factors of food item
ex. spicules
- effective against sympatric predators, allomone adaptation
against co-occuring predators
- appropriate anatomical distribution, allomone adaptation
- repel before attack is fatal
- eg. digestive glands - not appropriate
- hold chemical in superficial body structures
- eg. nudibranch cirri
why is survival after attack especially important, allomone adaptation
only way to pass on the genes!
spanish dancer nudibranch
- undulation
- feeds on red sponge, maybe gets colour from them
spanish dancer allomone study
- extract and purify metabolite
- add to tasty pellet in varying concentrations
- co-occurring fish predator
- 10 control + 10 experiment food pellets offered
- offered in random order
results of spanish dancer allomone study
-sig. difference in treated vs control down to 0.05% concentration dry weight
concentration of allomone in spanish dancer body parts
- highest in egg mass
- high in dorsal mantle, digestive gland and gonad
spanish dancer metabolite
dihydrohalichondromide
- secondary metabolite
- modified from halichondromide primary metabolite in sponge prey
why is secondary metabolite in internal organs
- difficult to separate purely
- passing through digestive organs onto egg mass
de novo synthesis
made by the organism
Melibe de novo allomone
terpenoid synthesis from acetate building blocks
- tag radioisotopes to follow synthesis
- novel feeding strategy
- sensory cell detects predator
- release product through pore
saponin
- detergents
- punch holes in biological membrane
- disturb cholesterol
- if predator bites will rupture mouth membranes - irritant
echinodermata saponin
- toxins
- de novo synthesis, direct acquisition
- common in sea cucumber, sea star
sponge microbes
- up to 40% of sponge volume
- diverse phylotype
spone cyanobacteria
- found right under pinacocyte (outer membrane)
- cyano. toxin release may fn to resist predators and competitors
bryostatin
- found in Bugula bryozoan and nudibranch predator
- evidence that it is metabolize by bacteria
- may also have use in humans for anti-tumor treatment
other indirect selection of chemical defense, amphipod domicile
- cut discs of algae to make tent domocile
- choose chemically defended kelp
- put in arena with different kelps to see which it chooses
- select toxic majority of time
other indirect selection of chemical defense, arctic amphipod
- hold on to clione with pereiopods
- assume clione have chemical defense
clione chemical defense test
- fish acceptance/ rejection tests
- separate clione and fish chunks – clione rejected every time
- grind up clione and add to fish pellets – clione still rejected
- amphipod w/ and w/o clione – again, clione rejected
aposematic colouration
advertises toxicity
testing ascidian tadpole larvae aposematic colouration
- bright orange
- high E supply, good food source
- add larvae to tank w/ co-occurring predator fish
- 90% rejected
- 80% survival
- feed unpigmented larvae to same predator
- 37% rejected
- suggests predator remembers colouration and avoids
testing predator memory of aposematic colouration
- offer fish aposematic tadpoles until they are completely ignored = experienced fish
- inexperienced fish offer non-pigmented prey, accept
- inexperienced fish offered bad tasting fish - rejected or ignored
- experience fish given good tasting, dyed orange prey, ignored = remembered
- inexperienced f given tasty dyed fish - majority accepted
mimicry
edible animal resembles noxious animal
Hydrostat examples
- tube feet
- lophophore
- tentacles
- annelid body
hydrostat criteria
- fluid maintained at constant V
- deformable container
- container must resist tension
- wrapped in muscle and connective tissue
muscular hydrostat
- unconventional
- solid mass of muscle tissue, no fluid compartment
- cephalapod arm
- mollusc foot
other types of hydrostat
- any incompressible material at constant V
- eg. parenchymal cells of turbellarian
- squid tentacle
- elephant trunk
- tongue
skeleton features in stiff and hydrostat
- support
- transmit force by muscle shortening
- re-extend antagonistic muscles
- exploit mechanical advantage (force or displacement)
muscle shortening and re-extending in hydrostat example
earthworm movement
change in shape for cylinder of constant volume, D vs L
non-linear
- exponential
- diameter decreases rapidly with small increase in length
- then diameter asymptotes w/ further increase in L
mechanical advantage in hydrostat
- a small change in L makes an exponential change in D
- displacement advantage
squid tentacles
- 8 arms maximize force to hold prey
- 2 tentacles elongated to maximize displacement
how squid maximize displacement
- having large length
- -> a small change in D (at large L) = a large change in L
squid tentacle muscles
- longitudinal: undergo large extensions, obliquely striated
- circular muscles, transverse muscles, radial muscles: speed! - x-straited (shorter shortening)
wall tension
- circumferential tensile stress = longitudinal tear
- axial tensile stress = circumferential tear
circumferential tensile stress =
= 2 X axial tensile stress
= (internal pressure x radius of cylinder) / wall thickness
consequences of circumferential tensile stress
- highly dependent on r
- the larger the radius the greater the tension (like a heart shaped balloon)
- easier to inflate long thin structures if widened first (tentacles, tube feet)
- must limit/ control shape change
- must prevent ruptures
collagen
stiff, fibrous tissue
- steep stress/strain curve
- requires lots of tension to extend
direction of collagenous connective tissue fibres
- circumferentially? - avoid circum. tear, but needs to expand that way
- lattice work not parallel to direction of tension
latticework of fibers
- initially give readily
- as approach parallel, requires a lot of stress to extend further
- J-shaped S/S plot
role of collagenous connective tissue
- reinforce walls of container
2. control and limit shape change
mesoglea time-dependent properties, extension vs log time
- t_o: little-no extension, behaves like solid
- t_1: minutes-1h later, begins extension
stiffening with spicules
stiffening dependent on:
- spicule density
- spicule size
- spicule form (anisometric)
mesoglea S/S plot w/ w/o spicules
w: large slope increasing
w/o: very small slope
what is mesoglea
- connective tissue
- collagen reinforced
- extracellular matrix
- highly hydrated
- random confirmation, tangled, non-branched proteoglycan polymers
sea cucumber tissue hardening
ossicles
stress/strain plot tells us
stiffness
anisometric
axis i > axis j
-orient in direction against tension
Phases of predatory act
- Search and detection
- Pursuit
- Subjugation
abiotic conditions to defend against
- temperature variability
- UV
- exposure
biotic conditions to defend against
- competition
- overgrowth
- predation
red queen hypothesis
RQ ordered nave to run on ground moving backwards faster and fast - must continually adapt to change
meaning of RQ hypothesis
predators and prey interact in a way that imposes selection in a reciprocal fashion
-force each other to continually adapt
search and detection phase defences
- camouflage, transparency, crypts, mimicry
- size, hiding
- peripheral vision
- activity patterns, migration
pursuit stage defense
- running: pattern, speed
- pooling behaviour (grouping)
subjugation phase defense
armour, body size, autonomy, toxicity, secretions
selection in the prey is generally strongest in which phase
whichever phase their predator is weakest in
hypotheses of adaptation must be tested
- phylogeny
- effectiveness
- consider other ideas
test hypotheses of adaptation, phylogeny
is trait derived or ancestral
test hypotheses of adaptation, convergence
- lab and field experiments
- correlation in space and time
- evidence of convergence
types of defensive traits
- structural
- chemical
- behavioural
- induced
induced defences =
phenotype plasticity
parts of gastropod shell
protoconch whorl spire body whorl aperture outer lip
shell-crusher strategies
- apertural lip crush
- spire crush
- apertural lip peel
aperture lip crush
- outer lip of shell most vulnerable
- crush in molar
spire crush
-put spire close to fulcrum of claw to increase force advantage
gastropod shell defences against crushing predators
- overall thickening of shell
- thickened apertural lip
- apertural teeth
- narrowed aperture
- reduced spire
- thickened tubercles and varices
helmet snail, adaptation to shell-crushers
- apertural teeth strengthen outer lip
- very narrow aperture\
cone snail, adaptation to shell-crushers
- reduced spire
- thick walls
- dissolve old interior layers
cowries, adaptation to shell-crushers
- no spire
- aperture teeth
- very narrow aperture
tubercles, adaptation to shell-crushers
studs, spines
porcupine fish
- related to puffer
- very powerful jaws
- robust teeth
- prey = tropical gastropods
- RQ hypothesis
effect of tubercles on crushing attempts
- increases effective diameter
- reduce stress
- focus force
effect of tubercles on crushing attempts, increase effective diameter
- can’t get shell as close to fulcrum
- reduce mechanical advantage of jaws
effect of tubercles on crushing attempts, reduce stress
-distribute force over broader are of shell
effect of tubercles on crushing attempts, focus force
-increased chance of damaging predator
critical size
size that gastropod must be to avoid predation
critical size of congeneric species pair (+/- spines)
-gastropods w/ strong spines have lower critical size
experimental manipulation of tubercles
- file off to compare same species, reduce confounding factors
- critical length smaller in spines gastropods
survey of gastropod family Thiadidae
- structures only found below 40º latitude
- no structures above 40º
correlation between Thiadidae structured fishes and predators?
- 2/3 of crushers are found in tropics
- gastro. w/ adapted shells appear in fossil record around Triassic
- shell crushers around Jurassic
Lake Tanganyika
- 2nd largest FW lake
- gastropods and brachyuran crabs
- FW gasto. usually have thin shells, not here
- for any given shell length snails had thicker shell than snails not in lake T
- same w/ crab chela
SEM provides
- magnified images
- 3-dimensions
- shape and surface topography
- large depth of field
- non-reversed images
how to get 3-dimensionality with 2D image
- shading!
- light reflectance
- exploit the fact that our eyes are adapted to sun shining down on objects
SEM basic instrument components
- electron gun + pole piece
- lenses
- scan coil
- secondary electron detector
- monitor
compound light microscope basics
- light, glass
- E source focused and bent by condensor
- tranparent specimen for light to pass
- objective lense expands beam and therefore image
- magnification achieved by glass concavity
SEM basics
- electrons , EM lense
- energy source is e-
- focus beam w/ magnetic field
- scan coils rapidly deflect beam back and forth
- secondary e- emitted
- magnification is aspect ratio between actual and output screen
rapid scan rate, SEM
- low resolution
- real time response to image adjustments
slow scan rate, SEM
- high resolution
- delayed response to image adjustments
how to focus SEM
- intermediate scan rate
- reduce area of scan
defensive behaviours
- avoidance
- escape
- retaliation
distinguishing features between avoidance and escape/retaliation behaviour
nature of the stimulation
-direct vs indirect
avoidance behaviour, olive snail
- local species
- surface at night
- burrow during day
- enormous foot
- diel activity pattern
- protection from visual predators (birds, sea stars)
olive snail experiment
- aquarium w/ sediment
- seastars in separate tank w/ water flow through
- cue induces hiding
- continued cue reduces surfacing behaviour
Zoea larvae
- anomurans, brachyuran
- multiple zoea stages
- 1st stage no migration
- 1st stage responds to shadow reflex = sinking behaviour
- ctenophore kairomone ?
zoea larvae experiment
- zoea in glass tube
- different levels of irradiance reduction
- descending density increases at 50% light attenuation = shadow reflex
- add ctenophore kairomones == sig. difference in descension response at even lowest attenuation level
Sabellidae escape behaviour
-startle reflex
startle reflex criteria
- all-or-none response
- high threshold
- short latency
startle reflexes governed by
giant axons
startle reflex, all-or-none
- non-graded
- don’t withdraw partially
startle reflex, high threshold
-need strong stimulus to elicit
not feather duster, sabellidae
startle reflex, short latency
- minimal t period btw stimulus and response
- rapid neural circuit due to giant axon
velocity of action potential, V =
kD^e
k = constant
D = axon diameter
e = exponent (usually around 0.5)
from velocity of action potential equation,
V highly dependent on diameter
-giant axons significantly faster
giant axons often dedicated to
defensive behaviour
Aglantha digitale, giant axons
- hydromedusa
- local, open ocean
- unique fishing behaviour
- giants axons unique use – 2 uses
Aglantha fishing behaviour
- slow swim
- circular muscle contractions of bell
- swim up in water column
- flip over w/ tentacles up
- descend slowly
- catch plankton w/ tentacles
Aglantha escape swim
-rapidly swim away when disturbed
Aglantha giant axons
- ring giant: interneuron, nerve ring around periphery of bell
- radial motor giants: giant motoneurons
interneuron
neutron between sensory and motor neurons to send messages btw the two
study of Aglantha giant axon
- measure action potential w/ electrodes
- find 2 different action potential speeds on same axon
action potential
-depolarization by opening of ion channel, often Na
how does Aglantha have different action potential speeds
- 2 different types of ion channels
- fast a.p. = Na ion
- slow a.p. = Ca ion
Tritonia nudibranch, neurons
- seapen feeder
- dv flexion if touched by seastar
- pattern generator neurons create repetitive movement
lobster defenses
- escape, tail-flip
- retaliation, claws, antennae
- defense, armour
spiny lobster
long, spiny second pair antennae, damaging
slipper lobster
tank-like
thick carapace
tenaciously clinging periopods
lobster tail-flip
clawed lobster: giant axons mediated
spiny, slipper: no giant axon
3 lobster ‘types’ offense vs defense experiment
- tether animals to stakes
- 5 intact of each, 5 modified
- slipper modified: tape back grasping claw
- Spiny: cut off second pr. antennae
- Clawed: remove cheliped
- record mortality after 4 and 24 h
results of lobster offences vs defense experiment
- manipulated had higher mortality in all species
- slipper lobster had very low mortality in all cases
- clawed had highest mortality in all cases
- retaliation not the best defense
induce defences, conditions for selection
- heterogenous environment
- reliable cue signaling predator risk
- conditional phenotype reduces predation risk
- costly when predator absent
Nucella induced defense of egg capsules
- 2 islands near Bamfield
- different thickness of egg capsule walls
- island 2 has higher density hole-drilling isopods
specific time in development that organism can respond to envrionmental cue
window of competence
Rotifer features
- paired ciliated cephalic lobes, foot w/ 2 toes and adhesive pedal gland
- jaw apparatus (mastax) lined w/ chitonous teeth (trophi)
- many have rigid body w/ reinforcing cytoskeletal elements = lorica
Keratella induced defense
- freshwater rotifer
- less than 1mm
- some w/ greatly elongated posterior spine
- chemical affluent from Asplanchna induces long posterior spine in Karetella
Asplanchna rotifer sp.
- feed on karatella
- parthenogenic offspring - diploid egg develops in mother w/o fertilization
what kind of chemical does Asplanchna release to cause change in Keratella
kairomone
observations of predator-prey interactions between rotifers
attack: encounter - no significant difference btw long spine and short spine
capture: attack - very sig. diff., LS captured about 1/2, SS about 3/4
ingested: capture: sig. diff.
why asymmetrical spine elongation?
-possibly to conserve energy, if 1 does the trick why waste E on 2
Branchionus variabilis rotifer morphological AND behavioural polyphenism
- rotifer
- elongate spines (both) in presence of pred. cue
- facultative epibiont
- Asplanchna cue induces behaviour change – attach to cladoceran for protection
Costs of induced defense, rotifers
- eggs? females amictic so no effect on egg production
- but does reduce mictic success– less resting eggs w/ higher [kairomone]
Rotifer life cycle
- amictic female (2n) can reproduce w/o fertilization over and over
- in bad conditions amictic female produces mictic (1n) – fertilization – resting egg (mictic fm)
Cladoceran inducible defense
- Daphnia spp.
- ‘exuberant morphs’
- helmets, armour
- defense against gape limited predators
Resource allocation, Cladoceran inducible defense
- exoskeleton growth requires ca. 20% more energy for crested
- reduces reproductive output by ca. 60/400 lifetime eggs
Membranipora membranacea inducible defense
- bryozoan, asexual, oldes zooid at centre, colony has 4mth life-span
- nudibranch predator colour matches
- calcified sidewalls
- in presence of Doridella (nudi.) peripheral zooids respond- develop spines around walls
cost of Mm spine growth
reduce Mm growth rate
reduce nudibranch feeding
nudibranch chemical that causes induced defense in Mm
kairomone
Acanthina gastropod
- gastropod predator of barnacles
- have labial tooth
- ram tooth into barnacle operculum plates
Acanthina induces what defense in Cthamalus
bent morphology
Possibilities for occurrence of bent Cthamalus morphology
- barnacles w/ fixed bent genotype selectively recruit to substrate w/ snail mucus
- barnacles have conditional bent phenotype induced by snail mucus
to test Possibilities for occurrence of bent Cthamalus morphology
- plastic plate, drill depressions for settlement
- place in field, wait for settlement, map
- put predator mucus on plate
- wait again
- re-map and compare
if barnacles have inducible morphology
expect the same amount of bent morphology in the recruits before and after predator presence – no selective recruitment
if barnacles w/ fixed bent morphology are selectively recruited
-expect more bent recruits after mucus –recruit bent barnacles in presence of predator
results of testing possibilities for occurrence of bent Cthamalus morphology
3 plates show near equal proportions before and after
= no selective recruitment
cost of bent morphology, Cthalamus shell mass : body length
= slightly lower slope in bent morphology, some effect but not alot
cost of bent morphology, Cthalamus # eggs : body length
- significant difference
- bent morphology much less eggs, particularly at low body size
- trade-off w/ fecundity
Nucella induced defense,
crabs feed on by peeling back apertural lip
- predator affluent induces aperture lip thickening
- Predator + prey in flow through tank to Nucella = even greater change! detect affluent of damaged conspecific
Littorine, periwinkle snail induced defense
- European green crap voracious invasive predator
- crab induces thicker shell
- thicker shell also appears to be occurring over time
induced predator phenotype, green crab
- if fed thicker walled snail – w/i a few moults develop more powerful chelipeds
- -arms race
light =
particles of energy
= photons
photons travel in
waves
visible light
400 -650nm
to perceive light must have
photopigments
most common photopigment
rhodopsin
what do photopigments do
- absorb photons
- open ion channels
- change cell membrane voltage (depolarize, hyper polarize) = bioelectric potential
quality of our visual field =
visual accuity
ability to distinguish details, visual
resolving power
-how close together 2 dots can come and still be resolved as separate
Visual acuity depends on
- resolution
2. contrast
Resolution
-image detail, resolving power
how resolution impacts visual acuity
- density of photoreceptors (high density = high detail)
- focusing ability of lens
contrast, impact on visual acuity
- differential light absorbance (btw object, bckgrd)
- differential light scattering (btw obj, backgr)
example of contrast
- words written in a box
- no contrast
- can’t see
- no difference in light absorption and scattering of words relative to background
seeing transparent tissues
- we can see because of contrast
- differential light absorption/refraction of the tissue
photic zone of open ocean
euphotic = 200m
disphotic zone
200-1000m
- sufficient light for vision but not PP
- mesopelagic
zone of no light
Aphotic
bathypelagic
options for avoiding search/detection phase in the pelagic zone
- mirrored surfaces
- counter shading/illumination
- transparency
- all minimize contrast
Effectiveness of mirrored surfaces, pelagic
- if predator approaching from side
- effective b/c background homogenous
counter shading/illumination
- lighter ventral surface (predator bellow)
- light emitting cells on ventral surface
- reduces silhouette/shadow
how to achieve counter shading
Guanine crystals
-2 types: cuboidal, flat
cuboidal guanine crystals
- small, jumbled
- scatter reflected light
- matte white surface
- suitable for lightening ventral surface
flat guanine crystals
- large, overlapping
- reflect light uniformly
- shiny
- eg. fish scales
transparency
- camouflage regardless of predator angle
- multiple convergences
- highly correlated w/ pelagic lifestyle
examples of transparency
- hydromedusa
- larvacean
- ctenophore
- pteropod
why no transparency in terrestrial habitats
-refractive indices
air = 1 , SW = 1.35, cytoplasm = 1.34 - 1.55
-much easier to achieve in water
-terrestrial organisms require more robust (often opaque) structures to hold up against gravity
-more places to hide in terrestrial
-UV protection
how to achieve transparency
- thinness
- eliminate pigments
- surface micro-bumps
- ultrastructural specialization
thinness
thin tissue = less opportunity for light refraction
Problems with eliminating pigments
- eyes require melanin
- food - digested tissues are opaque
- sunscreens - seen by UV vision
Phronima sedentaria transparency
hyperiid amphipod
- fibre optic eye - smaller, simpler, less pigment
- eat tunicate and hide in its tunic
fibre optic eye
crystalline cone – focus light down to reticular cells – minimizes needed eye size
how to ‘hide’ gut contents, transparent organisms
- red gut epithelium
- particularly protects against bioluminescent prey
why use red tissues
- bioluminescence typically 470nm (blue-green) -doesn’t penetrate red
- also b/c red absorbed first in water column?
problem w/ sunscreen and transparency, experiment
- FW fish preying on daphne w/ photoreceptors
- videotape both in aquarium
- pursuit distance = when fish turns and pursues prey
- PD same max w/ and w/o UV
- w/o UV distribution shorter tails, higher max
- more shorter PD w/o UV
Copepod sunscreen carotenoids
- astaxanthin
- scavenges free radicals (ROS)
- when fish predator is present reduce level of pigment
- trade-off
surface microtuberances, transparency
- help reduce contrast
- reduces ability to see organism outline, blurs outline
- less surface area to refract light
Bioluminsecence
- 80% of pelagic ocean animals
- major light source in mesopelagic
- mostly blue emission (470nm)
- most NOT from bacteria
bioluminescence original evolutionary origin
- antioxidant hypothesis
- originally likely to scavenge for ROS
- oxidation gives off light (side effect)
original bioluminescent molecule
Luciferin
luciferin
- absorbs photons of light
- electron excitement
- electrons fall, give off E as light when oxidized
- requires light to give off light at longer wavelength
- requires luciferase or photoprotein
bioluminescence definition
- chemical reaction w/i organism that emits light
- create light w/o light
luciferase
enzyme that catalyzes luciferin reaction
photoprotein
- molecule w/ binding sites for luciferin and O2
- co-factor (usually Ca++) causes conformational change of photoprotein allowing interaction
functions of bioluminescence
- communication, sexual signal
- attraction of prey, lure
- illumination of prey, flashlight
- defense from predator
functions of bioluminescence, predator defense
- startle
- counterillumination (hiding)
- misdirection
- distractive body part (dropped off)
- burglar alarm
Burglar alarm hypothesis
organism 3 preys on 2, preys on 1
- 1 emits light when attacked by 2
- light attracts 3 to eat 2
biomineralization
-organisms produce solid from inorganic precursor
mineral vs biomineral
-biominerals are composites = mineral + organics
biomineralization in
Archae Bacteria Protoctista Fungai Plantai Animalia
mineral
- solid consisting of inorganic anion + cation
- defined by chemical composition AND morphology
- crystalline or amorphous
Example of different crystal morphologies
CaCO3 occurs as vaterite, calcite, aragonite, or amorphous
organic component, biomineral
- helps control biomineralization process
- becomes incorporated into mineral component
- can influence mechanical properties
types of biominerals
- ca. 60 different types
- common cations: Ca, Si, Fe, Mn, Zn, Cu
- common anions: carbonate, phosphate, sulphate
functions of biominerals
- protection from predator, environment/ armour
- feeding (radular teeth, jaw)
- support/ stiffen skeletal
- anchorage
- storage for important ions
- sensory reception
- statocyst
- magnetite crystals in magnetotactic bacteria
- diatom frustules
biomimetic
synthetic methods that mimic biochemical processes
mechanism of biomineralization
- space delineation
- subdivision of space by org matrix
- generating saturated solution
- nucleation
- growth and shape modulation
- cessation
mechanism of biomineralization, space delineation
- sponge spicules, space inside ring of cells
- gorgonian spicule, space inside one cell
- echinoderm ossicles, space inside multinucleated cell
Bivalve shell, space delineation
EPS - extrapallial space
- between mantle fold and shell biominerl
- where ions are deposited and diffuse
Bivalve shell, minerals at site
- CO3 from active transport of CO2 from environment
- Ca++ brought in using ATP powered Ca/H antiporter within mantle fold
Mytilus prismatic shell layer
-organic matrix surrounding calcite crystals
Nacreous gastropod shell layer
-aragonite crystals
gastropod glycoprotein material and polymorph formed
- original: aragonite, calcite
- Forn: vaterite
crack propogation, composite material
- much more energy for cracks to persist across different materials
- softer materials generally dissipate crack energy
plywood construction
- longitudinal axis shifted in each successive layer
- stiffens (increase flexural stiffness)
- strengthens by resisting crack propagation
- mollusc shell has same form
examples of biomineral functions
- statocyst
- magnetite crystals in magnetotactic bacteria
- diatom frustules
Energy to propogate crack
proportional to diameter at tip of crack
-having a space in the structure (eg. holes) increases the diameter of the crack, therefore increases required energy
why shell dissolution (organisms own shell)?
- enlarge aperture
- enlarge living space
- buffering
- remodelling
- mineral recycling
shell dissolution, enlarge aperture
- waterflow
- keyhole limpet
- scaphopod
shell dissolution, enlarge living space
-cone snail dissolves inner layers of overgrown shell walls
shell dissolution, buffering
-anaerobic respiration creates acids that must be buffered
shell dissolution, remodeling
- may lose or change shell at different life stages
eg. nudibranch
shell dissolution, mineral recycling
dissolve and store CaCO3 to recycle into new exoskeleton
OA
increased atmos CO2
- 40% of ff’s in atmos.
- pH of ocean 0.1 lower than pre-industrial
- pH 0.3-04 units lower by 2100
- depression of carbonate ion concentration
ocean carbonate reactions
CO2+H2O–H2CO3
H2CO3 –H+HCO3
HCO3- – H + CO3 2-
H+ + CO3 2- — HCO3 -
results of ocean carbonate reactions
- lower pH
- increase in [H] results in -reduction of carbonate ions (CO3 2-)
- increase in bicarbonate (HCO3 -)
- calcium carbonate dissolution
CaCO3 dissolution and saturation horizon
- dissolution causes saturation horizon to shoal threatening to dissolve previously deposited structures
- CCD higher form aragonite
amount of marine species that are molluscs
23%
OA ecosystem impacts
- Food webs
- Competitive interactions
- Ecosystem services
- economic importance
OA impact, pteropods example
- pelagic, huge swarms, large importance in food web
- aragonite shell, begins to dissolve w/i 48 h or understaurated waters
mollusc embryonic shell
- initially amorphous CaCO3
- less able to isolate calcifying fluids
- strong kinetic demand for CaCO3 precipitation
- limited energy budget
consequence of initially forming amorphous CaCO3 shell
-less stable than calcite, aragonite
why are larvae less able to isolate calcifying fluids
periostracum is more leaky than adult form
sea urchin and OA
- sea urchin lives across variety of CO2, pH
- larvae have calcareous spicules supporting larval arms– fundamental to functions
Adaptive capacity to respond to OA, study
- collect sea urchin adults
- fertilize eggs, rear large under normal and elevated CO2
- measure features
- larval development and morphology showed little response
- frequency of allele transcripts (skeleton building genes) substantially different
- natural selection in low pH condition
- genetic variation could be reservoir of resilience
for a population to respond to change
- Genetic variation w/i population
2. Population robust w high reproductive capacity
groups of broadcast spawners
almost all: - echinoderms -cnidarians -bivalves some mollusc
Problem w/ external fertilization
- high risk of wasted gametes
- only a few hours in water until non-viable
test magnitude of external fertilization problem
- inject sea urchin w/ 0.5 M KCl to make spawn
- have eggs waiting at different distances away
- determine amount fertilized, easy to count, fertilization envelope
test magnitude of external fertilization problem, results
20% or less fertilization at distance greater than 20cm
test magnitude of external fertilization problem, implication
two urchins must be spawning at near exact same time and location to be successful
fertilization success may be increased if
- cluster of organisms spawning
- higher current speed (greater than 0.2 m/s)
allee effect
-population density effect on rate of population increase (#offspring, individual)
strategy to minimize gamete waste
- reproductive aggregations
- synchronized release of gametes
- sperm attractants
synchronized release of gametes
- key to respond to environmental cue
- eg. corals, hydrozoans
Spirocodon hydromedusae spawning cue
light
- sperm develop beneath epidermal epithelium
- loss of microvilli = pore formation – allows sperm release
- gaps appear in response to onset of darkness and heal shut w/i 40 min
- darkness must remain for 30+ minutes
GBR spawning
- mass spawning event
- all release gametes at same time in ‘balls’, packets of eggs and sperm
- 5-8 days after new moon in Oct.
Spawning cue for GBR
- increased SW T, photoperiod
- Lunar cue
- Light-ff cue (only after sunset)
why October?, GBR
wind speed lowest in Oct.
- influences currents
- strong wind dissipate gametes too much
Caballes spawning cue
- crown of thorns starfish
- polyp predator
- various cues in lab to try to induce: T increase
- males have lower threshold to release than fm in most scenarios
sperm attractants
- spawned eggs release chemical signals to modify sperm movement
- species specificity
sperm attractant molecules
Ascidians: suffocated steroid
Sea urchin: peptides
Abalone: tryptophan
Abolone sperm attractant experiment
-tryptophanase shows sperm attractant improves fertilization success
acrosome reaction
- sperm have acrosomal membrane and and enzymes
- after contacting egg jelly, membrane breaks down, acrosomal enzymes digest jelly coat so coat sperm/egg can fuse
Bindin
- gamete recognition protein of sea urchin
- exposed on acrosomal process acrosome reaction
- bindin receptors on vitelline envelope of egg
- facilitate conspecific gamete binding
simultaneous fusion of 2+ sperm
polyspermy
consequence of polyspermy
-fatal for egg
blocking polyspermy
fast- membrane depolarization upon fusing, temporary
slow: cross-linking of vitelline envelope
male density and reproductive failure in spawning organisms
low density = low sperm concentration
high density = polyspermy
different alleles of bindin
- LOW sperm density = fertilization enhancement
- HIGH sperm density = minimizes polyspermy
Red sea urchin bindin alleles
LD - greater success at low m density
HD - greater success at h.d.
change in concentration of Red sea urchin bindin alleles over time
- animals 200 ya had higher LD – lower population density
- animals now have higher HD frequency – higher population density
- increased risk of polyspermy
Aplysia fertilization
California sea hare
- simultaneous hermaphrodites
- copulate (internal fert.)
- breeding seasons (spring-summer)
- reproductive aggregations (12-15 individuals)
- egg laying (packed in jelly string, initially sticky)
- complex life history
Aplysia life cycle
- eggs w/i capsule embedded in string of jelly
- veliger: to 34 d, planktotrophy
- metamorphosis 34-37 doh
- juvenile 40-60 doh
- adult has siphon, parapodium, tentacles
- adult lays egg mass
hermaphroditic challenges
must:
- keep gametes separate
- prevent self-fertilization
- store self and received sperm
- have fertilization chamber
- encapsulate eggs
hormonal control of egg laying
- initiates egg laying behaviour, back and forth waving of head to to attach egg mucus to substrate
- Aplysia abdominal ganglion (visceral)
abdominal ganglion
- surrounded by connective tissue sheath
- contains bag cells
bag cells
- neurosecretory cells
- neurons w/ axons
- secrete egg laying hormone (ELH)
- self-activitating
ELH
- small peptide (36 a.a.’s)
- released from vesicles during bursts of bag cell depolarization
- autocrine and endocrine activity
- initiates ovulation
ELH paralogs
Aplysia genome has 5 paralogs
- duplication and divergence
- 1 undergoes tc, translation, processing in bag cells - generate ELH
- tc, tl in albumen gland = attraction
attractin
pheromone
peptide
58aa
other Aplysia peptide pheromones
enticin
temptin
seductin
contact pheromones
physical contact w/ recently laid egg mass intiates release of ELH
Carcinus reproduction
- European green crab
- copulation window - post- female ecdysis
- guard mate
- penis from base of last walking leg
- pleopods 2 push sperm along groove into female
- hold brooded eggs onto abdomen w/ pleopods
Carcinus uridine disphosphate
UDP
- in fm urine
- waste product of chitin biosynthesis
- i.e. signal of ecdysis
consequence of UDP production
- activates male mating behaviour
- fm sex pheromone
- males show seasonal sensitivity/response to UDP (highest in mid season)
basic life history patterns
- planktotrophic larvae
- lecithotrophic larvae
- Aplanktonic (direct development)
planktotrophic vs lecithotrophic fecundity
plankt: high
lecith: low
aplanktonic: very low
Brisaster life history
- heart urchin
- facultative planktotroph
Gunnar Thorson
- Danish marine biologist
- pioneer in larval ecology
- influential publications
Thorson’s law
- species producing feeding larvae rare at higher latitudes and deep depths
- -trend exists but many exceptions
optimal life history theory
Vance 1973
- important variables affecting recruitment of juveniles:
1. fecundity
2. developmental time
3. mortality risk - all depend on egg size
optimal life history theory, fecundity
-negative linear rltship w/ egg size and fecundity
optimal life history theory, development time
negative linear
egg size vs development time
optimal life history theory, mortality
positive linear
development t, mortality risk
Vance prediction for optimal egg diameter
U-shaped
-smallest and largest have highest recruits
problems with Vance theory
- empirical data
2. phylogenetic reconstructions
protonephridium
- terminal cell = ultrafiltration
2. duct cells = selective absorption
Neptunea egg capsule
1 viable embryo
many nurse eggs
Liracbuccinum egg capsule
also have nurse eggs but variation in viable embryos and # nurse eggs
- 1 v.e., 130-170 n.e.
- 3-12 embryos, 10-40 n.e.
Liracbuccinum hatching size vs hatchlings per capsule
- negative linear
- less hatchlings = greater hatching size
parental provisions of eggs
yolk
albumen
nurse eggs
value of encapsulating egg material, Conus
-length of t w/i egg capsule directly correlated w/ thickness and puncture resistance of egg capsule
larval defensive strategies
- spines
- crown-of-thorns seastar: large pink larvae w/ saponins
majority of inverts life history
planktonic
back to paleozoic
why have pelagic larval stage`
- ancestry
- dispersal
- resource availability
- predation avoidance
benefits of dispersal
- resources
- oxygen
- reduce competition
- mating – heterogeneity
larval duration adapted for dispersal
very short
test abundance of predators in pelagic relative to benthos
- float brachyuran larvae in water on line weighted down
- one line at bottom, one at 3m
- glue larvae onto line
- pull up after 3hrs
- tally number eaten
results of predator abundance test
- more benthic larvae lost
- more larvae lost at night
expected consequences of dispersal
- extensive gene flow btw distant populations
- low speciation rates, minimal local adaptation
- low extinction rate
why does dispersal cause low extinction rate
- spreads risk
- survive local catastrophe
evidence for expected consequences of dispersal, gene flow
low genetic differentiation among populations
evidence for expected consequences of dispersal, minimal local adaptation
extinction, speciations in fossil record
evidence for expected consequences of dispersal, low extinction rate
spread of invading species
test of genetic differentiation, nudibranchs
- 2 species, similar in many ways
- rocky shores of Great Britain
- feed on bryozoans
- annual life cycle
- spawn during winter
- 1 has longterm planktotrophic larvae (3mth), other 1-2 days
- map distribution
test of genetic differentiation, nudibranchs, long-term planktotrophic larvae
- gene w/ 3 alleles
- alleles expressed in pretty similar frequencies over large area
- lots of genetic exchange
- long time, lots of time for exchange
test of genetic differentiation, nudibranchs, short-term planktotrophic larvae
gene w/ 2 alleles
much different allele frequencies around isles, even populations close together
-high heterogeneity
-consistent w/ short-lived larvae
gastropod shell, embryo, larvae, etc.
transitions in shell whorls mark stages of development
Thorson’s shell apex rule for gastropods
protoconch retained at apex of shell
-size and shape of protoconch indicates planktotrophy or lecithotrophy
duration of fossil gastropod species, planktonic vs non-planktonic
planktonic species appear to have persisted significantly longer, 12-4my
-non-planktonic max 6-8, majority 1-2my
neogastropod pelagic speciation
35-65 MYa
- Atl coast
- trend towards increased non-pelagic species
- speciation?
Varnish clam
- native to Korea, Japan
- introduced to Vancouver harbour 1980s
- spread to SOG and Washington by 1998
evidence of unexpected consequences of dispersal
- test of species selection
- genetic structure
- paradox of rockall
Phylogenetic test of species selection
- must know phylogeny to consider something speciation
- if ‘burst’ of speciation after a trait evolved then probably trait selected for
- if trait is on different tree branches then not selected for, not speciaition
test speciation in cone snails
- 70 species
- aplanktonic secondarily adapted for found on different branches
- no evidence of selection
unexpected consequences of dispersal, genetic structure
- unexpected genetic heterogeneity
- more genetic variation along coastline than expected
Paradox of Rockall
- NAtl, 400km W of land
- 30My isolation
- 110ft diameter, 63ft high
- lots of inverts live there
- must have dispersal stage to get so far..
- but all aplanktonic..
- only self-recruits would be likely to keep it populated
Conus, Cape Verdes Archipelago
- 600km off W Africa
- 50 endemic species
- aplanktonic
- 2 clades
- 2 founder species, egg mass rafted to islands
local recruitment
- larval retention
- self recruitment
- may have been founder of wide dispersal but return phase was lost
- if parents successful in habitat then probably good
mechanism to control larval dispersal and recruitment
-environmental cues
flood tide transport
- Ebb tide: low S, Megalopae remain on bottom
- Flood tide: M ascend into water column as S rises
- turbulence promotes continued swimming
- end of flood tide, M descend as salinity drops
- brought back to parental habitat
- take advantage of prevailing currents
settlement
- behavioural process
- cessation of swimming
- adherence to substrate
- REVERSIBLE
Metamorphosis
- developmental process
- loss of larval characters
- emergence of functionalization of juvenile characters
- NONREVERSIBLE
metamorphic competence
- stage of life
- maturation great enough for metamorphosis
delay of metamorphosis
- competence and induction
- possiblity variable per species
consequences of delay of metamorphosis, negative, abolone
Abalone
- lecithotrophic larvae
- 11 days
- delay in absence of inducer
- reduced post-larval survival
consequences of delay of metamorphosis, no effect, Phestilla nudibranch
- facultative planktotrophy
- delay in absence of metamorphic inducer
- no effect found on post-metamorphic lifespan or fecundity
consequences of delay of metamorphosis, positive effect, moon snail
- continue to grow after reaching competence
- if meta. delayed, get larger, release from predators, may increase survival
Metamorphogenesis
- loss of cells/tissues
- De novo differentiation of cells/tissues (set-aside cells)
- remodelling of larval cells/tissues
why is considering metamorphogenesis important
- sometimes metamorphosis is a minimal change of tissues - ex. slipper limpet only loses velar lobes
- sometimes its a huge change! ex. sea urchin!
sea urchin metamorphogenesis
- catastrophic metamorphosis
- juvenile rudiment small mass of tissue inside of larvae
- complete change of form must be accompanied by changes in internal cells/tissues
induction of settlement and metamorphosis
1 associative
- gregarious
- avoidance
- all chemical cues
Associative settlement and metamorphosis cue
- prey
- habitat quality indicator
- water flow indicator
Abalone induction cue examples
- chemical from red coralline algae
- phycobiliprotein
- indicator of good water flow
environmental induction cue come from conspecific
- sexual reproduction
- good habitat indicator
- protection of new recruits
Associative settlement and metamorphosis cue
environmental induction cue come from an organism of different species
gregarious settlement and metamorphosis cue from
conspecifics
gregarious tube-dwelling polychaete
- Phragmatopoma
- cement holding tubes together induces metamorphosis
sand dollar gregarious settlement
- adult chemical component induces S, M
- adults exclude tanned
- tenaid predator of larvae
- S, M w/ adults offers protection
Avoidance settlement and metamorphosis
- environmental cue
- inhibits metamorphosis
- superior competitor
- predators
thickness around boundary layer as Re # increases
becomes thinner
mechanisms to capture suspended particles
filtering scan and trap direct interception adhesion ciliary mechanisms
critically important for oyster reef success
height
primary source of DOM in ocean
exudate from phytoplankton
epidermal epithelial cells of marine inverts have intrinsic membrane proteins in the apical cell membrane that enable import of dissolved organic molecules against concentration gradient
sodium-dependent co-transporter
endosymbiont acquisition of microbial symbiont from parent
vertical transmission
enzyme in hosts of photosynthetic endosymbionts to prevent ROS damage
superoxide dismutase
excess photosynthate released by corals as
mucus
Solemya reidi bivalve have ctenidia populated by prokaryotic endosymbionts that utilize
hydrogen sulfide as energy source
skeletons perform functions by accommodating forces, they may
- resist force
- transmit force
- store energy of force
mechano-enzyme directly responsible for muscle cell shortening
myosin
obliquely-striated muscles have greater __ than cross-striated
working length
internal projection of arthropod exoskeleton analogous to tendons
apodemes
describe S/S plot of highly resilient material
- S/S plots during loading and unloading would be exactly the same
- length of material before and after would be same (extension)
internal fertilization accomplished either by
- transfer of spermatophores
- direct introduction via organ (penis)
