BIOL 321 Flashcards
where does the vast majority of primary production occur
upper 50m
depth of sunlight
200m
waters oxygen carrying capacity
2.5% of air by volume
oxygen movement in water
300,000X slower than in air
Reynolds number
Re
intertial : viscous forces
low Re
highly viscous
small fish in water
all movement requires propulsion (no gliding)
Linnaeus taxonomic classification scheme
Kingdom Phylum Class Order Family Genus Species
Taxon
any named group of organisms that is sufficiently distinct to be assigned to a category
Monophyletic
a group derived from a single common ancestor that contains all descendants of that ancestor
paraphyletic
group derived from a single common ancestor that does not contain all descendants of that ancestor
paraphyletic example
Invertebrates, reptiles
percent of described species that belong to phylum Chordata
5%
Largest extinction in history
P - T extinction, 250mya
95% of species-level diversity lost
Binomic species name
Generic name specific name
italicized on computer, underlined by hand
Abbreviating species name
Generic name can be abbreviated (A. species) after being spelled out once, only if there is not another genera that starts with the same letter
Species name with researcher who described it
sometimes first name is put after the species name, not underlined/italicized
Balanus amphitrite Darwin
unless described by Linnaeus then species name is followed by L.
may also be followed by date
Euphausia superba, Dana 1858
When a species is reclassified
descriptors name is placed in brackets Ilyanassa obsoleta (Say)
proposed replacement to Linnaean system
PhyloCode
rankless
domains
3 - higher than kingdoms
bacteria
archaea
eukarya
kingdoms
6 Eubacteria (bacteria) Archaebacteria (Archae) Fungi (Eukarya) Protista (Eukarya) Planti (Eukarya) Animalia (Eukarya)
Eukaryote
cells contain nuclear and membranes around organelles
convergence
independent evolution of similar features in species of different lineages
features resemble each other that are not from an LCA
Analogous features
convergence
Plesiomorphic
primitive, ancestral, original trait
ESTs
expressed sequence tags
Ecdysozoa
molting animals
2 protostome clades
Ecdysozoa
Lophotrochozoa
Homologous features
ancestral
Apomorphic
derived, advanced trait
A novel evolutionary trait that is unique to a particular species and all its descendants and which can be used as a defining character
direction of evolutionary change
polarity
evolving towards ancestral or derived character?
classic taxonomy
Evolutionary Systematics
Evolutionary Systematics weighting
characters with more phylogenetic information are given more weight
how Evolutionary Systematics are constructed
homologous characters used to deduce general relationships
resemblance taken in to account before completed
Evolutionary Systematics and paraphyletic groups
not troubled by
i.e. groups like Reptilia are ok in classic taxonomy
Evolutionary Systematics downfalls
slow
requires experience
lacks objectivity and standardized methodology
Phylogenetic Systematics
Cladistics
how Cladistics are constructed
only with synapomorphies
Cladistics and paraphyletic groups
NOT ok
all taxa must contain all descendants of an ancestor
Cladistic benefits
standardized methods and procedures
accommodates molecular data
does not require experience like Evolutionary Systematics
Synapomorphy
shared character derived from common ancestor in which it originated
evolutionary novelties
How to construct Cladistics with molecular data
start at same spot along code
compare 1 bp at a time
if b.p.’s are same = no phylogenetically useful info
1 bp difference = 1 evolutionary event
Problems with molecular data in Cladistics
deletions/insertions - sequences have to be re-aligned
LBA
long branches attract
- rapidly evolving gene sequences produce longer branches that tend to group closely together
- a form of systematic error whereby distantly related lineages are incorrectly inferred to be closely related
- enough changes have occurred that lineages look similar
When b.p. changes are believed to have occurred too many times, erasing signs of molecular evolution
Saturated sequence
two-branched
biramous
as in crustacean appendages
subtidal
live below tidal line
rarely exposed to air
planktonic
mobile w/ negligible locomotion
subject to currents
drift
deposit feeder
ingest sediment, digest organic material as sediment moves through digestive tract
single branched
uniramous
insect appendages exclusively uniramous
ectosymbiont
live near or on body of other participant
both symbionts benefit
mutualism
one symbiont benefits while the other is neither benefited nor harmed
commensalism
term for symbiont that benefits in commensalism
commensal
Saturation
reduced appearance of sequence divergence that results from reverse mutations, homoplasies (convergence) and other multiple changes occurring at single sites along two lineages
symbiont that lives within the body of the other participant
endosymbiont
Parasitism
depend on host for life
obligate
may or may not improve hosts activities
Ancestral state
the character state exhibited by the ancestor from which current members of a clade have evolved
Apomorphy
any derived or specialized character
Autapomorphy
a derived character possessed by only one descendant of an ancestor, and thus of no use in discerning relationships among other descendants
Clade
a group of organisms that includes the most recent common ancestor of all its members and all descendants of that ancestor
every valid clade forms a “monophyletic” group
Cladogenesis
the splitting of a single lineage into two or more distinct lineages
Cladogram
pictorial representation of branching sequences that are characterized by particular changes in key morphological or molecular characteristics
Derived state
an altered state; modified from ancestral condition
apomorphic state
Homology
characters that have the same evolutionary origin from a common ancestor, often coded for by the same gene
Homology is the basis for
all decisions about evolutionary relationships
homoplasy
independent acquisition of similar characteristics from different ancestors
Monophyletic taxon
a group of species that evolved from a single ancestor and includes all descendants of that ancestor
Every valid clade
must form a monophyletic taxon
Node
a branching point on a cladogram
outgroup
a group of taxa outside the group being studied
outgroups are used to
‘root’ the tree and imply the direction of evolutionary change (polarity)
paraphyletic group
group of species sharing an immediate ancestor but not including all descendants of that ancestor
parsimony
a principle stating that, in the absence of other evidence, one should always accept the least complex scenario
pleisiomorphy
ancestral/primitive character
polarity
direction of evolutionary change
polyphyletic grouping
incorrect grouping containing species that descended from two or more different ancestors
members do not all share the same immediate ancestor
When a gene sequence loses its phylogenetic signal due to numerous base-pair substitutions
saturation
sister groups
two groups descended from the same immediate ancestor
synapomorphy
derived character that is shared by the LCA and two or more descendants
homologous characters that define clades
taxon
any named group of organisms
Invertebrate lifestyles
sessile
sedentary
motile
invertebrate habitats
majority marine - most hospitable
freshwater - more challenging
terrestrial - most challenging
challenges with freshwater habitat
maintaining osmotic pressure
water is often ephemeral
wider temperature fluctuations
challenges with terrestrial habitat
avoiding desiccation
retaining water
excreting toxic byproducts (urine)
types of benthic habitats (marine or fresh)
epifaunal
infernal
interstitial
feeding methods in invertebrates
suspension feeding detritivores deposite feeders herbivores carnivores
Metazoan pie chart
invertebrates are 95% of Metazoans
Invertebrate pie chart
beetles >1/4
flies, bees/wasps, butterflies, other insects, chelicerates, crustacea, molluscs, vertebrates (~1/16), other
arthropods = ~7/8
pelagic habitats (marine or fresh)
planktonic
Grazing carnivores
exploit sessile organisms
Predators
feed on actively motile prey (as opposed to grazing)
scavengers
feed on dead organisms (carnivory)
types of deposit feeders
selective
non-selective
why is phylogeny important
essential for asking questions about evolution (must know polarity)
cladogram
diagram of a phylogenetic hypothesis
nested sets of sister clades
branch point
node
multicellularity evolved
from unicellularity multiple times uniquely (at least 7)
Animal multicellularity requires
cell adhesion
cell specialization and interdependence
embryonic differentiation
Importance of cell adhesion
all cells come from single founder cell (fertil. egg)
to become multicell. they must attach together
Why cell adhesion is not enough
some unicellular organisms attach together as well
Importance of cell specialization
KEY to multicell. "Division of labour" *Intercellular signaling VIP* organization otherwise chaos
Importance of embryonic differentiation
allows cells to become specialized and recruited to form functional body plan
also tells about evolution
Tissues
large aggregates of same type of cell
Metazoan tissue types
epithelial connective nervous muscle gametogenic
Epithelial tissue
likely most important
primary interface w/ outside environ.
line internal compartments - determines what goes in and out
Epithelia components
Apical surface flagella (not always) Intercellular junctions micro-villi (not always) basal surface nuclei basal lamina (not always) apico-basal polarity
Apical surface
apical membrane of a polarized cell is the surface of the plasma membrane that faces lumen or outside environment
intercellular junction
adherons
contact between cells
enable communication
reduce stress on cell
basal lamina
layer of extracellular matrix secreted by epithelial cells, on which the epithelium sits
point of attachment
permeability barrier
cell polarity
spatial differences in the shape, structure, and function of cells
apical-basal polarity
a specialised apical membrane facing the outside of the body or lumen of internal cavities, and a specialised basolateral membrane localised at the opposite side, away from the lumen
Importance of apical-basal polarity
secrete different materials
have different structures (e.g. flagella)
connective tissue
collagen cells not connected in extracellular matrix 'wander around' structural integrity (e.g. blood, bone)
Nervous tissue
specialized to transmit information
neurons have high density and diversity
allow message transmission throughout organism
how nervous tissue works
change in potential through the ion channels is carried down the length of the neuron
muscle tissue
specialized for shortening
important for animal movement
how muscle tissue works
actin and myosin slide relative to each other
Major groups of metazoans
Porifera Cnidaria Ctenophora Placozoa Bilateria
Porifera and Placozoa shared characteristic
no nerves
no muscles
Metazoan phylogeny hypotheses
- Porifera, (Placozoa, Cnidaria, (Bilateria, Ctenophora))
2. Ctenophora, (Porifera, (Placozoa, (Bilateria, Cnidaria)))
Problem with metazoan hypothesis 1
It has a trichotomy
trichotomy
3 sister groups following 1 node
perfectly/fully resolved phylogenies only have 2 sister groups
problem with metazoan hypothesis 2
just controversial new data (molecular)
Porifera habitat
marine and freshwater
Porifera lifestyle
sessile adults
suspension feeders - mostly bacteria, some plankton
aquiferous system
interconnected system of water canals
unique to sponges
do sponges have tissues
yes
what tissues do sponges have
nerve/muscle - no
connective tissue - yes
epithelial tissue - yes
name of sponge epithelial tissue
protoepithelia
Protoepithelial tissue
less differentiated than other metazoans
Sponge interior compartment
spongocoel
atrium
empty space
sponge species
8000
98% marine
non-self recognition
alloincompatibility
as in sponges
flagellated cells lining spongeocoel
choanocytes
‘funnel cells’
collar cells
form choanoderm
collar cell functions
generate curent to maintain circulation in/through sponge
capture food particles
capture sperm
choanoderm
interior sponge tissue - facing spongocoel
collar of collar cells
apical flagellum surrounded by microvilli
middle sponge layer
mesohyl
wandering cells in mesohyl
archaeocytes
Mesohyl
gelatinous
non-living
acellular but containing live cells
Archaeocyte features
amorphous amoeboid wander in mesohyl - cytoplasmic streaming essential functions develop into specialized cells
Archaeocyte functions
digest food particles from choanocytes store digested food role in non-self recognition may produce flagellated sperm and egg role in waste elimination
Sponge Support Elements
spicules
fibers
Spicule structure
siliceous
calcareous
fiber structure
spongin (collagen-like)
secrete spongin fibers
spongocytes
secrete spicules
sclerocytes
spongocytes and sclerocytes come from what types of cells
archeaocytes
sponge water entry
ostium
porocyte
sponge water exit
osculum
support element functions
maintain sponge shape
discourage predation
systematics (systematics)
dormant sponge structure
gemmule
gemmule features
dormant structure
certain times of yr
mostly freshwater, especially temperate latitudes
resistant to desiccation, freezing, anoxia
withstand unfavourable conditions
asexual reproduction - multiple clones
formation of gemmule
archaeocytes phagocytize other cells to accumulate nutrients - cluster together w/i sponge - surrounding cells secrete thick protective covering capsule - parent sponge dies - gemmules released in to water - enter metabolic arrest - survive - break open and release cells in favourable conditions
Vernalization
many gemmules must spend several months at low T before capable of hatching
cells in outer sponge layer
Pinacocytes
Pinacocyte features
flattened contractile cells
form pinacoderm layer
line incurrent canals
Pinacocyte contraction
major/minor sponge shape change
regulate flow by changing incurrent opening size
levels of sponge construction
basic –> complex
asconoid, syconoid, leuconoid
Increased sponge complexity achieved by
increasing invagination of choanocyte layer away from spongocoel
increased flagellated surface area
Majority of sponge types (complexity)
leuconoid
sponge Classes
Calcarea
Demospongiae
Hexactinellida
Homoscleromorpha
How sponge Classes are defined
chemical composition
support element morphology
Class Calcarea characteristics
CaCO3 spicules only class to include all 3 complexities only class w/ extant asconoids
Class Demospongiae characteristics
largest class ≥80% of all species mostly leuconoid spicules/fibers = spongin and/or silica, some chitin NO CaCO3 only class w/ freshwater species
Family Cladorhizidae
Demospongiae carnivorous most lack ostia, oscula, choanocytes engulf prey in epithelial cell and new filaments may have symbiotic bacteria
Class Hexactinellida features
“Glass Sponges”
syconoid or leuconoid
entire sponge is syncytial
interconnected 6-ray spicules of Si and Chitin
Syncytial
multinucleate mass
not separated in to cells
Type of reproduction in sponges
asexual- fragmentation or gemmules/buds
sexual- sperm and eggs
Gamete producer in sponges
many species are hermaphroditic so individuals produce both gametes
Sponge sexual reproduction
choanocyte- sperm capture- dedifferentiate to amoeboid form- move sperm to mesohyl- egg fertilized in mesohyl
Phylum Placozoa defining characteristics
small, multicellular, amorphous, mobile
no body cavity, digestive system, nervous system
2 layers of ciliated epithelium sandwiching multinucleate contractile cells
cells in a Placozoa
~1000 per layer
~3000
Phylum Placozoa species
only 1 described, poorly understood
Trichoplax adherents
molecular work suggests ~10 unknown
Placozoa size
~2mm in lab
much smaller in field
Placozoa genome
smallest of any known animal
98 million b.p.’s
Placozoa habitat
unknown
Placozoa cells
no basal lamina
ventral layer = columnar cells w/ flagella
glandular cells secrete digestive enzyme for extracellular digestion
upper layer contains ‘shiny spheres’ for defense
dissagregated cells can reform fn animal
regenerate pieces that are cut off
Placozoa reproduction
asexual - budding, fragmentation
binary fission
possibly sexual
Placozoa mitochondrial genome
largest known
43,079 b.p.’s
more closely related to unicellular organisms?
basal group or secondary loss?
Choanoflagellate
unicellular heterotrophs collared, flagellated look like individual choanocytes but also form colonies possibly evolved in to sponges?
Sponge asexual reproduction
fragmentation
gemmules
sponge fragmentation
bit of sponge body separates, piece of somatic tissue grows in to new organism
sponge sex
mostly hermaphroditic (not simultaneously), can switch sex in next spawning season
sponge sperm
differentiate from choanocytes or archaeocytes
broadcast spawn in to surrounding sea water through osculum
sponge eggs
differentiate from archaeocytes in mesohyl
sponge larvae
released from osculum
flagellated, swimming
allows for dispersal
looks like an olive with short little hairs at end
diapause
period of suspended development, especially during unfavorable environmental conditions (e.g. gemmule)
Cladorhizidae spicules
hook-shaped spicules on tendrils
act like velcro, hook on to exoskeleton of prey
new species of deep ocean carnivorous sponge
Chondrocladia
‘harp sponge’
Late Jurassic time
145 MYA
sponges in Jurassic
siliceous sponge reef belt (hexactinellida), 7000km, anywhere on planet, between NA/Baltica and Gondwana, extinct at end of Jurassic
how do sponges persist as sessile organisms
- secondary metabolites
- intracellular bacterial symbionts synthesizing secondary metabolites
secondary metabolites
defence
may be: unpalatable, toxic, antibacterial
BC sponges
Hexactinellid reefs formed by 3 species of glass sponge (not same species as from Jurassic)
discovered in 2005
unique to BC, nowhere else
sponge internal communication
allow ions into membrane - potential difference - message propagated through whole body - can create whole body response to external disturbance
how can a sponge propagate a message through its whole body
one cell at a time
open and close.. neighbour opens and close.. neighbour..
close all cells - stop flow of water in response to environmental disturbance
How Professor George Mackie was able to test membrane potential in sponges
cut up, disagregated cells, they reformed a fleshy clump, put clump on parent sponge, tissue formed around = tumor/graft which an electrode could be attached to
skeleton
solid or fluid system permitting muscles to be stretched back to their original length following a contraction
may be protective, supportive as well
why is a skeleton necessary
muscles can’t do repetitious movement alone
muscles can
shorten/relax
muscles can not
actively extend themselves
how muscles work
antagonize each other
work opposite to each other
e.g. bicep, tricep
aquatic animal skeleton
many use fluid for muscle interaction
why aquatic animals can use liquid skeletons
don’t need extra structure/support like terrestrial organisms (gravity, lack of buoyancy)
hydrostatic skeleton requirements
cavity w/ incompressible fluid
cavity surrounded by flexible outer membrane (deformable)
constant fluid volume
deformable covering or antagonistic muscles
why incompressible fluid is important for a hydrostatic skeleton
to transit pressure changes in all directions
additional hydrostatic skeleton requirement if progressive locomotion is to occur
animal must be able to form temporary attachment to substrate
cnidaria defining characteristic
secretion of complex intracellular organelles called cnidae; planula larvae
Cnidaria habitats
aquatic - marine and freshwater
by far greatest diversity in ocean
Cnidaria marine habitats
benthic and/or pelagic
most cycle between both, some spend whole life in one or other
Cnidaria lifestyle
solitary and/or colonial
sessile/sedentary and/or mobile
predatory (some contain photosynthetic symbionts)
Cnidarian species
> 11,000
>99% marine
cnidaria body plans
medusa polyp some have both as stages some have both at once some are only one stage
Cnidaria major characteristics
true gut (carnivore)
diploblastic
radial symmetry (all life history stages)
nerve net
cnidocytes
alternation of generations (many, not all)
cnidaria tissue layers
epidermis
gastrodermis
diploblastic
cnidaria gelatinous layer
mesoglea
mesoglea
gelatinous
nonliving
may contain living cells from embryonic ectoderm
diploblastic early development
zygote cleavage - 8-cell stage - cleavage - blastula - gastrulation - becomes 2 layers of cells
blastula
hollow ball of cells
gastrulation
invagination
gastrula
2 layers of cells after gastrulation (endoderm and ectoderm)
space between 2 layers of gastrula cells
blastocoel
opening in gastrula
blastopore
Cnidarian blastopore
becomes mouth
cavity inside of gastrula (inside ectoderm)
Archenteron
future gut
why is radial symmetry appropriate for sessile/sedentary organisms
not moving w/ a leading end
sitting still- predators/prey can approach from all sides
Cnidaria epidermis cell types
epitheliomuscle cells nerve cells cnidocytes gland cells interstitial cells
epitheliomuscle cells
in epidermis of cnidarian apical side = bona fide epithelial basal side = muscles w/ actin/myosin sensory cells intra-epithelial neurons
apical surface
facing lumen or external environment
cnidarian sensory cells
neurons in epitheliomuscle cells reach up to apical surface
cnidarian intra-epithelial neurons
neurons in epitheliomuscle cells are embedded in epithelium (in other Metazoans, below epithelium)
basal surface
bottom edge of the cell or tissue adjacent to the basement membrane
Cnidarian nerves are arranged
in a nerve net
appropriate for radial organism transmit stimuli out concentrically to all body parts
choanocyte functions (Porifera)
maintain water flow
capture and ingest particles
capture sperm
transform in to sperm (some species)
why choanocytes must maintain water flow
bring in food particles, gases, remove waste products (uric acid, CO2)
how choanocytes capture particles
caught on sticky mesh between microvilli
choanocyte food digestion
intracellular
often initial digestion then transfer to archeocytes
archaeocyte functions
primarily responsible for food digestion
store nutrients
transform in to gametes
synthesize skeletal elements
pluripotent cells
very capable of differentiating in to different cell types (e.g. archaeocytes)
basic cnidarian body parts
mouth (between tentacles) tentacles GVC body stalk basal disk
cnidocytes
synthesize cnidae (e.g. nematocysts) nettle/stinging thread organelle secreted in cnidoblast discharge explosively variety of functions one of most complex intracellular secretion products known
types of nematocysts
>30 described types many types in one individual main groups 1. glutinants 2. volvent 3. penetrant
glutinant nematocysts
tubule has open end containing adhesive material
volvent nematocysts
threads that wrap around and capture prey
penetrant nematocysts
penetrate through exoskeleton
tubule has open end with neurotoxins
how nematocysts work
Ca+ moves in to capsule increased molality water drawn in to capsule pressure increase pressure discharges capsule capsule turns inside out
nematocyst structure
round, proteinaceous capsule, open at one end hinged operculum cnidocil by opening (trigger) hollow, coiled tube in capsule (thread) may contain barbs
cnidocyte functions
food capture
defense
temporary adhesion to substrate
why barbs don’t poke in to capsule of cnidocyte
they point in
cnidae is turned inside out when ejected
how symbionts avoid stinging from cnidae
secrete mucus that prevents nematocyst from firing
discharged nematocyst
cnidocyte nematocyst capsule barbs thread (tubule) sloughed off - not reusable regenerated from interstitial cells (stem cells)
cnidocyte discharge by
chemical and tactile stimulation
perceived through cnidocil
cnidocil
cluster of modified cilia
hairlike sensory process
Cnidaria gastrodermis cell types
nutritive muscle cells
enzymatic gland cells
some cnidarians also have cnidocytes and nerve cells in gastrodermis
medusa vs. polyp mesoglea
mesoglea much more hydrated in medusa - thick and jelly-like
Cnidarian phylogeny (Classes)
Anthozoa s.g. to Staurozoa s.g. to Hydrozoa s.g. to Scyphozoa s.g. to Cubozoa
Subphylum Medusozoa
Staurozoa, Hydrozoa, Scyphozoa, Cubozoa
Cnidarian classes that have polyp and medusa stage
Hydrozoa, Scyphozoa, Cubozoa
Subphylum Anthozoa includes
anemones, corals, sea pens
used to be called Class
another name for epitheliomuscular cells
nutritive cells
implication of Cnidaria having only mouth
only one opening
no anus
must expel undigested remains of one meal before consuming more
why is the taxonomy we use most parsimonious
1 evolutionary change (acquiring medusa stage) as opposed to 2 changes (loss of medusa in Anth. and 1/2 loss in Staur.)
hydrostatic skeleton functions
maintain shape
transmit force of muscle contraction (to produce movement)
protection
cnidaria muscles important for hydrostatic skeleton
circular and longitudinal
Class Anthozoa characteristics
absence of medusa, operculum, cnidocil
circular mitochondrial DNA, ciliated groove in pharyngeal wall, coelenteron partitioned by sheets of tissue
all marine
cnidaria respiratory system
no respiratory structures
Anthozoa species
~6000
70% of Cnidarians
Sea anemone inflation
open mouth, contract longitudinal muscles, expel all water (of h.s. skeleton), results in chewed bubblegum form
sea anemone inflation
ciliated siphonoglyphs draw in water, slowly stretches back out - hours - days
mesoglea responds like silly putty - stretches back out slowly
Anthozoa reproduction
Asexual - vision, budding, pedal laceration
Sexual
Anthozoa fision
break body in to 2 parts (transverse or longitudinal plane) - reform rest of organism
Anthozoa budding
somatic tissue extends in to a bud that differentiates tentacles and other body parts, then separates
Anthozoa pedal laceration
common in anemones
bleb/pinch off part of foot (oral disk) that regrows its parts (form of fragmentation)
Anthozoa sexual reproduction characteristics
dioecious gametes arts from gastrodermis broadcast spawn gametes fertilization external or internal free-swimming planula larvae
dioecious
separate males and females
Anthozoa subclasses
Hexacorallia (Zoantharia)
Octacorallia (Alcyonaria)
Hexacorallia
sea anemones- solitary
stony corals - colonial, solitary
tentacles around mouth in multiples of 6
mesentaries
sheets in Anthozoa GVC to increase SA
Hexacorallia parts
6 pairs of 1º mesenteries
1 pair siphonoglyphs
stony corals have CaCO3 skeleton
Hexacorallia corals
scleractinian
hermatypic or ahermatypic
reef-building corals
hermatypic
Class Octocorallia
sea pens, sea fan, sea whip, soft corals - pipe coral all colonial have central axis 8n tentacles, septa pinnate tentacles
colonial Hexacorallia
polyps connected via GV - all tissue layers are continuos in a tunnel, GVC is continuous
polyps on top of CaCO3
pinnate tentacles
numerous lateral outfoldings (pinnules) along tentacles
side branches
colonial Octocorallia
interconnections lined by gastrodermis
polyps are not full individuals - embedded thick matrix mesoglea (soft coral)
CaCO3 spicules in mesoglea
may have proteinaceous axial skeleton
Anthozoa larvae unique
only Cnidarian planula larvae that feed
Anthozoa feeding
primarily carnivorous
transfer food - mouth - tubular pharynx (don’t directly to GVC)
siphonoglyphs
ciliated grooves from mouth down pharynx
Tropical coral reefs
very high biodiversity and biomass
very clear water needed - nutrient poor
unicellular photosynthetic organisms
photosynthetic symbionts (corals)
zooxanthellae - dinoflagellates
zoochlorellae - chlorophytes
reef building corals
hermatypic
chlorophytes
green algae
when zooxanthellae/zoochlorellae ‘overproduce’
corals release products as mucus which is used by other organisms
photosynthetic unicells reside where in Cnidarian
within gastrodermal cells of host (intracellular symbiont)
what do photosynthetic unicells provide Cnidarians
nutrition
sunscreen molecules
Anemone territory defence
inflate acrorhagi (fighting tentacles) - normally can't be seen have very potent nematocysts
cold water coral groups
forests of Octocorallia reefs of Hexacorallia no photosynthetic symbionts very deep increase niche space
anthozoa surfaces
oral surface (tentacle end) aboral surface (basal disk end)
Anthozoa mouth
shaped like a barbell (bilaterally symmetric)
bells lined with siphonoglyphs
mouth in Anthozoa leads to
gullet (esophagus)
medusae swimming
contract circular muscles - expel water (jet propulsion)
no antagonistic muscles - bell ‘springs back’ and re-expands to original shape
why there are receptors in medusa not polyp
motile - must monitor surroundings more carefully
polyp vs medusa, GVC
polyp - simple sac
medusa - interconnected canals
polyp vs medusa, reproduction
In cnidarians w/ alternation of generations
polyp - asexual
medusa - sexual
Class Hydrozoa characteristics
alt. of gen. greater representation of polyp stage mesoglea lacks cells >3000 species mostly marine gastrodermis lacks nematocysts 2 subclasses
medusa body parts
mouth - manubrium - stomach bell mesoglea radial canal ring canal tentacles circular muscles
ring canal
around periphery of bell
radial canals
out from stomach to edge of bell (4)
manubrium
muscular cylinder at one end
medusa surfaces
exumbrellar surface - ‘top’
subumbrella surface - ‘underneath’, mouth side
Subclass Hydromedusa (Hydrozoa)
mostly marine freshwater e.g. Hydra thick mesoglea posses velum gonads develop from epidermis
velum
muscular shelf of tissue
goes in towards mouth from edge of medusa
velum function
increases speed and agility
restricts aperture - increase water velocity
can open to the side for turning
Hydrozoa polyps
majority colonial (modular)
interconnected, continuous GVC
polymorphism
perisarc
colonial polyps with specialized polyp types
polymorphism (Hydrozoa)
feeding, reproducing
(can also have 3rd type of polyp, defensive)
perisarc
non-living chitinous protective coating around polyps (Hydrozoa)
Hydrozoan reproductive polyp produces
medusa
hydroids
colonial Hydrozoans that form branching colonies
often have protective coating
e.g. ostrich plume
Hydra
freshwater
separate, distinct polyps
may contain zoochlorella
lack medusa
Order Siphonophores
Hydrozoans complex colony pelagic, free floating polymorphic polyps + polymorphic medusa very toxic clustered modules along stem
Siphonophore example
Portuguese man-of-war
Siphonophore body parts
float (gas filled) swimming bells stem feeding polyps tentacles reproductive medusa buds
swimming bells, siphonophores
modified medusa
don’t produce gametes
jet propulsion
Siphonophore genetics
all genetically identical
express different parts of genome
very novel way of achieving complexity
Class Scyphozoa
local Scyphozoa
Aurelia sp. - moon jelly
gastric pouches
have gastrodermis derived gonads (like Anthozoa)
rhopalium
8 around margin of bell
complex set of photoreceptors, gravity receptors, chemo-, mechano-
Hydrozoa gonads
arise from epidermis
Scyphozoan life cycle
adult medusa – eggs + sperm – fertilized egg – planula larva – scyphistoma polyp – strobila – ephyra – medusae
Scyphozoan reproduction
strobilation
transverse fission of strobila to form multiple ephyra
Scyphozoan budding
budding may occur during scyphistoma stage
Scyphistoma
polyp with tentacles
body form that grows from larva
may bud
ephyra
‘baby medusa’
produced from strobila
genetically identical (from same strobila)
Class Staurozoa
least known medusa + polyp stalked on aboral end modified tentacles around periphery - anchors adhesive structures small, most
Staurazoa life cycle
no swimming stage
no free medusa
gametes released in seawater
planulae not ciliated (creep)
5 major clades of metazoan
Porifera Cnidaria Ctenophora Placozoa Bilateria
Phylum Placozoa only described species
Trichoplax adherens
Trichoplax adherens
1883, FE Schulz smalles metazoan genome intertidal, warm, marine very small amoeba-like
Placozoa body features
ciliated epithelium contractile cells btw epithelium no nerve cells no basal lamina possible chemical defense cells enzyme-secreting cells bona fide intracellular junctions
Placozoa movement
move via cilia and contractions
Placozoa feeding
move over food particle
transient space around particle
secrete digestive enzymes
digest externally
Placozoa reproduction
asexual - binary fission, budding
sexual suspected but not observed
earliest Bilateria fossils
trace
~Precambrian-Cambrian boundary
evidence of active burrowing?
Bilateral symmetry associated with
actively motile lifestyle
leading end of body
Bilaterian characteristics
two body axes
triploblastic
How genes
Bilaterian axes
anterior-posterior (A-P)
dorsal-ventral (D-V)
Bilateria dermal layers
ectoderm
endoderm
mesoderm
Hox genes
encode positional identity along A-P axis
Functions of Bilateria internal compartments
digestion transport nutrients and gases hydrostatic skeleton source/storage of gametes role in excretion and osmoregulation
why Bilateria have internal compartments
must provide nutrients to all the different body parts - especially important in large animals
internal compartments allow for specialization of function (unlike GVC in Cnidaria)
Types of secondary body compartments in Bilateria
acoelomate
pseudocoelomate
eucoelomate
Acoelomate
mesoderm completely fills area between ectoderm/endoderm
may contain various compartments
Bilateria ‘Superphyla’
Lophotrochozoa
Ecdysozoa
Deuterostomia
Pseudocoelomate
mesoderm only along inside edge of ectoderm - doesn’t fill entire body compartment
e.g. nematodes
Eucoelomate
epithelium from mesoderm forms separate compartments L/R
control what goes on in body by apical-basal polarity
compartments can specialize
epithelium from mesoderm
mesothelium
compartments formed by mesothelium in eucoelomate
eucoelom/coelom
compartment in pseudocoelomate
pseudocoel
concentration of sensor organs at leading end of body
cephalization
cephalization =
formation of A-P axis
how were taxonomic trees ordered in 1940s
morphology
embryonic development
L. Hyman, 1940 Bilateria tree
Platyhelminthes - Nematoda - (eucoelomate divergence) - two branches
Deuterostomia (Echinodermata, Hemichordata, Chordata)
Protostomia (Mollusca, Arthropods, Annelida)
Deuterostomia vs Protostomia, cleavage
D - radial
P - spiral
Deuterostomia vs Protostomia, mesoderm origin
D - endoderm
P - mesentoblast
Deuterostomia vs Protostomia, eucoelom origin
D - enterocoely
P - schizocoely
Deuterostomia vs Protostomia, blastopore fate
D - anus
P - variable (rarely just anus)
germ layer
group of cells that behave as a unit during early stage of embryonic development
give rise to distinctly diff. tissues and/or organ systems
key mesoderm derivatives
muscles
circulatory systems
deuterostome formation
enterocoely = evagination of endoderm - club shape - coelomic pouches pinch off - coelomic vesicles
Protostome formation
schizocoely =
mesentoblasts - gradual enlargement and arrangement into compartments
mesentoblasts
cluster of cells in protostome
Radial cleavage
cleavage planes parallel and perpendicular to cell axis
daughter cells lie in same plane as mother cells
serial cleavage
spindle axes 45º
at 8-cell stage top cells are smaller
Bilateria tree based on molecular studies comparing nucleotide sequences of rDNA
Protostomia - Lophotrochozoa, Ecdysozoa
Deuterostomia - Echinodermata, Hemichordata, Chordata
Superphylum Lophotrochozoa, Phylums
Annelida
Mollusca
Platyhelminthes
(+ others)
Superphylum Ecdysozoa, Phylums
Arthropoda
Nematoda
(+ others)
interesting nematodes closer to arthropods than annelids
Ecdysozoa characteristics
cuticle (exoskeleton) periodically moulted to allow growth
no motile cilia/flagella
Ecdysozoa sperm
have flagella-like feature but not motile
NO motile cilia/flagella
colinearity
organization of Hox genes in chromosome = order of their expression along AP axis of developing animal
Hox genes encode
transcription factors (proteins) Tc factors bind to DNA and restrict downstream gene expression
Hox gene groups
4 main groups that are similar enough to have originated from single ancestral gene
4 groups unique to Bilateria
Radiata Hox genes
2 groups
Earth age
> 4.5by
described species
~1.7 million
undescribed species
probably 10 million
earliest known unicellular eukaryotes
~2by
earliest known Metazoans
542-635my Ediacaran fauna South Australia burrow fossils no hard parts
best studied invertebrate fossils
Burgess Shale
BC
525 my
Phylum Platyhelminthes
Lophotrochozoa
flatworms
free-living freshwater/marine/terrestrial, parasitic
free-living terrestrial flatworms
confined to very humid environments
parasitic platyhelminths
e.g. tapeworm
75% of phylum are parasitic
Phylum Platyhelminthes general characteristics
bilateral symmetry triploblastic cephalization aceolomate gut with one opening (GVC) dorso-ventrally flattened cerebral ganglia, long nerve cords prtonephridia hermaphroditic, complex reproductive system
Class Turbellaria
free-living flatworms
not true clade
paraphyletic
Platyhelminth gut
gut circulates nutrients and gases so it is appropriate to call it GVC
Platyhelminth dorso-ventral flattening
no internal tubules for circulatory/gas exchange
gases don’t have to travel as far
gas exchange is affected by SA:V ratio
Turbellaria body plan
bilaterally symmetric
auricle - ear-like chemosensory structures
eyes - photoreceptors
Turbellaria eyes
can not form images
detect shadows
Turbellaria mouth
mid way down ventral surface
leads to muscular pharynx
Turbellaria pharynx
can sometimes be extended out of body for feeding
Turbellaria feeding
mostly predators or scavengers
- secrete digestive enzymes
- swallow prey whole
- terrestrial flatworms have unique feeding
Turbellaria enzyme digestion
enzymes digested by pharyngeal glands
begin digestion outside body
suck-up semi-digested soup
Terrestrial flatworm feeding
grasp prey w/ adhesive secretion
ensnare prey in sticky mucus
neurotoxins
tetrodotoxin
binds to Na channels
blocks action potentials
Turbellaria GVC
not a simple sac
series of interconnected side branches
Turbellaria locomotion
ciliary-mucus crawling
muscular crawling
body undulations for swimming
duoglands
ciliary-mucus crawling, Turbellaria
secrete mucus layer, beat cilia, swim over secretion
Turbellaria duogland
viscid gland (adhesive) + releasing gland, inside of supporting cell
Helps turbellarians with muscular crawling and body undulations
parenchyma cells
Parenchyma cells
full of water at constant volume
can act as hydrostatic skeleton
ganglia
concentration of neurons
Turbellarian nervous system
cerebral ganglia
2 longitudinal nerve cords
Peripheral nerve plexus
Protonephridia
hollow cell in excretory system containing a tuft of rapidly beating cilia that serve to propel waste products into excretory tubules
Protonephridial functions
osmoregulation (maintain salt, water balance)
excretion of ammonia (waste product of protein catabolism)
Protonephridium structure
invagination in epithelium = duct
end of duct = terminal cell
basal lamina around duct + terminal cell
flagela in middle of terminal cell go down duct
flame bulb
name for terminal cell b/c flagella are beating so much it looks like its flickering
function of flagella in protonephridial function
beating of flagella expels water down duct
(-) pressure
draw interstitial fluid into terminal cell through cytoplasmic processes
function of basal lamina in protonephridial function
size selector - ultrafiltration
otherwise everything would leave
Selective reabsorption
particles that are accidentally lost through terminal cell can be re-absorbed through duct
Waste in the protonephridium is released through the
nephridiopore
Turbellaria reproduction
Asexual
Sexual
Asexual reproduction, Turbellaria
transverse fission plane
divide body in half - regenerate missing half
common in free-living flatworms
Sexual reproduction, Turbellaria
hermaphroditic
internal fertilization
comple m/f reproductive systems
Turbellaria male reproductive system
a series of testis - sperm moves down to sperm duct - moved in to seminal vesicle (stored until copulation) - penis - male gonopore (genital pore)
Turbellaria female reproductive system
ovary (1 or more pairs) – oviduct – yolk glands – female gonopore – copulatory bursa (sperm storage)
Turbellaria copulation
each worm delivers sperm to the other
hypodermic/traumatic impregnation
use stylit to stab in to body and deliver sperm to body interior
Phylum Platyhelminthes Classes
“Class Turbellaria” - free-living
Class Trematoda - flukes (endoparasite)
Class Cestoda - tapeworms (endoparasite)
Amount of Platyhelminthes that are parasitic
75-80%
benefits of being a parasite
protection against predators
stable, predictable environment
Endoparasitism adaptations
Attachment structures
Modified body wall
Strategies to invade new hosts
High reproductive potential
why endoparasites need adaptations
maintain preferred position within host
reproduce - don’t want a lot of individuals in single host or host will become compromised
Platyhelminthes endoparasite body wall modifications
loss of cilia reduction of musculature reduction of sensory structures nutrient absorption resist host defenses
why Platyhelminthes endoparasites adapt body wall
no active movement - don’t need cilia/muscles and don’t need to monitor surroundings
nutrient absorption - live in ‘nutrient soup’
Platyhelminthes endoparasite strategies to invade new host
complex life cycle w/ definitive and intermediate host
definitive host
the host in which the parasite is sexually mature
role of intermediate host life stage
parasite is in larval stage
the way in which the parasite is able to invade the definitive host
may have >1 intermediate host
Platyhelminthes endoparasite reproductive potential
have many eggs - since chance of getting to definitive host is low
polyembryony - even more eggs
polyembryony
asexual duplication of developmental stages
Class Trematoda
flukes
2 suckers, pharynx
e.g. Opisthorchis, Schistosome
Class Trematoda morphology
Mouth at anterior end surrounded by oral sucker short pharynx below mouth (inside) ventral sucker eggs in uterus (about 1/3 of body) ovary seminal vesicle testes Intestinal caeca (from pharynx down sides of body)
Opisthorchis (Clonorchis) sinensis
Oriental Liver Fluke
Trematode
Opisthorchis sinensis life cycle
Adult in human (liver bile ducts)– eggs released in feces – eaten by snails – miracidium (larva) – sporocyst – polyembryony – redia – polyembryony – cercariae (free-living) – fish – metacercariae (in fish muscle) – eaten by human
O. sinensis miracidium
highly ciliated
hooklets for burrowing in to snail digestive gland
O. sinensis sporocyst
full of germinal balls
absorbs nutrients across wall
each germinal ball develops in to another sporocyst
O. sinensis redia
also contain germinal balls
anterior mouth
O. sinensis cercaria
hatch out of snail host
many cercaria from only 1 miracidium (1st larva)
muscular tail - free-swimming
swim to find 2nd intermediate host (fish)
burrow through gills into circulatory system of fish, migrate to muscles
O. sinensis metacercaria
round cyst
cyst wall
in fish muscles
O. sinensis function of first intermediate host
boost numbers
O. sinensis function of second intermediate host
exploit feeding habits of definitive host
complete life cycle
having the male and female reproductive organs in separate individuals
dioecious
Schistosoma spp.
2nd most prevalent and destructive human disease
tropical
dioecious (unusual in Platy.)
many species w/ different definitive hosts
Schistosoma spp. affects where/how
eggs deposited in mesenteric veins
puncture vein, move through circulatory system
try to reach digestive system
Schistosoma spp. life cycle
develop in fresh water – burrow in to body of snail – polyembryony – circariae – swim around in water – directly infect definitive host by burrowing in to skin and entering circulatory system
mesenteric vein
veins that drain large and small intestines (no direct route out of body to export eggs)
swimmers itch
Bird schistosomes - try to burrow in to your skin but bird epithelium is thinner so they can’t make it through human skin
Trematode life stages that undergo polyembryony
sporocyst
rediae
results of Trematode polyembryony
genetic clones
exploit intermediate host to enhance fecundity (fertility) of parent worms
Trematode polymorphism
1 instance found of soldier and reproductive polymorphs (rediae)
soldier is much smaller, non-reproductive, large mouth, very active, attacks non-clonal individuals that may have also invaded host
Class Cestoda morphology
anterior hooks 2 anterior suckers (look like eyes) NO mouth neck strobila (proglottids)
generative region of Class Cestoda
duplicative trunks bud off from neck
Anterior end of Cestoda
scolex = hooks + suckers
Class Cestoda characteristics
typically vertebrate definitive host
hooks on to digestive tract
fertilization can occur between separate proglottids
proglottid
duplicative trunk section
contains complete M&F reproductive structures
strobila is the combined set of proglottids
when filled w/ eggs, break off terminally
Taenia life cycle
adult tape worm in carnivore – proglottids – feces on ground – eaten by herbivore – oncosphere (egg) – hatches – burrows through gut wall – cysticercus – eaten by carnivore (e.g. wolf)
Taenia oncosphere
4 central hooks for burrowing through herbivore gut wall
Taenia cysticercus
still looks egg-shaped, encysted in herbivore
excess scolex inside definitive host in digestive lumen
scolex latches on
encyst
enclose or become enclosed in a cyst
excyst - escape from cyst
Echinococcus sp.
Cestoda 2-3mm long adult has 3-4 proglottids carnivore def. host (usually wolf/coyote) hydatid cyst
Hydatid cyst
unique to Echinococcus sp.
terminal proglottid is a HUGE ball filled w/ cystocercai undergoing polyembryony
Phylum Annelida lifestyles and habitats
motile, sessile, sedentary
marine, freshwater, terrestrial
Significant innovations in the Annelid body plan development
gut w/ mouth + anus metamerism eucoeloms gut muscularization blood vascular system
Annelid gut
bidirectional: mouth - anus
allows specialization of different digestion steps, increases digestions efficiency, appropriate for active lifestyle
Annelid metamerism
duplication of trunk segments
generation zone btw last metamere and pygidium
pre-Annelid ancestor morphology
prostomium - trunk - pygidium
mouth - digestive tract - anus
Annelid post-metameric ancestor morphology
prostomium - peristomium - 4 metameres - regeneration zone - pygidium
mouth - digestive tract - anus
Annelid eucoelomic compartments
2 compartments around gut lined w/ mesoderm
connected by dorsal/ventral mesentaries
1st segment of Annelid
peristomium
Annelid gut muscularization
increased digestion efficiency by being able to move material down gut while organism remains stationary
Annelid coelomic compartments interior
lined w/ cilia to circulate gases, maintain homogeneity rather than allowing gradient to form at surface so that diffusion will continue
mesentery
double layer of mesothelium mid-dorsally and mid-ventrally between coelomic compartments (in each metamere)
Annelid last segment
pygidium
not a metamere
Annelid blood vascular system
convey nutrients/gases between metameres through dorsal/ventral blood vessels
also segmental blood vessels
segmental blood vessels
each metamere has blood vessels between d/v blood vessels in each coelomic compartment
Annelid blood movement
dorsal blood vessel is lined with epitheliomuscle cells that pump it
Functions of coelomic compartments, Annelids
circulation of nutrients and gases
hydrostatic skeleton
role in excretion, osmoregulation
storage of gametes
Annelid hydrostatic skeleton
metamerism aids the ability to thrust - change shape of body w/o allowing pressure to be conducted to rest of body
Peristaltic Burrowing
alternation of circular + longitudinal-muscle-contraction waves
Forward movement produced by contraction of circular muscles, which elongates body; contraction of longitudinal muscles shortens and anchors body
Needed for peristaltic burrowing
fluid-filled coelom (hydrostatic skeleton)
circular + longitudinal muscles
Setae (chaetae)
Setae
chitinous bristles
important in locomotion
diagnostic of Annelids
Annelid excretion
dorsal bv is leaky fluid passes through basal lamina– circulates through coelomic comp. - in to metanephridium - out of body
Annelid excretion, basal lamina
ultrafiltration
Annelid excretion, metanephridium
tube-like structure in-to coelomic compartment
selective reabsorption
opening to coelom is in a different metamere than opening to external environment
metanephridium external opening
nephridiopore
functional significance of metameres
facilitate regional pressure differentials (help generate unidirectional thrust)
dorsal blood vessel leaky cells
podocytes
coelomic compartments gametes
gametes generated by mesothelium
stored in eucoelom
Annelid nervous system
dorsal brain
ganglionate ventral nerve cord
Annelid dorsal brain
2 cerebral ganglia in prostomium
Annelid nerve cord
ventrally under v.b.v
1-2 ganglia in each metamere
How chaetae work
held erect on shortened fat metameres to maintain position in burrow
past Annelid taxonomy
Polychaeta s.g. to
Oligochaeta s.g. to
Hirudinea
Oligo. + Hiru = Clitellata
groups that didn’t fit in past Annelid taxonomy
Pogonophora (tubeworm)
Echiura (spoon worm)
Sipuncula (peanut worm)
trouble with past Annelid taxonomy
groups didn’t have a clear position
Polychaeta was not monophyletic (para)
New Annelida taxonomy
developed w/ molecular taxonomy
we will focus on
Errantia and Sedentaria
both contain polychaetes
Errantia
active lifestyle
many annelid plesiomorphic traits
Sedentaria
-sedentary/sessile
diverse, derived traits
Errantia examples
Nereididae
Glyceridae
Polychaeta
polyphyletic group
Sedentaria examples
Arenicolidae Sabellidae Terebellidae Siboglinidae Echiuridae
Nereididae
Errantid
ragworm
paired, well-developed parapodia on each metamere
high concentration of cephalic sensory appendage
Errantia lifestyle
active - burrowing, surface crawling, swimming
why they have lots of sensory appendages
Errantia habitat
marine
Errantia morphology
well-developed, similar parapodia on most metameres
eversible, armed pharynx
prominent head appendages - sensory reception
Errantid parapodium morphology
2-lobed
2 muscular rods w/ bundle of chitinous chaetae
Errantid parapodium lobes
dorsal lobe = notopodium
ventral lobe = neuropodium
Errantid parapodium rods
acicula - responsible for back and forth movement (stroke, recovery)
Errantid acicula function
traction when crawling
surface area when swimming
(due to the chaetae)
Errantid locomotion
2-gear slow crawling rapid crawling (stroke, recovery) parapodia on opposite sides of body are out of phase stroke propagated down length of body
Errantid rapid locomotion
lateral body undulations
effective stroking augmented by convex curvatures of body thrusting against medium
convex curve = effective stroke
Errantid jaws
at end of everted muscular pharynx
grab/shred/capture prey
fossilized records
Glyceridae
Errantid
blood worm
red - hemoglobin
live in burrows - low O2 environment
Glyceridae ancestral traits
prostomium
small parapodia
Glyceridae tunnel
interconnected tubes
anterior end near entry - detect movement - lung out w/ long muscular pharynx
Glyceridae jaw
4 jaws at end of everted pharynx, each w/ venom gland
Sedentaria lifestyle
sedentary/sessile
permanent burrows or secreted tubes
Sedentaria morphology
reduced parapodia
regional specialization of parapodia
pharynx may evert but not armed
some elaborate head appendages for feeding
Arenicolidae
Sedentary 'lug worm' muddy sand substrate j-shaped burrow reduced parapodia no jaws
Arenicolidae parapodia
only on mid section
neuropodia - reduced to ridge w/ chaetae
notopodium - elaborate dendritic branching gill
Arenicolidae pharynx
no jaws
filter feeder
covered w/ stick lapilli - ‘mop up’ sediment
Arenicolidae feeding
anterior at end of J-shaped burrow - peristaltic body movement - pull water in - H2O percolates through sand at head end - escapes through sink hole - leaves behind particles
J-shaped burrow ‘head end’
‘blind end’
Arenicolidae waste disposal
back up out burrow entrance - stick anus out - eject fecal material = fecal castings
Sabellidae
Sedentary 'feather duster worm' sessile secreted, proteinaceous tube find on docks entire life in tube
Sabellidae crown
radioles (tentacles) - ciliated, create water currents
capture phytoplankton, carry down central axis to mouth
suspension feeding
Sabellidae parapodia
minimal anterior extensions for crawling up/down tube
Radiole pigment spot
photoreceptor
Sabellidae
Terebellidae
Sedentaria 'spaghetti worm' surface deposit feeder under rocks 2 tentacle types
Terebellidae tube
cemented together local particles (shell debris, sand)
Terebellidae parapodia
very small/reduced
Terebellidae tentacles
long white - feeding
red, fine, short - gas exchange
Siboglinidae
Sedentaria giant vent worms previously not known to be annelid secreted tube red plume/tentacles
Siboglinidae morphology
red tentacles - not feeding
opisthosome
trophosome
Siboglinidae opisthosome
segmented posterior (metameres) - each has coelomic compart., paired chaetae bundle
Purpose of Siboglinidae posterior chaetae
hanging on to tube
Siboglinidae trophosome
contains sulphide oxidizing bacteria - intracellular bacteria
chemosynthesis metabolic pathway
H2S (sulfide) + O2 – SO4 (sulfate) + E
E drives calvin benson cycle – fix organic carbon
Echiuridae
Sedentaria
trunk buried in sediment
deposit feeder
elongate anterior end extends to environment
Echiuridae morphology
paired setae
trunk
prostomium - long anterior extension (elongate prostomium homolog)
Bonellia
genus in Echiuridae
long, ciliated, forked prostomium
green
Echiuridae labelled w/ anti-serotonin antibody
highlife segmentally arranged neurons = metameric pattern of neuronal cell bodies
only preservation of metamerism
Annelid reproduction (ancestral)
Dioecious (gonochoristic)
Gametes from mesothelium
Broadcast spawn
External fertilization in seawater
Annelid gametes
from mesothelium of eucoelomic compartment
stored in euceolomic comp.
Annelid spawning
broadcast
gametes escape coelom via coelomoducts or metanephridia
Class Clitellata Subclasses
Oligochaeta (earthworms)
Hirudinea
(leaches)
Siboglinidae branchial filaments
increase surface area for gas absorption
Gases needed for Siboglinidae symbionts
O2
CO2
SO4 (sulphate)
branchial filaments connect to trophosome
Marine Annelid reproduction
dioecious
external fertilization broadcast spawn
trochophore larva
Marine Annelid gametes
from mesothelium
stored in coelom
escape through coelomoducts or metanephridia
Epitoky
morphological transformation into a sexual individual
Annelids undergo epitoky
to leave benthic habitat and swim up in water column
when do Annelids undergo epitoky
in response to environmental cues, all at same time for reproductive purposes
Annelid epitoky - the changes
large eyes (to detect enviro. cue)
parapodia enlarge
ripe gametes in coelomic compartments
regression of gut
enlargement of parapodia in epitoky (Annelid)
enlarged for swimming paddles
chaetae increased for efficiency
regression of gut in epitoky (Annelida)
only in some species
using every bit of energy they can for reproduction (then die)
Type of transformation (epitoky, Annelida)
Direct transformation
Posterior transformation
Posterior budding
Direct transformation (epitoky, Annelida)
whole worm undergoes transformation and swims up in water column
why is epitoky dangerous
the swimming up-column ‘in-mass’ (swarming) proposes a high predation risk
Posterior transformation (epitoky, Annelida)
only posterior transforms – breaks off – posterior 1/2 swims up
Posterior budding (epitoky, Annelida)
Epitokes bud off of posterior end and swarm up in water column
trochophore larva
apical ciliary tuft
stomach, mouth, anus, complete digestive tract
2-3 bands of cilia
feeding or non-feeding
trochophore larva circumferential ciliary bands
prototroch - anterior, swimming
metatroch - posterior, feeding
trochophore larva feeding
prototroch effective stroke (down) draws particles toward metatroch – metatroch effective stroke (up) draws particle in to food groove – short cilia draw particle to mouth
trochophore larval development
begin adding metameres to posterior end (pygidium) - lose cilia - crawl away as juvenile annelid
Clitellata characteristics
Sednetaria no parapodia 2 pairs of setae/metamere hermaphroditic clitellum
clitellum
several adjacent metameres swollen with glandular cells
functions in reproduction
Annelid movement
peristaltic burrowing through sediment
alternating contractions of circular and longitudinal muscles
contraction of circular muscles, Annelida
contracting fluid in metamere and pushing anterior forward
maintaining position in a burrow
shortened/fattened metameres + erect setae push against sides of burrow
oligochaete digestive system
regional specialization
mouth – pharynx w/ dilator muscles – esophagus – crop – gizzard – intestine – anus
Annelid gizzard
breaks up material
physical maceration
Annelid intestine
chemical break-down of material
absorb material
Annelid intestine features in cross section
typhlosole
chlorogogen
typhlosole
infolded gastrodermis in centre - increase surface area for enzymatic gland cells and absorptive cells for digestion
chlorogogen tissue
specialized mesothelium
intermediary metabolism
what is intermediary metabolism
glycogen/fat synthesis and storage
hemoglobin synthesis
protein catabolism
urea synthesis
importance of urea synthesis
ammonia is toxic - hard to flush out in terrestrial animals
urea less toxic (but metabolically expensive)
Oligochaete reproduction
pseudocopulation
2 worms in clitellum secreted ‘sleeve of mucus’ - transfer sperm to seminal receptacle
Oligochaete reproduction post-copulation
clitellum forms hard, proteinaceous cocoon + nutrients – slips down – collects egg - slips down – collects sperm – slips off anterior end
oligochaete reproductive structures
clitellum
male gonopore
female gonopore
seminal receptical
invasive earthworms
native worms died from glaciation – agriculture brought them from Europe/Asia - spread by fishing - damaging forest not adapted for them
how earthworms can damage a forest
the plants are adapted to nutrients in the top soil layers - worms mix the nutrients down
Hirudinea
Sedentaria, Clitellata leeches, bloodsuckers no parapodia, setae clitellum, suckers hermaphroditic dorso-ventrally flattened fixed n metameres
Hirudinia locomotion
swim and crawl
“looping”
Hirudinia locomotion body features
no setae
anterior/posterior suckers
dorso-ventrally flattened
leech looping
posterior sucker attaches to substrate - contract circular muscles - elongate - anterior sucker attaches – release pos. sucker - contract long. muscles -…
Hirudinia swimming
dorsal/ventral undulations
Hirudinian parasitism
ectoparasitism attach on w/ anterior sucker 3 jaws buccal secretions dilator muscles of pharynx
Hirudinian jaws
cuticle elaborated/sculted to form cutting blades
may leave Y-shaped incision on host
Hirudinian buccal secretions
topical anesthetic (so host is unaware)
vaso-dilators (expand vessels to increase flow)
anticoagulants (hirudin)
Hirudinian pharynx dilator muscles
expand lumen of pharynx - creates negative pressure - blood gets sucked in to body (similar to oligochaete pharynx)
Hirudinian digestive system
jaws – pharynx – crop – crop caeca – intestine – anus (below anterior sucker)
crop caeca
extensions of crop for wall expansion during feeding
why do Hirudinia need crop caeca
blood is high H2O - need a lot to get nutrients - have to expand alot to get good meal
Hirudinia excretion
metanephridia
two smaller Lophotrochozoan groups
Phylum Nemertea
Phylum Rotifera
Phylum Nemertea
'proboscis worms' 'ribbon worms' long, thin, dorso-ventrally flattened, ciliate epidermis secrete celephane-like tube highly extensible predatory *proboscis
Nemertea habitat
mostly marine, shallow water benthic, rock or sediment
Nemertea movement
motile
muscular/cilia crawling
peristaltic-type movement (deformable body)
Proboscis
mesothelium sac lined w/ circular muscle, above mouth, contains extendible proboscis - attached to proboscis retractor muscle - may be barbed and toxin bearing
how proboscis is ejected
proboscis sac filled w/ fluid - circular muscle contraction - increased fluid pressure - propel prob. out
Nemertine body compartments
Rhynchocoel (prob sac) - mesothelium
lateral blood vessels - coelomic compartments
Nemertine blood vessels
epithelium - true coelomic
exterior lined w/ basal lamina
interior ciliated
apicobasal polarity exactly like miniature annelid compartments
Nemertine reproduction
dioecious
transient gonads
broadcast spawn
free swimming larva
Nemertine gonads
concentrated cells - repeated clusters of gametes - down length of body, ducts form in reproductive season - broadcast spawn
Nemertine larva
trochophore-like
external fertilization
juvenile worm develops inside of larva body -metamorphosis- breaks out - eats larva body
Phylum Rotifera
'wheel animalcules' ciliated corona small 0.1-0.5mm pseudocoelomate eutely some syncytial lorica
Rotifer corona use
swimming
phytoplankton capture
pseudocoelomate
secondary body compartment not derived from mesothelium
eutely
following development constant n cells - never more - every animal the same
lorica
intracellular cytoskeletal elements
meshwork of keratin-like protein fibres
thin/flexible or thick/rigid
Rotifer morphology
corona - 3 ciliary bands, mouth, master
trunk - stomach, protonephridia, anus
foot + toes
Rotifer cilia
function like trochophore larva (direct food to mouth) through convergence
mastax
pharynx with trophi (chitinous plates)
Rotifer diversity
swimming, sessile in secreted tube, herbivore, predatory, swim by moveable stiff lorica extensions (plates/scales), colonial
Rotifer freshwater survival
protonephridia
cryptobiosis
amictic-mictic life cycle
protonephridia role in freshwater survival
help to maintain osmotic balance
cryptobiosis
expel all water - survive long time as ‘dried up flake’ - rehydrate in favourable condition
Rotifer life cycle
favourable conditions: amictic female (2n) – diploid egg – amictic female –
unfavourable: amictic female - mictic female (2n) - haploid egg - haploid male - fertilized egg (2n) - amictic female
amictic
incapable of being fertilized : parthenogenetic : producing eggs that develop without fertilization
Rotifer reproduction during favourable conditions
parthenogenesis
how amictic/mictic reproduction helps Rotifer survive winter
fertilized eggs can enter diapause
“winter eggs”
“diapause eggs”
thick secreted coating that withstands freezing/dessication
