Lophotrochozoa (Bilateria) Flashcards
All belong to which cade?
Bilateria
What’s special about lophotrochozoa
within bilateria, most phyla belong to clade lophotrochozoa
Main bilateria characteristics
- bilateral symmetry
- triploblastic development (3 germ layers)
- most have digestive tract with 2 openings
what are the 3 major clades of bilaterally similar animals according to molecular evidence?
- deuterostomia
- lophotrochozoa
- ecdysozoa
lophotrochozoa have how many body forms?
18 phyla total
5 major, large ones
Lophophore is what?
crown of ciliated tentacles
what phyla are lophophore’s present in?
brachiopods and bryozoans
trochophore larva is what?
shaped like spinning top and very small
generally translucent
present in some clade members
what’s different about lophotrochozoas?
no unique morphological features - derived characteristics - shared by all members
some clade members lack both features
what phyla does a marine flatworm belong to?
Platyhelminthes
how many species of Platyhelminthes?
roughly 20,000
key characteristics of Platyhelminthes?
- free living, freshwater and marine
- reproduce sexually and asexually
- triploblastic development - mesodermal layer
what does acoelomates mean
no body cavity, triploblastic development
what are the 3 basic tissue layers?
ectoderm
mesoderm
endoderm
what is the ectoderm?
epidermis, rise to nerve cells
what is the mesoderm?
solid filling in invertebrates
what is the endoderm?
gut lining in flatworms and humans
why do flatworms have no formal organs for gas exchange?
high surface area relative to mass
gas has short distance
lack blood supply, organ to transport blood
characteristics of Platyhelminthes (flatworms)
- intracellular digestion
- sac like gut: undigested items ejected via mouth (no anus)
- no circulatory system
Platyhelminthes feeding and digestion
- pharynx connects mouth and intestine which can be protruded to capture prey
- many carnivores, some feed on algae
- slime toxins
- some hit prey with hard, spiked penis
locomotion of Platyhelminthes
glide
body covered in cilia
cilia provide fence for propulsion
nitrogenous waste excretion of Platyhelminthes
nitrogenous waste eliminated across general body surface through opening in body wall
what are protonephridia?
bundle of flame cells - tubules
reproduction of Platyhelminthes
assexual reproduction and regeneration via fission
highly regenerative - memory retained even if they need to grow a new head
Platyhelminthes nervous system
- nerve cords with simple brain
- bilaterally symmetrical
eye spots mean…?
can learn to overcome light avoidance
shared basic characteristics of bryozoa and brachiopoda
- crown of ciliated tentacles
- U-shaped alimentary canal
- no head
- sessile - don’t move, stationary
- ‘coelomates’ - triploblastic (form pockets)
How many species of Bryozoa
roughly 4000
what are known as ‘moss animals’
bryozoa
where are bryozoa usually found?
UK, on kelp washed up on beach
basic characteristics of bryozoa
- small
- colonial
- hard exoskeleton - contribute to reef building
body plan of bryozoa
- U-shaped gut
- lophophore to feed
- anus, stomach, intestine
- retractor muscle to draw lophophore ack into body
what is a statoplast?
an asexually produced encapsulated bud of a freshwater bryozoa that is released upon disintegration of the parent colony in Autumn, remains inactive through winter
how many species of brachiopoda
roughly 350
characteristics of brachiopoda
- sessile bottom dwellers
- shells on dorsal and ventral sides (unlike bivalve molluscs but otherwise resemble them)
- all marine
brachiopoda are divided into 2 classes
articulata and inarticulata
Anatomy of inarticulate brachiopods
- the pedicle valve (dorsal) larger than the brachial valve (ventral)
- organs in coelom with contractile heart
what does the pedicle valve do?
attached the animal to the seabed
Anatomy of articulate brachiopods
- open and close shells in different ways
- named after tooth and socket joint
- clear lophophore
what does the name ‘Rotifera’ mean?
wheel bearer - refers to crown of cilia at anterior end
characteristics of Rotifera
- fresh water
- anus and mouth
- small
- cilia for feeding and jaw for grinding
body plan of Rotifera
- anterior end = head region
- modified muscular pharynx - Master (intricate jaws)
- trunk contains visceral organs
- supported on food and substrate
- not a coelmate
Rotifera have roughly 1000 what?
limited cells (specialised organs also)
3 Rotifera classes have 3 reproduction types:
- gonochoristic
- parthonogenesis
- bdelloidea
what does gonochoristic mean?
have a specific sex
what does parthenogenesis mean
females that produce more females from unfertilised eggs (don’t need males)
what does bdelloidea mean?
strictly asexual reproduction for 40-11 million years
what is a Turbellaria?
Platyhelminthes
all subgroups that aren’t parasitic
free living mix of parasitic and non-parasitic species
Turbellaria reproduction
- all are simultaneous hermaphrodites and fertilise eggs internally
- mate by penis fencing
what is penis fencing?
try to impregnate each other, loser adopts female role
what are trematodes
sub group of parasitic flatworms
known as flukes
what are Cestoda?
tapeworms
live mostly in vertebrates
hooks and suckers
what is a proglotids?
sac of sex organs
taenia sodium infections
- eating meat with cysticerci = intestinal infection
- infection with eggs or faeces means cysticerci can form in connective tissue and brain
- can cause epilepsy and death
what is the leading cause of epilepsy in humans?
neurocysticercosis
what forms to Molluscs include?
clams/oysters/squids/octopods/snails
are typical molluscs symmetrical?
yes, bilaterally
ventral surface of molluscs
flattened and muscular to form sole or foot
dorsal surface of molluscs
covered by childlike shell to protect underlying internal organs
What is the mantle?
epidermis, it secretes its shell
what are shells made out of?
calcium carbonate
what is the result of the epidermal sections of the mollusc shell being continual
the shell increases in diameter and thickness at the same time
what does the pair of gills do
they project from mantle cavity
water enters lower cavity up through gills
Bivalvia = what?
class of molluscs that are compressed and possess a shell with 2 valves that enclose the entire body
examples of bivalves
mussels/clams/scallops/oysters etc
characteristics of bivalves
- most marine
- suspension feeders
- no head or radula
- no brain - nerve network
shell of bivalves
- left and right valves that attach and articulate with each other
- dorsally held together by hinge ligaments
- valves close with adductor muscles - outer hinge ligament is trenched and the inner compressed
benefits to have a shell and adductors
- defense
- prevent desiccation
- support internal organs
Mollusca body plan in bivalves
- edges of mantle folds form incurrent and excurrent siphons
- cilia direct water flow over gills for gas exchange and filter feeding
- the radula is absent
feeding of molluscs
most = filter feeders
gills modified to increase food capture
cilia on gills to capture food particles
food particles transported in a stream of mucus to the mouth
digestion of molluscs - bivalves
- cilia in stomach cause rotation and churning
- suitable particles to digestive gland
- waste material pushed to rectum and removed via anal pore
generalise bivalve body plan
- foot attached ventrally
- gills covered by mantle folds
- edges of mantle folds form siphons
- mantle function in gas exchange
differences in different brachiopod and bivalve muscles with their shells
articulate brach = tooth and socket
inarticulate brach = no teeth, adutor muscles, celome pressure
bivalve molluscs = elastic hinge ligament
what are the main clades within the mollusca phyla?
8 total
main:
- cephlapoda = octopi, squid
- bivalvia = clams, mussels etc
- gatropoda = snails, limpets etc
main characteristics of molluscs
- one of largest phyla
- microscopic to enormous
- marine, fresh water, terrestrial
- filter feeders
- grazers, carnivores
- most gonochoristic
- all soft bodied
how many species of mollusca?
roughly 93,000 species
3 main parts of a generalised molluscs body plan
- muscular foot (movement)
- visceral mass (organs)
- mantle (fold tissue over visceral mass, excrete shell)
where does fertilisation occur in molluscs?
externally in the sea water
molluscs stages of development
gastrula - trochophore - veliger - adult
what is a gastropoda’s circulation
heart delivers blood to heat/foot and viscera in mantle cavity
gastropoda open circulation
blood also has a role in hydrostatic skeleton
gastropoda make up how much of molluscs species?
75%
what are limpits
uncoiled gastropods
characteristics of gastropoda
- only molluscs to have invaded land
- univalve coiled shell is typical
- few metazoan clades have colonised marine, freshwater and terrestrial habitats successfully
how are pearls formed?
inside shell of certain molluscs as a defence against an irritant e.g parasite
immune response
what makes up mother of pearl?
mantle deposits layers of aragonite and conchiolin
how do gastropoda feed
varied, ciliary feeders
scavengers
predators
most use radula
what are the 3 subclasses of gastropoda
- Prosobranchia - periwinkle, limpets
- Opisthobranchia - sea hares, sea slugs
- Pulmonata - land and freshwater snails and slugs
reproduction in gastropoda
penis is everted and sperm exchange external
Pulmonata = hermaphrodites
copulation ususally courtship involving circling, oral and tenticular contact
what are cephalopoda
subclass of molluscs
octopods, squids, cuttlefish and nautilus
characteristics of cephalopods
- all marine
- 2-70cm average but can be giants
- active predators
how many cephalopoda species
600
form and function of cephalopoda
internal shell or absent shell = modern form
Special about nautilus
only species of cephalopod that retains external shell
nautilus shell characteristics
- divided by transverse septa into internal chambers
- perforated septum in the middle by the siphuncle
- living organism retained in last segment of shell
- funnel derived from foot
- tentacle derived from the head
limitations on nautilus for having a shell
lots of water resistance
limits speed
shell could implode with sudden changes
gastropods nervous system
simple, sensitive foot for attacks and substrates
cephalopods nervous system
essentially have a brain
nerves expanded
ganglia concentrated and fused to form brain
what protects the brain of a cephalopod
cartilaginous cranium
cephalopoda feeding and nutrition
present radula
jaws in buccal cavity
beak can bite and tear tissue
tissue pulled into buccal cavity by radula
pair of salivary glands empty into buccal cavity
what do octopi do to their prey
secrete poison and enzymes into prey
what do squid feed on
fish, crustaceans and other squid
what do cuttlefish feed on
invertebrates like shrimp and crabs, swim on bottom
what do octopods feed on and how
- clams, snails, crustaceans and fish
- paralyse them with their bite
- live in dens - lie and wait for food
cephalopod visual system
- nerve fibres behind retina
- thought to not have colour vision
- squids have colour patten and signal each other with colour due to chromatic aberration which could be maximised due to pupil shape and size
colour change in cephalopod
manipulation of chromatophores
squid and octopus darken in colour when alarmed
some colour changes correlated with aggression
some colour displays associated with courtship
cuttlefish example of using colour
court female with one signal side of body and use the other signal side to show it’s a female to the rest of the population
ink sacs in cephalopoda
ink sac opens behind rectum, gland secretes fluid
used to confuse predators
ink released when alarmed
reproduction in cephalopoda
male seduce female with display
fertilisation takes place in mantle cavity
complex copulation
one of males arms modified to intermittent organ
male receives spermatophores from his funnel and inserts into female mantle
development of cephalopoda
direct development, no larva stages
what is different about squid reproduction?
they often die after they have played their eggs
and they have mass copulation events and fertilisation
