9: Lophotrochozoa Flashcards
What is Bilateria split into?
Lophotrochozoa (Spiralia)
Ecdysozoa
Deuterostoma
How many lophotrochozoa phyla are there?
13 (out of 35)
‘Defining’ lophotrochozoa features
Lophophore: ring of ciliated feeding tentacles
Trochophore: planktonic larvae with several bands of cilia
Not all have both
What does Gnathifera include?
Rotifera
Micrognathozoa
Gnathostomulida
Feature of Gnathifera
Pronounced jaw called a mastax (tooth plate)
Normal name for Rotifera
Thorny-headed worms
Features of Rotifera
Usually freshwater
Live between grains and sediment (interstitial) and loose in water
Pseudocoelomate
Tiny (0.1-1mm)
No cell division, only cell growth- can’t regenerate lost body parts or repair damage
Body of Rotifera
Crest of cilia called a corona (feeding and locomotion)
‘Foot’ with ‘toes’ that adhere to substrate
Brain and nervous system
Rotifera feeding
Suspension feeders- currents of water generated by corona bring food towards
Also predation on other rotifers
Can also be parasitic
Rotifera cryptobiosis
Shut down in unfavourable conditions
State of suspended animation until conditions improve
Like tardigrades
Normal name for Micrognathozoa
Jaw animals
Micrognathozoa features
Only 1 species, discovered in moss in Greenland
125 micrometres
Interstitial (sediment)
Micrognathozoa body
Divided into head, thorax and abdomen
Complex jaws with over 16 movable elements
Micrognathozoa reproduction
Only females have been found, suggests asexual reproduction
2 kinds of eggs for conditions:
Thin shell that hatches quickly in a few days
Thick shell that lays dormant to see out the harsh winter
Normal name for Gnathostomulida
Jaw worms
Gnathostomulida features
Microscopic worms
Over 100 species
Live in marine sediment
Can endure very low oxygen
Gnathostomulida body
Impressive set of jaws
No body cavity, circulatory or respiratory system- too small
Sensory organs are modified cilia in head, used to locate food
Gnathostomulida reproduction
Hermaphrodites
Each has a single ovary and one or two testes
Egg ruptures through body wall
No larval stage
What does Rouphozoa include?
Gastrotricha
Platyhelminthes
Normal name for Gastrotricha
Hairybacks
Gastrotricha features
Abundant in marine and freshwater
0.05-4mm
Around 790 species
Gastrotricha body
Long, bottle shape Covered in bristles and spines Bands of cilia for propulsion Gut, muscle, brain, kidneys Pseudocoelomate No respiratory/circulatory structures
Gastrotricha feeding
Diatoms, bacteria, protozoa
Use cilia on head to gather food
Normal platyhelminthes name
Flatworms and tapeworms
Platyhelminth features
Around 30,000 species
1mm-30m long
Can be free-living or parasitic
Regenerative ability- if cut into new pieces, each becomes new worm
Platyhelminth body
Acoelomate, have a digestive cavity
Two nerve chords in the most developed
Eye spots
Platyhelminth feeding
Wrap around prey
Adhesive organs
Some secrete toxic mucus
Stab with a pointy penis that comes out of their mouth
Platyhelminth changing host behaviour
Make fish stay further form cover
Increase probability of stickleback predation
Vermizoa are made up of
Annelida
Nemertea
Vermizoa synapomorphies
Closed blood vessels
Central nervous system
Annelid features
Soft-bodied, muscular, elongate
Most aquatic, some terrestrial
Segmented- key to success
Annelid body
Repeated segments divided by septa
Each segment has own coelom, muscles, nervous control, excretory organs etc (called metamerism)
Rigidity provided through internal water pressure (hydrostatic skeleton)
Circular muscles make segments longer
Closed circulatory system
Several hearts
Annelid reproduction
Varied:
Oligochaetes and leeches are hermaphroditic
Marine are typically sexual and show epitoky
What is epitoky?
The atoke is the benthic azexual creature that cannot breed
Atokes bud new creatures from their body
In breeding season epitokes form, which float to the surface
Epitokes explode, releasing gametes into the water
Ecological importance of annelids
Fertilisation- they drag organic matter underground
Aeration
Tunnels provide water drainage
Prevent compaction, which promotes plant growth
Nemertea normal name
Ribbon worms
Nemertea features
Longest animal on planet- bootlace worm 55m long
Almost all are marine
No segmentation
Like flatworms, but have a mouth and anus
Nemertea reproduction
Adult and larval stages
Broadcast spawning
Planktonic larvae
Some can reproduce asexually
What makes up Lophophorata?
Brachiopoda
Phoronida
Bryozoa
Lophophore features
Have a lophophore- crown of feeding tentacles sat on a calyx
Generate water flow towards mouth with cilia
Normal name for Brachiopoda
Lamp shells
Brachiopoda features
300 existing species
Very cold oceans
Look like bivalve molluscs, but shells on upper and lower as opposed to left/right sides
Normal name for Phoronida
Horseshoe worms
Phoronida features
12 species in 2 genera Benthic marine Secrete a chitinous tube Project lophophores into water to feed Oldest found is from Devonian
Bryozoan normal name
Moss animals
Bryozoan feaures
5500 species,from 0.5mm to 1m colonies Colonies made up of zooids Sessile filter feeders Zooids connected by web of tissues Sometimes division of labour
Bryozoan feeding
Birds head with beak and mandible- grab debris and organisms
Vibraculum- long bristle moved with muscles, sweep settling debris from the colony
What is Tetraneuralia made up of
Entoprocta
Cycliophora
Mollusca
Tetraneuralia features
One pair of ventral and one pair of lateral nerve chords
Entoprocta normal name
Nodders, goblet animals
Entoprocta features
Around 170 species
All but 2 are marine
Often found living on worms and bryozoans
How do entoprocta differ from bryozoans?
Lack a true lophophore
Different gut arrangement- anus is inside feeding tentacles
Cycliophora features
Discovered on Norwegian lobster mouthparts
3 species
Mollusca features
From 1mm to over 20m
Marine, freshwater, terrestrial
117,350 species
Appeared mid-Cambrian
Mollusca body
Unsegmented, soft body
Open circulatory system
Mantle skin secretes calcium carbonate shell (absent in cephalopods, slugs and nudibranchs)
Muscular foot
Mouth with rasplike radula and chitinous teeth
Gastropod feeding
Radula is supported by the odontophore
Movement of odontophore is controlled by buccal muscles
Worn down teeth at one end are continually replaced from the back
Radula adaptations
Beak in some cephalopods
Siphon in cone snails- like a harpoon
Bivalves have lost the radula as they are filter feeders
Examples of gastropods
Land snails, slugs, sea angels
Gastropod adaptations
Foot enlarged for locomotion Spiral shell due to torsion of the body Only one hole in the shell Do not always have a shell though! Eg. sea angels Sex organs all on one side
Examples of cephalopods
Squid, cuttlefish, octopus, nautilus
Cephalopod features
Highly specialised marine predators
Complex brains and sensory organs
Elaborate eyes- convergent to ours
