Ecdysozoa Flashcards
Arthropoda and allies (ecysozoa)
Bilateria
3 points
- directional
- 3 layers of cells
- complete digestive tract (mouth and anus)
Arthropoda and allies (ecdysozoa)
Protostomia
- blastopore becomes mouth
Ecdysozoa
4 points
- grow my ecdysis (moulting exoskeleton)
- Lack locomotory cilia
- Amoeboid sperm
- “teeth” within the foregut (basal)
- Ring of spines around the mouth (basal)
classfication (online)
super phylum: ecdysozoa
Phylums: Nematoda Onychophora Tardigrada & others not the focus
Priapulida (or penis worms) - not the focus
3 points
- burrow in slime mouths open
- predators soft bodied invertabrates
- cuticle warty and superficially segmented (not tissue deep)
- body divided into presoma: barrel shaped, can be retracted into trunk, spiny region about mouth
trunk: spiny
Kinorhyncha - not the focus
6 points
- live in mud or sand
- feed on organic detritus or diatoms
- segments
- chitinous cuticle
- head invertible covered in circlets of spines
- move by thrusting head forward and contracting body. spines anchors
nematoda (round worms or thread worms) - focus
basics
4 points
- over half od species parasitic
- elongate, spindle shapes - adapted for interstitial spaces
- sensory system well developed
- oral stylet (piercing needle)
nematoda - focus
feeding
3 points
- saprophage - dead organic matter
- herbivores - pierce plant suck contents. some crop pests
- predators - target soft bodied slow moving prey
nematoda - focus
parasites
4 points
- intestinal nematodes - human infections
- filarial nematodes - filarisis and related diseases
- can be used in pest control
- hookworms, pinworms, whipworms (Can live with unless a lot)
nematomorpha (horsehair or gordian worms) - not focus
8 points
- Free living in fresh water as adults
- Larvae are parasites of arthropods
- Extreme hair-like body, thick cuticle
- No excretory or digestive system
- Larvae absorb food directly from host
- Adults survive on stored energy reserves
- Parasite-mediated behaviour modification
Causes hosts to drown themselves - Adults emerge often with explosive force
Loricifera - not focus
- sediment living
- protective outer lorica
- invertable spiny head with oral stylets
Onychophora (velvet worms) - focus
body plan
4 points
- Thin, flexible cuticle of chitin
- Worm-like segmented body
- Each segment has a pair of clawed, lobe-like legs
- Head made of three segments:
Appendages modified into antennae, jaws, and papillae
Onychophora (velvet worms) - focus
respiration
3 points
- Tracheal respiratory system
- Spiracles -
Openings on body surface
Lead into tufts of tracheal tubes - Trachae -
Unbranched
Lead straight to organs
May be supported by chitin strands
Onychophora (velvet worms) - focus
circulation
3 points
- Haemocoel -
Body cavity filled with haemolymph (‘blood’)
Partitioned into sinuses - Haemolymph carries nutrients only, not oxygen
- Contractile heart plus body movements help circulate the haemolymph
Onychophora (velvet worms) - focus
nervous system
3 points
- Paired ventral nerve cords -
Connected by commissural nerves
No true ganglia (congregations of nerve bodies) in segments - Antennae are principal sense organs -
Tactile
Hydroreceptors (detect water vapour) - Simple eyes at the base of the antennae
Onychophora (velvet worms) - focus
Digestion and excretion
4 points
- Foregut is chitin-lined -
Dilated pharynx
Narrow oesophagus - Midgut
Fills most of body cavity - Hindgut
Very short - Each segment has -
a pair of metanephridia
(Primitive coiled kidneys)
its own external pore
Onychophora (velvet worms) - focus
reproduction
3 points
- Females larger than males
- Indirect internal fertilisation:
Male produces spermatophores
Inserted into female gonopore - Live-bearing (viviparous) or egg-laying (oviparous) species
Onychophora (velvet worms) - focus
ecology
- Tropical and sub-tropical and wet temperate distribution
- Specialised for life in leaf-litter
- Papillae on head:
Slime glands = nets of strong, stretchy threads
Defence
Capture of prey - Some species form social groups:
Female dominated
Live and hunt together
Aggressively defend territory from other groups
Tardigrada (water bears) - focus
Bodyplan
4 points
- Four body segments
Each segment has paired appendages
Mostly head; missing the genes that form the trunk in other segmented animals. - Exoskeleton, often divided into segmental plates
- No respiratory system
Diffusion of oxygen from water across body surface - Haemocoel
Function uncertain other than hydrostatic skeleton
Tardigrada (water bears) - focus
nervous system
5 points
- Large dorsal brain
three median lobes
Two lateral lobes - Double ventral nerve cord
- Segmental ganglia
- Eye spots
Light sensitivity - Hairs on body and legs
Contact chemo-reception
Mechano-reception
Tardigrada (water bears) - focus
digestion and excretion
3 points
- Liquid feeders using stylets to pierce plant cells or animal prey
Within a buccal cavity - Pharynx
sucking - Three tubular glands associated with rectum
May be associated with excretion
Tardigrada (water bears) - focus
Reproduction
3 points
- Separate sexes but females predominate
- Aquatic
Females moult before egg deposition
Males inject sperm into old cuticle before female emerges
Eggs fertilised in space between old cuticle and female’s body
Old cuticle becomes an egg case - Semi-aquatic species
Internal fertilisation
Tardigrada (water bears) - focus
Ecology
- Cryptobiosis
- Most of a tardigrade’s life spent in a desiccated ‘tun’
Resistant to extreme temperatures and pressures, air, water and food deprivation, and radiation
Arthropoda - intro
basics
5 points
- Segmented animals
Each segment has jointed appendages, usually specialised in function - Exoskeleton
- Haemocoel (blood-filled cavity)
Replaces coelom of embryo - Dorsal heart
- Ventral nerve trunks
Arthropoda - intro
exoskeleton
2 points
- Rigid skeleton:
Provides protection and muscle attachment
Limits growth, restricts diffusion / excretion, reduces external stimuli
- Laminated. Muscle layers of worms
Epicuticle – wax and tanned proteins
Exocuticle – chitin, pigments, thickened
Endocuticle – chitin, flexible
Arthropoda - intro
Circulation
3 points
- Haemocoel divided into sinuses
- Haemolymph
Bathes tissues
Primarily for transport of nutrients
May have respiratory function - Contractile heart
Ostia permit the haemolymph to enter, pushed forwards
Arthropoda - intro
nervous system
4 points
- Double ventral nerve trunks
- Segmental ganglia
- Brain made of fused cerebral ganglia
Protocerebrum receives optic nerves
Deuterocerebrum receives antennal nerves
Tritocerebrum receives second antennal nerves, where present
- Brain is above digestive system
Arthropoda - intro
Evoloution - Last common ancestor of all arthropods (c.500 Mya) had:
7 points
- Modular body plan
- Chitin exoskeleton
- Branched (or unbranched) appendages on each segment
- Ventral mouth
- Pre-oral antennae
- Dorsal eyes
- Marine, probably a sediment feeder