Nematodas Flashcards
How are they comapred to mollusca
They are species complex
Where are they found and their form
Marine
Maiofauna ( biomonitoring)
In parasitic form eg threadworms or pin worms
What are they important for
Biomonitoring
What forms can namatode take
Parasitic worms the most
Eg. Threadworms and pinworms
How many nematodes yet to be found - diversity
3 million per square meter (soil)
Model org - C elegans - free living soil nematodes
Phylum nematode -> Protostome clade-> ecdysozoa
Describe protosomes claded
Extraordinary diverse
Ectysozoa - 3 subclass
Divided based on molecular similarities
Some structural too
List the 3 subclasses of ecdysozoa
Scalidophota
Panarthropoda
Nematoida
Q- Why are they placed here with the arthropod and not with annelis
Shed their Cuticle in order to grow
Characterostocs of nematods
T- Triplobastic, bilateral , vermiform, unseg, blastocoelomates / pseudocoelomate (most common)while others are acpelomates
B- cylindrical body
P- pointed at ant and post
C- have a thick , multilayered cuticle
J- juveniles molt
- longitudinal muscles and not cir muscles diff with ANNELIDS
- sense organs - cephalic. Caudal/ohasmids
- no circulatory, resp system
- complete dig system
- Unique secretory -excretory system ( have rennettes cells or set of collecting ducts)
- epidermal is cellular or syncitial, not cilliated
- long epidermal nerve cords
- gonochotistics - many diff modes
- eutely
- free living and parasitic
Describe the pseudocoelom
- gut not lined with cells drived from mesoderm
How are nutrient circulated
Diffusion and oasmois
Effects of pesudocoelomate
No circular muscles or supporting mesetaries
Organs held loosley and not well developed
No circulation system , therefore through diffusion.
Describe the cuticle of nematode
Flexible - you see how it goes wiggly woogly, that also means it is lighter and thinner then mineral skeletons eg bivalves
No cillia , chitin, and emzymes (metabolically active)
Which form need cillia
Parasitic forms
Nemotoda lacks cillia
Why are enzymes present on the cuticle
Metabolically active
What is the diff btw nematoda and bivalves
Thinner and lighter then mineral skelton (bivalaves)
What is absent in the free living form of nematoda?
Inner cuticle layer thicker (fibrous layer) in terrestrial and parasitic form
Cilia is also needed in parasitic worm
How is the tegument in trematode & cestode different compared to Cuticle in nematode
Cestode (tapewprms) have microtriches and trematode (flukeworms) and nematodes DONT have microtriches
Tegumemt in trematode - made of multiple layers whole tegument is one expended layer , amd syncytial
Tegument in cestode is not multilayered but is syncytial with microtriches
Cuticle in nematode (no tegumemt) is multilayered but not syncytial
What is the imp Cuticle
Support
Movement
Prevent drying - cuticle is semipermeables due to the lipids
Role in secretion, excretion and substances uptake
How do nematoda grow
Shed by molting (3-4molts - instar to adult)
Controled by hormones
Regularly shed cuticle via excdysis (or molting)
In arthropods - the hormone controll is the ecdysozo, but ecdysozo doesnt control molting in nematoda
How is the outer body look like
Can be varied:
Smooth
Sensory setae
Wartlike bump
Ridges
Grooves
Epidermis of nematoda
Cellular to syncytial
Thicken sinto ventral, dorsal & lateral longitudinal cords
Muscles in nematoda
Have Longitudinal muscles - 4 quadrants
Muscles connected to dorsal and ventral nerval cords by muscle arm rather than nerve extension in the neuron
How is the muscles connection dif compared to other animals
Other animals Should have Netve extension in the neuron
Can nematodes use perastaltic burrowing …..
No, they dont have cir muscles
Movement in nematodes - how do they move
Have waves of long mus contraction
They travel back over the org
Propeells the body formward
But also
They act against the hydrostautic skl and cuticle (imp of cuticle)
Free living form - need to have contract in subs to occur
Modes of feeding for nematode
Carnivores (plankton, benthic)
Deposits
Detritivores
Microscavengers (feed on fungi &bacteria on dead org or fecal )
Plant parasites of plants - nematodes use stylets
Chemautrophic bacterial symbiosis in gut or cuticle ( eg sulfide rich envr)
Regional specilization of nematodes
Mouth surr by 6 lips ass with papilae and cuticular flaps
Spines, teeth, jaws
All these structure are ringly arranged around the mouth itself
Nov 29 before feeding and digestion
Digestive tract in Nematodes
Buccal cavity -> muscular pharynx (oesophagus)
Intestine-> rectum-> cloaca-> trophosome (food storage)
Buccal cavity
Many shes and sizes
Muscular pharynx
Subdiv into distinct muscular region
Function -?
Rectum
Subterminal ventral anus
Initial and final degestion
Initial - extracellular
Final intracellular in intestince
K
I
J
K
L
M
Structure for circulation and gas exchanges in nematode
No
What are their parasitic forms
Hemoglobin
Excretion
Do nematode have nephridia ? What do they have instead?
No they dont
Rennet cells
Function of rennet cells
Connect directly to the excretory pore (anus in females and cloaca in males) only in free living for,s and not parasitic
Some groups have lost rennet cells , which forms ?
Parasites (C and D)
Kin toprotonephridia cells
Osmoregulation
Parasitic forms with no rennet cells,what do they have
Protonephridia with no cillia
Osmoregulation in nematoda
By rennet cells
Outer body the cuticle is deferentially permeable (impermeability due to lipid transfer protein) , allows water in but not out
Advantage in a hyper tonic envr
Not adv in a hypotonic envr
Explanation - more solute outside and less water outside, water want to leave , but cuticle doesnt allow it to leave
Vv explanation
Nervous system of nematoda
Nerve ring in circle composed of axonal dendrtic processe of neurons
Long nerves (dorsal , ventral , lateral) ass to the nerve ring
Has lateral commissures that connect all the long nerves
Nerve ring also connects to anterior nerves
Difference btw nervous system and other organism
Has neuronal cell bodies in a bundle w/0 ganglia bcz no network of nerve fibres but often referrred to as ganglia
Body cavity has muscle processes that connect to longitudinal nerve cords instead of the other way around
Anteriors nerves function
Have sensory function
Leads to sensory structures
Sensory str Eg senssilaa - general term for sensory structure eg spine
And Labial pappilae
Focus on mechanical and chemo sensory function
Dorsal cord function - motor
Lateral cord
Lateral cord
Sensory but not as well dev as anterior nerves
Ventral - main nerve trunk
Sensory and motor
Sense organs
Amphids -
Amphids function
chemo sensors
Amphids are conposed of
Modified cillia
Amphids are located in
Lateral part of the head
Amphids derived from
Are derived from modified cillia
2- phasmids
Posterios
Function in chemoreceptor
3- sense organ ?
Pigment cup ocelli
Reproduction in nematodes
HOGLY DIVERSE
MAINLY Gonochoristics With sexual dimorphism
Males - smaller and curved
Females are larger and straight
Males reproductive system in nematoda
Smaller
Cloaca
Copulatory apparatus - spicule
Some have a gubernaculum - guide the spicule into female vagina
Pheromones to locate each other
+ the doagram i made small one in lab
Females reproductive system in nematoda
Mid ventral gonoppre separated from anus
+ the diagram i made in lab
Fertilization/copulation
Come together
Males wraps curved posteior part around the female gonopore leading into her vagina
HIGH REPRODUCTION DIVERSITY of nematodes
hermaphrodite
Parthenogenesis
Pseudogamy - when the copulate with diff sps sperms that are utilized to start the egg to undergo parthenogenesis (it initiates the egg becoming a zygote ) , BUT NO FERTILIZATION OCCURS
Trioery - in a population MANY DIFF REPRODUCTION WAYS OCCURRING
What happens (development) after internal fertilization
1- Lay eggs in the envr
Zygote with harder egg shell
2- Facultative vivipary - zygote hatches inside uterus
- the female doesn’t survive bcz as the zygote grow they feed on mother
3- hermaphrodite (ovotestis)- self fertilization
4- direct development - free living
Development in free living forms
1- Direct developmemt after internal fertilization
2- Some have a resistant juvenile stages (dauer stage)
- c elegans occurs at when 2nd stage molt into adult
Dauer stage helps survive in stress full conditions
…..
Life cycle and developments in parasitic forms
So,e have a specialized stage i….
Whipworm vs roundwarms lifecycle
W- all the dev stages donot occur in the human host
Opp in round waorm
Whipworm lofe cycle
Mates in human guts
Fertilised eggs in host faeces
Ingestion of embryos
+ lifecycle diagram
Roundworm life cycle
Complete all stages of dev in human host
+ diagram
