Phylum Platyhelminthes Flashcards
bilateria (triploblasts)
- Directional active movement with a purpose
- Last big split
- Triploblast → 3 embryonic tissue layers
- Monophyletic group
whats so great about being a bilaterian
- Having a mesoderm layer
- Ectoderm = skin and nerves
- Endoderm = organs
- Mesoderm = connective tissue, bone, muscles, blood vessels
aecolomate
o No coelom
o Fill blastospace with cells
o Organs float around, unorganized
o Flatworms, small animals
pseudocoelomate
o Fluid filled
o Nematodes
o False body cavity, no mesoderm lining of gut
eucolomate
o Mesoderm lines gut, organs and coneects them all together
o Segmentation
o Bigger and more complex organisms because things are separated
cephalization
o Leads to movement in 1 direction
o Development of anterior and posterior due to forward movement
o Sense environment with head first → development of sense organs
o Mouth in head
o Does not mean they have a head → just concentration of sensory organs at front
early sensory systems
- Statocyst in acoelomorpha
o Ball that helps to sense things - Ocelli in turbellaria (planaria)
o Little eye sports (no images, just light and dark)
acoelomorpha
- Marine
- Most are very small → need microscope
- Statocyst for orientation
- No anus, don’t really have a gut (syncytial digestive vacuole instead)
- Extracellular digestion → digest with juices outside and them absorb them
- No coelom
- Photosynthetic bacteria that are symbiotic so they get energy from that
xenacoelomorpha
- Purle socks
- New phylum discovered in feb 2016
platyzoa
- Platyhelmithes
- Flat small often no coelom
- Shwos different groups of phyletic ree
- Non parasitic and parasitic groups separated
- No last common ancestor for non-parasitic
- Poly and paraphyletic (how??)
characteristics of platyzoa
- Literally flat and worm
- 20000 species
- Acoelomate, bilateral, vermiform
- Most parasitic
- No anus (most)
- Flame cells (excretion and osmoregulation)
- Well developed reproduction (most hermaphrodites)
- Four classes (phylogeny under debate)
generic platyhelminthes
- Internal cavity = parenchyma
- Flat bc need to be small → no systems, small for surface area and to be able to do things at the cellular level
o Dorso-ventrally flattened
flame cells
- Mini kidney
- Filters fluid from inside body
- Removes metabolic waste
- Controls osmotic pressure
o Lots of microtubules and microvilli to retain ions
o Flame cells + tube cells = protonephridia
class tubellaria
- Small (<5mm) but can get up to 50cm
- 4500 species
- Mostly free living
o Marine, freshwater, terrestrial (damp)
o Swim and glide with muscles, cilia, mucus
skin and muscle of tubellaria
o Skin and mucle: • Cilia on epidermis • Epidermis contains rhabdites • Attach and detach system – dual-gland adhesive organs (ability to stick to things with adhesive and then unstick) • All found in rhabdites
feeding of tubellaria
o Muscular pharynx in ventral centre of body (mouth not at anterior end it is part way down ventral line)
o Intestines can be simple like 1 line or branched to diffuse throughout body bc no circulatory system
o Extracellular or intracellular digestion
o Scavengers, predators
nervous system of tubellaria
o Cephalization
o Concentrated nerve sections → diffuse nerve plexus and ladder like pattern
o Auricles → ear like lobes packed with chemoreceptive and tactile cells
o Statocysts for orientation, rheoreceptors (currents), ocelli (eyes)
reproduction of tubellaria
o Asexually → fission and regeneration (break part and it will regrow)
• 20% of cells are adults stem cells
• Need 1 297th of body to grow new worm
o Sexually
• Hermaphrodites,
• Internal fertilization with copulation
• Have sex → don’t just release gametes into water
• Penis fencing → fight to inject penis because you don’t want to be mom bc its very energy consuming and you have to do more to survive and dad just walks away like its nothing
• If cant find a mate it injects its penis into itself (selfing)
key features of parasitic class
- Skin (tegument)
o Syncytial → non ciliated (not separated) epidermis
o Unites group into neodermata (diff skin) - Digestive system
o Lacking in some groups because they just absorb nutrients from host - Nervous system
o Minimal cephalization - Reproduction
o Different among classes
o Reproduce continuously
class trematoda
- Adaptations for parasitism
o Hooks onto host, enzymes, penetration, cyst forms - 11000+ species
o Only 6 parasitize humans - Most have complex life cycle
o Many have 2 hosts per life cycle (subclass digenea)
example life cycle fo digenea flukes
- Fertilized eggs in feces
- Eggs hatch in intermediate host (first host)
- Asexual amplification in intermediate
- After amplification swimming form goes to infect vertebrate
- Goes to definitive host
- Sexual reproduction in definitive host once they have matured
- Affects 2000000000 million people every year and can lead to death after many years
common digenean flukes
- Liver flukes → undercooked/raw fish
- Blood flikes
o Free swimming part burrows into skin and into blood stream (no fish)
o Schistosomiasis
o Enters human skin directly and enters blood vessels and intestines
o Can cause many indirect symptoms and ifections
o Swimmers itch
class mongenia (one host)
- On skin/gills of fish
- Ectoparasitic → lives on outside of body and anchors to side (opisthaptor attachment)
- Eats what is going by it
- Simple life cycle
o Eggs – ciliated larvae – adult
class cestoda
- Tapeworms
- No real harm unless infection gets so big that it clogs kidneys
- Long flat bodies
o Scolex = attachment to host
o Proglottids = conveyor belt = reproductive units
o No digestive system → eats when host does
o Microtriches to increase surface area for absorption (like microvilli) - Reproductive factories
o Main body = strobila
o Not true segmentation
o Youngest at head, mature (gravid) posterior
o Fertilization from same or diff strobila (can fertilize itself)
o Constantly releases egg and sperm
o Single proglittid can release 50000 eggs
o Eggs from uterine pore
