Lecture 4 Flashcards
what features unite Lophotrochozoans
bilateral symm with some degree of cephalization
organ system-level organization
incomplete gut: no respiratory or circulatory systems
protonephridia (excretion, osmoregulation)
nervous system with anterior ganaglia and longitudinal, ventral nerve cords
monoecious with internal fertilization (not usually a M and F at same time)
why is monophyly of platyhelminthes in question
no defining features so you cant group them
describe how the nervous and excretory systems are more complex in turbellarians compared to those of Cnidarians
Turbellarians have a centralized, bilateral system with a basic brain, while cnidarians have a diffuse net with no brain.
excretory system of turbellarians
excretion via protonephridia (the first kidneys)
nervous system of turbellarians
some have fibers that coalesce to form cerebral ganglia
others have paired lateral nerve cords joined by commissure branches
have sensory and motor nerves present
general anatomical features of turbellarians
free living flat worms
benthic, marine and fresh water
mobility due to circular and longitudinal muscle fibers and cilia on ventral surface
predatory
polyphyletic (not a valid taxon)
describe the general life history of digenean trematodes
general anatomical features of tapeworms
rostelium
scolex (basically the head)
sucker
neck
immature proglottid
mature proglottid
*attachment varies between species
no digestive system
rudimentary nervous and excretory systems
phylum platyhelminthes
flat - worm
no universal defining features
> 34,000 species
Acoelomate (does not poses a body cavity) ; mesodermally derived parenchyma tissue (large loosely filled tissues
classes of platyhelminthes
turbellaria (planarians)
trematoda (flukes)
Monogenea (monogenetic flukes)
cestoidea (tape worms)
turbellarian reproduction
many reproduce asexually by transverse fission
monoecious; during copulation sperm is deposited into copulatory sac of partner. sperm moves to genital chamber and moves through oviducts where fertilization occurs
fert eggs move down oviduct and incorporate yolk produced by vitellaria
eggs deposited in protective cocoon
most species have direct development; some have larvae stage
trematoda
parasitic flukes
~ 10,000 species
two subclasses: Digenea and Aspidogastrea
several are medically important
very complex life histories
typically live within a digestive system; cushy enviro has allowed them to simplify their anatomy
have tegument; an adaptation to life as an internal parasite , syncytial (fused cells),
outer tegument/ the glycocalyx, overlies a basement membrane
inner tegument
cells of the epidermis fuse
class monogenea
mostly ectoparasites of fishes
gill flukes
class cestoidea
tape worms
highly specialized gut parasite of vertebrates
~3500 species
intermediate host(s) in life cycle
anatomically simple
some medically important
