L 13 - chaetognatha and aschelminth Flashcards
aschelminthes
thought to have pseudocoeloms. - some do, some dont.
- now used as grouping of convenience
common names chaetognatha nematoda nematomorpha priapulida rotifera
C - arrow worms nematoda - roundworm. nematomorph - horsehari worms penis worm rotifers. include acanthocephala (spiny-headed worms.
phylum chaetognatha
how scientific name arose?
swims in open ocean water
array of movable raptorial bristles surrounding mouth.
arrow worm bc long, slim with stabilizing fins.
molecular data puts chaetognaths with protostomes
- morphological support?
ventral nerve cord, circumesophageal connectives
chaetognatha deuterostome-like characteristics
multiple eucoelomic cavities, arose by enterocoely.
blastopore - not mouth. mouth 2nd. but coelom =/= deutero bc blastopore =/= anus.
heterocoelous development of chaetognath led to what thought?
transitional phylum btw proto & deutero.
- fossils found from around that time
coelem sets in chaetognatha
- other characteristics?
3 sets, separated by septae
1 in head, pair in trunk, pair in tail
- continuous gut, anal opening. no specialized gas/circulatory systems. - movement allows for circulation.
- mouth surrounded by set of long movable grasping spines: retracted by hood-like extension.
- non-image forming eyes
repro in chaetognatha - mating? - fertilization? -brooded? - development? cleavage? blastopore?
- simultaneous hermaphrodites.
- mating observed - mating dance
-transfer of masses of sperm. mass placed nearby and swim over to fertilize. - most lay egg immediately
direct development
cleavage more like spiral
blastopore opens on posterior end, closes. not mouth or anus.
feeding of chaetognatha
detect disturbance of water by arrays of vibration - detecting cilia.
- subdue prey w tetrodotoxin
phylum rotifera
all endoparasites
includes acanthocephala
non-acanthocephalan rotifera
small, move w beating cilia corona . pseudocoelomate. most solitary, few colonial. free-swimming; some sedentary. - build cases out of sand or fecal pellets. / armor called lorica - eutely.
lorica =
rigid intracellular protein layer within syncytial epidermis.
internal mouthparts of non-acanthocephalan
mastax (mast = chew) made up of number of small parts - called trophi
internal characteristics
protonephridia, simple NS, no circulatory, gas-exchange.
eyespot detect light.
cyclic pathenogenesis
asecual repro of diploid daughters by amictic females = good condition
bad condition = haploid sons produced by mictic females.
sons copulate w other mictic females, eggs stay dormant until conditions are better.
anhydrobioasis
eggs dry “hibernate” - add water = back to life
feeding of rotifers
active hunters - grab prey w raptorial trophi. feed on small particles, chew off substrate, whirl toward mouth usuing coronal cilia.
seisonidea
small group of non-acanthocephalans. ectoparasitic - live on crustacean - feed on host eggs or body fluid. very reduced corona, entirely sexually reproducing. sister to parasitic acanthocephala
acanthocephalans
characteristics
habitat?
coelom?
endoparasitic. live in guts of vertebrates, crustaceans.
no corona, mastax, mouth, gut.
large pseudocoelem.
spiny eversible head to anchor in gut lining.
5 phyla in achelminthes
- which are spiralian? ecdysozoan?
chaetognatha - non-spiralian, non-ecdysozoan
rotifera - spiralian
priapulida - ecdysozoan
nematoda - ecdysozoan
nematomorpha - ecdysozoan
feature that rotifers & acanthocephalan share?
syncytial epidermis
repro of non-acanthocephalan rotifers
direct development
separate sexes.
- may be pathenogenetic. amictic female = asexual amictic females. mictic female = haploid son copulates with other mictic female
repro in acanthocephalan
separate sex. sperm transferred via copulation.
acanthocephalans famous for?
changing behaviour or intermediate hosts to ensure they get eaten by final hosts
what are ecdysozoan animals?
3 phyla?
moulting animals. shed cuticle at least once in life cycle
– priapula
nematoda
nematomorpha
phylum nematoda: common name?
x-section?
habitat?
round in x-section.
terrestrial, freshwater, marine.
gut, circulation, body muscles in nematoda
mouth, muscular pumping phrynx, straight gut, terminal anus.
- no circulatory or gas-exchange systems.
- body wall muscles exclusively longitudinal.
coelom of nematode?
pseudocoelomate: mesodermally derived tissue on one side of coelom
how many nerve cords? functions?
4 - dorsal + ventral for locomotion. 2 lateral - sensory
different about muscle/nerve interaction?
muscle sends projections to nerves instead of normal opposite
repro in nematodes
herm, separate sex or combo.
- sperm transfer via copulation.
- direct development
- determinate cleavage and eutely.
feeding in nematodes
free-living. strong pharyx to suck in liquids. pedators with hooked teeth.
some are human parasites
use by humans to control insects
entomopathogenic
phylum nematomorpha
- different life stages
free living. mostly freshwater. juvenile are parasitic.
adults are long, dark thick cuticle
nematomorpha - pseudocoelom?
no filled with mesenchyme
muscles, gut in nematopmorph
gut is reduces, lack circular muscles.
head in larva of nematomorph
larva has spiny eversible head.
- parasitize terrestrial insects.
- grow to gigantic size in hosts body and burst out
phylum priapulida
penis worm
- free-living benthic
thick-bodied. predatory
distinct feature of priapulida
distinctive caudal appendage.
cns, coelom in priapulida
single large pseudocoelom.
not much of a brain, but have circumesophageal connectives.
repro in priapulida
separate sexes, free-spawning.
deuterostome-like development.
