Zoology -
PSEUDOCOELOMATE ANIMALS – Phylum Aschelminthes
Things you need to know from this chapter.
i. What does a
rotifer look like?
ii. Where do you
find rotifers?
iii. How do
rotifers reproduce?
i. What are
they known as?
ii. What do they
prey on?
i. General
characteristics of all roundworms.
ii. Know the
general life cycles & ways to avoid infection with the
iii. following
parasites…
1. Ascaris lumbricoides
2. Necator americanus
3. Trichinella spiralis
4. Filarial
worms
iv. What causes
elephantiasis? How is it spread?
v. What causes
river blindness? How is it spread?
vi. What causes
dog heart worms? How are they spread?
i. Why are they
called horsehair worms?
ii. Know their
general life cycle.
i. Where do you
find them?
ii. What do they
eat?
iii. How do they
reproduce?
i. When were
they discovered?
ii. Where do you
find them?
i. Where do you
find them?
ii. How do they
eat?
I.
Compared and Contrasted to Acoelomate Animals
A. They are like the acoelomate animals in that
they…
1. They are bilateral “worms”
2. Cephalization
3. Lack circulatory and respiratory systems
B.
They are more complex than the acoelomate animals in that they…
1. They have a pseudocoelom derived from the
blastocoel.
2. They are more mobile.
3. They have more complex reproductive systems.
4. They can store wastes for discharge out of
the body.
5. They have a complete mouth to anus digestive
system
II. What is a pseudocoelom?
A.
Structure
1. The
original ______________________ of the embryo persists
as a space
or cavity between digestive cavity and the body wall.
2.
Since it lacks the peritoneal lining of a true coelom, it is a
Pseudocoel
“____________________________________”.
B.
Biological Contributions
1.
Pseudocoelom generally provides greater freedom of movement.
2.
There is space for more development of digestive, excretory, and
reproductive
systems.
3. It
is simpler to distribute materials throughout the body.
4.
This provides a storage area for waste products to be later
discharged.
5. As
a ______________________ organ, the cavity is a base for
muscles
that provide movement.
III. Pseudocoelomates
A.
A term which
refers to animals with a pseudocoelomate body plan is Aschelminthes.
1. _____________________________________ -- A heterogeneous
phylum of small to microscopic wormlike animals; individuals are
pseudocoelomate and
mostly
unsegmented and are covered with a cuticle.
B. Except in parasitic ______________________,
the digestive tract is
complete
(from mouth to pharynx to intestines to anus).
C.
Digestive tract, gonads and excretory organs are within the
______________________.
D. In some,
the epidermis secretes a nonliving
______________________.
IV.
Lophotrochozoan phyla – the Aschelminthes that do NOT molt
A. Phylum Rotifera
1. Rotifers
have a ciliated crown, the ______________________ that
beats like
a rotating wheel.
a.
Rotifers are highly diverse in color, size and shape; some are
colonial.
b.
Rotifers are found worldwide (______________________
distribution)
with over 1,800 species known.
c.
Most are freshwater species but a few are
______________________
(living in salt water),
______________________
(living on dry land) or parasitic.
d.
Many endure ______________________ (drying out) and
temperature
changes by ______________________.
2.
Reproduction
a.
Rotifers are usually ______________________
1)
Males are smaller than females.
2) In
some classes, males are unknown, and in others,
males
occur only briefly.
b.
Bdelloidea females are ____________________________,
producing
diploid eggs that hatch into diploid females.
c.
Monogononta females produce diploid
______________________
eggs that form diploid females, or
haploid
______________________ eggs that, if not fertilized,
become
haploid males.
B. Phylum Acanthocephala – _____________________________ worms
1. All
spiny-headed worms are parasites in the intestines of
______________________.
a. Its
proboscis has rows of recurved spines that penetrate and
may
rupture host intestines.
b.
Larvae develop in crustaceans or insects.
c. They never infest humans.
2.
Form and Function
a. The
body is somewhat flattened.
b.
Both longitudinal and circular body wall muscles are present.
c.
There is no respiratory system or heart.
d. They
lack a digestive tract and absorb all nutrients across the
tegument,
which bears some enzymes.
e.
Shelled embryos discharged in the feces do not hatch until
eaten
by an intermediate host, often _____________________.
f.
Larval acanthors burrow through beetle intestine and develop
into
juvenile cystacanths in the insect hemocoel.
V.
The Ecdysozoan phyla – Aschelminthes that do molt
A. Phylum Nematoda: ______________________
1.
About 12,000 species are described; perhaps a half million exist.
a. They
live in virtually all habitats in all biomes; topsoil may
contain
billions per acre.
b.
Nematode parasites exist in nearly all animal and plant
species;
1)
They are economically important.
c.
Free-living nematodes feed on bacteria, yeasts, fungal
hyphae
and algae.
d.
Predatory nematodes eat rotifers, tardigrades, small
annelids
and other nematodes.
e.
Nematodes are also important as food for mites, insects,
larvae
and fungi.
2.
Form and Function
a.
Distinguishing Characteristics
1)
They have a cylindrical shape.
2)
They have nonliving cuticle.
3)
Muscles in the body wall only run longitudinally.
b. The
pseudocoel serves as a hydrostatic skeleton against
which
longitudinal muscles work.
c. An
outer, thick, noncellular cuticle is secreted by the
underlying
hypodermis.
d. The
cuticle has layers of crisscrossing collagen, providing
elasticity
but constraining expansion.
e.
Digestion
1) The
alimentary canal consists of mouth, pharynx, a
non-muscular
intestine, a short rectum and the anus.
f. Reproduction
1)
Most nematodes are dioecious with males smaller
than
females.
2)
The male has copulatory spicules to hold the
female vulva open against
hydrostatic pressure.
3)
Fertilization is internal and eggs are stored in the
uterus
until deposited.
3. Some
nematodes are important pathogens of humans; most are tropical.
a. The
________________________________________of
humans:
Ascaris lumbricoides
1) Ascaris
lumbricoides occurs in up to 64% of people
in
some areas of the southeastern
2) More
than 1.2 billion are affected worldwide.
3) A
female Ascaris lays 200,000 eggs a day, passing
out in
the host’s ______________________.
4)
Embryonic development completes in two weeks.
5)
Viable eggs remain after signs of fecal matter have
disappeared;
eggs survive long periods in soil.
6)
When a host swallows ______________________,
juveniles
hatch and burrow through intestinal wall.
7)
Carried through the heart to the
______________________,
they break into the
alveoli
and are carried up to the tracheae.
8) Coughed
up and swallowed, they mature in the
______________________
two months after they were swallowed.
9)
They feed on ______________________________
and
may block or perforate the intestines.
10) Infection avoidance:
b. Enterobius
vermicularis: Pinworms
1) It
is the most common ______________________
parasite
in the
2)
Adults live in the large intestine and cecum.
3)
Females, about 12 mm long, migrate to the anal
region
at night and lay eggs, causing ____________.
4)
Scratching the anal region contaminates hands and
bedclothes.
5)
Eggs develop rapidly and become infective within
six
hours at body temperature.
6)
When ______________________, they hatch in
the duodenum
and mature in the large intestine.
7) Members
of this order have haploid males from
unfertilized
eggs; females are diploid and come from
fertilized
eggs.
8) Infection avoidance:
c. The most common human ______________________:
Necator americanus
1) The
anterior end of these small (9-11 mm) worms
has a
hook-like curve.
2) The
males and females are separate.
3)
Large plates in their mouths cut into intestinal
mucosa;
then they suck the ___________________.
4)
They pump through more blood than they digest;
heavy
infections cause ______________________.
5)
Eggs pass in ______________________ and
juveniles
hatch in soil where they live on
______________________.
6) If
human skin comes in contact with soil, infective
juveniles
burrow through ______________________
to
______________________.
7)
Similar to Ascaris, they travel in blood to lungs, are
coughed
up to be swallowed, and mature in the
intestine.
8) Infection avoidance:
d. Trichina
Worm: ________________________________
1)
While tiny, this worm can cause potentially lethal
______________________.
2)
Adult worms burrow into the intestinal mucosa and
females
directly produce ______________________.
3)
Juveniles penetrate blood vessels and circulate
throughout
the body to all tissues and spaces.
4)
They penetrate skeletal muscle cells, redirecting
gene
expression of the musculature so it loses its
striations
and becomes a _____________________to
the
parasite.
5)
When meat containing live juveniles is eaten,
worms are liberated and mature in the
______________________.
6)
They infect humans, hogs, rats, cats and dogs;
hogs
can become infected eating uncooked scraps of
infected
meat or rats.
7)
Heavy infections cause death; about 2.4% of the
U.S.
population is infected, mostly lightly.
8) Infection avoidance:
5. Filarial
Worms - Eight species of
filarial nematodes infect
humans;
some cause major and serious diseases.
a. Wucheria
bancrofti and Brugia malayi live in the
______________________
system.
1) The
worms cause inflammation and
blockage
of the lymphatics.
2)
Females release live young, tiny
______________________,
into blood and
lymph.
3)
______________________ ingest the
microfilariae
when they feed; the worms
develop
to the infective stage and move into
the
mosquito bite wound when it feeds.
4)
______________________ is caused by
repeated
exposure; swelling and growth of
connective
tissue causes enormous swelling of
body
parts.
b.
River blindness or ______________________ is
carried by
______________________ and infects 30 million people in tropics.
c. Dog
heartworm, ___________________________,
is
carried by mosquitoes and is most common
filarial
worm.
B.
Phylum Nematomorpha – “________________________________”
1.
Resemble coarse hairs from a horse’s tail.
a.
People believed they spontaneously generated when a
horse’s tail fell into water. The name stuck.
2.
Form and Function
a.
Adults are free-living in moist habitats; juveniles are
parasites
of ______________________.
b.
They range from 10 to 70 cm long but only 0.3 to 2.5 mm
in
diameter.
c.
Circulatory, respiratory and excretory systems are lacking.
d.
Juveniles only emerge from the arthropod host when
______________________
is nearby.
e.
Females discharge eggs into water; juveniles hatch and
gain
entry to the arthropod host.
f.
After months in an arthropod host, the mature worm
emerges
into nearby water or during rainfall.
g.
Somehow, the parasite stimulates terrestrial insects to
seek
water.
C.
Phylum Kinorhyncha
1.
Kinorhynchs are small (usually less than 1mm long) marine
animals
that feed on ______________________ (a photosynthetic
single
celled organism enclosed by a shell of silica).
a.
About 75 species are known.
b.
They are cosmopolitan.
c. The
body is divided into 13 segments with spines but no
cilia.
d. It
cannot swim, but anchors in its silt or mud burrow with
spines.
2.
Reproduction
a.
Sexes are separate with paired gonads and gonoducts.
b.
Development includes a series of six juvenile stages and
a
nonmolting adult.
D.
Phylum Loricifera
1.
Loriciferans were recently discovered (____________________) in spaces between
marine grains.
a. They are tiny, less than ¼ mm.
b. They are apparently widely distributed.
E.
Phylum Priapulida
1. 18
species of these marine worms occur in colder waters.
a.
Some are tube dwellers and feed on _________________
(a
mass of dead or decaying organic matter).
b.
Priapulids have cylindrical bodies under 15 cm long.
c.
They burrow by body contractions and orient their mouth
at the
surface.
d. A
chitinous cuticle covers the body and is molted
regularly.