Transcript Worms - MATES-Biology-I

Worms
Ch.7 – Marine Bio Book
Ch.34/35 – Biology Book
Developed by Dave Werner
MATES
Bilateral Symmetry
Cut body one way = 2
identical halves (fig7.12b,
p.120)
 (bi = two, latus = side).
 Orientation includes:
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Anterior
Posterior
Dorsal
Ventral
Symmetry Comparison
Flatworms
Phylum Platyhelminthes
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Simplest – dorsoventrally flattened (flat
backs & bellies)
triploblastic (composed of three
fundamental cell layers)
Real organs & organ systems
no body cavity other than the gut
Central nervous system = simple brain
(aggregation of nerve cells)
lack an anus; the same pharyngeal
opening both takes in food and expels
waste
must respire by diffusion, and no cell
can be too far from the outside, making a
flattened shape necessary
Platyhelminthes
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Life without a coelom : The image at left is a fluke (possibly
a species of Probolitrema). Flukes, like other parasitic
flatworms, have complex life cycles often involving two or more
host organisms. At right, a planarian (Dugesia). Planarians are
free-living flatworms, and have a much simpler life history. They
inhabit freshwater, and are carnivores (even without teeth) or
scavengers. Most are less than a centimeter long.
Marine Flatworms
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Marine flatworms : The marine flatworms (polycladids) are the
largest of the free-living flatworms, sometimes reaching lengths of
15 centimeters. Polycladids get their name from their highly
branched digestive cavity. These individuals were photographed on a
reef near the island of Guam.
3 Groups of Flatworms
1. Class Turbellariafree-living, include the
planarian, Dugesia,
found in the oceans,
fresh water, & in
moist terrestrial
habitats, a few are
parasitic
 Parisitic Video Clip
 Body Invaders
 Parisites
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2. Class Trematoda, or flukes, all parasitic, have complex life cycles
specialized for parasitism in animal tissues. Members of one major taxon
of flukes, the Digenea -- which includes the human lung fluke -- pass
through a number of juvenile stages that are parasitic in one, two, or
more intermediate hosts before reaching adulthood, at which time
they parasitize a definitive host.
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Flatworms include non-parasitic worms such as planaria, which live in water, and parasitic
flukes and tapeworms. The human liver fluke infects over 75% of the people in parts of Japan,
China, and South Asia. The adult fluke, about 3/4 inch long, lives in the bile ducts of the liver;
its eggs (1) pass from the body in the feces. The eggs, containing larvae, are eaten by water
snails (2) and then develop into another form, which passes into the water. They then bore
into the bodies of fishes (3). When raw fish is eaten (4) - as is common in the Orient - the
young worms swim from the intestine into the fine branches of the bile duct and grow to
maturity.
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3. Class Cestoda, or
tapeworms, are
intestinal parasites
in vertebrates, and
they also show
anatomical & life
history
modifications for
parasitism.
Use suckers or
hooks to latch on
50 ft worm found in
Sperm Whale
Beef
Tapeworm - The cestodes (tapeworms) Taenia saginata (beef tapeworm) and T.
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solium (pork tapeworm). Taenia solium can also cause cysticercosis
Life Cycle:
Ribbon Worms
Phylum Nemertea
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about 900 known species (fig.7.14, p.128, 121)
the European nemertine Lineus longissimus has been known to reach 30
meters (nearly 100 ft) in length,
Most nemertines are marine
Proboscis-wraps around the prey, and toxic secretions immobilize the prey
Stylet-piercing barb
nemertines are carnivorous; most feed on small invertebrates like
crustaceans and annelids, but some feed on the eggs of other
invertebrates, and a few live inside the mantle cavity of molluscs and feed
on microbes filtered out by the host.
nemertines have major features that flatworms lack, notably a
complete gut with an anus, and a system of blood vessels. This
vessel system may in fact be homologous with the coelom, or fluidfilled lined body cavity
True organsw/ organ system & central nervous system
Proboscis
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Prostoma rubrum, an
example of the
phylum Nemertea,
with its long proboscis
everted.
 Fig 7.14, p. 121
Nematodes - Roundworms
Phylum Nematoda
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Nematodes are the most numerous multicellular animals on earth
Most common in soil & marine sediments
nearly 20,000 described species (>500,000 total)
1,000 somatic cells
possess digestive, nervous, excretory, and reproductive systems,
but lack a discrete circulatory or respiratory system
range from 0.3 mm to over 8 meters
The largest nematode ever observed is Placentonema gigantisma,
discovered in the placenta of a sperm whale w/ 32 ovaries
Found inhabit intestines of seals & dolphins & flesh of fish (sashimi)
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Humans - hookworm, trichinosis and elephantiasis
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Intestinal Roundworms, of which Ascaris is a
common form, infect wild and domestic animals and
man. Eggs drop to the ground in animal feces. Humans
are infected by eating contaminated food. The diagram
at right shows the life history of Ascaris. Eggs hatch
into larvae in the intestinal tract and bore through
intestine wall (1). Blood carries larvae to lungs (2),
where they grow. They are then coughed up or crawl
up windpipe to back of mouth (3), are swallowed (4),
and mature in intestine (5). A female worm living in the
intestine may have millions of eggs in its body. These
pass out in feces (6) and, if eaten by other animals,
start the life cycle over again.
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Hookworm, once a serious disease in the
southern U.S., is still common in the warm areas
of the world. Infected people lack energy. The
hook-worm life cycle is like that of intestinal
roundworms except that infection occurs as
larvae hatched in the warm soil bore through the
skin, usually on the soles of the feet, to enter the
blood.
Trichina Worm
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Round Worm
The trichina worm lives inside the
small intestine of a host animal, where
it mates and reproduces. Once her
eggs have been fertilized, the female
burrows into the intestinal wall and
releases her larvae. The larvae migrate
into the lymph channels of the
intestine, from which they enter the
bloodstream and travel to all parts of
the body. When the larvae reach the
skeletal muscles they burrow into the
muscles and form tough cyst-like
cocoons. The host secretes lime salts,
which are deposited in the capsule,
eventually transforming the capsule
into a completely calcified cyst. The
worms may live in the cyst for years
until they are consumed and digested
by another mammal.
Nematode Worms
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Marine Nematode - Draconema
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Here Parborlasia corrugatus
worms are eating fish eggs. P.
corrugatus has a one-way gut
with a large mouth and a closed
circulatory system; nemertean
worms are the simplest animals
with a circulatory system. Like
other proboscis or nemertean
worms, the wedge-shaped head
of P. corrugatus has a fluid-filled
cavity used to rapidly shoot a
barbed proboscis which the worm
uses to capture prey and defend
itself [1]. This harpoon-like
proboscis has adhesive secretions
which secure prey. P. corrugatus
is chemically defended by an
acidic mucus (pH 3.5) which
potential predators avoid [4].
Segmented Worms
Phylum Annelida
Everybody's favorite, worms. . .
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earthworms, leeches,
polychaetes
about 9000 known
species
Segmentation
Hydrostatic Skeleton
Coelom
Cerebral Ganglion
Polychaete Worms
Class Polychaeta
Mostly marine- 10,000
species
 2-4 in.
 Proboscis w/ jaws
 Parapodia – flattened
extensions
 Setae – bristles (Fig.
7.15)
 Closed Circulatory System
 Gills w/ capilaries on
parapodia & body allow
respiratory exchange
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Polychaete External Anatomy
Nereis species
Clam or Sand Worm
Video Clip
More Annelids
Class Oligochaetes –
small, live in
mud/sand
 Marine relative of
earthworms
 Lack parapodia
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And More Polychaetes
Leeches (Class
Hirudinea) – mostly
FW, marine species
are found attached to
fish & inverts
(parasitize)
 Sucker at each end
w/ no parapodia
 hermaphroditic
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Phylum Pogonophora
Beard Worms
(pogonophorans) –
lack a mouth and gut
(fig. 7.17) – use
symbiotic bacteria to
manufacture food.
 4in.-7ft. – Read
fig.7.17
 Vestimentiferans –
hydrothermal vent
worms
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Crawdad says " Hay-dee ! "
This is my buddy
Crawdad. He lives in
a 'holler by the
crick' near
Tahlehquah OK.
Those are tequila
worms in his beard
... kind of a rastaokie thing, I guess.
 He's a trip.
 Whoops! Wrong
Picture
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Leeches in the eye of an unfortunate soul who drank from
the wrong pond in India. Probably Hirudinaria granulosa.
- Mark E. Siddall
Peanut Worms
Phylum Sipuncula
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Soft, unsegmented
bodies (fig. 7.18,
p.124)
320 known species
.4in.-14in.
Deposit feeders
Peanut shaped
Echiurans
Phylum Echiura
Marine
 Look like soft
unsegmented
sausages buried in
mud/sand
 Spoon-like or forked
proboscis (fig 13.9,
p.272)
 Deposit feeders
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