Presentation About Marine Flatworms

1. MARINE FLATWORMS

2. PHYLUM PLATYHELMINTHES
• Greek: Platys-flat ; Helminths-worms.
• They have drosoventrally flattended body
• Bilaterally symmetical
• Triploblastic
• Acoelomate animals
• Organ level of organization
• Respiratory and circulatory organs are absent
• Simple diffusion for transport of oxygen

3. • They are hermaphrodites

4. CLASSIFICATION

5. CLASS
•Cestoda(Tapeworms)
CLASS
•Trematoda(Flukes)
CLASS
•Turbellaria
Flatworms were once divided into three groups:

6. CLASS TURBELLARIA
• Free-living
• Common in fresh water, marine and moist
terrestrial habitats
• Majority are marine
• found in benthic regions

7. ORDER POLYCLADIDA
• A highly diverse group of free living flatworms
• They are large flamboyantly coloured
flatworms
• They resemble the nudibranches
• Characterized anatomically by having a highly
branched and irregular gut and a PHARYNX
PLICATUS
• They have been known as inhabitants of
tropical reefs for about 150 years.

8. HABITAT
• mainly benthic and
• found in shallow marine habitats among rocks
and crevices in a bay, lagoon or on a reef.

9. KingdomAnimaliaanimals
Eumetazoametazoans
Bilateriabilaterally symmetrical animals
Protostomiaprotostomes
Platyhelminthesflatworms
ClassTurbellaria
OrderPolycladida
FamilyCallioplanidae
FamilyCestoplanidae
FamilyCryptocelidae
FamilyEmprosthoparnygidae
FamilyEuryleptidae
FamilyHoploplanidae
FamilyLatocestidae
FamilyLeptoplanidae
FamilyPericelidae
FamilyPlanoceridae
FamilyPlehniidae
FamilyPolyposthiidae
FamilyProsthiostomidae
FamilyPseudoceritidae
FamilyStylochidae
CLASSIFICATION

10. MORPHOLOGY & ANATOMY
• Dorsoventally flattened
• Sizes range from less than
one millimeter to over 30
centimeters
• They are extremely
delicate
• Typically elongate or oval
with smooth dorsal surface
• PSEUDOTENTACLES-simple
folds of the anterior
margin
• MARGINAL RUFFLES-
tending to increase in
number with size

11. • The worms nervous
system is ladder-like
composed by a pair of
longitudinal nerve cords
running the length of the
body which are
connected by transverse
commissures.
• It culminates at the
anterior cerebral ganglion
knot, which is a large ball
of neuronal cells in or
near the head.

12. • eyes are located on the ventral and dorsal
pseudotentacles
• eyes are not capable of forming images but are
sensitive to changes in light direction and intensity
• polyclads have a well-developed battery of
chemosensory detectors
• located on the ventral pseudotentacles
• Specific molecules are released from food or
mating partner and become entrained in the flow.
• that can be sensed by the worms chemoreceptors
• smell is the major determinant of the worms
behavior in their natural habitat.

13. • Flatworms have primitive balance organs called
STATOCYSTS.
• Nearby the head, mouth and pharynx can be
detected(pharynx plicatus)
• This type of pharyngeal tube exhibits a longitudinal
and a concentric muscle layer which can extremely
change the shape of the pharynx and can pump
fluid into the gut cavity
• SUCKERS-used to adhere animals to their substrate.
• Facilitate capturing of small invertebrates
• Ingestation of food
• Hermaphrodites
• Nocturnal animals

14. Pseudo tentacles made out folded edges of
the body margin. Mouth is on the underside

15. • Besides the
reproductory system,
the gut with its
numerous lateral
intestinal branches is
the second organ which
accounts for a high
percentage of the
worms body volume
• Blind digestive system
i.e the wastes are
expelled through
pharynx

16. ventral view of Paraplanocera
oligoglenaand shows most of its organs
through the almost transparent body wall. The
white branched central structure is the highly
ruffled pharyngeal tube (pharynx plicatus)
which can be everted through the mouth
which is located in the center of the body. The
pale whitish network extending through most
of the body is the multi-branched gut which
gives these worms the name "polyclad"

17. EXCRETION

18. For excretion and osmoregulation, polyclads have specialized functional units,
called protonephridia

19. REPRODUCTION

20. • Sexual reproduction
• They copulate to engage in mutual cross-fertilization
• as hypodermic insemination,
• The majority of their body volume is made of testes and
ovaries.
• Pseudotentacles help gather chemosensory information to
find a mating parter.
• When a mating partner is found, the two hermaphrodites
have a dual or "penis fence" to see who bears the burden
of motherhood which is much more energy costly.
• The two worms will dance and attempt to stab one another
with their double-prong penis stylet.
• When the thin tissue of the loser is stabbed, it is
immediately inseminated and the loser retreats to bear the
burden of motherhood.

21. • Eggs are fertilized as they meet sperm and
pass down the oviducts.
• While still inside a protective shell or capsule
is formed around the eggs.
• The capsule surrounding the egg is hardened
when released by the worm into the
surrounding environment
• Polyclad eggs are usually laid in thin sheets
with sticky secretions
• No parental care

23. • They can be found underneath boulders
nearby colonial ascidians, one of their
preferred prey.
• After about ten days of development free
swimming, transparent larvae hatch
(=müller's larvae).

24. MÜLLER'S LARVAE
, Müller's larvae are characterized by eight lobes
•. Lobes carry beating cilia which allow a ciliate-like swimming
After metamorphosis miniature adult worm is formed

25. FOOD AND FEEDING

26. • Feeds mainly on ascidians as well as small
crustaceans.
• They feed like a starfish, gliding over the
organism and extruding their pharynx that
releases enzymes.
• The enzymes digest the tissue of their prey then
suck the body liquids.
• Their prey includes tiny animals such as protozoa
and worms, sessile animals such as ascidians and
molluscs, and some have been observed eating
shrimps and crabs.

27. Eurylepta leoparda (Freeman, 1933) feeds on the
solitary ascidian Corella willmeriana. Several juveniles
are inside of each tunicate. After they have eaten
the entire contents, they crawl around for another
victim (PHOTO © Sandra Millen).
Prostheceraeus moseleyi (Lang, 1884) reaches a
length of up to 3 cm. It is distributed throughout
the Mediterranean Sea and the temperate
eastern Atlantic and apparently feeds on
tunicates of the genus Clavelina
(PHOTO © Peter Wirtz).

28. PREDATION AND DEFENSE

29. «««
Pseudoceros bifurcus Prudhoe, 1989 with an
hugh bite mark testifying an aborted feeding
attempt, assumably by a fish. Due to the
excellent regenerative capacity of flatworms,
epithelial cells at the edge of the wound have
already closed over the lesion. In a few weeks
the missing body part will be replaced
completely.

30. • Aposematic colouration or warning coloration
• Polyclads contain strong toxins such as tetrodotoxin
• Are warning of their unpalatability and that their
visual predators, fish, will quickly learn to avoid
them by recognition of their distinct and bright
color pattern

31. MIMICRY

32. • Mimicry, in biology, phenomenon
characterized by the superficial resemblance
of two or more organisms that are not closely
related taxonomically.

33. «««
Pseudoceros imitatus (Family Pseudocerotidae,
Order Polycladida), described by Newman &
Cannon 1994, is an obvious example for a
number of invertebrates which are very similar
in shape and colour to phyllidiid nudibranchs. P.
imitatus relies on its similarity to Phyllidiella
pustulosa for protection.
«««
Phyllidiella pustulosa Cuvier, 1804
(Family Phyllidiidae, Order Nudibranchia) is a
tropical reef nudibranch which displays itself
obviously during the day, apparently immune
to fish attack by extremely noxious chemicals
which they can exude as a milky white
secretion. P. pustulosa seems to serve as
mimicry model for Pseudoceros imitatus

34. • «««
Pseudoceros bajae Hyman, 1953 (upper
specimen) mimics the colour pattern
of the sea slug Hypselodoris
ghiselini Bertsch, 1978 (lower panel),
which
can be observed in Californian waters.

35. This flatworm of the genus Pseudobiceros (upper
photo)
mimics the colour pattern of Glossodoris
symmetricus
Rudman,1990 (lower photo), a chromodorid
nudibranch
(Family: Chromodorididae) which is commonly
found in the
Indian Ocean.

36. Pseudoceros sapphirinus Newman & Cannon, 1994
(upper photo) mimics
the colour pattern of Philinopsis gardineri (Eliot, 1903)
(lower photo),
a sea slug of the order Cephalaspidea (Family: Aglajidae)
which is distributed throughout the Indo-Pacific Ocean.

37. «««
Another striking example of polyclad -
chromodorid mimicry.
Pseudoceros zebra Leuckart 1828,
derived from
North Coast of KwaZulu-Natal, South
Africa.
(PHOTO © Valda Fraser)
«««
Chromodoris fidelis Kelaart, 1858, a sea
slug
of the
family Chromodorididae (Order: Nudibr
anchia).
(PHOTO © Valda Fraser)

38. »»»
Thysanozoon/Acanthozoon sp.
(Family: Pseudocerotidae,
Order: Polycladida
(PHOTO © Mary Jane Adams)
»»»
Phyllidia ocellata, (Cuvier, 1804)
(Family: Phyllidiidae,
Order: Nudibranchia).
(PHOTO © Wolfgang Seifarth)

39. «««
Pseudobiceros gloriosus Newman & Cannon,
1994
(Family: Pseudocerotidae, Order: Polycladida)
(PHOTO © Wolfgang Seifarth)
«««
Dendrodoris arborensis Collingwood, 1881
(Family: Dendrodorididae, Order: Nudibranchia
)
derived from Izu Peninsula, Sagami Bay, Japan
(PHOTO © Jun Imamoto)

40. »»»
genus Eurylepta (upper photo)
mimics the colour pattern of Phyllidia
polkadotsa Brunckhorst, 1993
(lower photo). This sea slug belongs to the
family Phyllidiidae and
is known from Hawaii, the Banda Islands
of Indonesia and Taiwan.

41. Many flatworms are tiny.
This one was hardly 1cm long
Eating Yellow clustered bead ascidians
Some may be nearly transparent

42. ECOLOGICAL IMPORTANCE
Economic Importance for Humans: Positive
There are no known positive economic effects of this
species on humans.
Economic Importance for Humans: Negative
There are no known negative economic effects of this
species on humans.

43. CONSERVATION STATUS
• Not listed among the threatened animals.
• They are very delicate creatures and like other creatures
of the intertidal zone, flatworms are affected by human
activities such as reclamation and pollution.
• Trampling by careless visitors, and overcollection of their
food source can also have an impact on local
populations.
• IUCN red list -not evaluated
• US federal list -no special status
• CITES -no special status
• State of michigan list -no special status