Marine flatworms
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Presentation About Marine Flatworms
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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
- 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.
- 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).
- 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