PLATYHELMINTHES
PRESENTED BY-
SONALI BAZALA
REGISTRATION ID- 19MSLSAS19
DEPARTMENT OF ANIMAL SCIENCES
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Community
Ask the community
Ask the community for help and clear up your study doubts
University Rankings
Discover the best universities in your country according to Docsity users
Free resources
Our save-the-student-ebooks!
Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors
Platyhelminthes are free-living and symbiotrophic flatworms. The soft body of the flatworm is bilaterally symmetrical.
Typology: Slides
2018/2019
1 / 13
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download PLATYHELMINTHES AND CLASSIFICATION and more Slides Zoology in PDF only on Docsity!
PLATYHELMINTHES
PRESENTED BY-
SONALI BAZALA
REGISTRATION ID- 19MSLSAS
DEPARTMENT OF ANIMAL SCIENCES
INTRODUCTION
The word Platyhelminthes is derived from Greek words
platys- broad or flat and helminth- worm.
The animals of this phylum have Dorso-ventrally
flattened body and therefore are commonly called as
flatworms.
Gegenbaur (1859) placed flatworms in a separate group
and gave the term Platyhelminthes. This phylum includes
13000 species.
Level of organisation:
(^) They are the first animals to have reached the organ level of organisation.
Germ layers:
(^) Platyhelminthes are first triploblastic animals. They consist of three germ layers- ectoderm, mesoderm and endoderm.
Coelom:
(^) Although they are triploblastic animals, bearing mesoderm, but coelom (i.e. Mesoderm-lined body cavity) is lacking in them. Hence flatworms are Acoelomates. (^) the space between body wall, alimentary canal and other organs is filled with a peculiar connective tissue called parenchyma.
Digestive tract:
(^) Simple and incomplete (^) Digestive tract is absent in tapeworms.
Respiratory and circulatory systems are absent.
(^) Gaseous exchange in aerobic flatworms occurs by diffusion through body surface.
Skeletal system:
(^) Exoskeleton as well as Endoskeleton are completely absent. However, hydroskeleton (fluid in parenchymal network maintains the body shape). (^) It also helps in gliding movements.
Parasitic adaptations:
(^) Hooks: Adhesive structures, present in Taenia (^) Suckers: Act as suctorial organs, adhesion as well as ingestion. Present in Fasciola. (^) Thick tegument: Protective layer that protects parasitic worms from the digestive juices of host.
Reproduction:
(^) Flatworms are hermaphrodite except Schistosoma. (^) They mainly reproduce sexually by producing ova and sperms. (^) Asexual reproduction is mainly by transverse binary fission. (^) Fertilization is cross and internal. (^) Regeneration is well marked in some flat worms like Planaria.
Development:
(^) Indirect development, involving many larval stages and more than one host. (^) In Liver fluke miracidium, sporocyst, rediae, cercaria and metacercaria larvae are present. (^) In tapeworm hexacanth, onchosphere and cysticercus larvae are found.
Unique features:
(^) Parenchyma (^) Flame cells (^) Ladder-like nervous system (^) Self-fertilization occurs in some flat worms.
Advancement over Ctenophores:
(^) Triploblastic (^) Organ-level of organisation (^) Developed copulatory organs
Examples:
(^) Dugesia- Planaria (^) Fasciola hepatica- Liver Fluke (^) Taenia solium- Pork tapeworm (^) Echinococcus granulosus- Dog tapeworm
CLASS 3: TREMATODA
(^) Endo or ectoparasitic worms. (^) Body unsegmented. (^) Body is covered with cuticle and bears one or more suckers. (^) Mostly hermaphrodite but some unisexual forms are also found. (^) There is present a single ovary but testes are two to many. They show a complicated life cycle. (^) Example: Fasciola, Schistosoma
CLASS 4: CESTODA
(^) Endoparasites (^) Segmented body. Body is divided into two to many proglotids. (^) Each proglotid has one to two sets of hermaphrodite reproductive organs. (^) Life cycle is complicated. (^) Example: Taenia solium
Recent Research:
(^) Planarians, such as Schmidtea mediterranea , have emerged in recent years as powerful models to study the basis of stem cell regulation and tissue regeneration.
- (^) Published by James J. Collins Department of Pharmacology, UT Southwestern Medical Center, USA in 2017. (^) In a recent paper in Nature Genetics, a group of scientists sequenced, assembled and annotated the genomes of 45 helminth species, more than doubling the number of available helminth genomes. The goal was to compare genes and gene families between species to help identify common features, potential drug targets, and insights into the processes involved in parasitism.
- (^) Published on BugBitten in Jan. 2019.