The Acoelomate animals


Introduction:
1. some cephalization & bilateral symmetry
2. platyhelminth or flat worms
3. true organ
4. protostome & spiral cleavage
5. simplest excretory and circulatory system
6. mesoderm in the form of muscle fiber &
mesenchyme (paranchyma)
7. mouth & anus
8. Three phyla are:
a. platyhelminthes
b. nemertea
c. Gnathostomulida

Main characteristics:


1. triploblastic
2. bilateral symmetry
3. flat dorsoventrally
4. tegument
5. true muscles
6. acoelomate
7. incomplete digestive system in some; i.e.
gastrovascular type absent
8. some have eye spots
9. flame cells or protonephridia
10. mostly monoecious
11. class Turbellaria mostly free living

Phylum Platyhelminthes:


- paranchyma
-msot monogenea are ectoparasitic
-all trematodes & cestoda are endoparasitic
-indirect and direct life cycle
-final host is vertebrates in most cases
-Triploblastic, Cniderians were not
-body fluid moves by muscylar contraction

Class Turbellaria:


-free-living, mostly marines
-Planarians
-epidermis ciliated on ventral side
-mouth on ventral side, no anus
-simple life cycle
-spiral cleavage
-gastrodermis has phagocytes
-they are carnivorous
-metabolic waste by diffusion thru the body wall
 -Rhabdite cells
-three types of muscle: longitudinal, circular, & radial
-parenchyma cells
-protonephridia = flame bulbs
-Planaria excrete water out, why?
-metabolic waste diffuse out thru the body wall
-flame cells for osmoregulation
-nerve pluxes & brain bilobed
-Three types of neurons: sensory, motor, & association
-ocellia or light-sensetive eye spot
-asexuall regeneration
-Turbellarians are monoecious but practice cross fertilization
-Fertilization in female oviduct

Class Trematoda:


-all parasitic flukes
-tegument
a. has no cilia
b. syncytial

-

two suckers: mouth & ventral side

Give two reasons why tegument is beneficial to platyhelminth?


subclass Digenea:
1. intermediate host
2. final host

Life cycle:
egg --->miracidium ---> sporocyst --->rediae -->
get into snailin snail in snail

cercariae ciliated larva

---->

metacercaria encyst
in snail on vegetation or meat

---> adult

Why this type of life cycle?
single egg can rise to many progeny

Fasciola hepatica
 "liver-rot"
 Clonorchis sinensis
 -metacercaria in meat
 1. oral sucker & ventral sucker
2. testis
two testis--->two vas efferentia--->one seminal vesicle--->ejaculatory duct
cirrus not present in Clonorchis

Schistosoma
-old name Bilharzia
-male bigger
-gynecophoric canal
S. mansoni : in large intestine
 S. japanicum : in small intestine
 S. haematobium : in urinary bladder
 There are no metacercarial & radia stages
-ulceration
-swimer's itch: S. dermatitis

What method of Biological control can you think of?
Paragonimus westermani
-lung flukes
-crab is intermediate host

Class Monogenea:


-all parasetic on gills or external surface of fish
-ectoparasitism & infestation
-direct life cycle, single hsot
-egg---> single larva, oncomiracidium---> adult
-opisthaptor
-Gyrodactylus cylindriformis

Class Cestoda:


-Tapewporms
Their body has three major parts:
A. scolex: suckers, hooks, for attachment
B. neck: asexual reproduction
C. Strobila: chains of proglottids
-no digestive sytem, so how do you think they obtain their food?
-nearly all monoecious
-scolex or holdfast
-adults in vertebrates
-intermediate host are invertebrates
-germinative zone
-cross fertilization possible
-usually do not harm their host

Taeniarhynchus saginatus
-cysticercus in beef
-scolex has 4 suckers & no hooks
-excretory ducts have flame cells

Life cycle in cattle:
egg---> oncospheres ---> bladder worm or cysticerci
in human:
cysticerci becomes adult & shed eggs

Taenia solium:
-adult in human & juvenile in pork
-cysticerci in human also possible
-cerebral cysticercosis
-rostellum: when scolex has both suckers and hooks

Diphyllobothrium latum

Echinococcus granulosus : unilocular hydatid
-found in dogs & other canine
-human as intermediate host
-cysticercus is hydatid cyst

List 4 or more different adaptation techniques that cestods develop to be successful?

Phylum Porifera

Class Calcarea
Scypha, Leucosolenia,
Class Hexactinellida
glass sponges
Class Demospongiae
bath sponges
Class Sclerospongiae

Phylum Cnidaria


Class Hydrozoa
Obelia , Hydra , Gonionemus ,
Physalia (man-of-war)
Class Scyphozoa (True jellyfish)
Aurelia , Chrysaora , Cyanea
Class Cubozoa (sea wasps or box jellyfish)
Carybdea
 Class Anthozoa (sea anemones and corals)
Metridium

Phylum Platyhelmithes


Class Turbellaria
Planarian (Dugesia )
Class Trematoda (Flukes)
Clonorchis (human liver fluke), Fasciola (ship liver fluke), Schistosoma (human blood fluke), Paragonimus westermani
Class MonogeneaGyrodactylus , Cylindriformis
Class Cestoda (Tapeworm)
Dipylidium caninum , Taenia pisiformis, Taeniarhynchus saginatus , Taenia solium , Diphyllobothrium latum , Echinococcus granulosus