Platyhelminthes Lab

Platyhelminthes Lab


Planaria w.m. under microscope 4x


Planaria in 3 representative regions under microscope 10x


Image result for planarian anatomyPlanarian is in the class Turbellaria. They live in both saltwater and freshwater ponds and rivers. However, some species are terrestrial. Planaria are capable of regeneration of lost body parts. For example, if a planarian split lengthwise or crosswise, it will regenerate into two separate individuals. Some planarian species have two or more eye-spots (ocelli) that can detect the intensity of light. Their eye-spots act as photoreceptors and are used to move away from light sources. Planaria have three germ layers (ectoderm, mesoderm, and endoderm), and are acoelomate (they have a very solid body with no body cavity). Most planarians digestive tract consists of a single opening, while Tricladida planarians consist of one anterior branch and two posterior branches. Planarians are able to move by beating their cilia on the ventral dermis. They have a very simple organ systems and digestive system that consists of a mouth, pharynx, and a gastrovascular cavity. They secrete digestive enzymes from the mouth to begin external digestion. The pharynx connects the mouth to the gastrovascular cavity. When they eat, the food is passed from the mouth to the pharynx into the intestines where it is digested by the cells lining the intestines. This allows nutrients to diffuse to the rest of their body. They receive oxygen and release carbon dioxide by diffusion. They have a ladder-like nerve system, that responds in a coordinated manner. There are both sexual and asexual planaria. Planaria that are sexual are hermaphrodites, which mean they have both testicles and ovaries. Planarians produce offsprings when one of their gametes combine with the gamete of another planarian. So they are able to give and receive sperm. When the eggs develop inside their bodies, they are shed in capsules. Weeks later, the eggs hatch and grow into adults. Sexual reproduction increases genetic diversity, while in asexual reproduction, the planarian slipt into two (head and tail), and regrow each half by regeneration. 

Fasciola hepatica w.m. under microscope 4x

(penis area)

Reproductive System of Fasciola Hepatica

Fasciola Hepatica Cercariae, w.m. under microscope 40x

Fasciola Hepatica

Fasciola Hepatica Metacercariae w.m. under microscope 10x

Fasciola Hepatica. Metacercaria

Fasciola Hepatica Miracidia: w.m. under microscope 40x

Fasciola hepatica. Miracidium larva

Fasciola Hepatica Redia, w.m. under microscope 10x 

Fasciola Hepatica

Fasciola hepatica is a parasitic trematode of the class Trematoda and phylum Platyhelminthes. It can infect the livers of various mammals, including humans. It is currently classified as a plant/food-borne trematode infection, often acquired through eating the parasite’s metacercariae encysted on plants.  It plays a large importance in the economy and is studied frequently. Fasciola hepatica lifecycle is indirect and can occur in cattle, sheep, and buffaloes. Its life cycle goes through the intermediate host and several environmental larval stages. The intermediate hosts of F. hepatica are air-breathing freshwater snails from the family Lymnaeidae. There are also different types of lymnaeid snails. This parasite develops only in one or two major species on each continent. The metacercariae are then released from the freshwater snail as cercariae and form cysts on various surfaces. When mammalian host eats this cyst, they become infected. Humans can become infected as well by eating freshwater plants such as watercress. “Inside the duodenum of the mammalian host, the metacercariae are released from within their cysts. From the duodenum, they burrow through the lining of the intestine and into the peritoneal cavity. They then migrate through the intestines and liver, and into the bile ducts. Inside the bile ducts, they develop into an adult fluke.” In humans, it takes 3 to 4 months for F. hepatica to mature from metacercariae into an adult fluke. The adult flukes are able to then produce up to 25,000 eggs per fluke per day. “These eggs are passed out via stools and into freshwater. Once in freshwater, the eggs become embryonated, allowing them to hatch as miracidia, which then find a suitable intermediate snail host of the Lymnaeidae family. Inside this snail, the miracidia develop into sporocysts, then to rediae, then to cercariae. The cercariae are released from the snail to form metacercariae and the life cycle begins again.”

Life Cycle of Fasciola HepaticaLife History of Fasciola Hepatica

Clonorchis Sinensis w.m. under microscope 4x

Image result for Clonorchis sinensis

Schistosoma in copula w.m. under microscope 10x

Image result for Schistosoma

Schistosoma is in the class Trematoda. They are parasitic flatworms responsible for a highly significant group of infections in humans termed schistosomiasis. The adult flatworms are able to parasitize blood capillaries of either the mesenteries or plexus of the bladder, depending on the infecting species. They are unique among trematodes and have distinct sexual dimorphism between male and female. Adult schistosomes have a basic bilateral symmetry, oral and ventral suckers. They have a body covering of a syncytial tegument, a blind-ending digestive system that consists of a mouth, esophagus and bifurcated caeca; “the area between the tegument and alimentary canal filled with a loose network of mesoderm cells, and an excretory or osmoregulatory system based on flame cells.” Compare to other trematodes, the schistosomes are dioecious; have separate sexes and display a strong degree of sexual dimorphism. The male schistosomes are considerably larger than the female. “The male surrounds the female and encloses her within his gynacophoric canal for the entire adult lives of the worms. As the male feeds on the host’s blood, he passes some of it to the female.” Some of the chemicals the male pass on to the female will complete the female’s development, and allow them to reproduce sexually.

The lifecycle of schistosomes includes two hosts: a definitive host ( human) where the parasite undergoes sexual reproduction, and a single intermediate snail host where there are a number of asexual reproductive stages. 

Life Cycle of Schistosoma

Echinococcus Granulosus Adult under microscope 4x

Image result for Echinococcus granulosus Adult

Dipylidium Caninum Composite w.m. under microscope 4x

(4 regions)

Image result for Dipylidium Caninum

Taenia pisiformis scolex under microscope 4x 

Image result for Taenia pisiformis scolex 

Taenia 4 regions: w.m. under microscope under microscope 4x

Taenia pisiformis is commonly known as the rabbit tapeworm and is in the class Cestoda. It is an endoparasitic tapeworm which causes infection in lagomorphs, rodents, and carnivores. The adult Taenia pisiformis typically occur within the small intestines of the definitive hosts, the carnivores. Lagomorphs, which are the intermediate hosts, are infected by fecal contamination of grasses and other food sources by the definitive hosts. The larval stage is often referred to as Cysticercus pisiformis and is found on the livers and peritoneal cavities of the intermediate hosts. Eggs that are introduced into the environment by infected canine feces contain gravid proglottids that house the T. pisiformiseggs. The T. pisiformiseggs will eventually be released to form the proglottid onto nearby vegetation. “The eggs are then ingested by a rabbit or from any member of the Leporidae family. Once inside the rabbit’s gut, the larva or oncosphere phase will then penetrate into the intestinal wall until they reach the bloodstream.When the worm reaches the liver the larva transforms into a cysticercus form. This cysticercus will stay in the liver for about two to four weeks, then move to the peritoneal cavity where it will wait for the definitive host to eat the rabbit. The definitive hosts are ether dogs or other members of the Canidae family. Once ingested, the cysticercus finds its way into the intestine and attaches to the intestinal wall with hooks and suckers. After the worm has time to develop and grow in size, the gravid proglottids are released from the distal end of the parasite and passed in the feces to start a new cycle.”

Life Cycle of Taenia saginata







Photo by Pavel Kirillov is licensed under CC BY-SA 2.0

2 thoughts on “Platyhelminthes Lab”

Leave a Reply

Your email address will not be published. Required fields are marked *