Morphological observation experiment of tapeworm

Summary

This experiment is from the official website of Parasitology, School of Medicine, Shandong University.

Operation method

Morphological observation experiment of tapeworm

Principle

Tapeworms belong to the flat phylum of Platyhelminthes, are parasitic, dorsally and ventrally flat and symmetrical. The body is long, segmented, with no body cavity but filled with spongy parenchyma cells, and the visceral organs are distributed. They are hermaphrodites, with female and male reproductive organs in each segment, and have no mouth and digestive tract. The life history requires an intermediate host. Chain tapeworm (Taenia solium) is also called pork tapeworm, pork tapeworm or hooked tapeworm. Adult tapeworms parasitize the small intestine of human beings and cause pork tapeworm disease; larvae parasitize the subcutaneous, muscular or visceral organs of human beings and cause cysticercosis. The obese tapeworm (Taenia Saginata), also known as beef tapeworm, beef tapeworm, or tapeworm without hooks, belongs to the same family of tapeworms and genus Taenia with the pig tapeworm, and both of them have similar morphology and developmental process. The tapeworm is parasitized in the small intestine of human beings, and after the rupture of the gestational segments when they are discharged from the final host, the eggs are released and swallowed by the intermediate host, and then develop into cysticerci in their muscles or connective tissues, and after consuming undercooked meat containing cysticerci the eggs of the pork tapeworm are swallowed by human beings, and then they can form cysticerci in subcutaneous tissues and in organs such as the brain and eyes. Especially, chain tapeworm patients can develop cysticercosis through autoinfection, so the chain tapeworm is more harmful than beef tapeworm.

Move

I. Self-observation

1. Slide specimen of tapeworm eggs: the eggs of pig tapeworm and beef tapeworm are so similar that they cannot be distinguished from each other. The eggs are round, yellowish, about 30-40 micrometers in diameter, with thick embryonic membranes and radial stripes, and contain six hooked larvae.

tapeworm egg

2. Porcine tapeworm pregnancy node slide specimen: the node is observed with the naked eye or magnifying glass, it is rectangular in shape and the interior is mainly a root-like branching uterus, which is filled with eggs. Two types of tapeworms can be distinguished according to the number of lateral branches of the uterus (7-13 for pig tapeworms and 15-35 for bovine tapeworms). In the specimen made, the uterus is filled with painting ink, so that its branches are ink-black when the uterus dries.

3. Porcine tapeworm cysticercus: it is a milky-white, translucent vesicle, oval in shape, the size of a soybean grain, with the head of the worm sunk into the vesicle, and the vesicle is filled with liquid. Made of slide specimens of cystic caecilians of the head and neck have been extended, the head has four suckers and parietal protrusion and hooks, the structure and adult worms are the same.

Adult chain tapeworms Adult obese tapeworms

Chain tapeworm head joints Fat tapeworm head joints

Chain tapeworm gestational nodes Fatty tapeworm gestational nodes

II. Demonstration

1. Adult tapeworms of two species: adult tapeworms are ribbon shaped, dorsoventrally flattened, creamy white, hermaphroditic, and have segmented bodies with cephalic, immature, mature and pregnant segments.

Morphological identification of the two tapeworms (see table below)

imago (adult, sexually mature insect, the final stage of its development)	pork tapeworm	Beef tapeworm
Length (meters)	2～4 meters	4～8 meters
Head	ca. 1 mm in diameter, with small hooks	Approx. 2mm in diameter, without small hooks
Number of segments	8000～1000	1000～2000
Number of lateral branches of uterus	7～13	15～35
Segment shedding	Several segments together, often passively discharged	Often a single segment actively crawls out of the anus
Cercariae	Head with small hooks, parasitized on pigs or humans	No hooks on the head, parasitized only on cattle

2. Two tapeworm life history specimens: note the similarities and differences in the life histories of the two tapeworms.

3. two gross specimens of cysticercus parasitized in muscle: note the parasitism in muscle.

4. head segments of two adult tapeworms: note the suckers on the head, the presence or absence of parietal protrusions and hooks.

5. a case of porcine cysticercus (cysticercus) parasitizing the human eye: learn about a case report of cysticercosis and observe the morphology of the two cysticerci removed from the vitreous body of the eye in this case.

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