Lab 12 Nematoda

7/30/2019 Lab 12 Nematoda

1/18

Kingdom Animalia

Clade Ecdysozoa

Phylum Nematoda (Roundworms)


2/18

Clade EcdysozoaAlthough the clade Ecdysozoa is defined

primarily by molecular evidence, it includesanimals that shed a tough external coat(cuticle) as they grow.

The group derives its name from ecdysis,ormolting.

The ecdysozoan clade consists of eightanimal phyla and contains more known

species than all other protist, fungus, plant,and animal groups combined.

The two largest ecdysozoan phyla,

Nematoda and Arthropoda, are among themost successful and abundant of all animal


3/18

Phylum Nematoda Nematodes, or roundworms, are found in most

aquatic habitats, wet soil, moist tissues of plants,and the body fluids and tissues of animals.

Nematodes range in length from less than 1 mm to

more than a meter.

The cylindrical bodies of roundworms are covered

with a tough exoskeleton, the cuticle.

As the worm grows, it periodically sheds its old

cuticle and secretes a new, larger one. Nematodes have an alimentary tract and use the

fluid in their pseudocoelom to transport nutrients,

since they lack a circulatory system.


4/18

Phylum Nematoda

Nematodes usually reproduce sexually.

The sexes are separate in most species, and

fertilization is internal.

Females may lay 100,000 or more fertilized eggs

per day.The zygotes of most nematodes are resistant

cells that can survive harsh conditions.

Free-living nematodes play a major role in

decomposition and nutrient recycling, but little is

known about most species.

Other species of nematodes parasitize animals,

including some species that benefit humans by


5/18

Nematoda: Parasitic

Filarial WormGuinea Worm

Hook Worm


6/18

Trichinella spiralis

Trichinella spiralis causes trichinosis when the

nematode worms encyst in a variety of humanorgans, including skeletal muscle. Humans acquire this nematode by eating

undercooked meat that has juvenile wormsencysted in the muscle tissue.

Parasitic nematodes hijack cellular functions oftheir hosts to evade their immune systems.

Some species inject molecules that induce thedevelopment of root cells that provide nutrients

to the parasites. Trichenella in human muscle cells controls the

expression of muscle cell genes that code forproteins that make the cell elastic enough to

house the nematode.


7/18

Pork Round Worm


8/18

Trichinella Spiralis Whole Mount


9/18

Loa Loa


10/18

Loa Loa


11/18

Dirofilaria


12/18

Adult worms1 live in the lumen of the small intestine. A female may produce up to 240,000 eggsper day, which are passed with the feces 2. Fertile eggs embryonate and become infective after18 days to several weeks 3, depending on the environmental conditions (optimum: moist, warm,shaded soil). After infective eggs are swallowed 4, the larvae hatch 5, invade the intestinalmucosa, and are carried via the portal, then systemic circulation to the lungs 6 . The larvaemature further in the lungs (10 to 14 days), penetrate the alveolar walls, ascend the bronchial tree

to the throat, and are swallowed 7. Upon reaching the small intestine, they develop into adultworms 1. Between 2 and 3 months are required from ingestion of the infective eggs to ovipositionby the adult female. Adult worms can live 1 to 2 years.


13/18

than females and possess a hooked

tail.


14/18

Ascaris
http://www.curezone.com/image_gallery/parasites/ascaris/default.asp?i=11&n=24


15/18

Ascaris Infection


16/18

Ascaris Male


17/18

Ascaris Female

Ovary Oviduct Females have a pair of ovariesattached to an oviduct

Each oviduct becomes a tubularuterus, forming a vagina that opens

externally through a genital pore


18/18

Lab Instructions: View all organisms listed in the chart

above in the microscope, stereoscope, preserved or on the

observation tray. Draw each organism in your lab notebook

and note the distinguishable characteristics of each. Review

internal anatomy of each organism.

Organism (Scienctific

Name)

Common

Name

Vertebrate

Habitat

Ascaris lumbricoides (Sl)

& (Sp)

Pork Round

Worm

Intestines

Dirofilaria (Sl) Dog Round

Worm

Lymph Vessels

Loa Loa(Sl) N/A Eye

Trichinella spiralis (Sl) Pork Round

Worm

Muscles

Documents

Lab 12 Nematoda