Adaptive Benefits of a Pseudocoelom a space between the guts and the body wall It is not lined with a peritoneum therefore is termed a false cavity It is an improvement over the acoelom ID: 932084
Download Presentation The PPT/PDF document "Zoology 2015 Nematoda Phylum Nematoda" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
Zoology2015
Nematoda
Slide2Phylum Nematoda
Adaptive Benefits of a Pseudocoelom - a space between the guts and the
body wall
It is not lined with a peritoneum therefore is termed a false cavityIt is an improvement over the acoelom of the platyhelminthes but not as advanced as the eucoelom / it lacks mesenteries
Slide3Phylum Nematoda
It does offer
adaptation potential
– Greater freedom of movementSpace for development and differentiation of digestive, excretory and reproductive organsStorage for waste productsSimple means for distribution and circulation of materials
Hydrostatic support for the body
Slide4Phylum Nematoda
General features of this phylum –
Very diverse phylum, about
25,000 species have been catalogued but estimate that there are 500,000 In good topsoil there are billions per acre of ground.
They live in all habitats, from mountains to the deep oceans, from the
polar ice
to the
tropics
Slide5Phylum Nematoda
Free-living nematodes feed on
yeast
, bacteria and algaePredatory nematodes feed on other invertebrates and protozoansNematode worms are important food for mites,
insects and fungiAlmost all animals and most plant species have nematode parasites
Slide6Phylum Nematoda
Form & Function of body systems –
Bilateral
symmetryComplete digestive system with both a mouth and an anus
Slide7Phylum Nematoda
Form & Function of body systems –
Nematodes all have a
cylindrical shapeMuscles in body wall only run longitudinallyNematodes express Eutely which means they all show a set number of cells
Examples – C. elegans Researchers use this worm
Females have 1057 cells
Males have 959 cells
Slide8Phylum Nematoda
Form & Function of body systems –
Dorsal
and ventral cords bear nerves while lateral cords bear excretory ducts
Longitudinal muscles run in four bands – between the nerve
and excretory cords
The digestive system
consists of
mouth
,
pharnyx
,
intestin
e,
rectum
and
anus
.
This is considered a
complete digestive system.
Slide9Phylum Nematoda
Form & Function of body systems –
Senses include
papillae (sensory hairs) at the head and tail and amphids on the head. Parasitic nematodes also have phasmids (chemo-receptors) at the tail endNematodes are
dioecious and the males are smaller
than the females and
fertilization is
internal
.
Males bear a pair of
copulatory spicules
.
Slide10Phylum Nematoda
Form & Function of body systems –
Nematodes have a non-cellular
cuticle that is shed between each of four juvenile stages (no larval stage) this is called moltingSkeletal system is hydrostatic
Slide11Nematode Parasites
Ascaris
lumbricoides – large intestinal roundworms of humans More than 1.2 billion people affected worldwideSoutheastern US more than 64% of people affected
Slide12Nematode Parasites
They feed on
intestinal contents
and a large infestation may block or perforate the intestines. They may cause a serious anemia in childrenFemales may be 50 cm – 20 inches) long and males 30 cm - (12 inches)
Slide13Nematode Parasites
Ascaris
Life CycleA female roundworm lays 200,000 eggs a day which pass out in the host’s fecesEggs remain viable for long periods in the soil – (10-20 years)
When a host swallows the eggs, juveniles hatch and burrow through intestinal wall into the blood supply
Slide14Nematode Parasites
Ascaris
Life Cycle (con’t)4. Carried through the heart to the lungs, they break into the alveoli and crawl upward into the trachea where they are coughed up and then swallowed with saliva
Slide15Nematode Parasites
Ascaris
Life Cycle (con’t)5. They mature in the intestine where they feed on the intestinal contents. They sometimes cause allergic reactions or perforation of the intestine which results in
peritonitis. Wandering worms may occasionally emerge from the throat or anus
and have even been known to appear wriggling out of the
ears, mouth or nose if there is a heavy infestation
Slide16Nematode Parasites
Ascaris
Life Cycle
Also seePage 311
Fig. 15-7
Slide17Nematode Parasites
Hookworm
Necator
americanus – the hookworm – name means “American Killer”These are small worms, only 11 mm and their anterior end has a dorsal curving hook (male)
Large sharp cutting plates in their mouth cut into the intestinal mucosa
and they attach and
suck
the host’s blood
(see page 310, figure 15-6)
Slide18Nematode Parasites
Hookworm
Hookworms become
blood pumps because they pump much more blood than they can digest, pumping the blood through their intestines, partially digesting it and absorbing the nutrients. They suck much more blood than they need for food and heavy infestations can cause anemia.Children with hookworms may experience retarded mental and
physical growth.
Slide19Nematode Parasites
Hookworm
Necator
life cycle –similar to that of the AscarisEggs pass in feces, but if soil conditions are warm and moist the eggs hatch and the juveniles live in the soil, eating bacteria
.When juvenile worms come into contact with bare skin, they
burrow
into the blood vessels and then they follow the same path as
Ascaris
to get to the intestine. Penetration usually occurs through soles of the feet. Southern US population had a
55%
infection rate at the turn of the century but because of the practice of
wearing shoes
the infection rate is now
5-10%
.
Slide20Nematode Parasites
Necator
americanus life cycle –
Slide21Nematode Parasites
Trichinella
spiralis – trichina wormCauses the potentially lethal disease trichinosisAbout 2.4% of the US population is infectedAdult worms are tiny, about
1.5 – 3 mm long
Colour
SEM of
Trichinella
spiralis
roundworms
Slide22Nematode Parasites
Trichinella
spiralis – trichina worm (con’t)Infection occurs when meat containing live encysted juveniles is eaten, adults burrow into intestinal mucosa and females give birth to live young
Muscle tissue with encysted larval trichina
Slide23Nematode Parasites
Trichinella
spiralis – trichina worm (con’t)E. Trichina worms infect hogs, rats, cats, and dogs . . . People usually become infected by eating undercooked pork.Hogs become infected by eating infected meat scraps or infected rats
.
Slide24Nematode Parasites
Trichinella
spiralis life cycleIn an infected host, living juvenile worms are born in the intestineJuveniles penetrate blood vessels and circulate through the body invading all organs, tissues
and intestinal spaces
Slide25Nematode Parasites
Trichinella
spiralis life cycleWhen they invade skeletal muscles, they redirect genes and muscle looses its striations and becomes a nurse cell of the parasite. This this encysted meat is eaten, it cause the infection.
While the juveniles are wandering in the body, they can cause death if large numbers invade the heart or the brain
.
Slide26Nematode Parasites
Trichinella
spiralis life cycle
Slide27Nematode Parasites
Enterobius
vermicularis – the pinwormThis is the most common worm parasite in the US but it causes little disease (just irritation)Adults live in the large intestine
They attain a body length of 12 mm
Slide28Nematode Parasites
Enterobius
vermicularis – the pinworm30% of US children are infectedUp to 75% of college students who live in dorms are infectedThere are several oral drugs that are effective against this infection but
all people living in the household must be treated because they are very infectious
Slide29Nematode Parasites
Enterobius
vermicularis – pinwormExhibit haplodiploidyMales are haploid – come from unfertilized eggsFemales are diploid – come from fertilized eggs
Slide30Nematode Parasites
Enterobius
vermicularis – the pinwormDiagnosed by scotch tape test or flashlight test
Slide31Nematode Parasites
Enterobius
life cycle – Adults live off of intestinal contents in the large intestineFemales detach from the intestinal lining and migrate to the anus at night to lay eggs on the external surface
. This causes intense itching.Scratching the itch contaminates
hands and bed clothes
Eggs develop rapidly and can become infective in
just 6 hours
at
body temperature
Contaminated hands put eggs into
mouth
and
airborne
–eggs hatch in the
duodenum
and mature in the large intestines.
Slide32Nematode Parasites
Enterobius
life cycle –
Slide33Nematode Parasites
Filarial Worms – “Elephantiasis”
Wucheria
bancrofti and Brugia malayi250 million people in the tropics are infected
Worms live in the lymph system and obstruct the ducts
Worms may grow to
100 mm
Females release live young called
microfilariae
which circulate in the blood stream
Wucheria
bancrofti
Brugia
malayi
Slide34Nematode Parasites
Filarial Worms – “Elephantiasis”
Elephantiasis is a disease caused by repeated exposure. Blockage and swelling of
lymph ducts causes gross enlargement of certain body parts
Slide35Nematode Parasites
Filarial Worms – “Elephantiasis”
Slide36Nematode Parasites
Filarial Worms –
River blindness
- another filarial worm disease
Microfilarial
worm infestation of eye tissue
Slide37Nematode Parasites
Filarial Worms –
Dog heartworm
is the most common filarial worm disease in the US. It reaches a 60% infection rate in the south and eastern seaboard states and can infect dogs, cats, otters and occasionally humans
.
Slide38Nematode Parasites
Dog Heartworm Life Cycle
Slide39Nematode Parasites
Filarial Worms Life Cycle –
Adult worms live in the
lymph ductsFemales bear live tiny juveniles called microfilariaeAt night, microfilariae congregate in vessels near the surface of skin
Mosquitoes transmit disease when they ingest the microfilariae as they feedThe microfilariae develop into the infective stage in the mosquito, considered the
intermediate host
and then they infect a new
definitive
host by moving into a bite wound through the
proboscis
of the mosquito.