Download Not the Phylum name 7 Phyla in this grouping

Aschelminthes:
Roundworms
Not the Phylum name
7 Phyla in this grouping
Characteristics
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Most are freshwater
Cylindrical
Unsegmented
Bilaterally symmetrical
Triploblastic (pseudocoelomates)
Dioecious
Thin, tough external cuticle
Characteristics
• Pseudocoelom
– 1st distinct body cavity
– Internal organs lie free in the
cavity
– Serves as a cavity for digestion,
circulation and helps with
locomotion
Characteristics
• Digestion
– Two body openings
– Mechanical breakdown of food,
digestion, absorption, feces formation
• Gas Exchange and Nitrogenous
wastes are diffused across the
surface of the animal.
Phylum Rotifera
• “wheel bearer”
• ~2000 species
• Characteristic ciliated organ: corona
– Provides locomotion and food gathering
(small microorganisms)
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Free-living
Primarily freshwater (<10% marine)
Pharynx contains mastax (jaws)
Some reproduce through parthenogenesis
Phylum Kinorhyncha
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“kinorinks”, “motion snout”
~150 species, <1 mm long
Burrow into the mud/sand with snout
Only found in marine environments
13-14 zonites (spines/plates)
– Young will grow and molt to get all
zonites
• Complete digestive system
Phylum Nematomorpha
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~250 species
“horsehair worms”
Adults are free-living
Juveniles are parasitic
– Arthropods (host)
• Beetle and cockroaches
– Found in Running/Standing Water
Phylum Acanthocephala
• “Spiny-headed worm”, “Thorny-headed
worm
• ~1000 species
• Endoparasites (2 hosts required)
– Juveniles: Parasites of crustaceans or
insects
– Adults: Parasites of mammals, birds, fish
(attaches to intestinal wall)
• Absorbs food directly through
tegument
Phylum Loricifera
• Most recently discovered (1983)
• Live in spaces between marine
gravel
• Spiny or brush head
• Separate sexes
• ~14 species
Phylum Priapulida
• ~16 species
• Marine worms (found in cold waters)
• Live buried in the mud/sand on the sea
floor
• Feed on small annelids and
invertebrates
• Separate sexes
• ~2 mm to 8 cm
Phylum Nematoda
• “True Roundworms”
• Some of the most abundant animals on
Earth. ~16,000 species
• One shovel of soil contains over 1
million nematodes (5 billion/acre)
• Mostly parasitic (plants/animals)
• Can be free-living in marine,
freshwater or terrestrial environments
Phylum Nematoda:
Characteristics
• Covered with tough cuticle
– Provides protection and resists digestion by host
• Unsegmented and tapered at both ends
• Absence of circular muscles, prevents them
from crawling…so they thrash about for
movement
• Excrete liquids through pore (tubular or
glandular system)
• Most are dioecious (females usually larger)
– Ex: Guinea worm: males (1”), females (2-4’)
• Juveniles will molt into adult body form.
Phylum Nematoda:
Ascaris Roundworm
• Giant intestinal roundworm
• Largest nematode (can grow over
1 ft)
• Doesn’t cause serious health
problems (may cause intestinal
blockage)
Phylum Nematoda:
Ascaris Roundworm
• Life cycle:
– Human eats veggies grown in infested soil (eggs)
– Eggs hatch in intestines, bore a hole through the
intestinal wall.
– The larvae will enter the blood stream and make
their way to the lungs.
– Larvae is coughed up the trachea and swallowed
back down the esophogus
– Ascaris roundworm will mature into adults and
reproduce in the intestines.
– Fertilized eggs leave the host (w/feces). Eggs
are protected by tough shells and can survive in
the environment for up to 5 years.
Phylum Nematoda:
Hookworm
• Life cycle:
• Attaches to intestine and sucks
blood- can cause much damage as
host often loses blood (anemia)
• Serious problem in warm, moist
areas where people walk barefoot
• Larvae develop in soil and enter
host through cracks in foot
• Life cycle like Ascaris
Phylum Nematoda:
Trichinella spiralis (The porkworm)
• Life cycle:
– Adult worms live in the small intestines of humans
(or other carnivores/omnivores).
– Adult females give birth to larvae, which enter
into the circulatory system and are carried to
muscle tissue.
– Larvae encyst in host’s muscle tissue (remain here
for many years).
– Another host must ingest infective muscle tissue
to continue the life cycle.
– Once ingested, the larvae excyst in their stomach
and make their way to the small intestine (molt 4
times) and become adults.
1 gram of pork
can contain
3000 cysts!
Phylum Nematoda:
Human Pinworm
• Most common roundworm parasite in the United
States
• Life cycle:
– Adult pinworms live in the lower region of the large
intestines
– At night, gravid females move to the rectum and
deposit eggs (and then die).
– The females and eggs produce an itching sensation.
– When the host scratches the itch, the hands and
bedding become contaminated with the eggs.
– Hands touch the mouth, eggs are swallowed and then
hatch.
– Larvae molt four times in the small intestine and
migrate to the large intestine.
Phylum Nematoda:
Filarial Worm
• Life cycle:
– Live in the lymphatic system and block vessels
– Fluid and connective tissue accumulate in these blocked
vessels and cause enlargement of various appendages
(called elephantiasis)
– The adults reproduce in the lymphatic vessels and the
larva are released into the blood stream.
– Mosquitos feed on humans, ingests the larvae (the
larvae molts twice) and then the larvae becomes
infective.
– Mosquitos feed on other human hosts and transfer the
larvae.
– The larvae molt two more times as they make their way
to the lymphatic vessels.
Phylum Nematoda:
Filarial Worm
• Filarial worms are very difficult to
eliminate from the lymphatic
system.
• The goal is to destroy as many
larvae as possible so that more
individuals are not infected.
• Heartworm is a filarial worm that
affects dogs…prevention is key!
Phylum Nematoda:
Guinea Worm
• Adult female can carry 3 million embryos
• Life cycle:
– Parasite will migrate just below the surface of the skin
and eventually emerge (most cases in the feet)
– Very painful blister forms (along with fever, nausea
and vomiting).
– Individuals try to soothe burning sensation by putting
feet in water, which causes the female to expel
thousands of eggs into the water.
– Larvae can live in freshwater for a few days before
finding a water flea (14 days)
– People drink water (along with water flea), flea is
digested releasing the larvae.
– Male and female will reproduce a few months later
(male dies), female spends the next year making her
way to the foot.
Phylum Nematoda:
Ascaris Roundworm
• Life cycle: