Zoology Ch 12 - Ecdysozans

What structure is the only common linkage within Phylum Ecdysozans?

cuticle

What is the cuticle are shared trait with?

arthropods (insects)

cuticle is periodically molted, restricts growth

How many phyla of Ecdysozans have pseudocoel?

4 of the 6

Describe general characteristics of Phylum Nematoda. (9)

• very common and diverse

• second largest to arthropods

• mostly free living, some parasitic

• notable lack of variation in size and shape

• the most abundant animal on earth

• all are water-based

• feed on organic material

• small, elongated, wormlike body w/ few external features

• cylindrical, unsegments, and tapered at both ends

What fraction of nematodes makes up the total animals of earth?

4/5 of animals are nematodes

How many nematodes were found in one cubic foot of soil?

6 million

Why is it good that nematodes feed on organic material? (3)

• aerate soil

• recycle nutrients

• decompose toxins and wastes

What percentage of nematodes are parasites?

60+%

In a study conducted in 1947, what percentage of the population had nematode parasites?

99%

Nematodes lack cilia, what structure allows do they have instead?

adhesive glands

What does it mean for nematodes to be eutely?

all individuals of a species have the same, fixed total number of somatic cells upon reaching maturity

What does the body wall of nematodes secrete?

cuticle containing collagen

Why is the cuticle important for nematodes? (2)

• protects against abrasion in soil and digestive enzymes

• allows survival in extreme conditions

What type of muscles do nematodes have?

longitudinal muscles only

What keeps the body wall of nematodes from collapsing if there are no circular muscles?

hydrostatic skeleton

What is the movement of nematodes?

a characteristic whiplike thrashing motion in “s” form

What is the nervous system of nematodes?

nerve ring with ganglia around pharynx

Do nematodes have circulatory or respiratory systems?

no

Do nematodes have a complete digestive tract?

yes, non-muscular intestinal cavity

What is the stylet of nematodes? What is it function?

a hard, hollow, spear-like mouthpart allows piercing and injection of enzymes

What do most nematodes eat?

living cells

carnivores, parasitic, coprozoic (feces), saprobes (decaying matter)

Do nematodes have internal or external fertilization?

internal fertilization

What do the sperm of nematodes lack?

lack flagella or cilia

What is unique about the eggs of nematodes? (3)

• 100,000 eggs/day

• highly resistant to environmental conditions

• can be dry for 3+ years and hatch

• can survive -317F and still hatch

Are there any distinctions between male and female nematodes?

males are shorter and possess distinct “hook” for reproduction

What is the Ascaris lumbricoides nematode?

Giant roundworm

• inflammation, pneumonia, intestinal blockage, bile and pancreatic blockage

• one of the most common human parasites

• 1.2 billion worldwide

• swallowed, penetrates the duodenum to blood stream, moves to live in heart. Then passes respiratory system to cough up and re-enter

• sticky eggs can persist in soil for 10+ years, resistant to bleach and formalin

What is Turbatrix aceti nematode?

Vinegar eel

• pH levels between 1.6-11

• found in vinegar, wines, beer mats, apples

• not parasitic

Do nematodes cause river blindness?

yes, caused by tsetse fly and can travel to the eye.

high infection rate

What is the golden nematode?

• parasite of potato plants, causes worldwide crop failures

• chemicals from plant attract adults and eggs to hatch

• sister species damage other plants and trees

• some sister species used as organic biological control

Sister species of what nematode can be used as organic biological control?

golden nematodes

What is the Dirofilaria immitis nematode?

Dog heart worm

• primary host of canines, but can also infect humans

• common in all 50 states, with high density in SE USA

• estimates of 45% of all pets infected

• requires 2 hosts: mosquito and canine

• resides in lungs and blood until population is high, then move to heart

• symptoms can take years and lead to heart disease

• difficult to treat

What is one of the most common nematode infections with 500+ million each year?

pinworms

Describe pinworm nematodes. (4)

• most common nematode infection

• temperate rather than tropical

• more common in caucasians

• not a major health concern

• eggs are not released into feces, but on skin

scotch tape test

Describe hookworm nematodes. (5)

• head is bent, mostly tropical

• dangerous, massive amount of blood consumed leading to anemia

• infect via contact on soil

• most species stay near skin, but human hookworms move to other systems

• can be hard to remove

How are hookworms contracted?

via contact with soil

Where are filarial worms common? Where do females lay their eggs?

• up to 4 inches long

• common in tropical areas

• females lay eggs in blood system for transmission (via mosquito)

What filarial worm nematode causes elephantiasis?

Bancrofti - filarial worm

How does Bancrofti cause elephantiasis?

by lymphatic system swelling

Give an example of filarial worms.

Guinea worm

• water transmitted via crustacean host

• humans are the only host

• prefer to live in lower extremities

• almost completely eradicated by Jimmy Carter

How can nematode parasitic infections be beneficial? (4)

• infections may have benefit in decreasing allergies by dampening the immune system

  • 60% of developing countries children not allergic to dust mites

• can destroy crops. but can control pest species

• fundamental in recycling nutrients within ecosystems

• “population control” by eating bacteria or pest plants

What worms makes up Phylum Nematomorpha?

Horsehair worms

Describe the general characteristics of Phylum Nematomorpha.

• all require water at some point

• adults- free living

• juveniles- parasites of insects

• no circulatory, respiratory, excretory system

• digestive system often degenerate or vestigial in adults

causes crickets to drown by overriding brain

Describe the general characteristics of Phylum Loricifera. (7)

• small phylum - 11 described

• meiofauna - living in sediments

• juveniles resemble adults except for pair of “toes”

• about the size of a large protozoan, but multicelled

• do have a brain, digestive, excretory, and muscular systems

• diecious

• found in methane seeps

Why is the Phylum Loricifera important?

useful for indicators of methane deposits

What is Phylum Kinorhyncha commonly referred to as?

“mud dragons”

Describe the general characteristics of Phylum Kinorhyncha.

• moveable beak

• marine only

• body divided into 13-14 plates with bear spines for movement

• head is completely retractable

• pseudocoel filled with amoebocytes

• can not swim, burrow in the mud and silt

• dioecious but no dimorphism

What is important characteristic of Phylum Kinorhyncha?

divided into segments (13-14 plates)

What does it mean for the pseudocoel of Kinorhyncha to have amoebocytes?

stem cells, can regenerate parts of their body

What is Phylum Onychophora commonly referred to as? (2)

velvet worms, “claw-bearers”

Describe general characteristics of Phylum Onychophora.

• originally marine, but now all terrestrial in tropical areas

• slime producers for defense

• “velvet” due to scales

• characteristics of annelids and arthropods

  • segmentation, appendages, baggy feet with claws

What are the functions of baggy feet in Phylum Onychophora? (3)

can uptake water through touch

muscles in feet for circulatory pumping

pheromone reception

What does the Phylum Tardigrada mean? What are they often called?

“slow step”; water bears

Describe the general characteristics of Phylum Tardigrada.

• freshwater, marine, majority are terrestrial

• have 8 unjointed legs that bear claws

• many are cosmopolitan

• dispersed by wind

• feed on plant or algae cells with stylets

• reproduce by parthenogenesis or sexually

What is the main habitat of Phylum Tardigrada

terrestrial; but many can live in temporary water films or permanent water

How can Phylum Tardigrada survive in extreme environments?

with cryptobiosis - reduction of water within body

• suspended state - can revive quickly as 4 minutes

• -328F-300F. radiation, boiling liquids, 6000X pressure of sea level, and in space, all from proteins they produce