ZOOLOGY – PHYLUM ARTHROPODA

THINGS YOU NEED TO KNOW FROM THIS CHAPTER…

1. What the following structures are…

a. Hemocoel

2. Tagmata
3. Chitin
4. Exoskeleton
1. What is dimorphism?
2. What is ecdysis? Why is it necessary? How many times do they do it before they reach adulthood? What are juvenile stages called?
3. Why is Phylum Arthropoda so important? (Hint: Why does it take us 3 chapters to cover it?)
4. What is the smallest and the biggest living arthropod?
5. Are most arthropods parasites, predators, or herbivores?
6. Why did the exoskeleton give arthropods such an advantage? (Hint: You should be able to discuss several reasons.)
7. How do arthropods have a more complex respiratory system?
8. What animals belong to Subphylum Trilobita?
1. When did they go extinct?
2. How did they live?
3. What are biramous appendages?
9. How many pairs and what types of appendages do the animals belonging to Subphylum Chelicerate have? Do they have mandibles or antennae?
1. Class Merostomata

i. What are eurypterids? Are they alive?

ii. Why is it important for us to learn about eurypterids?

iii. What are xiphosurids?

1. Why are they called living fossils?

2. What are their body segments called?

3. How do the walk? How do they swim?

4. What do they eat?

5. How do the mate?

2. Class Pycnogonida

i. What are they?

ii. Where do you find them?

3. Class Arachnida

i. What are the segments of their bodies called?

ii. How do they make their living (what do they eat)?

iii. Are the (in general) dangerous to humans?

iv. How do they benefit humans?

v. What order do spiders belong to?

1. How do they eat?

2. What special respiratory structure do they sometimes have?

3. How do they excrete wastes yet conserve water?

4. How do they detect vibrations?

5. How do they spin silk? What do they use it for?

6. How do they mate?

7. What is the genus name of black widows?

a. Why are they called black widows?

i. Is that a myth?

b. What type of venom do they produce?

c. What are the symptoms of a bite?

8. What is the scientific name of brown recluses?

a. What type of venom do they produce?

b. What are the symptoms of a bite?

9. What are the 2 introduced dangerous spiders?

a. Where are they common?

vi. What order do scorpions belong to?

1. What are the names of (and how many segments, if applicable) their body segments?

2. What are pectines?

3. What are spermatophores?

4. Are the scorpions in the U.S. dangerous?

vii. What order do harvestmen belong to?

1. What are they commonly called here?

2. How can you distinguish them from spiders?

3. Are they dangerous to humans?

viii. What order do ticks and mites belong to?

1. How do mites cause humans problems?

2. What diseases are carried by ticks?

I. Compared and Contrasted to Phylum Annelida (the segmented worms)

A. They are like annelids in that …

1. They are eucoelomate animals that show metamerism

a. Well-developed organ systems

2. Their nervous system is of the annelid plan

3. They have a complex muscular system capable of rapid

contractions

4. They have a complete digestive system

B. They are less complex than annelids in that …

1. They have an open circulatory system

a. They still have a dorsal contractile heart & arteries

b. The coelom is reduced to a _______________________

(the main body cavity that contains the blood)

C. They are more complex than annelids in that …

1. Their somites are more specialized for a variety of purposes,

forming functional groups called _______________________.

2. They have paired, jointed appendages

3. The soft cuticle of annelids has become a hard

_______________________ due to the addition of

_______________________ (a nitrogenous polysaccharide) and

often calcium carbonate (especially in crustaceans).

a. This provides the muscles with something resistant to pull

on.

b. They no longer have a hydrostatic skeleton.

4. They have special mechanisms (gills, tracheae, book lungs,

tracheae) for respiration

5. The sexes are separate (_______________________)

a. Often show _______________________ (sharp changes

in form during postembryonic development)

6. They show a wider occurrence of social organization

II. Characteristics of Phylum Arthropoda

A. Arthropodization

1. The soft cuticle of the ancestors of arthropods was stiffened by

deposition of protein and an inert polysaccharide, chitin.

2. Joints had to provide flexibility and a sequence of

_______________________ was necessary to allow for growth.

3. The hydrostatic skeleton function was lost, the coelom regressed

and open sinuses replaced them.

B. Phylum Arthropoda

1. This contains over _______________________ of all known

species.

2. The phylum has a rich fossil history dating to the late

_______________________.

3. Exoskeleton

a. The primitive pattern is a linear series of similar somites

with jointed appendages.

b. Many somites may be fused or combined into specialized

groups called tagmata.

c. Appendages are often highly specialized for division of

labor.

4. Sizes range from the _______________________ (four meters

in leg span) to the 0.1 mm long _______________________.

5. Their abundance and wide ecological distribution makes them

the most diverse animal group.

6. All modes of feeding occur among arthropods

a. Most are _______________________.

C. Classification of Phylum Arthropoda

1. Subphylum Trilobita

2. Subphylum Chelicerata

a. Class Merostomata

b. Class Arachnida (The coolest class of animals on earth –

at least in Mrs. Estlack’s humble opinion!)

c. Class Pycnogonida

3. Subphylum Crustacea (covered in Aquatic Mandibulates)

4. Subphylum Uniramia (covered in Terrestrial Mandibulates)

a. Class Diplopoda

b. Class Chilopoda

c. Class Pauropoda

d. Class Symphyla

e. Class Insecta

III. Why are arthropods so diverse and abundant (in other words successful)?

A. The diversity of species, wide distribution, variety of habitats and

feeding habits, and adaptations are due to a constellation of structures

and physiological patterns.

B. Versatile Exoskeleton

1. The _______________________ is highly protective but is

jointed, providing mobility.

2. The cuticle contains chitin bound with protein.

3. Thus the procuticle is lightweight, flexible, and provides

protection against dehydration.

4. Impregnation with calcium salts makes the procuticle very hard in

lobsters and crabs.

5. The cuticle is laminated and further hardened by

_______________________, a chemical process.

6. As the cuticle is thin between segments, it allows movement at

the joints.

7. _______________________, or molting, is the process of

shedding its outer covering and growing a new, larger one.

8. Arthropods typically molt _______________________ times.

a. Each stage between the molts is called an

_______________________.

b. The _______________________ of the exoskeleton is a

limit to ultimate body size.

C. Segmentation and Appendages for Efficient Locomotion

1. Usually each somite bears a pair of jointed appendages.

2. Appendages may function in sensing, food handling, walking or

swimming.

D. Air Piped Directly to Cells

1. Terrestrial arthropods use an efficient

_______________________ system that delivers oxygen directly to

cells.

2. Aquatic arthropods respire by various forms of efficient

_______________________.

E. Highly Developed Sensory Organs

1. Eyes vary from simple light sensitive ______________________

to a ______________________________________________.

2. Other senses accomplish touch, smell, hearing, balancing and

chemical reception.

F. Complex Behavior Patterns

1. Arthropods surpass most other invertebrates in complex and

organized activities.

2. Most behavior is _______________________ (or unlearned) but

some is learned.

G. Use of Diverse Resources through Metamorphosis

1. Many arthropods have metamorphic changes that result in

different larval and adult stages.

2. Larvae and adults eat different foods and occupy different habitat

and thus avoid _______________________.

IV. Subphylum Trilobita – an ancient group of arthropods

A. Trilobites arose before the Cambrian, flourished, and then became extinct _______________________ years ago.

1. They were bottom dwellers (________________________) and

probably were _______________________.

2. Ranging from 2 to 67 centimeters long, they could roll up like pill

bugs.

3. The body was divided into a _______________________,

_______________________ and _______________________.

4. The head bore antennae, compound eyes, a mouth, and jointed

appendages.

5. Each body somite except the last bore a pair of

_______________________ appendages.

6. One of the branches of the biramous appendage was fringed and

may have been a gill.

a. Arthropod appendages that are biramous have _______

___________________, an outer branch and an inner

branch. These branches may have separate functions.

b. In crustaceans, for instance, the inner branch of a leg is

used for walking, while the outer branch may be paddle-

shaped or feathery and often functions as a gill.

V. Subphylum Chelicerata

A. Characteristics

1. Chelicerates have ______ pairs of appendages including

_______________________, _______________________ and

______________________________________________.

2. They lack _______________________ and

_______________________.

3. Most suck liquid food from prey.

B. Class Merostomata: Subclass Eurypterida

1. Eurypterids

(______________________________________________) were

the largest of all fossil arthropods at _______________________ in

length.

2. They resemble both marine horseshoe crabs and terrestrial

scorpions.

3. It is widely accepted that life first evolved in the ocean.

4. There is good evidence that eurypterids (or an animal very like

them) were the first animal to emerge from the ocean to colonize

the terrestrial earth.

a. Other arthropods emerged from the ocean and

diversified.

b. They would be followed by a fish-like animal that evolved

into today’s amphibians.

1) From these animals reptiles evolved.

a) From reptiles, birds and mammals evolved.

C. Class Merostomata: Subclass Xiphosurida,

_______________________

1. The modern horseshoe crab is nearly unchanged from ancestors

in the Triassic period.

a. They are sometimes called

“______________________________________________.”

2. Five species in three genera survive.

3. Most live in _____________________________________ water.

4. Structures

a. An unsegmented shield or _______________________

covers the body in front of a broad abdomen and a

_______________________.

b. The cephalothorax has ________ pairs of walking legs

and a pair of _______________________ (the most anterior

head appendage that has been modified among chelicerates

to serve multiple purposes – envenomation, capturing prey,

or eating prey).

c. The carapace has two compound and two simple eyes.

5. They walk with their walking legs and swim with abdominal

plates.

6. They feed at night on _______________________ and small

_______________________.

7. During the mating season, they come to shore at a very high tide

to mate.

8. Females burrow into sand to lay eggs; males follow to add sperm

before she covers the eggs.

9. The young larvae hatch and return to the sea at the next very

high tide.

10. Larvae are segmented and resemble trilobites.

D. Class _______________________: Sea Spiders

1. Sea spiders vary from a few millimeters to larger sizes; all have

small, thin bodies.

2. Sea spiders occur in all oceans but are most common in

_______________________ waters.

E. Class Arachnida

1. There is a great diversity among scorpions, mites, ticks, daddy

longlegs and others.

2. Most are free living and more common in warm, dry regions.

3. Structures

a. Arachnid bodies are divided into a

_______________________ and _____________________.

b. The cephalothorax bears a pair of

_______________________, a pair of

_______________________ and ______ pairs of walking

legs.

c. Antenna and mandibles are _______________________.

d. Most are _______________________ and have claws,

fangs, poison glands or stingers.

e. Sucking mouthparts ingest the fluids and soft tissues from

bodies of their prey.

f. Spiders have spinning glands.

4. Over 70,000 species have been described.

5. Scorpions appeared on land in the Silurian; mites and spiders

were found by the end of the Paleozoic.

6. Most are _______________________ to humans and provide

essential control of injurious insects.

7. Some spiders are venomous and can cause pain or death in

humans; ticks may carry human diseases and mites can be crop

pests.

8. Order _______________________: Spiders

a. About _______________________ species of spiders are

known.

b. The body consists of an unsegmented cephalothorax and

abdomen joined by a slender _______________________.

c. The anterior appendages are a pair of chelicerae with

terminal _______________________.

d. A pair of _______________________ has basal parts that

help them handle _______________________ and

often facilitates mating.

e. Four pairs of walking legs terminate in

_______________________.

f. All spiders are predaceous, mostly on

_______________________, which are dispatched by

poison and fangs.

g. The injected venom liquefies and digests the tissues; this

is sucked into the spider’s stomach.

h. Spiders breathe by _______________________and/or

tracheae.

1) Book lungs are unique to spiders; parallel air

pockets extend into a blood-filled chamber.

2) Air enters the chamber through a slit in the body wall.

i. Spiders and insects have _______________________

for an excretory system.

1) Potassium, other solutes and waste molecules are

secreted into the tubules.

2) Rectal glands reabsorb the potassium and water,

leaving wastes and uric acid for excretion.

3) This conserves _______________________ and

allows the organisms to live in dry environments.

j. Sensory Systems

1) Most spiders have _______________________

eyes, each with a lens, optic rods and a retina.

2) They detect movement and may form images.

3) Sensory _______________________ detect air

currents, web vibrations and other stimuli.

k. Web-Spinning Habits

1) Spinning _______________________ is a critical

ability for spiders and some other arachnids.

2) Two or three pairs of _______________________

contain microscopic tubes that run to silk glands.

3) A liquid scleroprotein secretion hardens as it is

extruded from the spinnerets.

4) Silk threads are very strong and will stretch

considerably before breaking.

5) Silk is used for orb webs, lining burrows, forming

egg sacs and wrapping prey.

l. Reproduction

1) Before mating, the male stores his sperm in his

_______________________.

2) Mating involves inserting the pedipalps into the

female genital openings.

3) A courtship ritual is often required before the

female will allow mating.

4) Eggs may develop in a cocoon in the web or may

be carried by the female.

5) The young hatch in about two weeks and may molt

before leaving the egg cocoon.

m. Are spiders really dangerous?

1) Most fear spiders without good reason.

2) Spiders are allies of humans in our battle with

_______________________.

3) American tarantulas rarely bite and the bite is not

dangerous.

3.5) Below is a map (Discover 2005) of the distribution

dangerous spider species in the U.S.

Graphic by Don Foley

VENOMOUS AMERICAN ARACHNIDS

The United States has five groups of spiders that can cause serious injury.

1) The black widow is distributed throughout the U.S. (in fact, it has a worldwide distribution)

2) The yellow sac spider’s distribution hasn’t been mapped precisely, but it is believed to be distributed throughout the U.S.

3) The hobo spider has expanded its range in the Pacific Northwest (red in the map).

4) The brown recluse found in the South and lower Midwest (green in the map).

a. Other recluses are found in the Southwest (blue in the map).

Below is a second map, which shows the distribution of the various species of recluses in the U.S.

4) Species of black widow spiders (_______________

_______________________ ) are dangerous. There

are 3 species in the U.S.

a) They are called black widows because it

was believed they always ate their mate (the

male).

1) They do in captivity.

2) This occurs rarely in nature, only

when the female is very hungry.

b) The venom is _______________________.

c) Some people are slightly affected by the

venom, while others may have a severe

response.

i) Rarely fatal – only small children and

the elderly are typically at risk of death.

d) The first (typical) symptom is acute pain at

the site of the bite

e) The local pain may be followed by localized

or generalized severe muscle cramps,

abdominal pain, weakness, and tremor. In

severe cases, nausea, vomiting, faintness,

dizziness, chest pain, and respiratory

difficulties may follow.

f) Symptoms often diminish after a day or so

and cease after several days.

5) The brown recluse (_______________________

_______________________) spider has

_______________________ venom that destroys

tissue around the bite.

a) The venom is extremely poisonous, even

more potent than that of a

_______________________.

i) Recluse venom causes less disease

than a rattlesnake bite because of the

small quantities injected into its victims.

b) This venom is a collection of enzymes that

causes destruction of local cell membranes,

leading to local breakdown of skin, fat, and

blood vessels.

i) This process leads to eventual tissue

death called

_______________________ in areas

immediately surrounding the bite site.

c) Bites often go unnoticed initially because

they are usually _______________________

bites.

i) Many brown recluse bites cause just

a little red mark that heals without event.

ii) The vast majority of brown recluse

bites heal without severe scarring.

d) Symptoms usually develop 2-8 hours after a

bite and can include…

i) Severe pain & itching at bite site

ii) Nausea, vomiting, and fever

iii) Myalgias (muscle pain)

e) Initially the bite site is mildly red; the

redness gives way to pallor with a red ring

surrounding the area, or a "bull's-eye"

appearance.

f) The center area will then often

_______________________, which

over 12-48 hours can sink, turning bluish then

_______________________ as this area of

tissue dies.

g) This can leave a deep, infected wound that

enlarges, fails to heal, or heals slowly over 6 to

8 weeks, often leaving scarring behind.

h) Treatment for severe bites includes both

_______________________ (to stop the

immune response) and

_______________________ (to combat

infection of the wound)

6) Some Australian and South American spiders are

the most dangerous and aggressive.

7) There are two introduced spiders that are

dangerous and are becoming more common in the

U.S.

8) The yellow (golden) sac spiders (Cheiracanthium

mildei)

a) Transported easily, particularly in

agricultural products such as grapes.

b) They are well-established in California, the

Pacific Northwest, and southeastern Idaho.

c) They are very prone to bite defensively

(more so than any other significantly venomous

U.S. spider).

d) It is likely that many U.S. cases of necrotic

arachnidism ascribed to the brown recluse

spider outside of its natural range, are actually

yellow sac spider bites.

e) Bites generally produce instant, intense

stinging pain, not unlike that of the sting of a

wasp or hornet.

f) May be followed by localized redness,

swelling and itching; these manifestations may

or may not evolve into a necrotic lesion, but

when that occurs healing is usually complete

within eight weeks.

g) Systemic effects are usually not severe, but

when they occur may include chills, fever,

headache, dizziness, nausea, anorexia, and

sometimes shock.

9) The hobo spider, Tegenaria agrestis

a) Indigenous to western Europe that was

introduced into the northwestern United States

(Port of Seattle) sometime before the 1930's.

b) Introduction was almost certainly through

commercial shipping vessels, as egg cases

attached to wood, etc.

c) By 1968 it had become established as far

east as Spokane, Washington and Moscow,

Idaho, and as far south as Corvallis, Oregon.

d) The hobo spider is now the leading cause

of serious envenomation in the northwestern

United States.

e) Typically, defensive bites by the hobo

spider are lightning fast, then the animal

withdraws rapidly.

f) Very often the bite itself is painless.

g) Local effects are almost identical to those

produced by brown recluse spider.

h) Systemic, or generalized effects are seen in

about 45% of persons envenomated by hobo

spiders.

i) The most common reported symptom is

severe headache, which usually does not

respond to over the counter analgesics.

j) Victims may experience a dry mouth,

nausea, weakness and lethargy, dizziness,

visual disturbances, hallucinations, joint pain

and/or other undesirable effects.

k) About 15% of envenomated subjects are

poisoned severely enough to require

hospitalization.

l) In rare cases aplastic anemia (bone marrow

failure) can develop several weeks after the

bite, which results in a fatal outcome.

9. Order _______________________: Scorpions

a. Scorpions are more common in tropical and subtropical

zones but do occur in temperate areas.

b. They are _______________________ and feed largely on

insects and spiders.

c. Sand-dwelling scorpions locate prey by detecting surface

waves with their leg _______________________.

d. The cephalothorax has the appendages, a pair of medial

eyes and 2-5 lateral eyes.

e. The _______________________ has seven segments.

f. The _______________________ has five, long, slender

segments that end in a telson.

1) We call the _______________________ the tail.

2) We call the _______________________ the

stinger.

g. Under the abdomen are comblike

_______________________ that explore the ground and

help in sex recognition.

h. The stinger on the last segment has venom that varies

from mildly painful to dangerous.

i. Scorpions perform a mating dance where the male guides

the female over the _______________________ (a structure

that stores his sperm and that he has attached to the

substrate before mating).

j. Scorpions are ovoviviparous or viviparous and produce

from six to 90 young.

k. Of the many species of scorpions in the United States,

only one is considered to be life-threatening. This is the bark

scorpion, Centruroides sculpturatus (actually a synonym of

C. exilicauda) found in the Sonoran desert of Arizona.

1) The venom causes a stinging or burning sensation

at the injection site, often with very little swelling or

inflammation, but always with a positive "tap test" (i.e.,

extreme pain when the sting site is tapped with a

finger).

2) Systemic reactions include progressive

hyperactivity (restlessness) progressing to

convulsions, "roving eyes," ataxia (staggering gait),

thick tongue sensation, slurred speech, drooling,

hyperesthesia (excessive sensitivity of skin), muscle

fasciculations (twitches), abdominal pain and cramps,

and respiratory depression.

3) These symptoms usually subside within 48 hours.

4) Systemic reactions to scorpion stings (even to the

sting of the bark scorpion) are rare.

10. Order _______________________: Harvestmen

a. Harvestmen or _______________________ are common,

particularly in tropical regions.

b. Unlike spiders, their abdomen and cephalothorax join

broadly without a narrow pedicel.

c. They can lose most of their eight long legs without ill

effect.

d. Their chelicerae are _______________________ and

they feed more as _______________________ than do

spiders.

1) Myth: Their venom is extremely toxic to humans.

a) Their venom isn’t extremely toxic.

b) Their fangs are too short to puncture human

skin.

11. Order _______________________: Ticks and Mites

a. Acari are medically and economically the most important

arachnids.

b. About _______________________ species have been

described, many more are estimated to exist.

c. They are both aquatic and terrestrial, and inhabit deserts,

polar areas and hot springs.

d. Most mites are less than 1 millimeter long; ticks may

range up to 2 cm.

e. Acarines have complete fusion of cephalothorax and

abdomen with no sign of external segmentation.

f. House dust mites are free-living and often cause

_______________________.

g. __________________________________ are one of

many important agricultural pest mites that suck out plant

nutrients.

h. _______________________ are larval Trombicula mites;

they feed on dermal tissues and cause skin irritation.

i. The hair follicle mite Demodex is harmless but other

species cause mange in domestic animals.

j. Tick species of Ixodes carry _______________________.

k. Tick species of Dermacentor transmit _______________

______________________________________________.

l. The cattle tick transmits __________________________

______________________________________________.