Animal Diversity Exam 3 Part II: Arthropods

T/F: arthropods have the least advanced cuticle and ecdysis process.

False; they have the most advanced cuticle and ecdysis process.

Arthropods make up __% of all described living animals.

82%

Why are insects especially good at establishing in desert habitats?

Their hard exoskeleton reduces the risk of dessication

What benefit(s) do jointed appendages offer arthropods?

Allows for faster movement and a greater range of movement

Do arthropods exhibit advanced, simple, or no cephalization (generally speaking)?

Advanced cephalization; ganglia in some cases and lots of sensory organs (especially antennae)

The alimentary canal is another term for…

The gastrointestinal/digestive tract.

Most arthropods have what kind of respiratory system?

Tracheal/tube system

* What are the 6 main contributors to the success, abundance, and diversity of arthropods? Be sure to explain why each is beneficial.

1. Advanced exoskeleton (cuticle): protective without sacrificing mobility and reduced risk of dessication, but limits growth (requires molting)

2. Jointed appendages: allows for faster and wider range of movement; often specialized

3. Tracheal respiratory system: Air is delivered directly and quickly to body allowing for a higher metabolic rate

4. Highly developed and diverse sensory organs such as compound eyes, antennae, cerci, setae, halteres, ocelli, tympanum, etc.

5. Complex behavior: show capacity for learning, greater adaptability

6. Metamorphosis: Reduced intraspecific competition due to the strong differentiation of niches between larval and adult stages

Name the 5 subphyla of phylum Arthopoda (covered in this class).

1. Trilobitomorpha — trilobites

2. Chelicerata — chelicerates

3. Myriapoda — millipedes and centipedes

4. Crustacea — crustaceans

5. Hexapoda — hexapods

Trilobites are found in subphylum ___.

Trilobitomorpha

T/F: there are still a few species of trilobite around today, but they are heavily endangered.

False; all trilobites are exinct and found only in the fossil record.

Body regions of trilobites:

1. Cephalon — head region

2. Thorax — middle region

3. Pygidium — posterior region

Body regions of Phylum Chelicerata:

2 regions, cephalothorax (head+thorax) and abdomen

T/F: Chelicerates have no antennae.

True

To what body region do the legs attach to in Chelicerates?

The cephalothorax

How many pairs of appendages do Chelicerates have?

6 (12 total)

Describe the general name and function of the various pairs of Chelicerate appendages.

1st pair: Chelicerae, feeding

2nd pair: pedipalps, various (not locomotion)

Pairs 3-6: walking legs, locomotion

What are the 3 classes (covered in class) in Subphylum Chelicerata?

1. Merostomata — horseshoe crabs

2. Pycnogonida — sea spiders

3. Arachnida — arachnids

What are the 5 orders (covered in class) of Class Arachnida?

1. Araneae — spiders

2. Opiliones — harvestmen

3. Acari — ticks and mties

4. Scorpionida — scorpions

5. Pseudoscorpionida — pseucoscorpions

The carapace covers what body region of horseshoe crabs?

Cephalothorax

How many pairs of walking legs do horseshoe crabs have?

5 (pedipalps modified into walking legs)

What do male horseshoe crabs use to grasp females during mating?

Their chelicerae

The abdominal appendages of horseshoe crabs are modified into _____.

Book gills

Describe the habitat of sea spiders.

All marine; found in intertidal zones, coral reefs, and the deep sea

Sea spiders belong to class ____.

Pycnogonida

Diet of sea spiders:

Predators of small inverts; some scavengers and herbivores

What unique parenting trait do sea spiders exhibit?

The males brood the eggs until they hatch

Are sea spiders monoecious or dioecious?

Dioecious

Arachnids have a ___ diet.

Liquid; some blood feeders, other liquify prey with digestive enzymes, etc.

Arachnids have their mouthparts or pharynx modified into a ____ mechanism to accomodate for their diet.

Sucking

A thin ____ connects the cephalothorax to the abodmen in spiders.

Pedicel

Spider walking legs end in ___.

Terminal claws

How are the chelicerae modified in spiders?

They have terminal fangs with venom glands

Most spiders have how many ocelli?

Eight

Where are the sensory setae often concentrated in spiders?

The pedipalps

What respiratory system do spiders have?

Either book lungs or a tracheal system

Spider intestines have many ___ that increase surface area and improve absorption and digestion.

Ceca

Excretory system of spiders:

Most have malphigian tubules, some with highly modified metanephridia

Harvestmen are in order…

Opiliones

Ticks and mites belong to order…

Acari

In what two arachnid orders are the cephalothorax and abdomen indistinguishable?

Opiliones and Acari

T/F: ticks and mites exhibit metamorphosis.

True

How do you tell an immature tick from an adult?

Immature ticks will have 6 legs, adults will have 8.

Scorpions belong to order…

Scorpionida

The abdomen in scorpions is divided into two sections:

Preabdomen — first 7 segments

Postabdodmen — last 5 segments (last segment ends in stinger)

What appendage are modified into pincers in scorpions?

Pedipalps

What parental care is present in scorpions?

Females will brood young in reproductive tract; after initial development, young will live on the mother’s back until after their first molt

False scorpions belong to order…

Pseudoscorpionida

Do myriapods have uniramous or biramous appendages?

Uniramous (unbranched)

Myriapods have how many antennae?

2 (one pair)

Myriapods have what kind of respiratory system?

Tracheal (except for species with aquatic larvae, which have gills)

Excretion of myriapods:

malphigian tubules

Are myriapods monoecious or dioecious?

Dioecious

What are the tagmata (regions) of myriapods?

Cephalon and trunk

T/F: both centipedes and millipedes have a waxy cuticle.

False; myriapods have a non-waxy cuticle.

T/F: both centipedes and millipedes have repugnatorial (toxin) glands.

True

* How do you tell a centipede from a millipede?

1. Centipedes have one leg pair per segment, millipedes have two

2. Centipedes have “venom fangs” (modified first leg pair), millipedes do not

3. Centepede legs extend laterally from body (visible from above); millipede legs extend ventrally (not visible from above)

Describe the 5 pairs of appendages crustaceans have on their head.

2 pairs of antennae, 1 pair of mandibles, 2 pairs of maxillae

Are crustacean appendages uniramous or biramous?

Biramous (except for first pair of antennae)

Crustaceans have a ___ larval form with ___ pairs of appendages and a single ___.

Crustaceans have a nauplium larval form with three pairs of appendages and a single eye.

The respiratory organs of crustaceans, if present, are ___.

Gills

What are the 2 superclasses of Subphylum Crustacea?

1. Oligostraca (wierdos)

2. Vericrustacea (mostly normal stuff)

What three classes exist under Superclass Olicostraca?

1. Ostracoda — ostracods

2. Branchiura — fish lice

3. Pentastomida — tongue worms

What 4 classes exist under superclass Vericrustacea?

1. Branchiopoda — branchiopods

2. Copepoda — copepods

3. Thecostraca — barnacles

4. Malacostraca — crabs, shrimp, lobsters, and more

What five orders exist under class Malacostraca?

1. Euphausiacea — krill

2. Isopoda — isopods

3. Amphipoda — amphipods

4. Stomatopoda — mantis shrimp

5. Decapoda — crabs, lobsters

What are ostracods often confused for and why?

Bivalves due to bivalved carapace

Ostracods primarily reproduce via ___, meaning that ___ are rarely found.

Parthenogenesis; males

Fish lice belong to class ___.

Branchiura

What modification do fish lice have to grasp onto their hosts?

2nd pair of maxillae modified into suction cups

Fish lice are ___ on fish.

Ectoparasites (external parasites)

Tongue worms belong to class ___.

Pentastomida

Where do tongue worms typically reside as adults?

In the respiratory system of their hosts (endoparasites)

Branchipods use what for respiration?

They use their legs to make a water current and rely on diffusion (no gills); “legs as respiratory organs”

When conditions are prime, as they often are during the summer, branchiopods will exhibit what reproductive behavior?

Parthenogenesis

Copepods have a exoskeleton modified into a well-developed _____.

Cephalic shield

The cephalothorax and abdomen of copepods are called what?

Metasome = cephalothorax, Urosome = abdomen

T/F: copepods are filter feeders.

False; copepods are predators and feed on smaller planktonic organisms.

What are the plates of barnacles made of?

Calcium carbonate

Barnacles belong to class…

Thecostraca

Barnacles have ___ which help catch food particles.

Cirri

Are barnacles monoecious or dioecious?

Monoecious, but still generally cross-fertilize (outcross)

Krill belong to order:

Euphausiacea

What organisms are krill a vital food source for?

Baleen whales

What feature separates krill from shrimp?

Krill have more than 5 pairs of walking legs

What order of crustaceans include the only true terrestrial crustaceans?

Order Isopoda

Where can you find amphipod colonies?

On beaches, especially in bunches of organic matter like kelp

Where do mantis shrimp live?

In burrows of soft sediment within shallow tropical and subtropical marine environments

Mantis shrimp belong to order…

Stomatopoda

What adaptation makes mantis shrimp such good ambush predators?

Spring-loaded arms; break shells of prey

Crabs and lobsters are in order…

Decapoda

The gills of organisms in order Decapoda are enclosed in the ___ of the carapace.

Branchial chamber

Describe the tagmata and segmentation of a crayfish.

2 tagmata: cephalothorax and abdomen

Cephalothorax:

• 13 segments, 5 on head, 8 on thorax, each with 1 pair of appendages

• Covered by carapace w/ rostrum (nose looking thing)

Abdomen:

• 6 segments (each with 1 pair of appendages) + telson

  • 5 pairs of biramous swimmerets

  • Last segment = pair of uropod: flat, paddle-like

Describe the specific parts that make up a biramous appendage.

Protopod: base where exopod and endopod connect

Exopod: lateral, shorter

Endopod: medial, longer

Protopod made up of the internal gill, coxa, and basis

Describe the circulatory system of a crayfish.

Open (hemocoel); hemolymph leaves heart through sternal arteries and is returned by pericardial sinuses

Excretory organs of crayfish:

Green glands

Crayfish have 2 stomachs. What are they called and what do they do?

1. Cardiac stomach — mechanical digestion

2. Pyloric stomach — chemical digestion

* What are the layers of the cuticle in crustaceans?

Epicuticle > Procuticle [exocuticle > endocuticle (principle > membraneous)]

• Epicuticle: outermost layer; thin, made of proteins and lipids

• Procuticle: below epicuticle, collective term for exo- and endocuticle

  • Exocuticle

  • Endocuticle: made of principle and membraneous layers

    • Principle layer: strong, contains a lot of chitin and calcium

    • Membraneous layer: thin, made of chitin and proteins

The ___ is the living cellular layer beneath the exoskeleton that secretes the non-living cuticle.

Epidermis

* Describe the process of molting/ecdysis in crustaceans.

1. Epidermis separates from old endocuticle

2. Epidermis starts secreting new epicuticle, then exocuticle

3. Once epidermis is protected by the new epicuticle, molting enzymes are released which completely dissolve the old endocuticle to be reabsorbed

4. The extra room freed up by dissolving the old endocuticle allows for the exocuticle and endocuticle to be fully secreted

5. The animal takes in a lot of water and swells their body; the old epi- and exocuticle breaks/ruptures and the animal leaves the old molt behind

6. The new cuticle is stretched and unfolded, now unrestricted

7. Finally, the new endocuticle is secreted and the new cuticle hardens

* What hormones are related to ecdysis?

1. Molt-inhibiting hormone: keeps organism from molting, decreases in response to environmental stimuli to allow molting to begin; released from X-organ (base of eyestalks)

2. Ecdysone (molting hormone): released by the Y-organ (mandibles) when amount of molt-inhibiting hormone decreases