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Flashcards in Lecture 6 RH Deck (59)
1

What is the diversity of chelicerates like?

2nd largest group of arthropods

98% of chelicerates are arachnids

Most arachnids are spiders

Diversity is related to numerous uses of silk

2

What are some common features of chelicerates?

No antennae or mandibles

2 tagmata:
Cephalothorax
Abdomen

6 pairs of uniramous appendages:
chelicerae
Pedipalps
4 pairs of walking legs

Spines at the base of their appendages that are called macrobases

3

What are some features that only chelicerates don't have?

No mandibles

No antennae

4

What is the function of pedipalps?

for holding onto food or mates

5

What happens to book gills in spiders?

They are internalized and act like lungs

6

What are the classes of chelicerates?

Merostoma (horseshoe crabs)

Arachnia (spiders, scorpions, ticks, mites)

Pycnogonida (sea spiders)

7

What are the types of merostomatans?

Horseshoe crab: 4 living species (located on the East coast of US, S.E, Asia, Indonesia

Eurypterid (extinct for 230 million years and are successful predators in paleozoic seas, have reached almost 3m in length, likely ancestor of arachnids)

8

What are the orders of class arachnida?

Arachneae: True spiders

Opiliones (daddy longlegs; harvestmen)

Solpugida and amblypygi: Solifuges and whip spiders resemble spiders

Scorpionida: scorpions

pseudoscorpionida and uropygi

Acari: ticks and mites

9

What are the adaptations of class arachnida for terrestrial life?

Exoskeleton for support and protection

Waxy epicuticle

Book lungs and tracheae in spiders and scorpions and some spiracles can be closed

Internal fertilization and eggs are shelled

Several types of highly sensitive mechanoreceptors that detect air vibrations

10

What are the features of araneae?

40k species

Chelicerae have fangs for stabbing and tearing prey usually with venom glands

Predators with external digestion

1 pair of pedipalps for holding prey; 4 pairs of walking legs

Usually 4 pairs of eyes

Abdomen includes several fused segments No segmentation visible externally

Pedicel

Spinnerets

11

What is a pedicel?

Narrowing between abdomen and cephalothorax to allow more flexibility

12

What is a spinnerets?

Organs that produce silk to spin webs

13

What is the function of pedipalps?

Holding prey

14

What is spider silk made of?

Complex liquid-crystalline polymer which is a liquid of protein subunits which arrange into a crystalline matrix when pulled from secretory glands.

15

What are the features of spider silk?

Remarkably strong and elastic

7 types of glands produce silk of different properties for different functions

Glands are arranged in spools from which the spun silk emerges

Spools are arranged in spinnerets on abdomen that direct and place the silk

16

What are some uses of spider silk?

Locomotion

Feeding

Breathing under water by creating a balloon

Reproduction

17

How do spiders use their silk for locomotion?

Dragline for safety

Climbing or descent

Ballooning

18

How do spiders use silk for feeding?

They create a thread of sticky spiral with adhesive droplets

They use silk to immobilize prey while they digest it

19

What is the mechanism a spider uses for an abreviated orb web?

Spider sits between tension thread and attachment thread and senses vibrations

20

How do spiders use silk for reproduction?

Communication between mates

Wrapping mates

Wrapped food as offering

Transfer of spermatophore

Egg cocoons

21

What are the features of order opiliones?

AKA daddy long legs or harvestmen

Abdomen has external segmentation and lacks a pedicel

Do not produce silk or toxins. Feed more as scavengers but also as predators.

*The misnamed daddy longlegs in your house is a true spider

22

What are the features of order scorpionida?

Very ancient arachnids

Live in arid or humid habitats, often secretive and nocturnal

Small chelicerae with gnathobases

Large pedipalps with chelae to hold prey

No pedicel

Telson with a poison stinger

Detect vibrations from prey through air or substratum with several types of mechanoreceptors

23

What are the features of order acari?

cephalothorax and abdoman are fused but some mites might have a furrow

Mouthparts are on a short anterior projection

24

What are the features of ticks?

Larger and more triangular or rounded than mites

Blood-sucking parasites with short mouthparts that anchor into host

Can transmit a variety of pathogens

25

What are the features of mites?

Longer mouthparts for various feeding modes (herbivores, predators, scavengers and parasites)

Great economic impacts as crop pests and animal parasites

26

What do chigger larva feed on?

Skin

27

What are the features of class pycnogonida?

1000 species approx

Chelicerae and palps are on an extension of the cephalothorax. Abdomen is greatly reduced

Slow moving marine predators

Feed mainly on cidarians bryozoans and other soft bodied invertebrates with sucking proboscis

Body size up to 70 cm in the deep sea but most are less than 1 cm

28

What are Hox genes?

present in many invertebrate and vertebrate phyla

Some of these genes are homologous

They control the development of body regions bty regulating the activity of other genes

Order of genes on chromosomes matches the order in which they act on the anterior-posterior axis

29

What evidence suggests that insects evolved from crustaceans?

Significant modifications of segments and appendages can be created by simple evolutionary changes in developmental regulatory genes (eg hox genes)

30

What do studies of regulatory genes reveal about arthropod evolution to terrestrial life?

It evolved from biramous legs of ancestral taxa

The same regulatory genes are active during development in gill branches (exopod of crustacians), wing of insects, book gills of horseshoe crabs, and the book lungs, tracheae, and spinnarettes of spiders.

Serial repetition allows specialization to evolve by modifying particular regions in the body. Loss or modification of structures in certain segments converts a homonomous plan to a heternomous plan, producing specialized tagmata

31

What are the features of phylum onycophora?

Coelomates

Protostomes

Segmented

Like arthropods:

Cuticle is molted

Greatly reduced coelom

Tracheae

Like annelids:

Soft cuticle, noncalcified

Homonomous metamerism

Paired appendages that are fleshy and unjointed like parapodia

32

Where do onycophorans live?

In leaf litter of southern hemisphere rainforests

33

How do they eat?

They are predators that catch prey with sticky slime released from special glands.

34

What phyla are onychophorans similar to?

Annelids and arthropods

35

Which phyla are lophotrochozoa?

Platyhelminthes

Annelids

Molluscs

36

Which phyla are ecdysozoans?

nematoda

onycophora

arthropoda

37

What are the lophophorate phyla?

Ectoprocta (bryozoa)

Phoronida

Brachiopoda

38

What do lophophorates have in common?

They contain a lophophore which is a structure used for suspension feeding and gas exchange and is a ring of tentacles that are ciliated and gas exchange.

39

How do lophophores work?

Cilia move water through the tentacles and allows for food and gas exchange to take place

40

What are the traits that are common between lophophores?

Bilateral symmetry

Triploblastic

Complete gut (exception is one class of brachiopods)

Coelomate (3 separate compartments; protocoel, mesocoel, and metacoel)

Almost all are marine with the exception of a few freshwater ectoprocts

Benthic, sedentary or sessile

Uncephalised

Secrete a protective covering

U-shaped gut, anus is outside the lophophore

41

What are the 3 compartments of lophophore coeloms?

Protocoel

Mesocoel

Metacoel

42

What are bryozoans?

Moss-animals

43

What are the features of bryozoans?

Live in colonies

Each polypide lives in a zooecium with an orifice from which the lophophore extends above an extension called the introvert

No circulatory, gas-exchange, or excretory systems

44

What are the types of colonies that bryozoans can form?

Arborescent (branched colonies)

Encrusting (sheet structure)

45

How is the lophophore forced out of the body?

Coelom squeezed by contraction of parietal muscles forcing the introvert out releasing the lophophore.

46

How is the lophophore forced back in?

Retractor muscles pull on introvert

47

What is zooid polymorphism?

Among the colonies there are specialized individuals in the colony for each function.

48

What are the reproductive zooids of the colonies called?

Ovicell

49

What are the protective zooids of the colonies called?

Avicularium which contain mandibles that can "bite"

Vibraculum is a spiny zooid.

50

What are the features of phylum phoronida?

Only 2 genera and 14 species

Solitary worms

More organs than bryozoa (Blood-circulatory system, metanephridia)

Protective covering is a chitinous tube

Sedentary in sediments

51

What are the features of phylum brachiopoda?

All marine

Solitary

Calcareous bivalved shell (covers dorsal-ventral)

Pedicle may attach to substratum

Dominated over bivalve molluscs for several hundred million years but were eventually outcompeted

Important fossils for evolutionary studies

U shaped lophophore 2 arms

Blood-circulatory system, metanephridia

Adductor and abductor muscles

52

What are the types of larvae of bryozoans?

Coronate

Cyphonautes

53

What type of larvae do phoronids have?

Actinotroch

54

What do the larvae suggest about evolution of lophophorates?

Difference in larval forms give no evidence of a close relationship among phyla

Only the shared trait of a lophophore has been thought to unite these phyla as close relatives

Other aspects of their development are curious and fit neither protostomes nor deutrostomes

55

What are the features of rotiferans?

2000 species

56

What are the features of phylum chaetognatha?

100 species 1 - 12 cm in size

Coelomate

All are swift and voracious predators in marine plankton. Have teeth and grasping spines for this purpose

Phylogeny is highly debated: Protostomes or deutrostomes?! No simple morphological synapomorphy

57

What are the differences between protostomes and deutrostomes?

radial cleavage is seen in deutrostome

Spiral cleavage is typically seen in protostomes but not always

Method by which the coelom is
formed

Blastopore destination

58

What is the method by which a protostome coelom is formed?

Schizocoely whereby gut is separated from other pouches by early mesoderm cells forming pouches in the coelom..

59

What is the method by which the deutrostome coelom is formed?

Enterocoely whereby gut outpouchings form the coelom