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Animal kingdom > Chelicerata > Flashcards

Chelicerata Flashcards

1
Q

Chelicerata is composed of three classes: Pycnogonida, Merostomata, Arachnida

They are defined by their chelicerae

The Arachnida are the most diverse, comprising the spiders, scorpions, ticks, pseudoscorpions, solifuges, whip spiders and whip scorpions

A

..

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2
Q

Chelicerate

A
  1. Have chelicerae (pair of appendages in front of the mouth, usually modified as pincerlike claws)

Not the same as the chelae (pincers)

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3
Q

Chelicerata classification

A
  1. subphylum of arthropoda
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4
Q

Chelicerata classification 3 classes

A
  1. Class Arachnida
  2. Class Merostomata
  3. Class Pycnogonida
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5
Q

Chelicerata body plan

2 points

A

Body divided into two regions (May have a clear connector or pedicel):

  1. Prosoma (or cephalothorax)
    1st pair of appendages: chelicerae
    2nd pair of appendages : pedipalps
    3rd to 6th pairs of appendages : walking legs
  2. Opisthosoma
    Up to 13 segments and a tail spine
    2nd segment has gonopore
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6
Q

Respiration
Book gills
2 points

A
  1. Thin leaves of tissue filled with haemolymph

2. Pulsation of opisthosoma causes circulation

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7
Q

Respiration
Book lungs
3 points

A
  1. Spiracle opens into a chamber
  2. Hollow flat plates through which air circulates
  3. Haemolymph flows over inner surface and exchanges respiratory gases
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8
Q

Respiration

Trachea

A
  1. Spiracle leads into cuticle-lined tubes suspended in haemolymph
  2. Unbranched tracheae carry oxygen direct to organs
  3. May have tracheal lungs – clusters of tracheae in the haemocoel
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9
Q

Respiration

Haemocyanin

A

Copper-based respiratory pigment dissolved in plasma

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10
Q

Circulation

4 points

A
  1. Standard Arthropod system with dorsal contractile heart
  2. May have arteries which direct the flow of the haemolymph
  3. After emerging from aorta in head, haemolymph is routed to the rear via the book lungs
  4. Spiders only have short hearts in the opisthosoma

Aorta takes blood through pedicel into prosoma

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11
Q

Nervous system

6 points

A
  1. Basic arthropod system of ventral nerve trunk

Often fused into single nerve

  1. A nerve collar or nerve ring surrounds the oesophagus
    Most nerves to other parts of body arise from here
  2. One or more ganglia may be present
  3. Brain
    Protocerebrum associated with visual organs

Tritocerebrum associated with chelicerae

Sub-oesophageal ganglion

  1. Well developed tactile senses
    Every bristle is a sense organ
6. Good visual system
Simple eyes (ocelli)
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12
Q

Digestion

4 points

A
  1. Variable between groups
  2. Nearly all depend on a pumping system for fluid food

Part of the foregut, between the nerve ring and the mouth

Pharyngeal pump – chamber with dorsal folds, compressor and dilator muscles work antagonistically to pull liquids into pharynx

  1. Solid food is broken up
    Using chelicerae, aided by pedipalps or legs

Extra-oral digestion due to enzymes in saliva or midgut excretions

Arachnids have no jaws and a narrow oesophagus

  1. Midgut digests food and absorbs nutrients
    Arachnids have diverticula – highly folded and branched
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13
Q

Excretion 3 points

A
  1. Coxal glands
    Sacculus – extract wast water

Labyrinth – convoluted tubule where nitrogenous waste is added to the contents

Excretory pore – at base of each leg

  1. Malpighian tubules
    Arachnids only

Blind tubes attached to union of midgut and hindgut

Branched and tangle with diverticula of gut

  1. Primary nitrogenous product is guanin
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14
Q

Reproduction

4 points

A
  1. Arachnid males have pedipalps modified into copulatory organs
    Charge with sperm
  2. Various strategies for avoiding becoming a post-coital snack
    Courtship dances

Nuptial gifts

Restraining the female

  1. Spiders create an egg cocoon out of silk
    Protects from injury and desiccation
  2. May guard or carry the egg sac; carry young after hatching; or even feed the young.
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15
Q

Summary

The Arachnida are the most

A 
diverse class
comprising:
spiders, 
scorpions, 
ticks, 
pseudoscorpions, 
solifuges, 
whip spiders
whip scorpions
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16
Q

Summary

Chelicerata are define by their

A

Chelicerae

17
Q 
Class Arachnida (spiders)
6 points
A
  1. Unsegmented prosoma, typically with solid carapace
  2. Chelicerae and pedipalps
  3. Four pairs of legs
  4. Opisthosoma lacks appendages, often heavily modified
  5. Principally carnivorous
  6. Sensory hairs (primary for most arachnids), eyes, slit sense organs (detect air pressure)
18
Q

Class Arachnida
Scorpiones (scorpions)
3 points

A 
1. Prosoma
Chelate pedipalps (claws)

Single shield covers whole prosoma

  1. Opisthosoma
    Mesosoma of 7 broad segments

Metasoma of 5 narrow segments

Telson modified into venom gland and sting

  1. Stinging apparatus
    Venom used in subdual of prey and defence

Neurotoxic and painful

Usually specialised for invertebrate prey

Strong venom correlates with weak pedipalps

19
Q

Class Arachnida
Opiliones (harvestmen)
4 points

A
  1. all habitats, omnivorous
  2. Undivided prosoma
  3. 9 segmented opisthosoma
  4. Long, leg-like pedipalps
  5. Single pair of simple eyes in middle of prosoma
20
Q

Class Arachnida

Pseudoscorpiones (book scorpions)

A
  1. Claw-like pedipalps with venom glands
  2. Chelicerae have silk glands
  3. 0-2 pairs of simple eyes
  4. Flattened opisthosoma
  5. Phoresy – carried by other organisms
21
Q

Class Arachnida
Solifugae (camel spiders, sun spiders, wind scorpions)
5 points

A
  1. desert and semi-desert,
  2. predatory on large invertebrates and small vertebrates
  3. Large prosomal shield
  4. Two-jointed chelicerae, no venom
  5. Leg-like adhesive pedipalps
22
Q

Class Arachnida
Thelyphonida (Whip scorpions, vinegaroons, uropygids)
3 points

A
  1. Pedipalps have crushing jaws
  2. Elongated 1st legs used as sensory appendages
  3. Telson (tail) is sensory organ
    Acetic acid as defence mechanism
23
Q

Class Arachnida
Amblypygi (Whip spiders, tailless whip scorpions)
2 points

A
  1. Pedipalps are raptorial

2. Elongated 1st legs used as sensory appendages

24
Q

Class Arachnida

Araneae (Spiders)

A
  1. Prosomal segments fused
  2. Opisthosoma of 12 segments attached with narrow stalk
  3. Jointed chelicerae with venom glands
  4. Leg-like pedipalps for food handling and insemination (in males)
  5. Up to eight eyes
  6. Silk glands
25
Q

Class Arachnida
Araneae (Spiders) silk glands
4 points

A
  1. Silk is a protein extruded in liquid form
  2. Produced by a silk gland and emitted by spinnerets
    1-4 pairs (usually 3); only abdominal appendages in Araneae
  3. Many different types of silk
    Stiff for construction
    Sticky for prey capture
    Woolly to catch insect bristles
4. Uses:
Prey capture
Prey immobilisation
Dispersal via ballooning
Spermatophores and egg sacs
Nest construction
Guide lines and drop lines
Alarm lines
Pheromone trails
26
Q

Acari
Mites and ticks
5 points

A
  1. Fusion of prosoma and opisthosoma
  2. A capitulum formed from pedipalps and chelicerae
  3. Opilioacariformes
    Superficially similar to harvestmen
    10 genera, believed to be basal to the Parasitiformes
  4. Acariformes
    House dust mites, mange mites, feather mites
    Spider mites, gall mites, chiggers
  5. Parasitiformes
    Hard ticks and soft ticks
  6. probably polyphyletic
27
Q 
Class Pycnogonida (Sea spiders or pycnogonids)
6 points
A
  1. marine benthos, up to 70cm leg span
  2. Mouth on a proboscis, mostly carnivorous on sessile, soft-bodied invertebrates
  3. Caecae of midgut protrude down legs
  4. Narrow prosoma
    4 to 6 pairs of legs
    Ovigers: modified legs used for grooming and (in males) for carrying eggs
  5. Vestigial opisthosoma
  6. No organs for gas exchange or excretion
28
Q

Class Merostomata, Order Xiphosura (Horseshoe crab)

A
  1. coastal waters
  2. Prosoma covered by large dorsal shield
  3. 5-6 pairs of respiratory appendages on opisthosoma
    “book gills”
  4. Well-developed spine (telson)
  5. Pair of compound eyes, pair of simple eyes

Animal kingdom (14 decks)

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