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04 Nov. 2014 Arthropoda.ppt 2
Phylum Arthropoda (jointed feet )
• Huge group, > 1,000,000 species.
• estimate: 1,000,000 spp. arthropods 1,190,000 spp. animals
• ~ 84% of all animal species are arthropods!!
04 Nov. 2014 Arthropoda.ppt 3
Phylum Arthropoda
• How can we explain the success of the arthropods?
•
• Exoskeleton!
04 Nov. 2014 Arthropoda.ppt 4
Phylum Arthropoda• Exoskeleton of chitin and protein (= cuticle)• structure:
– epicuticle (oily, waxy)– exocuticle (chitin & protein)– endocuticle (chitin only)– epidermis secretes cuticle
04 Nov. 2014 Arthropoda.ppt 5
Problems associated with exoskeleton.
• Problem 1. MOVEMENT• Solution: Joints in
exoskeleton.• arthro-, = joint
• -pod, = leg, foot
– Exocuticle absent from joints; may form hinges.
– Endocuticle alone allows flexibility.
04 Nov. 2014 Arthropoda.ppt 6
Problems associated with exoskeleton.
• MOVEMENT• Solution: Joints in
exoskeleton.
– Exocuticle absent from joints; may form hinges.
– Endocuticle alone allows flexibility.
04 Nov. 2014 Arthropoda.ppt 7
Problems associated with exoskeleton.
• Problem 2. GROWTH• Solution: Molting
04 Nov. 2014 Arthropoda.ppt 8
Molting (1)
• Secretion of "molting fluid" to dissolve old endocuticle.
04 Nov. 2014 Arthropoda.ppt 9
Molting (2)
• New cuticle formed under old exocuticle.
• Break out of old cuticle Old cuticle breaks at
line of weakness
04 Nov. 2014 Arthropoda.ppt 10
Molting (3)
• Inflate with water/air to increase size while skeleton soft, – but soft skeleton &
gravity limit size;
– arthropods are mostly small.
• Hardening of new exocuticle.
04 Nov. 2014 Arthropoda.ppt 11
Growth stages
• Arthropod passes thru 3-20+ growth stages in life cycle.
• Some stop molting as adults (insects, most spiders)
• Some continue to molt (crayfish, tarantulas)
04 Nov. 2014 Arthropoda.ppt 12
Problems associated with exoskeleton.
• Problem 3. SENSORY INPUT
• touch– sensory setae connected
to neurons• smell & taste
– hollow sensory setae w/ chemosensitive nerve endings
04 Nov. 2014 Arthropoda.ppt 13
Problems associated with exoskeleton.
• Problem 3. SENSORY INPUT
• vision clear cuticle over
compound or simple eyes
04 Nov. 2014 Arthropoda.ppt 14
• Problem 3. SENSORY INPUT
• hearing tympanum =
endocuticle, vibrates like eardrum
trichobothria (right )
Problems associated with exoskeleton.
04 Nov. 2014 Arthropoda.ppt 15
Benefits of Exoskeleton: to individuals:
• Support• Locomotion
lever system
• walk, swim, fly
• Mechanical protection (armor)• Retards evaporation (in air) and/or osmosis
(in water) water balance.
04 Nov. 2014 Arthropoda.ppt 16
Benefits of Exoskeleton: to the phylum:
• Reduction of coelom & segmentation Abandoned hydrostatic system of annelid-like
ancestor) Coelom reduced to pericardial cavity• Segments fused = Tagmosis Specialization of body regions (= “tagmata”) Specialization of appendages
04 Nov. 2014 Arthropoda.ppt 17
Tagmosis
• Head (~ 4-6 segments) feeding, sensation
• Head appendages mandibles, maxillae, maxillipeds, chelicerae antennae
04 Nov. 2014 Arthropoda.ppt 18
Tagmosis
• Thorax (~ 3-6 segments) locomotion, grasping.
• Thoracic appendages walking legs, wings chelipeds
04 Nov. 2014 Arthropoda.ppt 19
Tagmosis
• Abdomen (~8- 30+ segments)respiration, reproduction, etc.
• Abdominal appendages abdominal gills (aquatic insect larvae) swimmerets (crayfish) filtering legs (barnacles) gonopods (crayfish, etc.) spinnerets (spiders)
04 Nov. 2014 Arthropoda.ppt 20
Tagmosis
• Number of segments/legs in each tagma varies by subphylum, class.Cephalothorax of 6 segments in Chelicerata
• 1 pr. chelicerae
• 1 pr. pedipalps
• 4 pr. walking legs
Cephalothorax of 13 segments in Crustacea (shrimps)• 2 pr. antennae
• 1 pr. mandibles
• 2 pr. maxillae
• 3 pr. maxillipeds
• 5 pr. walking legs (1st pair modified as chelipeds)
04 Nov. 2014 Arthropoda.ppt 21
Other arthropod characters
• Open circulatory system Dorsal heart pumps hemolymph over brain Hemolymph moves through hemocoel back toward heart Holes/valves in sides of heart let hemolymph in to go around
again.
04 Nov. 2014 Arthropoda.ppt 22
Other arthropod characters
• Respiratory systems Gills in aquatic/marine arthropods Tracheal systems in most terrestrial arthropods Book lungs (modified gills) in spiders & scorpions
04 Nov. 2014 Arthropoda.ppt 23
Other arthropod characters• Nervous system resembles that of annelid
Dorsal brain with nerves around esophagus Paired ventral nerve cords Segmental ganglia
• Often fused into 1-2 ganglia in each tagma
04 Nov. 2014 Arthropoda.ppt 24
Distinguishing Characters of Ph. Arthropoda
• Jointed exoskeleton• Tagmosis• Compound eyes
04 Nov. 2014 Arthropoda.ppt 25
Classification of Arthropoda
• Subphylum Trilobita
• Subphylum Chelicerata
• Subphylum Myriopoda
• Subphylum Crustacea
• Subphylum Hexapoda
04 Nov. 2014 Arthropoda.ppt 26
Classification of Arthropoda
• Subphylum Trilobita Class Trilobites
• Three-lobed head & body (left, middle, right)
• Diverse in Paleozoic ~540-240 MYA
• Extinct
04 Nov. 2014 Arthropoda.ppt 27
Classification of Arthropoda
• Subphylum Chelicerata Cephalothorax
• Jaws are chelicerae
• Pedipalps
• 4 pr. Walking legs
Abdomen
04 Nov. 2014 Arthropoda.ppt 28
Classification of Arthropoda
• Subphylum Chelicerata– Class Horseshoe crabs
• Horseshoe crabs• Scorpions ??
04 Nov. 2014 Arthropoda.ppt 29
Classification of Arthropoda• Subphylum Chelicerata
Class Arachnids• Lost compound eyes
• Spiders
• “Daddy-long-legs”
• Vinegaroons
• Mites & ticks
• Scorpions
• more
04 Nov. 2014 Arthropoda.ppt 30
Classification of Arthropoda
• Subphylum Myriopoda Class Centipedes
• One pair legs per segment,
• 1st legs are “fangs”
04 Nov. 2014 Arthropoda.ppt 31
Classification of Arthropoda
• Subphylum Myriopoda Class Millipedes
• Double segments (2 pr. legs per segment)
04 Nov. 2014 Arthropoda.ppt 32
Classification of Arthropoda
• Subphylum Crustacea 2 pr. Antennae
(antennules, antennae) Cephalothorax
• 13 segments & appendage pairs
Abdomen• variable among Classes
04 Nov. 2014 Arthropoda.ppt 33
Classification of Arthropoda
• Subphylum Crustacea Class shrimps Class barnacles
04 Nov. 2014 Arthropoda.ppt 34
Classification of Arthropoda• Subphylum Hexapoda
Class Insects• Head, thorax, abdomen
• 2 pr. Wings
• ~800,000 species, majority of all arthropods
04 Nov. 2014 Arthropoda.ppt 35
Why are Arthropods so successful?
• Exoskeleton tagmosis evolution of flight speciation 106 species of insects.
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