Unit 5 - Arthropoda Notes

Phylum Arthropoda

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Arthropod Groups

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Most Successful Animals:

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Characteristics of Arthropods:       

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Jointed appendages Exoskeleton Segmented (metamerism) Tagmatation – fusion of segments to form body regions open circulatory system Compound eyes Bilateral symmetry Ecdysis – “an escape”; growth by molting

Reasons for Success      

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Versatile exoskeleton Segmentation Oxygen piped directly to cells (terrestrial) Highly developed sensory organs Complex behaviors metamorphosis

Arthropod Segments  

Arthropod segments are grouped into body regions Some have two regions –

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Some have three regions –

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Head, thorax, abdomen

Many regions have multiple appendages –

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Cephalothorax, and abdomen

Appendages are modified for a particular function Phylum Arthropoda

Arthropod Appendages 

The head usually contains pairs of joint appendages, which are sensory and used in feeding – –

Antenna’s or feelers are first Followed by the jaws and mandibles which are used for biting and chewing  Mandible

and accessory mouth parts aid in handling the food and moving it towards the mouth

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Phylum Arthropoda

EXOSKELETON 

a.k.a. the cuticle: – –

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Composed of chitin Produced by the epidermis

Molting of the cuticle is called ecdysis

Arthropod Vision 

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Simple eyes – Light sensitive cells share a common lens Compound eyes – Thousand of closely packed units called ommatidia

COMPOUND EYE • Made up of repeating units

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METAMORPHOSIS Complete: egg  larva  pupa  adult

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Incomplete: egg  nymph  adult

Subphylum Chelicerata 

Includes: – – – – –

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Spiders Scorpions Ticks Mites Horseshoe Crabs

CHELICERATA      

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Approximately 70,000 species Chelicerae = fangs NO antenna NO mandibles 4 pair of walking legs 1 pair of pedipalps

Class Merostomata 

Limulus (horseshoe crabs) – –

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Largest chelicerates –

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First fossils 445 MYA Lived before dinosaurs

Up to 75cm long

Merostomata Body Form 

Segments: – – –

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Carapace Abdomen Telson

Blood is used by pharmaceutical companies to test for endotoxins and pathogens

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Class Arachnida

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Spiders Scorpions Ticks Mites

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ALL have book lungs

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Class Arachnida 

Chelicerae: 1st pair of appendages around mouth –

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Most are predators – –

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Often with poison

Inject enzymes into prey Suck fluid into pharynx

Class Arachnid 

2 Body Segments: –

Cephalothorax   

– –

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Chelicerae pedipalps 4 pair of walking legs

Abdomen EXCEPT mites & ticks

Order Scorpionida 

Pedipalps: –

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Enlarged to form pinchers

Abdominal Stinger

Order Araneae  Spiders

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Fangs with poison glands

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Silk glands

Arachnid Book Lung

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Dugesiella 

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tarantula

Latrodectus mactans  

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Black Widow neurotoxin

Loxosceles reclusa 

Fiddle Black Spider – – –

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Brown recluse Brown Violin

Necrotoxin

Loxosceles reclusa 

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Necrosis of tissue

Order Acari   

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Ticks Mites Full Tagmatation  all body segments fused

Order Opiliones   

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One body segment Short fangs Myth – not most venomous

Arthropoda Groups: 

Subphylum Trilobitomorpha: –

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Subphylum Chelicerata: – –

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Class Meristomata: horseshoe crabs Class Arachnida: spiders, mites, etc.

Subphylum Mandibulata: – –

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Class Trilobita: extinct trilobites

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Class Myriapoda: centipedes, millipedes Class Insecta: insects Class Crustacea: lobsters, crabs, etc.

Subphylum Mandibulata 

Class Myriapoda: –

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Class Insecta: – –

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Centipedes and millipedes

Most diverse animal class Flies, bees, beetles, ants, etc.

Class Crustacea: –

Crabs, lobsters, barnacles, copepod

Mandibulata Characteristics 

2 pairs of antennae –

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3rd segment bear mandibles –

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Anterior to feeding appendages

Jaws for chewing/grinding

Compound Eye

Class Myriapoda   

“many appendages” Fewer than 10  100s of appendages Millipedes – –

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Centipedes – –

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Mostly herbivorous Plain in color Carnivorous colorful

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Phylum Arthropoda

Class Insecta   

Most biodiverse class of animals! Only invertebrates that can fly 3 Body Regions – – –

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Head Thorax Abdomen

Typically 3 pairs of legs Have metamorphosis Oxygen goes directly into cells via spiracles

Class Crustacea 

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Lobsters, shrimp, crayfish, copepods, barnacles, crabs, pill bugs Have 2 pairs of antennae 3 mouthparts Swimmerets Gills Naupliar larval stage

Class Crustacea – Pill Bug  

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Only crustacean that is entirely terrestrial “rollie pollies”

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Fairy & Brine Shrimp, water fleas Freshwater

Phylum Arthropoda

Copepod

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Phylum Arthropoda

Barnacle Anatomy Testis Anus

Cirri Penis Mouth Stomach Ovary Cement gland

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CRAYFISH

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Phylum Arthropoda

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Phylum Arthropoda