10-12: Arthropods Flashcards by Rebecca Crummett

Ecdysozoa are made up of

Priapulida
Nematoda
Onychophora
Tardigrada
Arthropoda

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What is ecdysis?

Periodic moulting of the cuticle

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Normal name for Priapulida

Penis worms

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Priapulida features

Evertable proboscis lined with scalids
Circular nerve ring surrounding a pharynx
Burrowing pedatos

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Normal name for Nematoda

Round worms

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Nematoda features

Amphids- sensory organs on the head
Circular nerve ring surrounding a pharynx
Very simple
Freshwater, marine, terrestrial, parasites

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Nematoda model organism

Caenorhabditis elegans

First multicellular organism to have their whole genome sequenced

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Nematodes that cause human disease

Lymphatic filariasis (elephantiasis)
Caused by Wuchereria bancrofti
Worms transmitted through mosquitoes
Lodged in lymph
Cause thick skin, swelling of lower extremities

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Tardigrada normal name

Water bears

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Tardigrade features

4 pairs of unjointed legs with claws
Semiaquatic
Omnivores, carnivores, parasites
Cryptobiosis- dormant stages, form tuns to cope with freezing, drying, alcohol, vacuums

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Onychophora normal name

Velvet worms

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Onychophora features

Un-jointed walking legs
Fleshy antennae
Circulatory system + heart
Jaws
Slime glands
Paired ventral nerve chord

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What are lobopods?

Lobe-legged worms, including onychophora and tardigrada
Found fossil evidence
Eg. Hallicgenia

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Early arthropods

Anomalocaris: compound eyes, arthropod-like head appendages
Megacheira: specialised body appendages

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What’s the most diverse group in the animal kingdom?

Arthropods

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First animals to colonise land?

Arthropods

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How did prehistoric gigantism in arthropods occur?

Elevated atmospheric O2 levels- 35% vs. today’s 21%

Eg. sea scorpions, trilobites, dragonflies

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What are the 3 major arthropod sub-phyla?

Trilobites
Chelicerates
Mandibulates

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Arthropod features

Jointed appendages
Pronounced tagmatisation
Chitinous exoskeleton that they shed to grow
Highly cephalised, with intricate mouthparts
Gills in water, trachea on land
Excrete uric acid

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What is tagmatisation?

Fused segments, functionally specialised

Eg. head, thorax, abdomen

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Benefits of being an arthropod

Versatile exoskeleton
Air piped directly to cells
Highly developed sensory organs

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Trilobite features

15,000 species
Well preserved exoskeleton
Predators/filter feeders
Marine
V successful
Disappeared at the end of the Permian- maybe due to emergence of predators?

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Chelicerata groups

Pycnoginida
Merostomata
Arachnida

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Chelicerata features

75,000 known, estimated 750,000 altogether
Named after their mouthparts- the chelicerae
First appendages form chelicerae
Pair of pedipalps
4 pairs of legs
2 tagmata

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Proper name for sea spiders?

Pycnoginida

Pycnoginida features

Found in all seas, particularly polar | Carnivorous grazers

Pycnoginida reproduction

Males carry eggs and larvae External fertilisation, but get very close to reproduce Non-planktonic larvae, so slow dispersers

What are Merostomata?

'Legs attached to mouth' Sea scorpions Xiphosurida

Sea scorpion features?

Cambrian origin Apex predators in the shallows Not scorpions, probably didn't live in the sea

Scientific name for horseshoe crabs?

Xiphosurida

Xiphosurida features

Polyandrous mating External fertilisation Not a crab Copper-based blue blood

Arachnida groups

``` Spiders Scorpions Whip scorpions Mites Harvestmen ```

What were Trigonotarbida?

Related to spiders, but not ancestors Before true spiders in the Palaeozoic Oldest land arthropod No spinnerets

Spiders scientific name

Aranae

Aranae features

``` All carnivorous except one 2 tagmata Book lungs 2/3 spinnerets connected to silk glands Silk as strong as kevlar ```

Aranae hunting strategies

Web builders eg. orb weavers- hide on edge of web to avoid being eaten by birds Trapdoor spiders Fishing spiders Ambush hunters eg. trapdoor spiders- use silk triplines

Aranae reproduction

Indirect sperm transfer Some show parenting behaviour Cryptic female selection- mate, store sperm, then choose which to use, eg. wasp spiders Vibration, pheremones, arm movements

'Herbivorous' spider

Bagheera kiplingi | Eats Beltian bodies on acacia leaves- protected by ants in mutualism

Harvestmen scientific name

Opiliones

Opiliones features

6,000 species up to 4000m high Chew (masticate) food Generally only 1 pair of eyes Don't produce silk

Camel spiders scientific name

Solifugae

Solifugae features

Not true spiders Two pairs of chelicerae Carnivorous

Scorpion scientific name

Scorpiones

Scorpiones features

Massively enlarged pedipalps = pincers Harsh, arid habitats Tail with sting to inject venom into prey

Whip scorpion scientific name

Thelyphonida

Thelyphonida features

Vinegaroons Not scorpions First 2 pairs are sensory appendages Tropical/subtropical

Tailless whip scorpion scientific name

Amblypgi

Amblypgi features

Not scorpions First pair of legs are modified as sensors Pedipalps for grabbing prey- like a mantis Tropics/subtropics

Mites and ticks scientific name

Acari

Acari features

Very small Caves, thermal springs, polar extremes Many parasitic

Mandibulata features

Characteristic mandible jaws | First out of the sea in the Cambrian

Mandibulata are split into...

Myriapods Crustacea Insecta

Myriapoda are split into...

Diplopoda | Chilopoda

Myriapoda features

One pair of antennae Mandibles Non-branching legs (uniramous)

Millipedes scientific name

Diplopoda

Diplopoda features

``` Trachea and mandibles like insects 2 pairs of legs per segment Calcium carbonate in the exoskeleton Decomposers Every 7th segment, legs = sex organs Larvae have 1 pair per segment, like centipedes ```

Centipede scientific name

Chilopoda

Chilopoda features

Mainly carnivorous 1 pair of legs per segment Only one species can kill Legs modified into venomous fangs

Crustacea features

``` Marine, freshwater and terrestrial Synapomorphy = 2 pairs of antennae Many jointed appendages Biramous- split into 2 at the end Compound eyes raised on stalks ```

Crustacea divisions

``` Remipedia Cirripeda Isopoda Decapoda Hexapoda ```

What are Remipedia?

Blind, cave-dwelling Centipede-like appearance More closely related to insects

Scientific name for barnacles?

Cirripeda

Cirrepeda features

Adults are sessile, juveniles are usually planktonic Hermaphroditic Longest penis in relation to body size

What are Isopoda?

Woodlice, marine isopods

Isopod features

``` 4,500 marine, 500 on land Occupy niches not occupied by many other forms- 'refugia' Brood develops within females pouch Can be parasitic Some giant ones in cold, deep waters ```

What are Decapoda?

Crabs, lobsters, crayfish, shrimp

Decapod features

5 pairs of walking legs First is usually modified into pincers Mainly aquatic

What are Hexapoda?

Protura Diplura Collembola- 'springtails'