10-12: Arthropods Flashcards
Ecdysozoa are made up of
Priapulida Nematoda Onychophora Tardigrada Arthropoda
What is ecdysis?
Periodic moulting of the cuticle
Normal name for Priapulida
Penis worms
Priapulida features
Evertable proboscis lined with scalids
Circular nerve ring surrounding a pharynx
Burrowing pedatos
Normal name for Nematoda
Round worms
Nematoda features
Amphids- sensory organs on the head
Circular nerve ring surrounding a pharynx
Very simple
Freshwater, marine, terrestrial, parasites
Nematoda model organism
Caenorhabditis elegans
First multicellular organism to have their whole genome sequenced
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
Tardigrada normal name
Water bears
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
Onychophora normal name
Velvet worms
Onychophora features
Un-jointed walking legs Fleshy antennae Circulatory system + heart Jaws Slime glands Paired ventral nerve chord
What are lobopods?
Lobe-legged worms, including onychophora and tardigrada
Found fossil evidence
Eg. Hallicgenia
Early arthropods
Anomalocaris: compound eyes, arthropod-like head appendages
Megacheira: specialised body appendages
What’s the most diverse group in the animal kingdom?
Arthropods
First animals to colonise land?
Arthropods
How did prehistoric gigantism in arthropods occur?
Elevated atmospheric O2 levels- 35% vs. today’s 21%
Eg. sea scorpions, trilobites, dragonflies
What are the 3 major arthropod sub-phyla?
Trilobites
Chelicerates
Mandibulates
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
What is tagmatisation?
Fused segments, functionally specialised
Eg. head, thorax, abdomen
Benefits of being an arthropod
Versatile exoskeleton
Air piped directly to cells
Highly developed sensory organs
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?
Chelicerata groups
Pycnoginida
Merostomata
Arachnida
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
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’
