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What characteristics define an arthropod?
Bilateral symmetry, segmented bodies, exoskeleton, jointed appendages, and metamorphosis.
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What is the only extinct major group of Arthropoda?
Trilobites
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What are some major groups of Arthropoda?
Horseshoe crabs, arachnids, crustaceans, etc.
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What are some unique feature of horseshoe crabs?
Instead of hemoglobin, they have hemocyanin, which replaces the iron normally found in blood and makes the blood blue. They’re also related to spiders and scorpions, and their numbers are in decline.
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What important groups are there among the arachnids?
Scorpions, spiders (araneae), acari (ticks and mites), harvestmen/daddy-longlegs, amblypygi (tailless whipscorpions), millipedes, and centipedes.
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How many species of arachnids have been described so far?
Over 100,000.
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What characterizes the arachnids?
4 pairs of legs, two body segments (thorax and abdomen, pedipalps (homologous with mandibles), and they have no antennae or wings.
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What segment of the body are the legs of an arachnid attached to?
The cephalothorax
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What characterizes scorpions?
They have huge pedipalps, with large grasping claws. They also have a venomous stinger at the tip of their tail. They exhibit oviviparity, which means the females keep the eggs in their bodies until ready to hatch. They also show parental care, keeping the young on their backs until the first molt.
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How many species of scorpions have been described? How many of those have poison strong enough to kill a human?
1,500 species, of which 24 have poison strong enough to kill a human.
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How many species of harvestmen/daddy-longlegs have been described?
6,000 species
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What characterizes harvestmen/daddy-longlegs?
Omnivorous, non-venomous, pincher-like mouth parts, and extremely long legs. Their body segments are also fused.
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What characterizes the acari?
They’re the most diverse and abundant group of arachnid. Most are microscopic. They’re predaceous, scavengers, parasitic, and pathogenic. Some are phoretic?
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What does phoretic mean?
Phoretic means it’s an animal that attaches to another animal for transportation only.
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What characterizes amblypygids?
They are tailless whipscorpions. They are harmless, and have a second pair of appendages that are extremely long, which are used as sensory receptors.
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What characterizes spiders?
Four pairs of legs, small pedipalps that are leg-like, they have silk-producing glands or spinnerets, and fangs with venom.
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How do tarantulas catch prey?
They make silken retreats/burrows where they wait to ambush prey.
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How many species of spiders have been described?
40,000 species
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What family do jumping spiders belong to?
Salticidae
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How many described species of jumping spider are there?
5,000 species
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What’s the difference between millipedes and centipedes?
Millipedes have two pairs of legs per body segment, while centipedes only have one pair of legs per body segment. Millipedes are scavengers, while centipedes are predatory, with poisonous fangs.
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What characterizes crustaceans?
They have 5 pairs of legs, and other legs for swimming. The most dominant group of arthropoda in marine environments.
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How many species of crustacean have been identified?
60,000 species so far
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