1 subphylum chelicerata horseshoe crabs, spiders, ticks, mites, scorpions
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Subphylum ChelicerataSubphylum Chelicerata
• Horseshoe crabs, spiders, ticks, mites, scorpions
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Subphylum Chelicerata Subphylum Chelicerata (cont(cont’’d)d)
• Cephalothorax (prosoma)– Fused head and thoracic
region
– Sensory, feeding, locomotion
• Abdomen (opisthosoma)– contains digestive,
reproductive, excretory, and respiratory organs
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Subphylum Chelicerata Subphylum Chelicerata (cont(cont’’d)d)
• Appendages attached to cephalothorax– Pair of chelicerae (pincer-like feeding
appendages)
– Pair of pedipalps (usually sensing or feeding)
– four pairs of legs (5 in horseshoe crabs)
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Subphylum Chelicerata Subphylum Chelicerata (cont(cont’’d)d)
• Usually has eyes
• Never has antennae
• Most suck liquid food from prey
mite
Class MerostomataClass Merostomata
• Two subclasses: – Xiphosura (horseshoe crabs)
•Covered by carapace
•Have chelicerae, pedipalps, 3 pairs walking legs, & 1 pair digging legs
•book gills to obtain oxygen from sea water
– Euryptida (giant water scorpions) --extinct
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Class ArachnidaClass Arachnida• Spiders, ticks,
scorpions
• Most are predators
• Most harmless to humans
Order Araneae
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Class Arachnida (contClass Arachnida (cont’’d)d)
Special features to know:
•Use coxal glands and/or Malpighian tubules for nitrogenous waste/excretion
•Have book lungs (folds of body wall to form lungs)
•Air intake tubes: trachaea, which open to outside via spiracles
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Class Arachnida (contClass Arachnida (cont’’d)d)
Special features to know, continued:
•Sensory structures: sensilla
•Dioecious (separate male/female individuals)
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Class Arachnida (contClass Arachnida (cont’’d)d)
• Some ticks and mites spread disease, cause irritation
Dust mite mite
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Class Arachnida (contClass Arachnida (cont’’d)d)
• Lyme disease– Caused by tick
tick
Order ScorpionidaOrder Scorpionida• The Scorpions
– Prosoma fused into shield-like carapace
– Opisthoma contains digestive & reproductive organs
– Oviparous: lay eggs that develop and hatch outside the body
– Pedipalps and chelicerae
– Posterior stinger
•Only a few scorpions are toxic to humans
» Found in Northern Africa and Mexico, Arizona, New Mexico 11
Scorpion
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Order AraneaeOrder Araneae(the spiders)(the spiders)
• Some spiders (ie. black widow, brown recluse spider) give painful, dangerous bites
• Know how to identify them!
Black widow
Brown recluse
Black widow has red “hourglass” on ventral surface of opisthoma
Brown recluse has “violin” mark on dorsal side of prosoma
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SpidersSpiders• Prosoma: anterior segment
• Opisthoma: posterior segment
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Spiders (contSpiders (cont’’d) d)
• All predaceous– Mostly insects
• Chelicerae may have fangs
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Prey capture among the Prey capture among the spidersspiders
• Some species are cursorial predators– stalk and ambush
their prey (trap door spider)
– they usually have well-developed eyes
Jumping spider
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Prey capture among the Prey capture among the spiders (contspiders (cont’’d)d)
• Some are web-building spiders– Eyes not as well
developed
– sensory hairs for detecting vibrations
Grass spider
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• Many spiders (and mites) producing silk– Used for trapping prey, building nests,
forming egg cases
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Orb web construction
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• silk glands that open to the exterior part of the abdomen through spinnerets
spinnerets
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• Spider venom is used to subdue prey
• Venom liquifies tissues with a digestive fluid
• Spider sucks up soupy prey (ewwww!)
Wolf spider
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Spiders: Class AraneaeSpiders: Class Araneae
Spider love…..
• Spiders, like most arthropods, are dioecious
• Mating habits– Pheromones- chemicals that elicit
behavioral change
– Rituals- males pluck female’s web (pattern is species-specific)
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Spiders: Class AraneaeSpiders: Class Araneae
• Male builds small web, deposits sperm– Collects sperm in cavities of pedipalps
– Pedipalps have ejaculatory duct + embolus
– inserts pedipalps into female genital opening
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Spiders: Class AraneaeSpiders: Class Araneae
• Eggs laid in silk case– Carried, attach to web, bury
Wolf spider preparing egg sac
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A lycosid (wolf spider) preparing egg sac
M. C. Barnhart
25M. C. Barnhart
26M. C. Barnhart
27M. C. Barnhart
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Wolf spider parental care- after the eggs hatch, the young ride on mom for several days.
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CrustaceansCrustaceans
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The CrustaceansThe Crustaceans
shrimpcrabs
lobsters
amphipods
euphausids (krill)amphipods
Daphnia
• Phylum Arthropoda– Subphylum
Crustacea
•crusta= shell
• Lobster, crayfish, shrimp, crab, water flea, barnacles
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The Crustaceans (contThe Crustaceans (cont’’d)d)
• Aquatic (mostly marine)– a few terrestrial forms
• Major ecological and economical importance.
shrimp
lobsters
euphausids (krill)amphipods
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• Biramous appendages (at least primitively)– 2 main branches
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• Only arthropods with 2 pairs of antennae
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• Great specialization of appendages– Mouthparts chewing, grinding, handling
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– appendages strengthened for walking or protection (chelipeds, pincer-like claws)
cheliped
walking legs
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• Like other arthropods (+ unlike annelids), coelom is highly reduced
• Major body cavity is hemocoel (contains colorless blood)
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Respiration – gills (usually)
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• Compound eye is typical of phylum
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• Same Order, but different families
• Lobsters are bigger
• Lobsters are marine; crayfish live in freshwater creeks, ditches, or lakes
WhatWhat’’s the difference s the difference between a crayfish and a between a crayfish and a
lobster?lobster?
crayfish lobster
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Brine Shrimp (Artemia salina)
• cosmopolitan
• restricted to highly saline lakes and evaporation basins
• Dormant cysts= encased embryo
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BarnaclesBarnacles
“nothing more than a little shrimplike animal standing on its head in a limestone house and kicking food into its mouth” -Louis Agassiz
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BarnaclesBarnacles
• living and nonliving substrates
• most species secrete CaCO3 shell
• Head reduced, rudimentary abdomen
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KrillKrill
• Component of plankton
• Major food for whales