Invertebrates: Arthropods and Echinoderms

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InvertebratesArthropods and Echinoderms

• October 16, 2007

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Phylum Arthropoda

• Most species of any phylum (1 million)
• Segmented, bilaterally symmetrical body
• Jointed appendages
• Exoskeleton made of chitin
• Growth requires molting

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http//www.biologycorner.com/resources/arthropod_c
hart.gif
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Phylum Arthropoda - Subphylum Crustacea

• Most species marine
• Gills
• 2 pairs of antennae
• Zooplankton Crustaceans
• Copepods
• Krill
• Amphipods

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Phylum Arthropoda - Subphylum Crustacea

• Barnacles

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Phylum Arthropoda - Subphylum Crustacea

• Isopods

http//www.mbari.org/news/news_releases/2006/snail
size-images/giant_isopod_450.jpg
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Phylum Arthropoda - Subphylum Crustacea

• Decapoda
• Shrimp
• Crabs
• Lobsters

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Phylum Arthropoda - Subphylum Crustacea
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Phylum Arthropoda - Subphylum Crustacea
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Phylum Arthropoda - Subphylum Chelicerata

• Horseshoe Crabs

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Phylum Arthropoda - Subphylum Chelicerata

• Sea Spiders

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Phylum Echinodermata

• Entirely marine
• About 6000 species
• Pentaradial symmetry
• Spiny skin
• Complete digestive tract
• Endoskeleton
• Water vascular system

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Phylum Echinodermata

• Water Vascular System
• A network of canals, valves, and suckers
• Water is exchanged across a sieve plate, known as
  a madreporite
• Uses water pressure to operate many tube feet
• Tube feet can apply suction and also secrete
  mucus

http//animaldiversity.ummz.umich.edu/site/account
s/information/Echinodermata.html
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Phylum Echinodermata

• Class Asteroidea - Sea Stars

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Phylum Echinodermata

• Class Asteroidea
• Usually carnivorous
• Use tube feet to attach to their prey, and then
  feed by extruding their stomach, and digesting
  prey mostly outside their body

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Phylum Echinodermata

• Class Asteroidea
• Keystone Species

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Phylum Echinodermata

• Class Asteroidea

Crown of Thorns - Acanthaster planci
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Phylum Echinodermata

• Class Ophiuroidea

http//www.stanford.edu/bhackett/nautilus-2005-08
/pages/basket-star-(b).html
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Phylum Echinodermata

• Class Echinoidea
• Endoskeleton fused into a round, rigid test
• Movable spines and pedicellarie
• 5 rows of ambulacral grooves
• Herbivores

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Phylum Echinodermata

• Class Echinoidea
• Aristotles lantern - jawlike structure
• Made of specialized ossicles, and moved by
  muscles
• Has 5 teeth that come together in a point, and
  allow the animal to tear apart seaweeds or scrape
  algae off surfaces

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Phylum Echinodermata

• Class Echinoidea

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Phylum Echinodermata

• Class Holothuroidea - Sea Cucumbers
• Lack spines and obvious radial symmetry
• Endoskeleton reduced to small spicules in skin
• Have a respiratory tree
• Deposit and filter feeders
• Evisceration

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Phylum Echinodermata

• Class Crinoidea -
• Sea Feathers (unstalked)
• Sea Lilies (stalked)
• Suspension Feeders
• Capture food with tube feet and mucus
• Ciliated ambulacral grooves move food to mouth

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Road to Vertebrates

• Phylum Hemichordata
• Acorn Worms
• Deposit Feeders
• Live in U-shaped burrows
• Get organic matter from mucus-secreting proboscis

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Road to Vertebrates

• Phylum Chordata
• Subphylum Urochordata
• Subphylum Vertebrata