3454chapter21 - 3 Cryptobiosis—dormant dehydrated state...

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Lesser Protostomes (mostly Onychophora), Ch. 21 I. Several, minor phyla are closely related to the annelids and arthropods A. These were involved in the Cambrian explosion (535-530 mya) and survive in small #s today 1. Protostomous, eucoelomate, bilateral, triploblastic B. Sipuncula—peanut worms; benthic, marine worm-like critters, mostly deposit-feeders
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C. Echiura—spoon worms; similar in habit and appearance to Sipunculans D. Pogonophora—deep benthic, tube-dwelling, worm-like, live around hydrothermal vents 1. No mouth or digestive tract, live with mutualistic chemoautotrophic prokaryotes
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2. May actually be a polychaete order E. Pentastomida—lung and nasal endoparasites of reptiles, birds and some mammals
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3. May actually be a crustacean class F. Tardigrada—“water bears”, 1mm or less, live in water or water film around mosses/lichens 1. Many similarities to arthropods (molting, limbs, malpighian tubules) 2. Pierce and suck their food
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Unformatted text preview: 3. Cryptobiosis—dormant, dehydrated state that lasts for years and is very durable G. Onychophora—“velvet worms”, small terrestrial tropical predators of snails, worms, slugs 1. Changed very little in 500 million years 2. Have characteristics of both Annelids and Arthropods a) Early Cambrian ancestors of Onychophorans may be Arthro./Tardigrade ancestr. b) These early “Onychophorans” may have evolved from a Polychaete-like critter 3. Annelid-like characteristics a) Unjointed limbs b) Metanephridia and gonads in each segment c) No tagmatization 4. Arthropod-like characteristics a) No septa between segments b) Chitinous cuticle (very flexible) (1) BUT…they use a coelom-based hydrostatic skeleton (like annelids) c) Open circulatory system with hemocoels d) Trachea with spiracular openings for aerial gas exchange (like Uniramia) e) Single pair of antennae...
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3454chapter21 - 3 Cryptobiosis—dormant dehydrated state...

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