20. Crustaceans - Crustaceans Chapter 20 Subphylum...

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Crustaceans Chapter 20
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Subphylum Crustacea Crustaceans, subphylum Crustacea typically have biramous , branched, appendages that are extensively specialized for feeding and locomotion.
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Subphylum Crustacea Crustacea is divided into 5 classes. Current molecular phylogenies do not support the monophyly of all classes.
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Subphylum Crustacea - External Features Secreted cuticle is made of chitin, protein, and calcareous material. Heavy plates have more calcareous deposits - joints are soft and thin, allowing flexibility. Dorsal tergum and ventral sternum are plates on each somite lacking a carapace. Telson is not a somite - bears anus and may be homologous to the pygidium.
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Subphylum Crustacea Crustaceans are the only arthropods that have two pairs of antennae . They also have a pair of mandibles (jaw-like appendages) and two pairs of maxillae on the head. Each body segment usually has one pair of appendages. Ancestrally biramous except for the first antennae.
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Subphylum Crustacea - Appendages Members of Malacostraca and Remipedia have appendages on each somite. Other classes may not bear appendages on abdominal somites. Appendages have become specialized by evolving into a wide variety of walking legs, mouthparts, swimmerets, etc. from modification of the basic biramous appendage.
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Subphylum Crustacea The ancestral condition in arthropods is to have many body segments. Fewer segments and increased tagmatization is the derived condition.
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Subphylum Crustacea - Internal Features Muscular and nervous systems and segmentation exhibit metamerism of annelid-like ancestors. Hemocoel - persistent blastocoel that becomes filled with blood. Coelomic compartments remain as end sacs of excretory organs and gonads.
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Subphylum Crustacea - Muscular System Striated muscles make up a major portion of crustacean body. Most muscles arranged as antagonistic groups. Flexors draw a limb toward the body and extensors straighten a limb out.
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Subphylum Crustacea - Muscular System Abdominal flexors of a crayfish allow it to swim backward. Strong muscles located on each side of stomach control the mandibles.
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Subphylum Crustacea - Respiratory System Smaller crustaceans may exchange gases across thinner areas of cuticle. Larger crustaceans use featherlike gills for gas exchange. “Bailer” of 2nd maxilla draws water over gill filaments.
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Subphylum Crustacea - Circulatory Open circulatory system Dorsal heart - single-chambered sac of striated muscle. Valves in the arteries prevent backflow of hemolymph. Hemolymph conducted to gills, if present, for oxygen and carbon dioxide exchange. Hemolymph may be colorless,
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This note was uploaded on 04/17/2011 for the course ENY 3005 taught by Professor Staff during the Fall '08 term at University of Florida.

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20. Crustaceans - Crustaceans Chapter 20 Subphylum...

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