arthropods staring the crayfish part 1 – introduction & external anatomy
TRANSCRIPT
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ArthropodsStaring the Crayfish
Part 1 – Introduction & External Anatomy
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There are Four Main Groups of Arthropods
• Crustaceans (crayfish, lobsters, shrimp)
• Centipedes & Millipedes
• Arachnids (spiders)
• Insects (bugs, beetles, butterflies, grasshoppers, etc.)
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Crayfish – External Anatomy
• Crayfish are crustaceans
• Have an exoskeleton (2 parts)– Cephalothorax– Abdomen
• The part that covers the cephalothorax is called the carapace
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Cephalothorax Abdomen
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• Each segment of both the cephalothorax and the abdomen contain a pair of appendages.
• The cephalothorax is divided into 13 segments
• The abdomen is divided into 6 segments
• The head region also has 5 pairs of appendages.
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The long antennae are organs for touch, taste, and smell.
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The antennules are organs of balance, touch, and taste.
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The mandibles, or jaws, crush food by moving from side to side.
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Two pairs of maxillae hold solid food, tear it, and pass it to the mouth.
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• The second pair of maxillae also helps to draw water over the gills.
• Crayfish need water to flow over their gills so that they can breathe.
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The first 3 appendages on the chephalothorax are maxillipeds.
They hold food during eating.
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The chelipeds are the large claws that the crayfish uses for defense and to capture prey.
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Each of the four remaining segments contains a pair of
walking legs.
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The first 5 segments of the abdomen each have a pair of
swimmerets.
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• The swimmerets create water
currents and help with reproduction.
• Females attach eggs to the last three pairs of swimmerets.
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The 6th segment of the abdomen has a pair of flippers or uropods.
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In the middle of the uropods is the telson.
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On the ventral side of the telson is the anus.
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• The uropod and telson together make up the tail fan.
• The crayfish moves backward by forcing water forward with its tail fan.
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Is your crayfish a male or female?
• Locate the base segment of each pair of walking legs.
• The base segment is where the leg attaches to the body.
• Study the inside surface of the base segments of the 3rd and 4th walking legs.
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Male or Female?
• Female = observe a crescent-shape slit on the base segment of the 3rd walking leg (genital pore)
• Male = sperm duct opening on the base segment of 4th pair of walking leg.
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Genital Pore
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